monitoring of the energy consumption working points in the electric arc furnace · ·...

MONITORING OF THE ENERGY CONSUMPTION WORKING POINTS IN THE

ELECTRIC ARC FURNACE

JUAN CARLOS FORERO PÉREZ

PONTIFICIA UNIVERSIDAD JAVERIANA

ENGINEERING FACULTY

ELECTRONIC DEPARTMENT

BOGOTÁ, D.C.

2004

MONITORING OF THE ENERGY CONSUMPTION WORKING POINTS IN THE

ELECTRIC ARC FURNACE

JUAN CARLOS FORERO PÉREZ

Work degree to get the diploma of

Electronic Engineer

Director

HARTMUT SPIEGEL

Electric Engineer


ENGINEERING FACULTY

ELECTRONIC DEPARTMENT

BOGOTÁ, D.C.

2004

ARTICULO 23 DE LA RESOLUCIÓN No. 13 DE JUNIO DE 1946

"La universidad no se hace responsable de los conceptos emitidos por sus alumnos

en sus proyectos de grado.

Sólo velará porque no se publique nada contrario al dogma y la moral católica y

porque los trabajos no contengan ataques o polémicas puramente personales. Antes

bien, que se vea en ellos el anhelo de buscar la verdad y la justicia".


ENGINEERING FACULTY

ELECTRONIC ENGINEERING COURSE

RECTOR MAGNIFICO: R.P. GERARDO REMOLINA S.J.

DECANO ACADÉMICO: Ing. ROBERTO ENRIQUE MONTOYA VILLA

DECANO DEL MEDIO UNIVERSITARIO: R.P. ANTONIO JOSÉ SARMIENTO NOVA

S.J.

DIRECTOR DE CARRERA: Ing. JUAN CARLOS GIRALDO CARVAJAL

DIRECTOR DEL PROYECTO: Dipl. Ing. HARTMUT SPIEGEL

EXPLANATION IN LIEU OF AN OATH

Hereby I assure that the following work has been developed by me independently.

For all literally publications taken, exist the corresponding remarks.

Kehl, Germany, 12.08.2004.

Juan Carlos Forero Pérez

TABLE OF CONTENTS

Page

GRATEFULNESS I

FIGURES LIST II

ANNEXES LIST V

ABREVIATIONS VII

BIBLIOGRAPHICAL REFERENCES IX

TASK XI

INTRODUCTION XII

1 BADISCHE STAHLWERKE GMBH (BSW) 1

1.1 Partner companies 2

2 THE STEEL PROCESS 4

2.1 General description of the steel process in BSW 4

2.2 The principle of melting down in the EAF 5

2.2.1 Melting process stages 6

2.3 Energy providing 9

2.4 Furnace energy input 10

2.5 Present situation of energy reporting 12

3 THE STEEL PROCESS AS CONSUMER IN A CONSUMER-GENERATOR

CIRCUIT 13

3.1 Equivalent circuit for AC furnaces 13

3.1.1 Single phase equivalent circuit 13

3.1.2 Three phase equivalent circuit 15

3.1.3 Balanced furnace operation 16

3.1.4 Unbalanced furnace operation 18

3.2 Circle diagram for AC furnaces 20

4 HARDWARE AND SOFTWARE OF THE SYSTEM 24

5 BLOCK DIAGRAM OF THE MONITORING PROGRAM FOR ENERGY

CONSUMPTION 25

5.1 General description 25

5.2 Block diagram 26

5.2.1 Data acquisition 26

5.2.2 Storage: database 27

5.2.3 Calculations 27

5.2.4 Interface 28

5.3 Theoretical background 29

5.3.1 Data extraction phase 29

5.3.1.1 Electrical variables 30

5.3.1.2 Events 30

5.3.1.3 Constant parameters 30

5.3.2 Data processing phase 31

5.3.2.1 Additional variables 31

5.3.2.2 Heat number 32

5.3.2.3 Process state 32

5.3.2.4 Statistical concepts 32

5.3.3 Database 33

5.3.4 User interface 33

6 IMPLEMENTATION 34

6.1 Storage and database manipulation 34

6.1.1 Procedures 35

6.1.2 Manipulating procedures 36

6.1.2.1 Consulting procedures 38

6.1.2.2 Jobs 40

6.1.3 Tables 40

6.1.3.1 For calculations 41

6.1.3.2 For unfolding 41

6.1.3.3 For parametrization 41

6.1.4 Ordering and data flow 42

6.2 Rapid prototyping based on the Microsoft Excel program 42

6.3 User interface program 43

6.4 Tests 45

6.4.1 Data processing 45

6.4.2 Memory capacity 46

6.4.3 Interface 46

6.4.3.1 Systematic procedures 47

6.4.3.2 Data shown 47

7 MAN-MACHINE INTERFACE AND ITS FUNCTIONS 48

7.1 Circle diagram 49

7.2 Histograms 49

7.3 Information states 50

7.4 Power area index (PAI) 51

8 ANALYSIS 53

8.1 Phases symmetry 53

8.2 Stability of the arc 55

8.3 Best energy applied 56

8.4 Operation of the electrodes regulation system 57

8.4.1 Approach using the PAI 58

8.4.2 Approach using the measurements distribution 59

8.5 Scrap mixes 60

8.6 Equipment 60

8.7 The two EAF from BSW 61

8.7.1 Approach from the work tools 61

8.7.2 Approach from the system 62

9 CONCLUSIONS 64

GRATEFULNESS

The realization of this work was possible thanks to the disposition and cooperation of

several people.

My recognition goes to the companies Badische Stahlwerke GmbH and Badische

Stahl-Engineering GmbH in Germany, who gave me the possibility to write my thesis

between March 2004 and August 2004. My sincere gratefulness to Mr. Dipl.-Ing.

Hartmut Spiegel, automation department director, who supported me every moment

during my stage in this country.

By their valuable support and patience, specially in the programming area, thanks to

Mr. Ing. J. Gräßler, and for the video to Mr. A. Vogel.

To my father and brothers, who are my reason, pride and inspiration, and that have

offered me all the aid to the accomplishment of this work. To my mother who makes

me every day more clear the way with her radiating brilliance.

I

FIGURES LIST

Figure Title Page

1-1

Overview about BSW.

1

1-2

Production environment of the steel plant.

2

2.1-1

Steel production process. 4

2.2-1

Electric arc furnace.

5

2.2.1-1

Melting stages.

6

2.2.1-2

Scrap loading.

7

2.2.1-3 Formal description of the process based on a table.

8

2.3-1

Electric scheme distribution.

9

2.4-1

Control of the furnace energy input.

11

3.1.1-1

Single phase diagram of the furnace. Circuit layout,

equivalent circuit and simplified linearized equivalent

circuit.

13

3.1.1-2

Phasor diagram of voltages and currents.

15

3.1.2-1

Equivalent circuit and simplified linearized equivalent

circuit of the three phase arc furnace.

15

II

3.1.3-1

Relation between P, Q and S.

18

3.1.4-1 Time records of arc voltage, current and arc

characteristics: instantly after start melting, 7 minutes

after start melting and 27 minutes after start melting.

19

3.2-1

Curves of impedance Z and admittance Y.

20

3.2-2

Locus curve for the current, components of the current

and locus curve of the power.

21

3.2-3

Parameters of the power locus diagram.

23

5.2-1 Block diagram of the system. 26

5.2.3-1 Distribution of the information in tables. 28

5.3-1 Flow diagram and distribution of the system. 29

6.1-1 Global overview of the database distribution. 34

6.3-1 Global structure of the interface program. 43

7-1 Tree of functions. 48

7.1-1 Example of the locus diagram picture. 49

7.2-1 Example of the histogram picture. 50

III

7.3-1 States report. 51

7.4-1 Example of the power area index graph.

52

8.1-1 Symmetric and asymmetric phases behaviour. 54

8.2-1 Stable and unstable arc in the furnace. 55

8.3-1

Movement of the points in the circle diagram.

56

8.3-2 Working points on the states of the melting down

process.

57

8.4.2-1 Example of measurements distribution for active power,

reactive power and current.

59

8.7.2-1 Graphic of the power area index for the two furnaces. 62

IV

ANNEXES LIST

Annex Title

A

INTERFACE PROCEDURES AND INPUT VARIABLES NEEDED.

B

STRATEGIC TRIGGER ORDER FOR THE JOBS.

C

RELATIONSHIP BETWEEN PROCEDURES AND TABLES IN THE

DATABASE.

D

TYPICAL TABLE DESIGN IN THE DATABASE.

E

FIRST POWER LOCUS DIAGRAM APPROACH.

F

DIAGRAM OF THE STANDARD DEVIATION VERSUS TIME FOR

SPECIFIC HEAT IN EAF1.

G TOTAL OVERVIEW OF THE PHASES DURING THE PROCESS OF

MELTING DOWN IN THE EAF1.

H

TOTAL OVERVIEW OF THE PHASES DURING THE PROCESS OF

MELTING DOWN IN THE EAF2.

I

STATISTICAL TABLES OF THE ELECTRICAL DAILY REPORTS.

J

BSW TRANSFORMERS DATASHEET.

K

INTERNAL COMMUNICATIONS IN REFERENCE TO THE

ELECTRICAL PARAMETERS OF THE FURNACES.

V

L

THE OLD CIRCLE DIAGRAM MADE BY HAND.

M

THE NEW CIRCLE DIAGRAM APPLICATION.

VI

ABREVIATIONS

Phase angle.

AC Alternating Current.

approx. Approximately.

BAG BSW Ausbildungs-GmbH.

BDW Badische Drahtwerke GmbH.

BRH Badischer Rohstoffhandelsgesellschaft.

BSE Badische Stahl-Engineering GmbH.

BSN Badische Stahl-Nebenprodukte GmbH.

BST Badische Stahl Technologies Inc.

BSW Badische Stahlwerke GmbH.

°C Celsius degrees

DC Continuous Current.

EAF Electric Arc Furnace.

Eq. Equation.

frm From.

i.e. For example.

