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a-eberleREG-DPA

R

EGSys

Petersen Coil

Controller

REG DPA

with optional

Current Injection

Operating Manual

Issue: 2007-02-21_01

DeliveredSoftware - version:

_______________


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2 Druml: BA_REG-DPA_e_2007_01_01_012.doc

Operating manual

Copyright 2007 by A.Eberle Gmbh & CoKG. All rights reserved.

Edited by:

A.Eberle Gmbh & CoKG

Aalener Strae 30/32D-90441 Nrnberg

Tel.: 0911 / 62 81 08 - 0Fax: 0911 / 66 66 64

e-mail: [email protected]

Internet: www.a-eberle.de

The companyA.Eberle Gmbh & CoKGcannot be held liable for any damages or losses emitting fromprinting errors or changes in this operating manual.

Furthermore, A.Eberle Gmbh & CoKGdoes not assume responsibility beyond the guarantee period for anydamages and losses resulting from deficient devices or from devices changed by the applicant.


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Table of Content

1 Warnings and Information .........................................................................................................................71.1

Warnings............................................................................................................................................7

1.2 Delivery contents ...............................................................................................................................82 Application .................................................................................................................................................9

2.1 Notation............................................................................................................................................102.2 Basics of the Resonant Grounding.................................................................................................. 10

2.2.1 Principals of the resonant grounding....................................................................................... 102.2.2 Low ohmic single line-to-earth-fault: ........................................................................................ 132.2.3 Natural capacitive unbalance of the healthy network.............................................................. 142.2.4 Network analysis by the controller........................................................................................... 16

2.3 Disturbances of the Control Operation ............................................................................................ 202.3.1 Description of the network....................................................................................................... 202.3.2 Coupling phenomena for Une ................................................................................................... 212.3.3 Crosstalk of the load-current to Une ......................................................................................... 24

2.4 Control of the Petersen Coil............................................................................................................. 252.5 Control of the Petersen Coil with Current Injection ......................................................................... 272.5.1 Existing Algorithms .................................................................................................................. 272.5.2 New Algorithm .........................................................................................................................282.5.3 High Ohmic Earthfault Detection with the DIF-algorithm......................................................... 312.5.4 Types of multi-frequency Current Injections (CI) ..................................................................... 32

2.6 Solution for Control with REG-DP(A)............................................................................................... 352.6.1 Without "Current - Injection (CI)" ............................................................................................ 352.6.2 With " Current - Injection (CI)" ................................................................................................ 35

2.7 Current Injection(CI) .......................................................................................................................362.7.1 General ....................................................................................................................................36

2.8 Influence of the Petersen Coil on the use of CI............................................................................... 362.8.1 Influence of the design of the Petersen coil............................................................................. 36

2.9 Literatur............................................................................................................................................393 Technical Characteristics REG-DPA and CI ........................................................................................... 413.1 Electrical Data REG-DPA ................................................................................................................ 41

3.1.1 Regulations and standards...................................................................................................... 413.1.2 AC voltage input ( Uneand U12)............................................................................................... 413.1.3 Alternating current input I1( and I2) ...................................................................................... 413.1.4 Position signal ( Ipos ) ............................................................................................................. 413.1.5 20 mA analogue outputs....................................................................................................... 423.1.6 Binary inputs............................................................................................................................423.1.7 Relay outputs........................................................................................................................... 423.1.8 Reference conditions............................................................................................................... 423.1.9 Electrical safety........................................................................................................................ 433.1.10 Electromagnetical compability ................................................................................................. 43

3.1.11 Power supply ...........................................................................................................................443.1.12 Environmental requirements.................................................................................................... 443.1.13 Data Storage............................................................................................................................453.1.14 Display, Status.........................................................................................................................45

3.2 Optical Interface of REG-DPA......................................................................................................... 463.2.1 Electrical logical interface ........................................................................................................ 463.2.2 Optical transmitter.................................................................................................................... 463.2.3 Optical receiver........................................................................................................................46

3.3 Mechanical design of REG-DPA ..................................................................................................... 473.4 Terminal Blocks of the Controller REG-DPA................................................................................... 51

3.4.1 General information about the connections............................................................................. 513.5 Blockdiagram of the REG-DPA ....................................................................................................... 52

3.5.1 Level I ......................................................................................................................................54

3.5.2 Level III ....................................................................................................................................613.5.3 Example for the connection of the REG-DP(A) to a P-Coil without CI .................................... 67

3.6 Current Injection Controller CCI....................................................................................................... 683.6.1 Auxiliary voltage....................................................................................................................... 68


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3.6.2 AC - voltage inputs ..................................................................................................................683.6.3 AC - current inputs................................................................................................................... 683.6.4 Binary inputs............................................................................................................................683.6.5 Binary outputs: relays ............................................................................................................. 693.6.6 Controller for Current Injection ( CCI )..................................................................................... 70

3.7 Current Injection CI using CCI......................................................................................................... 753.7.1 Principal schemas.................................................................................................................... 753.7.2 Indoor version ..........................................................................................................................773.7.3 Outdoor version ....................................................................................................................... 773.7.4 19" version...............................................................................................................................783.7.5 Example for outdoor motor-drive version ................................................................................ 793.7.6 Example for 19" rack mounted indoor version......................................................................... 80