I Effective Current.

L Inductance.

LAN Local Area Network.

LF Ladle Furnace.

MaxP Maximum active power component.

MinP Minimum active power component.

MaxQ Maximum reactive power component.

MinQ Minimum reactive power component.

min. Minutes.

M1 Melting down first basket.

M2 Melting down second basket.

NDW Neckar Drahtwerke GmbH.

NOT OK Incorrect procedure operation.

VII

OK Correct procedure operation.

P Active Power.

PAI Power area index.

PCC Point of Common Coupling.

Proc Procedure

Q Reactive Power.

R Resistance.

Re Refining.

sp Systematic procedure.

Trafo. Transformer.

TRNSRV Trendy server.

U Phase to Phase Voltage.

UB Electrical Arc Voltage.

UL Induced Voltage of the Self Inductance.

Utr Secondary Transformer Voltage.

UV Ohmic Resistance Voltage.

X Reactance.

Y Admitance.

Z Impedance.

VIII

BIBLIOGRAPHICAL REFERENCES

Abbreviation Bibliography

[BSW97] Badische Stahlwerke Umwelterklärung 1997 BSW. Kehl 1997.

[BSWZ] BSW internen Zeichnungen und Aufnahmen (internal designs

and photographs).

[DÖB92] DÖBBEÖER, Arno, Siemens AG. Elektrodenregelung. VDEH-

Seminar from 20.05.1992 to 22.05.92 in Mönchengladbach,

“Elektrotechnik des Lichtbogenofens”.

[FSA93] WERNER Felger, SPIEGEL Hartmut, ARMBRUSTER Steffen,

HEIMKE Thomas and HOHENDAHL Kurt. Verteiltes

Automatisierungsystem im Elektrostahlwerk. Edition 113 from

Stahl und Eisen. Düsseldorf 1993.

[GMB98] G. Paul, M. Bock and BÜNEMANN Gerhard. Powerful EAF

Performance with Aluminium Current Conducting Electrode

Arms. Kehl, Germany 1998.

[HOR89] HORST, Weitzmann. BSW Badische Stahlwerke AG, Stahl

und Eisen. Düsseldorf, 1989.

[INT01] www.bsw-kehl.de

[INT02] www.steel.org/learning/howmade/eaf.htm

IX

[INT03] www.we.fh-osnabrueck.de/fbwe/vorlesung/edv1/node3.html

[INT04] www.calidad.org/s/histogr.pdf

[INT05] www.hyperdictionary.com/dictionary/

[INT06] www.itlp.edu.mx/publica/tutoriales/investoper2/tema44.htm

[POL92] POLKE, M., RWTH Aachen. Prozeßleittechnik. R. Oldenbourg

Verlag München Wien 1992.

[TIM01a] TIMM, Klaus. Equivalent circuit diagram of AC-furnaces.

VDEH-Seminar from 23.10.2001 to 26.10.2001 in

Luxembourg, “Electrotechnics of the Electric Arc Furnace”.

[TIM01b] TIMM, Klaus. Circle Diagram. VDEH-Seminar from 23.10.2001

to 26.10.2001 in Luxembourg, “Electrotechnics of the Electric

Arc Furnace”.

[TIM02] TIMM, Klaus. VDEH-Seminar from 19.03.1997 to 21.03.1997

in Düsseldorf, “Elektrotechnik des Lichtbogenofens”.

[WOL74] WOLF, Hellmuth. Nachrichtenübertragung.Springer-Verlag,

Berlin/Heidelberg 1974.

X

TASK

Theme

Monitoring of the energy consumption working points in the electric arc furnace

Background

In the company BSW GmbH, a performance analysis of the electric arc furnaces

during melting down process, must be accompanied by a circle diagram.

Making use of the programming tools, a helpful system is created to assist the

electrical furnace studies in the steel plant.

Future applications are oriented to the system to make a part of the set tools for

worldwide consulting.

XI

INTRODUCTION

The main target of steel making is to improve the process efficiency daily, by

obtaining the lowest operation costs in the melting steel grades, in the shortest

possible time.

Through the experience and based on different studies of the process, the engineers

of the steel plant have decided to orient their biggest efforts to the power

consumption reduction of the furnace. From this topic, it is possible to get more

advantages with the improvements.

The automation department in association with the electric department of the steel

plant, following the purpose to contribute with more tools to the engineering area,

have made an investigation of the resources in the furnace. They found the absence

of a visualization system of the electrodes operating points during the melting

process, is a weak point for further optimization.

This project has the target to get advantage of the electrical data information that is

collected in the general database. Up to now this information is available for

statistical reports. The system has two different visualization approaches:

- the first one, showing a circle diagram of certain heat of the furnace, describing

the tendency of the working points during the states of the process.

- the second one, to show the electrical behaviour of the furnace when changes in

the transformer features are made to improve the power applied and the

operating points.

The methodology used during the process of construction of the system is described

by the following steps:

- Steel process description.

- Analysis of the electric power supply.

- Theoretical approach to the power locus diagram.

XII

- Rapid prototype based on Microsoft Excel.

- Implementation of the system.

- Examples of analysis based on the two electric arc furnaces from BSW.

XIII

Juan Carlos Forero Pérez Pontificia Universidad Javeriana, Colombia / BSW, Germany Page 1


1 BADISCHE STAHLWERKE GMBH (BSW)

The steel plant BSW is the only steel manufacturer in the state of Baden-

Württenberg, Germany. It was established in 1968 in the city of Kehl and it is situated

at the Rhine riverside.

Figure 1-1: Overview about BSW.

BSW is one of the most productive electric steel plants in the world, which produces

reinforcing steel and hot-rolled rods for Europe.



Based on the row material, there are two ways to produce steel:

- Integrated process: steel production that uses iron mineral as raw material. In

this case, the mineral must be reduced by means of high furnace or direct

reduction.

- Semi-integrated process: steel production that uses scrap as raw material.

BSW consists of three different zones.

Figure 1-2: Production environment of the steel plant [FSA93].

Figure 1-2 shows the process flow for both production lines of the company. The

zone 1 is the scrap area, the zone 2 or melting area is composed for the electric arc

furnaces, ladle furnaces and continuous casting installations and the zone 3 is the

rolling mill area.

The company has about 750 employees who develop the activities in a productive

way and emphasise upon the awareness for the environmental protection and safety

work [INT01].

1.1 Partner Companies

Since 1983, BSW has developed a group of companies for itself. This group is busy

in different steelmaking fields.



In detail, the partners of this group are the following companies:

- Badische Stahl-Engineering GmbH (BSE), Kehl

- Badische Stahl Technologies Inc. (BST), Charlotte, North Carolina / USA

- Badische Stahl-Nebenprodukte GmbH (BSN), Kehl

- Badischer Rohstoffhandelsgesellschaft (BRH), Kehl

- BSW Ausbildungs-GmbH (BAG), Kehl

- Badische Drahtwerke GmbH (BDW), Kehl

- Neckar Drahtwerke GmbH (NDW), Eberbach / Neckar

- Besta Eisen und Stahlhandels GmbH, Lübbecke

The wire processing plants BDW, NDW and BESTA make reinforcing steels and

armouring wires with the final product from BSW. The technology subsidiaries like

BSE and BST offer worldwide consulting in order to improve the production methods.

In BAG the staff is trained and they become familiar with the newest techniques. The

BRH is responsible for the scrap purchase [HOR89].



2 THE STEEL PROCESS

2.1 General description of the steel process in BSW

Figure 2.1-1: Steel production process [BSWZ].

The installations, that are approx. 133.000 m2, have two AC electric arc furnaces

(EAF) of ultra high power (UHP) for scrap melting with the dipping of the electrodes

into the furnace. The liquid steel, is tapped into the ladle furnaces (LF), where alloys

are added to modify the chemical composition until obtaining the wished one. The

ladle with steel is transported to the continuous casting (CC) and it is vacated in a

distributor which contains five openings in the lower part; through them, the liquid

steel flows towards a mold where square blocks are formed. The blocks are cut by



using burners and the steel billets are produced. They are the intermediate product of

the melting plant. Following, they continue in the second important area called rolling

mill. Two kinds of products are manufactured here: rolled rods and normal rods

[BSW97] (see figure 2.1-1).

2.2 The principle of melting down in the EAF

Figure 2.2-1: Electric arc furnace [BSWZ].

An UHP electric arc furnace makes the process of the scrap melting in BSW.

Figure 2.2-1 shows the main parts of an EAF :

- Panel cooled by water

- Cover

- Work door

- Lance manipulator

- Tapping hole

- Exhaust hole



- Electrodes

The walls of the furnace have an internal coating (refractory) to bear up against the

high temperature. In addition, the panels are cooled by water.

The cover of the furnace can be turned; it will be opened during every heat for

charging the two baskets of scrap.

Through the work door, oxygen and carbon are injected into the furnace with a lance

manipulator. During melting down, these elements have the task of mechanical

handling based on their exothermic properties. In the last stage of the process

(refining), carbon and oxygen serve for chemical redox-reactions.

When the melting process had finished, the steel flows through the tapping hole into

the ladle. The tapping hole is located in the bottom of the furnace.

The elements for the electric energy transfer into the furnace are the electrodes. Due

to the three-phase power consumption, there are three graphite electrodes which are

controlled to stay away from the scrap and to keep a constant arc length during the

process.

2.2.1 Melting process stages

Figure 2.2.1-1 illustrates the single steps of the melting process.

Figure 2.2.1-1: Melting stages.



The steps are:

- Load first basket

- Melting down first basket (M1)

- Load second basket

- Melting down second basket (M2)

- Refining (Re)

Figure 2.2.1-2: Scrap loading [BSWZ].

Figure 2.2.1-2 shows the load of the scrap in the furnace. Baskets of approx. 42 tons

of capacity are loaded two times during the process (for M1 and M2).

Two kinds of thermal energy transfer are followed to melt the scrap: radiation and

convection.

During M1, the high temperatures allow the electrodes to melt the scrap by radiation.