4 REG-DP(A)..............................................................................................................................................814.1 Indication and Operation Elements ................................................................................................. 81

4.1.1 LCD Display.............................................................................................................................824.1.2 Keys.........................................................................................................................................834.1.3 Plug Connection at the Front................................................................................................... 83

4.2 Human-Machine Interface (HMI) ..................................................................................................... 84

4.3 Selection of the Display Mode......................................................................................................... 864.3.1 Resonance Curve.......................................................................................................... 874.3.2 Detail Display ................................................................................................................ 874.3.3 Current Injection Measurement...................................................................................... 884.3.4 Operation-mode Recorder....................................................................................................... 894.3.5 Statistics...................................................................................................................................91

4.4 SETUP.............................................................................................................................................935 Commissioning ........................................................................................................................................97

5.1 WinEDC...........................................................................................................................................975.1.1 Installation................................................................................................................................975.1.2 Shortcuts of WinEDC............................................................................................................... 995.1.3 Physical connection................................................................................................................. 995.1.4 Assumed settings on the REG-DP(A) ..................................................................................... 99

5.2 Firmware Update REG-DP(A) ....................................................................................................... 1005.3 REG-DP(A) R: Send the Standard Parameterization Set to device............................................. 1035.4 Check of Communication REG-DP(A) CCI .......................................................................... 1065.5 Calibration of the coil ..................................................................................................................... 1075.6 Linearization of the coil.................................................................................................................. 1105.7 Check of Current Injection............................................................................................................. 111

5.7.1 Requirements for Test of CI................................................................................................... 1115.7.2 Check of the Current Injection............................................................................................... 112

5.8 Check of Digital- and Analogue Inputs .......................................................................................... 1195.9 Check of Signalling on the Panel and to SCADA.......................................................................... 1205.10 Second Controller for example: REG-DP(A) V:............................................................................. 1225.11 System voltage unequal to 20 kV.................................................................................................. 123

6 Parameterization Software: WinEDC .................................................................................................... 125

6.1 General Functions of WinEDC ...................................................................................................... 1256.1.1 Parameterization....................................................................................................................126

6.2 REG-DP(A)....................................................................................................................................1326.2.1 General ..................................................................................................................................1326.2.2 Communication......................................................................................................................1366.2.3 Control ...................................................................................................................................1386.2.4 Commissioning ...................................................................................................................... 1566.2.5 Options...................................................................................................................................1806.2.6 Recorder ................................................................................................................................1826.2.7 Logfile ....................................................................................................................................183

6.3 Panel..............................................................................................................................................1856.4 Terminal.........................................................................................................................................1876.5 Logfile ............................................................................................................................................191

6.5.1 General ..................................................................................................................................1916.5.2 REG-DP (DAN)...................................................................................................................... 193

7 FAQ........................................................................................................................................................1957.1 REG-DP(A)....................................................................................................................................195


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7.2 Current Injection CI........................................................................................................................1958 Background Programming REG-L......................................................................................................... 197

8.1 The programming language REG-L .............................................................................................. 1978.2 List of the REG-L / ECL-Interpreter-commands ............................................................................ 197

9 SCADA...................................................................................................................................................199

9.1 Data Point list for IEC 870-5-103................................................................................................... 19910 Maintenance and Current Consumption............................................................................................ 20310.1 Cleaning information...................................................................................................................... 20310.2 Changing fuses..............................................................................................................................20310.3 Changing battery ...........................................................................................................................20310.4 REG-DPA Current Consumption................................................................................................... 20510.5 Replacing the device .....................................................................................................................20610.6 Storage Information .......................................................................................................................206


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 1.1 10BWarnings 7

1 Warnings and Information

1.1 Warnings

The P-coil regulator REG- DPA is exclusively designed for implementation in systems and equipment forpower systems. Only trained experts are permitted to carry out all required work. Experts are persons whoare familiar with the installation, mounting, commissioning and operation of these type of products.Furthermore, experts have qualifications which correspond with the requirements or their field of work.

The P-coil regulator REG-DPA left the factory in a condition that fulfils all relevant safety regulations. Tomaintain this condition and to ensure safe operation, the following instructions and warnings in this operatingmanual must be observed.

The REG-DPA Petersen-Coil controller has been designed to comply with IEC 10110 / EN61010(DIN VDE 0411), protection class I and was tested according to this standard before delivery.

The REG-DPA Petersen-Coil controller must be earthed via a protective earth conductor. Thiscondition is fulfilled when the controller is connected to an auxiliary voltage with a protective earthconductor (European power supply system). If the auxiliary voltage power supply system does nothave a protective earth conductor, an additional connection must be established from the protectiveearth conductor terminal to earth.

The upper limit of the permissible auxiliary voltage UHrespectively UAUXmay not exceeded, netherpermanently nor for a short period of time.

Before changing the fuse, separate the REG-DPA controller completely from the auxiliary voltage.The use of the fuses other than those of the indicated type and rated current is prohibited.