The arc has the geometric form of a cylinder [POL92]. In this way, the scrap is melted



from the center of the furnace towards its walls. Also, the volume of the charge in the

furnace is reduced. Normally, the M1 phase is considered until a reduction of 1/3 of

the original volume of scrap is obtained or when the energy consumption is near to

11.000 kWh and bath temperature of around 900 °C.

In the second part of the process, the second load is added to the first one and

getting advantage of the liquid steel from the first load, the scrap is melted by

convection in addition of the electrodes radiation. Normally, the M2 phase is

considered until the energy consumption of the furnace is near to 22.000 kWh.

In the final stage, a redox-reaction process is made to remove of phosphorus,

sulphur, aluminium, silicon, manganese and carbon from the steel [INT02]. The key

of this process stage is the temperature. After achieving an energy consumption of

approx. 30.000 kWh, and bath temperature of around 1620 °C, the tapping hole

opens and the liquid steel taps to the ladle located under the furnace.

For further operations and control based on computers, the process also can be

described in a formal way based on a table distribution as is shown in the

figure 2.2.1-3.

Step Transformer tap Energy consumption Current

1 9 500 kWh 55 kA

2 12 1500 kWh 56 kA

3 12 7500 kWh 52 kA

4 12 9000 kWh 56 kA

: :

Figure 2.2.1-3: Formal description of the process based on a table.

This table is the organizational grid for statistical evaluation of the actual data in the

monitoring system (see also annex K).



The average time that takes melting down for one heat is approx. 42 min. The

production runs continuously during the year, except repairing shut-down times.

2.3 Energy providing

BSW uses the public network as power supply to the furnaces and necessary

equipment for steel production.

Figure 2.3-1: Electric scheme distribution [BSWZ].

The electrical energy comes from the main network of 220 kV with a capacity of 6

GVA. In the point of common coupling (PCC), exists two identical transformers

which reduce the voltage of 220 kV to 110 kV, 100 MVA. The energy is

transported to the free air station, a distance of aprox. 20 km using copper

conductors. This station has four transformers:

- Two transformers of 110 kV / 20 kV, 80 MVA , that take the energy to an

exclusive common line for the furnaces supply (two EAF and two LF)

- A transformer of 110 kV / 20 kV, 40 MVA and



- A transformer of 110 kV / 20 kV, 45 MVA that leads the energy until a line in

order to supply other installations and equipments such as continuous casting,

gas systems, etc.

The 20 kV line, 670 MVA is the power supply of four different transformers:

- A transformer of 20 kV / 752 V, 74 MVA, 12 taps for the EAF1

- A transformer of 20 kV / 952 V, 75 MVA, 18 taps for the EAF2

- A transformer of 20 kV / 492 V, 36 MVA, that supplies the LF1

- A transformer of 20 kV / 300 V, 12 MVA, that supplies the LF2

2.4 Furnace energy input

The power supply of the furnace is delivered directly from the electrodes and its

environment. Figure 2.4-1 shows the two possibilities that control the furnace energy

input.

Two kinds of energy inputs are assigned at the same time:

- Change in the voltage: the voltage in the secondary side of the transformer

can be switched depending on the number of taps. This change will alter the

active power applied to the furnace.

- Change in the current: the movement of the electrodes over the scrap

produces an alteration of the arc length and therefore in the system

impedance. When the electrodes are low, the arc will be shorter and also the

current bigger. The conditions will be opposite if they are lifted.

These two methods allow the adjustment of the power. This control is generated

automatically after calculations that are made in relation to the parameters of the

electrodes control system previously established. It can be accomplished also



manually by the operator based on the target operations registered in a table as is

shown in the figure 2.2.1-3.

Figure 2.4-1: Control of the furnace energy input.



2.5 Present situation of energy reporting

The company BSW has a distributed computer system based on a local area network

(LAN), where the daily production is published in detail. All data is collected by the

systems or directly written by the staff on every shift.

Every day in the morning, a program runs in order to make the corresponding

statistical calculations of the last day of production. This program shows the results in

tables that can be consulted by the staff.

Currently, the work tools for the steel plant engineers are these Excel-based tables. It

means, all the calculations must be done in order to study the electric behaviour of

the furnace for a sample of several heats. To adjust sporadically the working points

of the electrodes, changes in the parameters of the transformer or in the regulation

control system are made and the engineers also build up manually graphics that help

them to observe the new furnace behaviour. The most important hand-made graphic

is the power locus diagram.



3 THE STEEL PROCESS AS CONSUMER IN A CONSUMER-GENERATOR

CIRCUIT

The following theory is oriented to the AC electric arc furnaces which BSW has. This

distinction is made because there are also companies that work with DC furnaces.

3.1 Equivalent circuit for AC furnaces

3.1.1 Single phase equivalent circuit

The electrical behaviour of AC furnaces depends directly on the transformer

voltages, the geometric distribution of the high current conductors and the associate

reactance.

The output voltage of the transformer (Utr) is divided in the electrical arc voltage (UB),

the voltage (UV) on the ohmic resistance (RV) and the voltage (UL) induced to the self

inductance due to the variable magnetic fields (see figure 3.1.1-1b). According to

Kirchhoff´s voltage law, the relation between the currents and voltages can be

described by the following differential equation:

Utr = UV + UL + UB = i RV + dt

diL + UB [Eq. 3.1.1-1]

Figure 3.1.1-1: Single phase diagram of the furnace. Circuit layout (a), equivalent

circuit (b) and simplified linearized equivalent circuit (c).



Specially for high power circuits, the voltage and current signals contain no

sinusoidal components in addition to the fundamental one that makes the time

domain analysis more difficult. Thus, the analysis is developed within those

restrictions.

For clarification purposes, all the analysis will be done based on the equivalent circuit

diagram by replacing the nonlinear characteristic of the arc by a linear variable

resistance RB (see figure 3.1.1-1c). By this way the electrical variables can be

calculated by means of complex calculation and represented as complex phasors.

Time domain Complex domain

UV = i RV UV = I RV

UL = dt

diL UX = I jW L = I jX

UB UB = I RB

According to the voltage complex equation, the current I can be calculated:

Utr = UV + UB + UX [Eq. 3.1.1-2]

Utr = I (RV + RB + jX) = I Z

The magnitude and phase of the impedance are:

IZI = 22BV X )R (R ++ , = tang-1

)R (RX

BV + [Eq. 3.1.1-3]

I I I = Z

trU =

2X 2)BR V(R

trU

++ [Eq. 3.1.1-4]



Figure 3.1.1-2 illustrates the respective vector diagram for all voltages and currents.

Figure 3.1.1-2: Phasor diagram of voltages and currents.

3.1.2 Three phase equivalent circuit

The elements that the EAF conform, are connected in start configuration. The high

tension cables followed by the electrodes close the loop in a neutral point 0 with the

arc. Thus, a circuital relationship is established and consists of a three phase

connection with inductance, loss resistance and arc voltage (see figure 3.1.2-1a).

Figure 3.1.2-1: Equivalent circuit (a) and simplified linearized equivalent circuit (b) of

the three phase arc furnace.

The current comes in through one phase and goes out through the other phases. In

that way,

i1 + i2 + i3 = 0 [Eq. 3.1.2-1]



Changing the electric arc length in one phase, generates current changes in all

phases due to the mutual coupling.

The effective inductances of the phases (see figure 3.1.2-1a) are the mutual

inductances between every two current loops.

L1 = M12,13 ; L2 = M23,21 ; L3 = M31,32 [Eq. 3.1.2-2]

The linearized diagram (see figure 3.1.2-1b) can be analyzed in the same way as in

the single phase (see figure 3.1.1-1). From this analysis,

Z1 = RV1 + RB1 + jX1 ,

Z2 = RV2 + RB2 + jX2 , [Eq. 3.1.2-3]

Z3 = RV3 + RB3 + jX3.

The following equations result for the phase to phase voltages:

U12 = I1Z1 – I2Z2 ,

U23 = I2Z2 – I3Z3 , [Eq. 3.1.2-4]

U31 = I3Z3 – I1Z1 .

The phase voltages are defined as:

U10 = I1Z1 ,

U20 = I2Z2 , [Eq. 3.1.2-5]

U30 = I3Z3 .

3.1.3 Balanced furnace operation

The furnace is in a balanced state when most of the electric variables are within

certain symmetry. The target of the melter is to achieved this state during the whole



process. When the furnace works in this operation mode, the distribution of the

power inside is better and the melting time is smaller.

For a first approach we assume a balanced system operation for the furnace. This

can be achieved with the ergodic check of the data in the interest intervals [WOL74]

[INT06].

The balanced state entails three phases similar operation. Thus, it is assumed that

the reactances, loss resistances, arc lengths and impedances are of the same

magnitude (see [Eq. 3.1.1-3]):

X1 = X2 = X3 = X ,

RV1 = RV2 = RV3 = RV , [Eq. 3.1.3-1]

RB1 = RB2 = RB3 = RB ,

Z1 = Z2 = Z3 = Z .

In addition, the phase voltages are identical and smaller than the phase to phase

voltages U by the factor 3 :

U10 = U20 = U30 = Utr = 3

U [Eq. 3.1.3-2]

In the case of balanced state, in all the phases the currents are:

I = Z3

U =

22BV X )R (R3

U

++ [Eq. 3.1.3-3]

The total apparent power consists of the real and reactive powers, like:

S = 3 U I

Q = 3 U I sin = 3 I2 X [Eq. 3.1.3-4]



P = 3 U I cos = PV + PB

The relation between the power types is shown in the figure 3.1.3-1:

S2 = P2 + Q2 [Eq. 3.1.3-5]

Figure 3.1.3-1: Relation between P, Q and S.

The power factor of the electric arc furnace will be then:

cos = SP

= IU3

P [Eq. 3.1.3-6]

3.1.4 Unbalanced furnace operation

The unbalanced electrical operation of the electric arc furnaces is more difficult to

analyze than the balanced one.