A REG-DPA controller which displays visible damage or clear malfunctioning must not be used andhas to be secured against unintentionally being switched on.

Maintenance and repair work on a REG-DPA controller with an open door may only be carried out byauthorised experts.

Warning signs

Please familiarise yourself with the nominal insulation voltage of the controller before connecting thedevice

Ensure that the voltages are connected via a disconnecting mechanism, and that the currenttransformer path can be shortened externally, to enable problem-free device replacement in case ofa device-fault.

When wiring, please ensure that the conductors are either bound short or kept sufficient short so thatthey cannot touch the boards of level II or III.

If a fault occurs ( connection becomes loose), no line that carries a voltage that is dangerous whentouched (>50 V) or line to which a nominal isolation voltage larger than 50 V is assigned, may comeinto contact with the touchable circuits in level II and III.


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1.2 Delivery contents

1 REG-DPA Petersen-Coil controller with built-in components

1 terminal diagram in English

1 operating manual in English

1 Parameterisation software

1 Nullmodem cable

1 Spare fuse

2 tools ( 7 mm Allen key and special screwdriver for the terminals on level II and III )


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10 2 1BApplication Druml: BA_REG-DPA_e_2007_01_01_012.doc

2.1 Notation

REG-DP(A) Controller for Petersen-Coil DAN Dispositivo Analizzatore di Neutro

EOR-DM Earthfault Detection for low- and high-ohmic faults

MCI Dispositivo Monitoraagio Condicioni diIsolamento

CI Current Injection ICCCI Controller for Current Injection CIC

ASC Arc Suppression Coil ( Petersen - Coil)

PIG Perdita di Isolamento GravePIL Perdita di Isolamento Lieve

2.2 Basics of the Resonant Grounding

The resonant grounding is one of the most important options in electrical network design to obtain theoptimal power supply quality. The main advantage of the treatment of the neutral point is the possibility ofcontinuing the network operation during a sustained earth-fault. As a consequence this reduces thenumber of interruptions of the power supply for the customer.

For the suppression of the arc the Petersen coil should be well tuned within limits, which are described in[1]for the different insulation levels. The increase in the cable lengths of distribution networks brings aboutthat on the one hand the level of the neutral-to-earth voltage is decreasing and on the other hand theresonance curves become sharper. The reason for the reduction of the neutral-to-earth voltage level ismainly due to the reduced capacitance tolerances of the new cables. Furthermore, the cables have smaller

losses compared to equivalent overhead lines. This is why, the damping of the network is reduced and theresonance curves become sharper.

A first idea to meet these demands on the control of Petersen coils is to make the measurement of theneutral-to-earth voltage more sensitive. But in this chapter it will shown that with this idea the results doesn'tsatisfy. The main reason for this is that the disturbances caused by the system due to, e.g. geometricallyasymmetric of installed cables, are higher than the measurement noise. Therefore the reasons for thedifferent disturbances of the neutral-to-earth voltage will be elaborated on the next pages. Finally, a newapproach for finding the resonance point also for smaller neutral-to-earth voltage levels will be presented.

2.2.1 Principals of the resonant grounding

In medium-voltage (MV) and high-voltage (HV) networks with resonant grounding the current over thefault location in the case of a single line-to-earth-fault is reduced by the use of the Petersen-Coil. For this thePetersen coil is adjusted during the healthy operation of the network to compensate the capacitive currentover the fault location by an inductive current. Fig. 2.2shows the simplified equivalent circuit used for a faultydistribution system where we assume ideal symmetrical three-phase voltage sources and negligible lineresistances and inductances.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.2 13BBasics of the Resonant Grounding 11

U3N

U2N

U1N

C1 C2 C3LP

Ip

IC2

IC3

N U1

U2

U3

Une

Earth

IF

ZF=0

I1

I2

I3

GP

Fig. 2.2: Simplified equivalent circuit for the resonant grounding

The phasor diagram of Fig. 2.3for a SLE with ZF = 0 is depicted in Fig. 2.3a. The situation of differentcoil positions of the Petersen coil and the resulting current IFover the fault location are shown in Fig. 2.3b.

Une U31

1

2 3

U21

Earth

IC2+ IC3ILp

IC2IC3

IGp IP

Uen

IGpIF

ILp

IC2+IC3

under-compensation

over-compensation

full-compensation

a) b) Fig. 2.3: a) Phasor diagram for a single line-to-earth-fault (SLE).

b) Reduced phasor diagram

LP, GP Petersen coil (inductance,conductance)C1, C2,C3 line-to-earth capacitancesZF impedance at the fault locationN star point of the transformer (neutral

point)U1,U2,U3 phase voltagesUne neutral-to-earth voltageIC2,IC3 capacitive current of the two sound

linesIP current of the Petersen coilIGP wattmetric part of IPILP inductive part of IP

IF current over the fault location

For the derivation of the mathematical model the following assumptions will be made (see Fig. 2.2):

The line-to-earth capacitances and conductances are symmetrical and the line-unbalance (capacitive and ohmic) is reduced to phase 1.