The electrical variables are strongly influenced by melting down process. Non-

stationary rectangular arc voltages occur during the start of the melting. The no-linear

behaviour is caused by rapid arc movements on the cold scrap [TIM02] (see

figure 3.1.4-1).



Figure 3.1.4-1: Time records of arc voltage, current and arc characteristics:

a) instantly after start melting, b) 7 minutes after start melting and c) 27 minutes after

start melting [TIM02].

There are two variables that fundamentally influence the unbalanced furnace state:

the current and the refractory element that protects the furnace against the high work

temperatures. It will be possible to balance just one of these at the same time.

If we have a look to the electric waves versus the time within the heat, we find that at

the beginning, the forms are more rectangular and through the time the waves

become to a sinusoidal form [TIM02] (see figure 3.1.4-1).



3.2 Circle diagram for AC furnaces

The relation between the electrical properties of the arc furnace and the arc

resistance can be described by the circle diagram.

Assuming the concept of balanced operation, the figure 3.1.1-1b illustrates the

equivalent circuit diagram of one phase. Based on the equation 3.1.1-3, the locus

diagram of the complex phasors as a function of the parameter RB, will be a parallel

line to the real axis (see figure 3.2-1a). In a short circuit (RB = 0) Z is minimum and

becomes maximum when RB tends to . The admittance locus diagram results from

the inversion of the Z locus diagram; it is the semicircle shown in the

figure 3.2-1b.

Figure 3.2-1: Curves of impedance Z (a) and admittance Y (b).

According to the ohmic law,

I = Z

Utr = Utr . Y [Eq. 3.2-1]

The current locus diagram is identical to the admittance locus diagram (see

figure 3.2-2a). For graphic reasons it has been turned 90° from the Y locus diagram.

According to the circle diagram, the value of the current I and its phase angle ,

change in relation to the phase voltage when the arc resistance varies between

RB = 0 y RB = . In the ideal short circuit (RB + RV = 0), there is a pure reactive



current ( = 90°) with a maximum current intensity I = Utr / Z limited by the reactance.

The short circuit current during the dipping of the electrodes (RB = 0) is slightly

smaller than the ideal short circuit current. When the arc length increases, i.e.

growing arc resistance, the angle decreases. At the apex of the circle, the active

resistance and the reactance arc, are equal ( = 45°). When RB tends to , the

current is zero.

Figure 3.2-2: Locus curve for the current (a), components of the current (b) and locus

curve of the power (c).



The current can be divided in the active component (I cos ) and the reactive

component (I sin ) (see figure 3.2-2b). Multiplying these components by the phase

voltage, the y-axis of the circle diagram takes the form of the active power P, the

x-axis the form of the reactive power Q and the distance from the origin describes the

apparent power S (see figure 3.2-2c). Multiplying by the factor 3 it gives the

progression of the power values of the overall three phase system.

The point of maximum real power input of the electric arc is at the phase angle

= 45° (cos = 0.707). In this point the effective resistance and reactance, and the

active power and reactive power are equal. The short circuit line of the figure 3.2-2c,

splits the active power up into the arc power PB and loss power PV. The points where

the arc power is bigger than the loss power will have a power factor of

cos > 0.707. In the ideal short circuit, the maximum reactive power corresponds to

the circle diameter that is shown in the figure 3.2-2c.

Qmax = 3 X

U tr2

= X

U2

, [Eq. 3.2-2]

Pmax = X2

U2

[Eq. 3.2-3]

According to these equations the maximum furnace power is determined by the

furnace voltage U and the reactance X.

The figure 3.2-3 shows the parameters of the power locus diagram. This figure gives

an overview of the graphic that is used in the visualization. Three different limit

curves can be seen in this illustration:

- In red color, the maximum apparent power of the furnace transformer.

- In blue color, the maximum furnace power.

- In green color, the stability line (cos > 0,87) [TIM01a].



Figure 3.2-3: Parameters of the power locus diagram.



4 HARDWARE AND SOFTWARE OF THE SYSTEM

Initially, the system was developed in a test computer where all the pertinent

implementations and checks took place. After a test operation of the system was

made, the automation department approved to dispose a new computer for its

installation. It had to fulfil certain characteristics for the correct development of the

system:

- Hardware: Pentium IV ® processor.

512 MB RAM.

Hard disc unit with 20 GB.

3com 10/100 Mbit/s Ethernet interface card.

17” monitor.

Keyboard.

Mouse.

- Software: Windows 200 server.

Microsoft SQL Server 2000.

Borland Delphi version 7.0.



5 BLOCK DIAGRAM OF THE MONITORING PROGRAM FOR ENERGY

CONSUMPTION

5.1 General description

The project developed is oriented toward build up a visualization system based on

the electrical variables that are sampled and stored in a database of the central

server (TRNSRV).

The system helps the melter operator and the engineers of the steel plant to analyse

the working points of the electrodes during the melting down process. To make it

possible, circle diagrams and additional informative graphics have been implemented

for several heats of the furnace. Also the system can work as a tool to analyse the

behaviour of the furnace when changes in the parameters are made.

In general, the task of the system is to improve the electrical conditions by means of

adjustments of the furnace operating points.

As software tools, they have been used two programming languages as:

- Microsoft SQL Server

- Borland Delphi

Microsoft SQL is a relational database. It makes easier the work, processing the

information through databases. A big part of the project is developed based on this

application.

By the other hand, for the user interface, the program Borland Delphi has been

chosen as development basic tool. Afterwards, there are described some advantages

to use this language such as:



- Handling facility

- Versatility and compatibility with other systems

- Extensive range of objects, components, global routines, types and variables

- Specific libraries that contains fonts for the graphics

So, all the programming oriented aspects are solved by the object oriented approach,

and engineers can concentrate efforts to the solution of the application task.

5.2 Block diagram

Figure 5.2-1: Block diagram of the system.

Basically, the system is divided in four blocks. Figure 5.2-1 describes every one of

these parts. First, the data acquisition. Next, the storage and processing and finally,

the data that is displayed by the interface. By this way the user can interact with the

system.

5.2.1 Data acquisition

This module includes the acquisition of basic variables that are needed for the

system. These variables are the common electric variables who normally exist in a

steel company. This is mentioned because the project has been developed with a

global vision, it means, to make it useful in other steel plants.

Data acquisition

Calculations

Storage: Database

Interface



This block has the task to create a new data source for the system in a local area. In

this way, the data access is made from local tables instead to contact the server

every time.

5.2.2 Storage: database

In this module, the storage of the large amount of data is made. In this part, the

system works with a database. By this way, is possible to access and organize the

information faster and efficiently.

This block is one of the most important parts of the system. The movement of the

data is done through it. All the modules have direct relation with this stage and they

establish many relations with the information stored here.

5.2.3 Calculations

In the calculations module, the operations of the system are realized. The calculation

procedure is developed step by step. At the beginning, there is a big volume of

data; this information is characterized and compressed until the final data is obtained.

Later, this information is displayed by the interface program.

In order to contribute with the engineering area to analyze the tendency and

operation of the furnace, the calculation procedure is based on the statistic

background that will be discussed more in detail afterwards. It is very important that

the project contributes with additional information. Thus, every working point won´t be

displayed in the system. Instead of it, a sampling mechanism is followed with an

analysis made by intervals.

As it was mentioned in previous paragraphs, all the modules are related with the

database in a certain way. Due to the considerable amount of operations that the



system will perform, the calculation block becomes the most important one. Then, at

this point is necessary to establish an organization for the tables that are created.

Figure 5.2.3-1: Distribution of the information in tables.

The figure 5.2.3-1 shows an overview of the tables distribution. The flow of the

information begins from the external level of data and finalizes with the specific data

for the visualization. The tables for the general data processing and the tables for the

human interface, are differentiated by the blue and red colors.

5.2.4 Interface

This module performs to display the database information into the mind of the steel

plant engineers. Until this point the information in the tables are just numerical

values. By this way, all the data is transformed in a graphical tool.

By means of the interface, is possible to have an approach with the information of the

tables. Also, this graphical option offers the possibility to make studies of the

electrical behaviour more in detail. The information that was shown by the interface

will depend directly of the study option that the engineers are carrying out.



5.3 Theoretical background

Figure 5.3-1: Flow diagram and distribution of the system.

The figure 5.3-1 illustrates the different stages of the system. Based on this diagram,

the phases of the project can be clarified. Each one of these components is

described bellow.

5.3.1 Data extraction phase

The management of the data is made by procedures and scheduled jobs. Every

procedure has a specific job assigned. It is necessary to create for every task a

procedure in the system. In this way, the data extraction works also in the same way.

The system requires three information sources:

- Electrical variables



- Events

- Constant parameters

5.3.1.1 Electrical variables

These are the minimum necessary variables to create the graphics of the system.

Actually, the electrical variables of the furnace are sampled every second by a

measurement system. The information is stored in TRNSRV that is the central server

from the plant.

The basic variables chosen for the system are: voltage, current and active power per

phase.

5.3.1.2 Events

It is necessary for the system to have a description of the tap changes during the

process. There, exists another table in TRNSRV where all the furnace events are

registered. Tap change of the transformer makes a part of this set of events.

By this way, a detail description of the duration when the transformer is working in a

certain tap is obtained. Following, this information is related with the variables

described in the paragraph 5.3.1.1.

5.3.1.3 Constant parameters

For its operation, the system needs constant values given directly by the

programmer. They have been designed special tables to stored this data.



Based on the circle diagram background, is necessary to know the maximum

parameters of the transformer. This is the first set of constant data. These values are

used for the diagram construction in chapter 3, paragraph 3.2.

Because of the two production lines of the company and the global applicability of

the system, a table with the furnaces information has been created. This table makes

the system flexible to changes and allows its work outside in other steel plants.

5.3.2 Data processing phase

After all the necessary information is stored already in the database, the manipulation

process begins. As it was mentioned in previous paragraphs, this process has the

target to classify the data from the statistic point of view. The criteria of this phase are

based on the parameters described bellow.

5.3.2.1 Additional variables

With the initial information collected, actions to get other electric variables are made.