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Fig. 2.4: Simplified equivalent circuit

For the equivalent circuit of Fig. 2.4the following equations

1 2 3

1 1 1

2 2 2

3 3 3

0

( )

( )

( )

P

ne P P

ne

ne

ne

I I I I

U Y I

U U Y I

U U Y I

U U Y I

= + + +

=

+ =

+ =

+ =

(1.1)

(1.2)

(1.3)

(1.4)

(1.5)

Hold, with the admittances

.

)()(

1

32

1

CjGYY

CCjGGY

LjGY

P

PP

+==

+++=

+=

(1.6)

(1.7)

(1.8)

Assuming a symmetrical three-phase system and using the abbreviation = 120jea with 210 aa ++= , we canwrite the voltages U2and U3in the form

2

2 1U a U= and 3 1U aU= . (1.9)Now eq. (1) yields to

2

1 2 3 1 1 2 30 ( ) ( )

ne PU Y Y Y Y U Y a Y aY = + + + + + + (1.10)

or equivalently2

1 2 31

1 2 3

ne

P

Y a Y aY U U

Y Y Y Y

+ +=

+ + +.

(1.11)

Using eqs. (1.6)- (1.8)(8), we get

)3()3(321

32

2

1

CCjGGYYYCjGaYYaY

+++=++ +=++

(1.12)(1.13)

and hence eq. (1.11)results in

1( )

U Une

U W C L U O

Y YU U

Y Y j B B Y Y = =

+ + +

(1.14)

withCjGYU +=

PW GGY += 3

CBC 3=

PL LB

1

=

unbalance of the fault location

wattmetric part of YO

capacitive part of YO

inductive part of YO.

The equivalent circuit of eq. (1.14)is depicted in Fig. 2.5. This circuit is valid for low ohmic single line-to-


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earth-faults as well as for the natural capacitive unbalance of the sound network provided that the previousassumptions are satisfied.

U1

Yu

BC

Uen= - Une

BLYW

IF

Fig. 2.5: Single phase equivalent circuit for the resonant grounding.

In the following subsections the dependence of Uneand IFon the tuning of the Petersen coil under the twomajor operation conditions will be discussed.

2.2.2 Low ohmic single line-to-earth-fault:

In the case of a low ohmic earth-fault the capacitive unbalancejBCis negligible. On the other hand theohmic admittance G is very high. As a result of these conditions the voltage on the resonance circuit Uneismore or less constant (see also Fig. 2.5). Fig. 5 shows the absolute value and Fig. 2.6the locus diagram ofthe current IFover the fault location as a function of the Petersen-Coil position Ipos= BLU1for a typical 20kV network ( BCU1 = 150 A, YWU1= 5 A and 1/YU= 1 ).

Fig. 2.6: Absolute value of the current IFover the fault location

Fig. 2.7: Locus diagram of the current IFover the fault location


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2.2.3 Natural capacitive unbalance of the healthy network

In this case the ohmic admittanceGis normally negligible compared to the capacitive unbalancejBCofthe network. As a consequence the current IFis more or less constant (see Fig. 2.5). In analogy to theprevious subsection Fig. 2.8shows the absolute value and Fig. 2.9the locus diagram of the neutral-to-earth

voltage Uneat the fault (unbalance) location as a function of the Petersen-Coil position Ipos= BLU1for atypical 20 kV network (BCU1= 150 A, YWU1= 5 A and 1/YU= 40 k).

Fig. 2.8: Absolute value of the neutral-to-earth voltageUne.

The resonance curve of the sound network can be described by the following three parameters:

Ures maximum voltage of the resonance curveIres corresponding coil position to Ures

Iw wattmetric current over the fault locationin the case of a low ohmic earth-fault

These parameters can be determined from the resonance curve in an easy way. At the resonance point( BC= BL ) eq. (1.14)simplifies to

Fig. 2.9: Locus diagram of the neutral-to-earth voltageUne.

1

U

resU W

Y

U UY Y= +.

(1.15)

In order to explain the meaning of the current Iw, let us consider the point of the resonance curve from Fig.


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2.8or Fig. 2.9where the relation1

2

ne

res

U

U= holds. Thus, under the assumption YU


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Fig. 2.11: Locus diagram of the neutral-to-earth voltage1/Une.

2.2.4 Network analysis by the controller

The controller makes all necessary recording for the estimation of the resonance point during its tuning.The controller shows the result directly on the screen.

With the following data:

Icom Actual value of the Petersen Coil; can include fixcoils

v Detuning in A or %Une Actual value of the zero-sequence voltageIw Wattmetric part of the current over te fault location in case of an solid grounded earthfault.Ice Resonance pointImin Minimum-value of the tuneable Petersen-CoilImax Maximum-value of the tuneable Petersen-Coil

According to the already evaluated curve of the value of the fault-current over the fault location, it ispossible to define the current during the healthy network in advance.


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Fig. 2.12: Absolute value of the current IFover the fault location

The current will be in any case a minimum at the resonance point Ires. In this case the capacitive current fromthe healthy phases and the current through the Petersen-Coil have the same size, but opposite directions.The resulting current is only the wattmetric part IWof IF, which is also calculated during the tuning operation.