The resulting data and these electrical variables, conform the set of basic variables

for the system.

The additional variables are:

- Power factor

- Apparent power

- Reactive power



5.3.2.2 Heat number

The heat number is a unique number assigned during the year to every melting

process in the furnace (see chapter 2, paragraph 2.1). This characteristic is very

important because it allows to differentiate all the heats of the furnace.

Every day, the values of the heat numbers are assigned and stored in a data bank.

The system copies this information and creates a relation with all the data previously

described. By this way, is established the query key in the system, it means, the

access to the data will be done based on the heat number and its respective year.

5.3.2.3 Process state

The furnace analysis of the engineers depends on the process state. Normally, they

divide the process in three global overviews: M1, M2 and Re. The process is

differentiated, based on the power consumption variable. Although, the information is

related with this power definition (see chapter 2, paragraph 2.2.1).

5.3.2.4 Statistical concepts

Statistical concepts that are used:

Standard deviation: this point is oriented to analyze the information when the furnace

achieves a stable operation. The data is reduced, based on the theory that standard

deviation entails [INT03]. Getting advantage of this calculation, the average value is

also stored to be used later.

Histogram: this tool helps to analyze the behaviour of the electrical variables in the

furnace. This theory is used to study the distribution of the set of electrical

measurements in the furnace [INT04].



5.3.3 Database

The database concept represents an advance for the storage and manipulation of the

information. Additionally of its easy use, this tool offers the possibility of short queries

times, stability, work security, easy interaction and connection with other programs.

The database makes the continuous management of data in the system. Due to its

importance, the actions and specially the procedures, are meticulously controlled to

assure their correct operation. By this way, many problems of the visualization

program link can be avoided.

5.3.4 User interface

The set of tools used here is oriented directly to create a friendly user interface. Each

application has its own display window. They are shown using menus and quick

access buttons. In addition, sheets have been created to inform the user about the

actual query parameters. Finally, print options make possible to follow the trend of

the furnace through the time.



6 IMPLEMENTATION

Basically, during the implementation of the system three steps were followed:

- Storage and data manipulation in the database

- Rapid prototyping based on the Microsoft Excel program

- User interface development

6.1 Storage and database manipulation

Figure 6.1-1: Global overview of the database distribution.



The figure 6.1-1 describes the data flow, procedures and the general order of the

tables in the database of the system. This structure is difficult to divide due to the

relationship between all the information. However, the following three levels have

been established:

- Level 1, where the data is copied from the external server TRNSRV

- Level 2, where the data is processed and manipulated

- Level 3, where the data is ready to be displayed by the interface

Three types of elements have been used with the database work:

- Procedures

- Jobs

- Tables

All of them are intimately related one to the other and they make possible the

success in the database work.

6.1.1 Procedures

The procedures are programs developed to work with the information stored in the

database. They are programmed in SQL (Structured Query Language) that is a

standard language for creating, updating and, querying relational database

management systems [INT05].

There are two kinds of procedures:

- Manipulating procedures

- Consulting procedures



6.1.2 Manipulating procedures

These procedures are responsible for making the necessary tasks for the system.

Depending on the level where they belong to (see figure 6.1-1), the procedures have

certain targets. These procedures are fixed, it means, the programmer is the only

one who can manage them.

This kind of procedures are shown in the figure 6.1-1. For reference, their names

have been created with the letters “Proc” at the beginning. The symbol “#”

differentiates the furnace 1 of the furnace 2. All the procedures work in a loop to

cover the daily heats of the furnaces. Following, there is a short description of every

one of them:

- Proc_EO#Trend_Copy: copies the information directly from the external data

source (see chapter 5, paragraph 5.3.1.1).

- Proc_EO#Trend_Data: using the basic data set of the last procedure, it

calculates the annexed variables described in the chapter 5,

paragraph 5.3.2.1.

- Proc_EO#Events: captures the different events during the melting down

process (see chapter 5, paragraph 5.3.1.2).

- Proc_EO#Trend_Aux: copies the information from the new local data source

to an auxiliary one.

- Proc_EO#Events_Tap: selects specifically the event called “tap” from the

events table.

- Proc_EO#Events_Update_Tap: relates the information of the auxiliary source

table with the taps and state of the process. This procedure makes easier and

quicker the access, due to the grouping and characterizing of the information.



- Proc_EO#Trend_SD: calculates the standard deviation based on the process

state.

- Proc_ChargeTaps: selects the different taps of the transformer without

repetition. This procedure interacts directly with the interface.

- Proc_EO#Trend_Data_SD: compresses and reduces the data based on the

standard deviation values calculated. By facility, in this point the information is

divided in four types: three for every phase and one for the total overview.

- Proc_EO#Trend_Data_Tend: calculates for every minute an average value

and standard deviation of this data set. Due to the amount of information, this

procedure is created to reduce the data and allow the user to see more

clearly the process developing. Later, this information is used by the interface.

- Proc_EOHistogram: creates the background data of the active power, reactive

power and current histograms. This procedure bases its calculations on the

parameters stored in the table EOHistogram_Info. This data is also displayed

by the interface.

- Proc_EO#CoefAnalysis: takes the maximum and minimum values for the

active and reactive power and evaluates their difference. By this procedure, is

possible to see the separation between the extreme points for both powers. It

works based on the concept of the power area index that is explained later.

- Proc_EOPowerArea: based on the data calculated in the previous procedure,

it defines the final analysis coefficient that is displayed by the interface.

- Proc_EOTrend_DelData: deletes the information from all tables. This

procedure is created to limit the amount of memory of the computer. It is a

condition that will avoid the system runs slowly, making it robust.



6.1.2.1 Consulting procedures

These procedures are the responsible to retrieve the information stored in the

database. They are dynamic, it means, they are triggered every time when the

consultations are required by the interface. These procedures work based on the

parameters defined by the user at the moment of the query.

For reference, their names have been created with the letters “sp” at the beginning.

Also, due to the shared work with several heats and variables, at the end of the name

this characteristic is differentiated.

This kind of procedures are described by:

- spSelectRangeHeatData: retrieves the location of the electrical information in

the tables for a set of heat range.

- spSelectHeatData: selects the electric data for one heat.

- spSelectMaxTrafoParam: retrieves the information of the maximum

parameters of the transformer (see chapter 5, paragraph 5.3.1.1). This

procedure is used for the starting of the system.

- spSelectTrafoParam: selects the maximum parameters of the transformer

based on the tap value.

- spSelectTap: retrieves the taps options for a heat during the melting down

process.

- spSelectAvailableHeats: selects the set of heats available in the tables.



- spHistogramDataEnergie: retrieves the minimum and maximum energy

consumption values registered for a heat.

- spHistogramData: selects the necessary data for the histogram graphics.

- spActualEnergieValues: retrieves the actual range values of energy

consumption registered.

- spEnergie_Int: updates the range values of energy consumption.

- spInfo_StateTapa: selects the work taps for the heat during the melting down

process.

- spInfo_StateTapb: retrieves a data set with the energy consumption values.

- spPowerArea: selects the power area coefficient for a range of heats.

The table in the annex A shows the relationship between every procedure previously

described and the main input variables. The first column corresponds to the

procedure and the other columns are the work variables; following, there is a short

description of them:

- StartHeatId: minimum heat number of the range

- EndHeatId: maximum heat number of the range

- Year: year of the heat range

- ActualHeat: specific heat number for analysis

- IdTrafo: transformer

- State: process state (M1, M2 or Re)

- Phase: process phase (R, S, T or Total)

- Tap: transformer tap



6.1.2.2 Jobs

The jobs are processes of automatic work developed in the system. Everyone has

the task to run an assigned procedure.

The jobs for the system have been created just for the manipulating procedures (see

paragraph 6.1.1.1). All of these procedures have their own job assigned. For

reference, the jobs names have been created with the letters “JOB” at the beginning

followed by the same name of the triggered procedure.

Due to the data flow, a strategic trigger order is defined for the jobs as you can see in

annex B. In the first column the job name is specified, in the second column the

procedure associated, in the third column the actual trigger time and in the fourth

column the repetition. The work order of the database has a direct relation with the

trigger time shown in the third column of the annex B. In addition, with color blue and

yellow the repetition type cab be differentiated.

By this way, the system is divided in several steps. This order must be kept due to

the relationship of the information. The trigger time can be shifted if the procedures

follow the same chronology.

6.1.3 Tables

The tables are the final step of the data flow in the database. They have the target to

store the information. The procedures and the tables keep a close relation to develop

the different calculations and queries of the system. For reference, most of the tables

names have been created in relation to the procedures which they are working with.

The tables can be differentiated depending on their task (see figure 5.2.3-1). Actually,

there are three kinds:



- Tables for calculations

- Tables for unfolding

- Tables for parametrization

6.1.3.1 For calculations

These kinds of tables are used directly to store the results obtained by the

procedures. Most of the tables of the system are for calculations. In the figure 6.1-1,

the tables with color blue belong to this type.

6.1.3.2 For unfolding

These are the necessary tables for the interface. The final information of the

procedures is stored in these tables. In the figure 6.1-1, the tables with color red

belong to this type. It is possible to observe that not all of them are located at the end

of a calculation line; it is due to the different options of the interface.

In the annex C, the relationship between the procedures and the tables are shown. In

the first column the procedure name is specified, in the second column the source

tables used in the calculations and the third column the target tables that store the

results. The table called Statistiklog_Data that appears in the last column, is for

checking the procedures operation (see chapter 5, paragraph 5.3.3).

6.1.3.3 For parametrization

These kinds of tables are used to store constant data necessary for the system. The

mentioned procedures and the interface work with these tables. Following, there is a

short description of them:

- EOHistogram_Info: stores the basic data for histograms calculations.



- MessProject: stores the different furnaces available in the system.

- TrafoParameters: stores the datasheet values of the transformers.

6.1.4 Ordering and data flow

The data flow is described in the figure 6.1-1. The order followed by the information

goes from level 1 through level 3.