With the detuning-parameter v the additional reactive part of the fault current can be defined.

Uen

IWIF

ILp

ICE = Ires

under-

compensation

over-

compensationfull-compensation

Fig. 2.13: Phasor diagram of the currents at the fault location

The value of the reactive current over the fault location may be calculated either as 'absolute value' or as'relative value'. The following equations are describing both variants of calculation:

Detuning in A: ][][][ AIresAIposAv = (1.20)

Detuning in %: 100*

][

][][[%]

AIres

AIresAIposv

= (1.21)

In both equations, a positivevalue define an 'overcompensation' and a negativevalue anundercompensation. A value of zerocorresponds to a tuning to resonance.


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Example:

Resonance current of the system: Ires = 150 A( this corresponds to the capacitive current over line-to-earth capacities in case of a solid earth fault ):

Actual position of the P-Coils: Ipos = 160 A

The absolute detuningthus is calculated to:

Av 10150160 +== ( => 10A overcompensation )

and the relat ive detun ingis calculated as follows:

%66,6100*150

150160=

=v

Advantages of the input of an absolute detuning:

The controller tunes the coil to a position, that the reactive current over the fault location is always of thesame size, independent of the network size,

The reactive current is equal for small and large systems. Furthermore, no fix coils installed in the samesystem have to be evaluated and taken into account for the calculation of the detuning. Most of the time, it isnot easy to define how many fix-coils and of witch size are included in the same system. Additional problemsarise from the possibilities to inform the controller of the actual sum-value of these coils. The result of thetuning is always a clear statement on the value of the 50 Hz component of the reactive current over the faultlocation.

In case of a detuning in per cent, the expected reactive current IV in A over the fault location is calculatedaccording to the following equation:

100

)( vIII

fixresv

+= (1.22)

Iv Detuning current ( Reactive current ) in AIres Current through the P-Coils in the resonance point. Ires corresponds to

the capacitive current of the system in case of an solid earth faultIfix Current of an additional fix-coil in the system

v Detuning in %

With a compensation in per cent, very large systems the resulting fault current can exceed the recommendedvalue for the self-extinguishing of the arc. (up to 20 kV: 60A, at 110kV approx. 132 A).


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Fig. 2.14: Fault current limits according to VDE 0228, part 2

The expected touch voltage in the case of an earth fault should be taken into consideration according to theDIN VDE 0101 as a further very important criteria for selecting the compensation. For this calculation theearthing impedances must be known or estimated.

Fig. 2.15: Time inverse curve according to VDE 0101


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2.3 Disturbances of the Control Operation

Following the previous discussion it seems to be very easy to find the resonance point of the sound network

even for very small neutral-to-earth voltages. The problem becomes more difficult because severaldisturbances generate a non-zero neutral-to-earth voltage Une. Thus, it is very difficult for the controlalgorithm to distinguish between real resonance points and fictitious resonance points caused by thedisturbances. Next we will discuss the different reasons for the disturbances of the measurement of Une:

1. High noise levels in the measurement of Unedue to, e.g. inductive and capacitive coupling on the linefrom the measurement winding of the Petersen coil to the controller. This effect can be reduced, by usingtwisted and shielded measurement lines.

2. Resolution of the A/D converter. The resonance maximum in cable networks is often less than 0.5 % ofU1. Thus, in order to identify a resonance curve the resolution should be in the range of 0.01 % of U1.

3. Harmonics in the zero-sequence system. They are filtered out by the controller.4. Unbalance of the voltage (dU1) coupled from the HV.

5. Unbalance of the voltage (dU1) due to manufacturing tolerances of the transformer in the range less than1 %. As a result a completely balanced HV-system generates an unbalanced system on the MV side.

6. An asymmetric load of the auxiliary system on the tertiary winding of the earthing-transformer (zig-zag)also generates an unbalance of the voltage (dU1).

7. Capacitive unbalance of the lines due to, e.g. the geometrical arrangement of the phases in overheadlines or due to the manufacturing tolerances of cables.

8. Coupling of the load current over the normally negligible line resistances and reactances (symmetric andasymmetric values).

9. Coupling of the load current over the normally negligible mutual coupled line reactances (symmetric andasymmetric values).

10. Measurement of the neutral-to-earth voltage Uneusing the open delta winding at the busbar instead ofthe auxiliary winding of the Petersen coil results in a constant amplitude and phase error. This is caused

by the different accuracy classes of the open delta winding and the transformer.11. Non-linearity between the measured coil position and the real susceptance of the Petersen coil. Thesensor for the coil position is a linear potentiometer, which gives a signal proportional to the air gap. Butthe susceptance of the Petersen coil is a non-linear function of the air gap.

12. Capacitive coupling from parallel lines of different voltage levels on the same lattice tower. To reduce therequired ground floor, lines with different voltage levels are installed on the same lattice tower. Due tothis, changes in the balance of one system are capacitively coupled to the second system.

13. Combination of the disturbances mentioned above where unbalanced loads are important.

In order to get an impression of the quantitative influence of some of these disturbances on the neutral-to-earth voltage Vne, in particular 4 to 9, we will subsequently investigate a simple 20 kV network.

2.3.1 Description of the networkThe network under consideration consisting of a trans-former, the Petersen coil, a transmission line and a

load is depicted inFig. 2.16.

U3N

U2N

U1N

Y3YPIP

N

U1

U2

U3

Une

Earth

Y2Y1

dU1

ZL3

ZL2

ZL1

ZM23

ZM12

ZM13

LineLoadZLoad3

N2

ZLoad2

ZLoad1

Transformer

I1 I2 I3

Fig. 2.16: Simple equivalent circuit for the investigation of some disturbances on Une.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.3 14BDisturbances of the Control Operation 21

Let us assume that the transformer (110 kV / 20 kV) is ideal with no losses and no leakage inductance

the line is 44.5 km long with zM12, M23, M13 = j 0.01665 /km,5

3,2,1 104251.9 = jy 1/( km)

and zL1,L2,L3= (0.233 +j0.1665) /km, the admittance of the Petersen -Coil has the value YP= (0.432 +j12.987) 1/and the load is within the range ZLoad1, Load2, Load3 = 38.5 - .

For the sake of clarity, we further assume without restriction of generality that unbalances of the transmissionline only occur in phase 1.The disturbances described in the items 4 to 9 can be reduced to the following three coupling effects, whichwill be discussed in more detail on the basis of the network of Fig. 2.16:

Unbalance of the voltage (dU1). Unbalance of the line-to-earth capacitances. Coupling of the load current over the normally negligible line resistances and reactances.

2.3.2 Coupling phenomena for Une

2.3.2.1 Unbalance of the voltage dU1

Under the assumption that all components of the network are symmetrical except for the unbalancedvoltage dU1we get the following relation between Uneand dU1

13 ( )

ne L C

L C P L C

U Y Y

dU Y Y Y Y Y =

+ + (1.23)

with

( )LLL

LjRY

+=

1

CjYC =

P

PPLj

GY

1+=

seriesline admittance

line-to-earth capacitive admittance

admittance of the Petersen coil.

The important information of eq. (1.23)is that even in a network with ideal symmetrical components (lineresistances, line reactances, mutual coupling, line-to-earth capacitances and loads) an unbalance

dU1will produce a non-zero neutral-to-earth voltage Une.In addition, the amplitude of this voltagedepends on different network parameters and has its maximum in the case when the Petersen coil is

adjusted. The relation1

/ne

U dU as a function of the coil position for the network of Fig. 2.16is shown in

Fig. 2.17.


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Fig. 2.17: Neutral-to-earth voltage due to an unbalance on the HV side

2.3.2.2 Unbalance of the line-to-earth capacitances

For this investigation we assume that dU1 = 0 andthat there is only an unbalance CY in the line-to-earth

capacitance in phase 1. Then the following relation

2

1 1 2

3

3

ne L C

n n

U Y Y

U Y Y

=

+

(1.24)

can be found with

.

1

))3(3(

))(3)((

2

2

1

CjY

ZY

YYYYYY

YYYYYYYYYY

C

Load

Load

LPLoadLCn

CLPCLCLoadLCn

=

=

++=

+++++=

(1.25)

The natural unbalance in the line-to-earth capacitance YCalso brings about a non-zero neutral-to-earth

voltage Une. Butnow Unealso depends on the load YLoadand hence on the load current due to theserial impedance of the line. As it can be seen from eq. (1.24)and eq. (1.25)this dependence is evenpresent if both the serial line impedance and the load are symmetrical. If there are additional asymmetries inthe serial impedances, e.g. due to asymmetrical mutual coupling of the overhead lines, the coupling effect

can be worse. Fig. 2.18depicts the relation1

/ne

U U as a function of the load current in the case of an

adjusted Petersen coil for the network of Fig. 2.16.

2

1 1 2

3

3

ne L C

n n

U Y Y

U Y Y

=

+


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.3 14BDisturbances of the Control Operation 23

Fig. 2.18: Neutral-to-earth voltage due to a capacitive unbalance and non-zero serial impedances in the line .

2.3.2.3 Unbalance of the serial impedances of the line

For this calculation the assumption dU1= 0 and a symmetrical network except for an asymmetry of 5% in ZL

of phase 1 is made. Since the formulas are rather complex only the graph of the relation1

/ne

U U in Fig.

2.19as a function of the load current in the case of an adjusted Petersen coil for the network of Fig. 2.16ispresented.

Fig. 2.19: Neutral-to-earth voltage due to an unbalance of the serial impedances in the line

The important result is that there is an increasing neutral-to-earth voltage Unedepending on the loadcurrent. If the load current is zero Uneresults from the capacitive current of the line itself. In some networksthe neutral-to-earth voltage is zero in the case of no-load operation of the network. The coupled voltages ofthe capacitive unbalance and of the unbalance of the serial impedances are compensating themselves. Butas it can be seen in Fig. 2.19the neutral-to-earth voltage Uneis increasing depending on the load.The asymmetry of a line may be caused for example by the kind of laying the cables, as shown in Fig.2.20a. If the cables are laid in a triangle (see Fig. 2.20b) the mutual coupling of the three phases is obviouslythe same. A similar situation can be found for overhead lines where an improvement can be made, bytransposing the phases.