As it was explained, the procedures and the tables form a team work. The access to

the tables has been defined particularly. Due to the unique parameters of heat

number and year (see chapter 5, paragraph 5.3.2.2), the tables are accessed

through them. This definition makes the system organized. In addition, a column

called “ID” is used as a key to manage the tables.

In the annex D, a typical design of the table is shown. In the left-top side, there is a

definition of every column followed by the data type and the length. In the first row we

find the ID, in the second the heat number (chargennummer) and in the third one the

year (jahresstempel).

6.2 Rapid prototyping based on the Microsoft Excel program

A rapid prototyping program was developed for the interface planning. This one was

an intermediate step between the data and the interface development. This program

was created using Microsoft Excel. With macros and visual basic programming, the

data were copied and illustrative diagrams were created.

Based on these graphics, it was possible to establish the architecture and the

interface options. In addition, the program helped to the variables definition and data

sampling reduction.



In the annexes E and F, you can see the first graphic approach of the system. In the

annex E, an example of the power locus diagram for one heat is illustrated. There, is

possible to see the distribution of the operation points particularly for the phase R.

The Y axis corresponds to the active power and the X axis to the reactive power. By

the other hand, in the annex F, the standard deviation for these points is shown. In

this graphic we can see how far every point from the average value in relation to the

time is.

6.3 User interface program

Figure 6.3-1: Global structure of the interface program.



Figure 6.3-1 describes the distribution of the forms and procedures for the interface

program. Due to the characteristic of object oriented programming from Delphi, every

form has its own procedures associated. Automatically, when the user accedes to the

templates, the procedures are available.

The forms have been created with the letters “frm” at the beginning. Following, there

is a description for every one of them:

- frmMain: it is the main template of the interface. Here, you see the circle

diagram and in this way is possible to invoke the other applications of the

program. This template has menus and some options so the user can change

the parameters of the analysis. In addition, informative displays have been

created to report the actual state of the query.

- frmSelMessProj: this template was created to choose the furnace in order to

be analyzed. This form has the options of the available furnaces in the system.

- frmSelection: the heat range and the year are selected in this template. The

furnace and these two variables, conform the main input parameters for the

system. If the user omit this declaration the system displays error messages.

- frmHistogram: this template shows the histograms.

- frmEnergie_Int: template that is used to change the parameters for the

histograms construction. Here, is possible to modify the range of energy

consumption which the graphics work with. By default, five options of values

have been defined.

- frmInfo_StateTap: this template shows the graphics for the transformer tap

and energy consumption versus time.



- frmPowerArea: this template is very important for the system. An index has

been created as alternative tool of analysis. It has been developed based on

the areas conformed by the operation points on the circle diagram. Afterwards,

this concept is extended and some analysis are developed using it. This

template shows the coefficient for the heat range selected.

6.4 Tests

The tests are the way through the project can be checked. Because of the block

system distribution (see figure 5.2-1), some tests were developed for every stage of

the implementation. Most of them are oriented to the data phase due to its

importance for the system.

There are two kinds of conditions to analyze:

- Data processing

- Memory capacity

6.4.1 Data processing

This point is oriented to the operations realized on the data. It must be controlled due

to the existence of unanticipated conditions i.e. range, type or null values, which

would generate functional errors in the system.

The procedures have been created in such a way to avoid these disadvantages.

Through the code, they check the results for themselves and active advanced

conditions automatically. In this way, the main loops of the program are developed

base on valid values.

A table in the database has been designed to register the correct operation for every

procedure. This table is called Statistiklog_Data. With values of “OK” (correct



operation) and “NOT OK” (incorrect operation), is possible to follow the behaviour of

the system through the procedures. Although, the failed part of the program can be

immediately identified and the improvements can be done easily.

In addition to the previous control process, the software of Microsoft Transact SQL,

offers an extra management possibility for the jobs (see paragraph 6.1.2.2). Because

of the close relationship between the jobs and procedures, the control task is more

easily implemented.

6.4.2 Memory capacity

For the general data process, the memory state becomes an important variable. The

system has available two different memories spaces:

- The first one, that is defined to limit the memory size of the database

- The second one, that is used for the transactions developed by the

procedures

For this point, a delete technique has been created. By means of a procedure, every

table is checked and the old information is deleted (see paragraph 6.1.2). This

condition is defined directly in the procedure by the programmer. Due to the amount

of information, is necessary to keep running this procedure in a short time frame (see

annex C).

6.4.3 Interface

For the interface, two kinds of controls are made:

- Systematic procedures

- Data shown



6.4.3.1 Systematic procedures

The procedures used for the interface consulting have been tested separately (see

paragraph 6.1.2.1). Before to bring them into the interface, each procedure is

simulated and the output values can be compared.

6.4.3.2 Data shown

The interface is evaluated according to the normal operation ranges and the previous

circle diagrams developed by hand. The results found in the new system, in

reference to the old one, were similar. Also, it was possible to have the point of view

of the steel plant engineer in relation with the power locus of the working points.



7 MAN-MACHINE INTERFACE AND ITS FUNCTIONS

Figure 7-1: Tree of functions.

Figure 7-1 illustrates the available functions of the interface. The interface has four

classes of functions such as:

- Circle diagram

- Histograms

- Information states

- Power area index (PAI)

Depending on the user requirements, every form is executed from the main template.

The user has to define the following parameters for the query that are:

- Heat range (depending on the available data in the database)

- Furnace (EAF1 or EAF2)

- Phase (R, S, T or Total)

- State (M1, M2, Re or All)

- Tap (depending on the heat under analysis)

Main Template

Circle diagram

Histograms Information states

Power area index

Parameters



7.1 Circle diagram

The principal function of the program are the circle diagrams. The power locus

diagram is based on the phase, state and tap parameters. This function shows to the

user the furnace electrical behaviour in the scrap melting process. In this way, the

analysis can be done in detail. For reference, the points in this function are displayed

in different color depending on the state of the process:

- Yellow for M1

- Aqua for M2

- Green for Re

- Red for all

Figure 7.1-1: Example of the locus diagram picture.

7.2 Histograms

This function shows three histograms of the following variables of interest:

- Active power

- Reactive power

- Current



These parameters have been chosen because they are the critical variables that

have to be analyzed by the engineers after some improve changes of the process

are made in the electrical parameters. The histograms are built for certain ranges of

energy consumption. These values are defined previously by the user (see chapter 6,

paragraph 6.1.3.3). In the diagrams the maximum and minimum values are selected

depending on the power consumption setting. After that, the range is divided in

intervals according to the sampling value and the program counts the distribution of

points within each interval (see chapter 5, paragraph 5.2.3). This function has been

created to display every time the histogram for one heat only.

Figure 7.2-1: Example of the histogram picture.

7.3 Information states

This function takes advantage of the information collected in the database. It gives an

overview of the electrical system behaviour versus time. As a tool, it displays the

graphics of the transformer tap and the energy consumption. Five heats are shown

continuously by this function.



Figure 7.3-1: States report.

7.4 Power area index (PAI)

The PAI helps to analyse the electrical behaviour of the furnace. Although has

immersed the concept of the working points separation. Taking the difference

between the maximum and minimum values of both powers (�

P and �

Q), a product

is made and the final index is the inverse:

�

P = MaxP – MinP �

Q = MaxQ – MinQ [Eq. 6.3.2.4-1]

PAI = )Q*P(

1∆∆

The function to evaluate the PAI and its inverse for the heat range, is selected by

the user at the beginning. The figure 7.4-1 shows an example of the function PAI.



Figure 7.4-1: Example of the power area index graph.



8 ANALYSIS

The target of this chapter is to interpret the information shown by the different options

developed in the system and take advantage of the data and curves displayed in the

graphics in order to improve the process.

The first step for the development of the analysis is the construction of the power

locus diagram based on the electric data. Annexes L and M show the old diagram

made by hand and the new version developed.

Several kinds of approaches have been tried for the system like:

- Phases symmetry

- Arc stability

- Best energy applied

- Operation of the electrodes regulation system

- Scrap mixes

- Equipment

8.1 Phases symmetry



Figure 8.1-1: Symmetric and asymmetric phases behaviour.

The figure 8.1-1 shows a comparison between symmetric and asymmetric phases

behaviour. Two heats of the furnace 1 have been selected as example. Both sides of

the figure describe the circle diagram for every phase R, S and T. On the left side the

heat number 105900 (year 2004) is displayed during the M1 state. It has nearly

asymmetric behaviour on its phases. On the right side, the heat number 105920

(year 2004) is displayed. These graphics display an asymmetric pattern on its

phases.

As it was described in chapter 3, there are many variables that take part in the

behaviour of the EAF. Due to that, the asymmetric analysis can be done in two ways:

for short and long time. Short time relates to the errors caused by the driven furnace



of the melter and by changes in the working parameters of the furnace i.e. mixes in

the scrap. The long time analysis is related to repetition of problems during several

heats. They appear due to electrical distribution problems.

8.2 Stability of the arc

Figure 8.2-1: Stable and unstable arc in the furnace.

Figure 8.2-1 shows a comparison between the stable and the unstable arc in the

furnace. The same heats of the previous example have been selected to illustrate

this one. The graphics describe the circle diagram as an overlay over the three

phases. On the left side, a stable arc operation during M1 is displayed. On the right

side, the arc operation is unstable for this heat due to the points distribution.

A rectangle which contains the operation points has been plotted in both graphics.

Differences in the area, allow to differentiate a better energy input in the furnace.

Approximitly the points means a constant work condition. The area is related with a

PAI which the system can be approached (see chapter 7, paragraph 7.4). This index

doesn´t mean directly that the furnace achieved the optimal conditions of operation;

in addition, the location of the points has to be studied. Afterwards, this analysis is

discussed.



8.3 Best energy applied

The location of the points in the circle diagram during the process is a guideline for

the electrical analysis.

Figure 8.3-1: Movement of the points in the circle diagram.

Figure 8.3-1 shows the curves of the circle diagram (see chapter 3,

paragraph 3.2) and the movement of the operation point on it. In this part, is

interesting to analyze the location of the operating points. When they are closer to

the common region of the curves, the behaviour of the system is better and the

energy saving increases.



Figure 8.3-2: Working points on the states of the melting down process.

In the figure 8.3-2 the heat number 105953 (year 2004) has been selected to

illustrate the difference between the states of the melting down process. The

behaviour during M1 and M2 is more or less the same. The points are situated inside

similar regions. Their location is near to the maximum apparent power of the

transformer and over the power factor line of aprox. 0.788. The distribution area of

the points is due to the scrap melting (see chapter 2, paragraph 2.2.1). By the other

hand, the working points in the Re state are in a better location. They are near to the

maximum values specified by the transformer. This operation mode is reachable

because in this state, the scrap is already melted and is only used to achieve optimal

chemical conditions (see chapter 2, paragraph 2.2.1).

This analysis shows that the operation target has to achieve a region in Re for all the

states of the process. It is difficult to obtain because of the variability of the system

features.

8.4 Operation of the electrodes regulation system

The transformer and the electrodes regulation system cooperate to control the

electrical behaviour of the furnace. These two elements are the most important for

the power applied to the furnace. Especially for the electrodes, set points are



specified for the regulating system. Within some times, these values are changed by

the process engineers in order to achieve the optimal electrical values (see

chapter 2, paragraph 2.4).

For this analysis, two tools were implemented:

- PAI

- Measurements distribution

8.4.1 Approach using the PAI

`BSW´ automation department is also responsible for the general electrical

maintenance in the company. Based on the alarms and the weak points of the

equipment, the staff take care of the systems in order to keep the normal process

operation.

In reference to the electrodes, the circle diagram gives an overview of their operation.

A constant extreme separation between the working points over several heats

indicates that there is a problem on the system.

Based on the PAI (see chapter 7, paragraph 7.4) a relation between some variables

of the system tried to be developed. Looking for this target, the variables `Tap-to-

Tap´ and `Power on Times´ included in the daily statistic report, were selected for the

analysis.

In the annex G and H, two heats for every furnace have been chosen. They were

pictured as their better operation points distribution. The annex I shows the internal

tables report where is possible to see the differences between the production and the

time interval when power was applied to the system. For EAF1, heat number 105400

(year 2004) has a power on time of 32.9 min. and heat 105402 (year 2004) 34.7 min.

For EAF2, heat number 205684 (year 2004) has a power on time of 31.9 min. and

the 205696 (year 2004) 34.7 min. The tap-to-tap values show which heats are better



than the others. It is important to consider that an analysis has to be done at times

when the system doesn’t receive energy. It means equal power of times. This

analysis was not performed for all the heats, so it can not be considered as

universally valid. This possibility of study is open for future analysis based on the

system developed.

8.4.2 Approach using the measurements distribution

The histograms function of the interface (see chapter 7, paragraph 7.2) is used in this

point of analysis. With this method of visualization, is possible to see the continuous

development for important process variables through the process stages.

Figure 8.4.2-1: Example of measurements distribution for active power, reactive

power and current.

In the figure 8.4.2-1, the number 105900 (year 2004) has been selected again as

example for the analysis. In relation to the energy consumption (see figure 2.2.1-3

and also annex K), graphic includes three different diagrams: active power, reactive

power and current in relation with the repetition of the points for every interval. Based

on the graphics, is possible to observe these variables.



The control target of the regulation is to concentrate values around one point.

Therefore, curves should follow a line at the set point. As it was mentioned, due to

the different factors involved, it is difficult to achieve. Therefore, the actual target is to

get a histogram similar to that shown in the figure 8.4.2-1 for the range of 9000 –

15000 [kWh]. For this period the electrodes work in a good condition because of the

stable state achieved for the system. It is also possible to see, the uniform

distribution of the operation points reflected in the graphics. In addition, for the range

between 500 – 1500 [kWh] the distribution of the measurements are bigger due to

the beginning of the melting process.

8.5 Scrap mixes

The scrap is the most important raw material used for the steel production. The

partner company BRH (see chapter 1, paragraph 1.1) supplies the scrap to BSW.

In the scrap yard, the cranes load the baskets with different kinds of scrap (see

chapter 2, paragraph 2.2.1). This method follows a specific order. It is known that

some types of scrap have better electrical properties than others because of the

composition. These features help the system to achieve an optimal energy

distribution in the furnace. Therefore, it makes sense to analyze the result of certain

scrap mix based on the electric furnace behaviour shown by the new system. Also, it

can be possible to plan certain tests in order to check the influence of the mixture.

8.6 Equipment

Due to the continuous process of the steel production, the maintenance of the

equipment is an important task. If one element is broken, the process stops until the

spare part is brought. Normally the small pieces are the more affected and the

maintenance jobs don’t require long shut downs.



In April of 2004, the EAF2 transformer was damaged. Fortunately, an old transformer

was available and the change was made quickly. A new transformer was bought and

in December of 2004 this change will be made. The start up of the system will be

then an arduous task for the staff. In these cases, the experience plays an important

role and the systems will help the process engineers to know all operation conditions,

through the following tools like:

- Statistic production data

- Furnace monitoring system of the process

BSW has an object description for the time before and after the investment. By this

way, the new development becomes a tool to get an optimisation of the parameters

in a shorter period of time.

8.7 The two EAF from BSW

Until this point, the possible analysis options of the system have been discussed and

makes sense now, to apply this background and compare the two EAF from BSW.

The advantages and disadvantages of each installation are summarized and also a

description can be developed using two different approaches such as:

- From the work tools

- From the system

8.7.1 Approach from the work tools

The melter operator and the electrical engineer, have the task to keep certain

electrical conditions in the system during the process. These characteristics have

been previously defined. To get this target, there are two ways which can be

followed: the transformer parameters or electrodes regulation system control (see

chapter 2, paragraph 2.4).



The transformer for the EAF1 has twelve taps and one for the EAF2 eighteen (see

annex J). For each tap, is possible to adjust the current without exceeding the

maximum apparent power value allowed. Even though, the engineer has less

possibilities to modify the electrical behaviour for the EAF1 than for the EAF2. If

these possibilities are not enough, he has to concentrate his efforts to control the

parameters of the electrodes regulation system, which are similar for both

installations.

At this point, the monitoring system gives him a quicker and complete feedback of his

actions.

8.7.2 Approach from the system

Figure 8.7.2-1: Graphic of the power area index for the two furnaces.

A global overview based on the system is developed for both furnaces.

Figure 8.7.2-1 shows the PAI and PAI inverse for the production during 6 days at

both installations. It is important to emphasize that similar conditions of operations

were fixed for this analysis. Because of the transformers don´t work in the same taps

(normally for EAF1 in taps number 9 or 12 and for EAF2 in taps number 7 or 10 or 14

or 16), for the study were selected, the tap number 12 for the EAF1 and the tap



number 16 for the EAF2. This is because these are the taps on which both systems

work most of the production time.

Comparing the graphics is possible to see that the EAF1 has smaller PAIs than the

EAF2. It means a bigger separation between the working points. An average value of

PAI inverse for the set of heats was calculated for both furnaces; that gave for EAF1

a value of aprox. 80 and for EAF2 a value of aprox. 200. The area is studied with

this coefficient, but it is not enough to synthesize the distribution of the points in the

power locus diagram.



9 CONCLUSIONS

After concluding the system evaluation, the following conclusions must be

considered:

Regarding to the specific targets

In the first approach of the system, three specific targets were proposed in the first

draft of the project. The following points are developed in relation of them:

- The necessary procedures to the general data processing were developed in

the database. Every one of those has a specific job in the system. Through

them, the following tasks are managed:

ü Automatic copy of the information from the external server (TRNSRV)

ü Calculation and organization of the data

ü Size control of the database memory

ü Consulting of the information to the interface

- An interface based on Delphi oriented-object programming was developed

and it is the final step of the system. Through it, the user has the possibility of

interacting with the system. Using its different options, the electrical behaviour

of the furnaces can be analyzed in detail.

- There are many variables that take part in the steelmaking process and all of

them are related. As it was mentioned in the chapter 2, the melter operator

has two ways to change the power applied to the furnace to get the best

electrical behaviour. Due to the usual changes in the parameters, the new

tool doesn´t allow to relate directly the cause of an incorrect system operation

with the regulation system. What is possible to do with the tool, is to develop

an evaluation of the influence between the variables that take part in the



system. This result can be observed in the circle diagram and in the other

options of the interface.

Regarding to the consulting area

From the consulting point of view, the steel process is analyzed based on two

criteria:

- Time analysis: ratio between power on and power off times

- Energy consumption: energy applied for the melting down process

In relation to the first one, the industrial engineering department from BSE developed

a machine which evaluates the process based on the power on and power off times.

Through a methodical theory which includes the time ratio between the power on

time and the heat preparation times, the engineers can improve the general steel

process.

Furthermore, a tool oriented to solve the second one was unavailable missed until

now and the new system is an alternative that can be used at this point. For this

reason, the electrical behaviour of the furnaces in other steel plants can be improved.

Regarding to the future

- From the beginning, the system was oriented to the analysis area. In this way,

the different options were developed to become a helpful tool for the steel

plant engineers. It means, combining the experience and the new

implementation, is possible to bring the system to the best operating

conditions.

- The second possibility is to develop a system that shows the operation values

on real time. Therefore, the melter can correct the system depending on the



distribution of the points in the circle diagram. This approach also can be

achieve with the new system realizing certain changes.

- In relation to the power area index described in the chapter 7, it was not

possible to establish a direct relation to the process variables. The analysis in

chapter 8 shows the reader the studies already made and also, for future

improvements, a new coefficient has to be found.

Personal experience

It is also important to mention the conclusions at the personal level.

- It changes the perspective about the application of technologies in industrial

processes. Always will be something to improve even when the newest

technology is already installed.

- This experience was a contribution to my engineering profit even though the

steel process is not a typical field for an electronic engineer. It was possible to

see other orientation for an electronic engineer.

- For the university and my country, the development of this project represents a

big challenge and an opportunity to group new technology and applications.