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1Z

M23ZM12

ZM13

2 3

1

2

3a a

2r

a) b)

ZM12 Z

M23

ZM13

a

Fig. 2.20: a) Single conductor cables in parallel

b) Single conductor cables in triangle.

2.3.3 Crosstalk of the load-current to Une

The following figures shows the change of Une

and Ipos over one week. The coil position was more or lessthe same during the whole period.

00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:000

1

2

3

2005-04-06 01:33:53

Uo/Vsek

00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00 00:00:00210

220

230

240

2502005-04-04 16:36:19:

Ipos/A

Fig. 2.21: Une and Ipos over one week

In this industrial network, there was no switching operation during the whole week.During the working hours of the week a remarkable increase of the zero-sequence voltage can be detected.The small peeks in the zero-sequence voltage are results from the search operation of the Petersen-Coilcontroller.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.4 15BControl of the Petersen Coil 25

The next figures shows the behavior for one day

00:00:00 03:00:00 06:00:00 09:00:00 12:00:00 15:00:00 18:00:00 21:00:00 00:00:000

0.5

1

1.5

2

2.5

32005-04-04 16:36:19:

t / d

Uo/Vsek

Fig. 2.22: Controller interface of the Petersen coil.

The change of the load during the morning break and the lunch time is recognizable in the behavior of Une.Also the working period from 7:00 to 17:00 can be recognized. The end of television between 21:00 and24:00 result in a slow change of Une.

The problem in this network is, that the zero-sequence-voltage Une is only about 0.2 % in the night andincreases during the day up to 1.5%. This is a special challange for the controller.

The parameter of the controller are set correct, if the controller is tuning not more than 10 times per day in acomparable system.

2.4 Control of the Petersen Coil

The only quantities being measurable for the controller are the actual coil position and the neutral-to-earthvoltage Une. Fig. 2.23depicts the controller interface of the Petersen coil.

ControllerL

Petersen-Coil

N

motor high

motor low

+UH

endswitch high

endswitch low

coil-position( air-gap )

Ven

= 0...100VAC

+ Pot

s Pot

Ven

Pot

R1

R2

E1

E2

Ipos

Ven

-UH

Fig. 2.23: Controller interface of the Petersen coil.

The task of the controller is to detect a change of the network configuration and to adjust the Petersen coil tothe new resonance point or to a predefined over- or under-compensated value. In the simplest version thechange of the absolute value of the neutral-to-earth voltage Uneis used as an indication of a switch operationin the network. With this approach not all changes of the network configuration can be detected. An

improvement can be made, by investigating the change of the neutral-to-earth voltage Unein the complexplane. To calculate the resonance curve parameters it is necessary to change the value of the Petersen-Coiland to measure the corresponding variation of the neutral-to-earth voltage Une. As shown in the sectionsbefore, the voltage Uneis corrupted by different disturbances. Summarizing the objectives, the controller has


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to distinguish between a real resonance point and a fictitious resonance point, in particular in the caseof small neutral-to-earth voltages and

to recognize switch operations during the tuning operation of the Petersen-Coil.

It has turned out that by means of a least-squares approach the parameters Ures,Iresand IWof theresonance curve of fig. 7 can be obtained in a robust way. The Petersen-Coil needs in its fastest operationmode about 60 s from one end-switch to the other. This requires that during the tuning operation about every0.5 s a new estimation is accessible. To avoid too high computational consumption the non-linear parameterestimation problem is transformed to a linear one.

For this purpose let us consider eq. (1.19)in the form

2

2 2 2

1

1 1

1

ne

W C L

U U

U

U T Y B B

Y Y

= =

+ +

(1.26)

or equivalently

.220222222

LULCCWWUU BTYBBBYYYY ++++=

(1.27)

Since2

T and BLcan be measured, we can rewrite eq. (1.27)for ndifferent measurement points in the form

=

2

2

3

2

1

2

21

...

...

12

.........

.........

12

L

L

L

L

nB

B

xx

x

TB

TB

(1.28)

with the abbreviations

.2222

3

2

2

1

CWWUU

U

C

BYYYYx

Yx

Bx

+++=

=

=

(1.29)

(1.30)

(1.31)

Eq. (1.28)can be solved with a classical least squaresapproach in order to obtain BC, YUand YWand

from this the parameters Ures,Iresand IWfor the construction of the resonance curve. It is worth mentioningthat for the sake of computational efficiency an on-line version of the least-squares algorithm is implemented.

However, some further steps in the preprocessing of the signals have to be taken to gain additionalrobustness against disturbances.

As an example Fig. 2.24shows the estimated inverse resonance curve (see eq. (19) and Fig. 2.10), by usingonly the marked samples from the measured values for the computation of the parameters. The realresonance point of the network is at 100 A.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.5 16BControl of the Petersen Coil with Current 27

Fig. 2.24: Inverse resonance curve estimated from the sampled values.