Furthermore, with the system I contributed to a company located in a

developed country, with a well establish technological infrastructure and

staffed with high technically trained people.

Others

- The project was developed as an analysis tool that will help to define the best

electrical parameters for an efficient operation in the EAF.



- The databases have a large historical register of the electric operation

variables, which helps to identify the heats with better energy consumption

and shorter tap to tap time, and also to look for the standardization of the

process.

- The circle diagram is one of the best existing tools for the improvement of the

EAF operating points. This graphical feature, helps in the analysis of the

system in a practical and didactic way. The operation points are easily located

and they help to adjust an efficient system operation.

- Based on the circle diagram, is possible to understand easily the complex

operation of a system as the electric arc furnace.

ANNEX A: INTERFACE PROCEDURES AND INPUT VARIABLES NEEDED

Procedure StartHeatId EndHeatId Year ActualHeat IdTrafo State Phase Tap

spSelectRangeHeatData X X X X X X X

spSelectHeatData X X X

spSelectMaxTrafoParam X X

spSelectTrafoParam X X

spSelectTap X X X

spSelectAvailableHeats X

spHistogramDataEnergie X X X X X

spHistogramData X X X X X

spActualEnergieValues X

spEnergie_Int X

spInfo_StateTapa X X X

spInfo_StateTapb X X X

spPowerArea X X X X X X

ANNEX B: STRATEGIC TRIGGER ORDER FOR THE JOBS

Trigger Job Procedure

time Repetition

JOB_EO1Events Proc_EO1Events 7:01:00 every 10 min.

JOB_EO2Events Proc_EO2Events 7:01:30 every 10 min.

JOB_EO1Trend_Copy Proc_EO1Trend_Copy 7:02:00 every 5 min.

JOB_EO2Trend_Copy Proc_EO2Trend_Copy 7:02:30 every 5 min.

JOB_EO1Trend_Data Proc_EO1Trend_Data 7:03:00 every 5 min.

JOB_EO2Trend_Data Proc_EO2Trend_Data 7:03:30 every 5 min.

JOB_EO1Events_Tap Proc_EO1Events_Tap 7:04:00 daily

JOB_EO2Events_Tap Proc_EO2Events_Tap 7:05:00 daily

JOB_EO1Trend_Aux Proc_EO1Trend_Aux 7:06:00 daily

JOB_EOTrend_DelData Proc_EOTrend_DelData 7:06:45 every 10 min.

JOB_EO2Trend_Aux Proc_EO2Trend_Aux 7:09:00 daily

JOB_EO1Events_Update_Tap Proc_EO1Events_Update_Tap 7:10:00 daily

JOB_EO2Events_Update_Tap Proc_EO2Events_Update_Tap 7:11:00 daily

JOB_EO1Trend_SD Proc_EO1Trend_SD 7:14:00 daily

JOB_EO2Trend_SD Proc_EO2Trend_SD 7:15:00 daily

JOB_EO1Trend_Data_SD Proc_EO1Trend_Data_SD 7:16:00 daily

JOB_EO2Trend_Data_SD Proc_EO2Trend_Data_SD 7:19:00 daily

JOB_EO1Trend_Data_Tend Proc_EO1Trend_Data_Tend 7:20:00 daily

JOB_EO2Trend_Data_Tend Proc_EO2Trend_Data_Tend 7:24:00 daily

JOB_ChargeTaps Proc_ChargeTaps 7:25:00 daily

JOB_EO1Histogram Proc_EO1Histogram 7:29:00 daily

JOB_EO2Histogram Proc_EO2Histogram 7:34:00 daily

JOB_EO1CoefAnalysis Proc_EO1CoefAnalysis 7:39:00 daily

JOB_EO2CoefAnalysis Proc_EO2CoefAnalysis 7:40:00 daily

JOB_EOPowerArea Proc_EOPowerArea 7:44:00 daily

ANNEX C: RELATIONSHIP BETWEEN PROCEDURES AND TABLES IN THE

DATABASE

Procedure Tables source information Tables work target

TRNSRV.Trends.dbo.EO1Trend, EO1Trend, Proc_EO1Trend_Copy

EO1Trend_Dates. EO1Trend_Dates.

TRNSRV.Trends.dbo.EO2Trend, EO2Trend, Proc_EO2Trend_Copy

EO2Trend_Dates. EO2Trend_Dates.

Proc_EO1Trend_Data EO1Trend. EO1Trend.

Proc_EO2Trend_Data EO2Trend. EO2Trend.

TRNSRV.Trends.dbo.EO1Ereignisse EO1Events, Proc_EO1Events

EO1Events_Dates. EO1Events_Dates.

TRNSRV.Trends.dbo.EO2Ereignisse EO2Events, Proc_EO2Events

EO2Events_Dates. EO2Events_Dates.

Prodstat.dbo.Chargenermittlung, EOEvents_Tap_Aux,

Prodstat.dbo.Rohdaten, EO1Events. Proc_EO1Events_Tap

EOEvents_Tap_Aux.

Prodstat.dbo.Chargenermittlung, EOEvents_Tap_Aux,

Prodstat.dbo.Rohdaten, EO2Events. Proc_EO2Events_Tap

EOEvents_Tap_Aux.

Prodstat.dbo.Chargenermittlung, EO1Trend_Aux,

Prodstat.dbo.Rohdaten, Statistiklog_Data. Proc_EO1Trend_Aux

EO1Trend.


Prodstat.dbo.Rohdaten, Statistiklog_Data. Proc_EO2Trend_Aux

EO2Trend.

Prodstat.dbo.Chargenermittlung,

Prodstat.dbo.Rohdaten, Proc_EO1Events_Update_Tap

EO1Events_Tap.

EO1Trend_Aux.

Proc_EO2Events_Update_Tap Prodstat.dbo.Chargenermittlung, EO2Trend_Aux.

Prodstat.dbo.Rohdaten,

EO2Events_Tap.


Prodstat.dbo.Rohdaten, EO1Trend_SD, Proc_EO1Trend_SD

EO1Trend_Aux. Statistiklog_Data.

EO1Trend_Data_SD_R,

Prodstat.dbo.Chargenermittlung, EO1Trend_Data_SD_S,

EO1Trend_SD, EO1Trend_Data_SD_T,

EO1Trend_Aux. EO1Trend_Data_SD_Total,

Proc_EO1Trend_Data_SD

Statistiklog_Data.


Prodstat.dbo.Rohdaten, EO2Trend_SD, Proc_EO2Trend_SD


EO2Trend_Data_SD_R,

Prodstat.dbo.Chargenermittlung, EO2Trend_Data_SD_S,

EO2Trend_SD, EO2Trend_Data_SD_T,

EO2Trend_Aux. EO2Trend_Data_SD_Total,

Proc_EO2Trend_Data_SD

Statistiklog_Data.

Prodstat.dbo.Chargenermittlung, EO1Trend_Data_Tend_R,

EO1Trend_SD, EO1Trend_Data_Tend_S,

EO1Trend_Data_SD_R, EO1Trend_Data_Tend_T,

EO1Trend_Data_SD_S, EO1Trend_Data_Tend_Total,

EO1Trend_Data_SD_T, Statistiklog_Data.

Proc_EO1Trend_Data_Tend

EO1Trend_Data_SD_Total.

Prodstat.dbo.Chargenermittlung, EO2Trend_Data_Tend_R,

EO2Trend_SD, EO2Trend_Data_Tend_S,

EO2Trend_Data_SD_R, EO2Trend_Data_Tend_T,

EO2Trend_Data_SD_S, EO2Trend_Data_Tend_Total,

EO2Trend_Data_SD_T, Statistiklog_Data.

Proc_EO2Trend_Data_Tend

EO2Trend_Data_SD_Total.

Proc_EOTrend_DelData All Statistiklog_DelData

Prodstat.dbo.Chargenermittlung, ChargeTaps,

EO1Events_Tap, Statistiklog_Data. Proc_ChargeTaps

EO2Events_Tap.

Prodstat.dbo.Chargenermittlung, EOHistogram, Proc_EO1Histogram


Prodstat.dbo.Chargenermittlung, EOHistogram, Proc_EO2Histogram



EO1Trend_Data_Tend_R, EOCoefAnalysis,

EO1Trend_Data_Tend_S, Statistiklog_Data.

EO1Trend_Data_Tend_T,

Proc_EO1CoefAnalysis

EO1Trend_Data_Tend_Total.


EO2Trend_Data_Tend_R, EOCoefAnalysis,

EO2Trend_Data_Tend_S, Statistiklog_Data.

EO2Trend_Data_Tend_T,

Proc_EO2CoefAnalysis

EO2Trend_Data_Tend_Total.

Prodstat.dbo.Chargenermittlung, Proc_EOPowerArea

EOCoefAnalysis. EOPowerArea.

ANNEX D: TYPICAL TABLE DESIGN IN THE DATABASE

ANNEX E: FIRST POWER LOCUS DIAGRAM APPROACH

ANNEX F: DIAGRAM OF THE STANDARD DEVIATION VERSUS TIME FOR

SPECIFIC HEAT IN EAF1

ANNEX G: TOTAL OVERVIEW OF THE PHASES DURING THE PROCESS OF

MELTING DOWN IN THE EAF1

Heat No. 105400 Heat No. 105402

ANNEX H: TOTAL OVERVIEW OF THE PHASES DURING THE PROCESS OF

MELTING DOWN IN THE EAF2

Heat No. 205684 Heat No. 205696

ANNEX I: STATISTICAL TABLES OF THE ELECTRICAL DAILY REPORTS

ANNEX J: BSW TRANSFORMERS DATASHEET

EAF1:

ANNEX K: INTERNAL COMMUNICATIONS IN REFERENCE TO THE

ELECTRICAL PARAMETERS OF THE FURNACES

ANNEX L: THE OLD CIRCLE DIAGRAM MADE BY HAND

ANNEX M: THE NEW CIRCLE DIAGRAM APPLICATION

monitoring of the energy consumption working points in the electric arc furnace · ·...

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