2.5 Control of the Petersen Coil with Current Injection

The tuning of the Petersen-Coil is a preventive operation already done in the healthy network. With theexisting methods it is not possible to determine the network parameters during a solid earthfault. The faultlocation and the resistance at the fault location are unknown and are not accessible for a measurement. Incase of a solid earthfault, the zero-sequence voltage is impressed and the measurement of the zero-sequence current at the fault location is impossible. The zero-sequence current can only be measured at thesubstation or in some cases at some dedicated switching-stations.

In the past, different control algorithms were developed. Most of these algorithms are based on thenecessity to move the Petersen-Coil. The development of today's distribution networks is characterized onone side by an increase of symmetrical cables, which results in smaller usable zero-sequence-voltagesand, on the other side, in an increase of the crosstalk of the positive sequence of the load current tothe zero-sequence system. With the decreasing zero-sequence voltage the controller must be set muchmore sensitive. Due to the crosstalk of the load current to the zero-sequence voltage, each change of theload current can release a tuning operation, which is, in most of the actual algorithms, combined with aphysical movement of the Petersen-Coil. Due to the disturbances the state and parameter estimation of thenetwork is much more difficult and results in a necessary movement of the Petersen-Coil over a longerdistance. Nevertheless, sometimes a correct tuning is impossible.

One problem arises because the motor-drive of the Petersen-Coil is only designed for few tuning operations

per day. The other problem arises because of the longer detuning time. This is caused by the increase oftuning cycles, respectively by wrong tuning positions.

Therefore on the next pages a method will be presented, which is able to find the correct tuning position,even if the natural zero-sequence voltage is zero, respectively if the disturbances in the zero-sequencevoltage are not negligible. Additionally, the number of necessary moving operations is reduced.

2.5.1 Existing Algorithms

Up to now, mainly the following algorithms are used to determine the network parameters respectively totune the Petersen-Coil. The relative change of the zero-sequence voltage is normally used as the criterion

for the detection of a switching operation in the network.


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1. Artificial EarthfaultBy measuring the current over the artificial earthfault location and searching for the minimum of the

current by tuning the Petersen-Coil, the tuning point and the parameters of the equivalent network can bedetermined. This method is actually only used to check the quality of a control algorithm.

2. Search of max | UNE

|This algorithm searches the maximum of the residual voltage. Improved versions of this algorithm

determine additionally the network parameters by using the 2 method. Alternative algorithms are using

least-square techniques to estimate the network parameters already from a part of the resonance curve.

3. Least square based on | 1/UNE|A lower sensitivity against disturbances can be reached by using an algorithm based on the inverse of the

resonance curve.

4. Locus Diagram of U0This method is based on the fact that a circle can be constructed with only three points. This method

assumes that the third point of the circle is the origin of the complex plane. A short detuning can be achievedfor example by switching a capacity in parallel to the Petersen-Coil. This switching results in a second point

of the locus diagram of UNE. Measuring the voltage with amplitude and angle it is possible to construct thelocus diagram.

5. 50 Hz Current InjectionThis algorithm is based on the idea to inject an artificial current into the neutral point of the system if there

is no unsymmetrical current from the natural asymmetry. The influence of the natural unbalance can bepartly compensated by using a differential measurement from two time points. Eq.Fehler! Verweisquelle konnte nicht gefunden werden.in combination with the coil position enables todetermine the network parameters.

( )CI W C LCINE

d IY Y j B B

dU= + (1.32)

2.5.2 New Algorithm

Principle

All the existing algorithms are based on the fact, that the residual voltage is generated either by the naturalunbalance of the network or by an artificial 50 Hz current injection. These methods are assuming, that thereis no change in the network respectively no change of the crosstalk of the load current during the calculationperiod. Please pay attention that the calculation period can last from several seconds up to severalminutes.

In reality there are a lot of situations where these assumptions are not valid, for example in the sphere ofheavy industry with symmetrical networks but heavy changes of load.

The new CIF-algorithm (Control by Injecting Frequencies) suppresses the 50 Hz crosstalk from the loadcurrent by using frequencies unequal to 50 Hz for the measuring and for the parameter estimation.

The simplified equivalent circuit with a current injection according to Fig. 2.25

Fig. 2.25: Simple equivalent circuit with current injection.


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results for the frequencies unequal to 50 Hz toFig. 2.26

Fig. 2.26: Simple equivalent circuit with current injection unequal to 50 Hz.

For the frequency fnthe admittance, seen from the current injection, can be described as:

_

__

1( )

CI fnW nCI fn U

nNE fn

IY Y Y j C

U L

= = + + (1.33)

For symmetrical networks with a small YUthis results in

_

__

1( )

CI fnW nCI fn

nNE fn

IY Y j C

U L

= + (1.34)

Using two different frequencies f1and f2one gets two complex equations with three variables, which leads tothe following solution:

1

_ 1

f

W

NE f

IY real

U

=

(1.35)

1 2_ 1 _ 2

2 21 2

( ) ( )CI f CI f imag Y imag Y

C

= (1.36)

_ 11 1

1

( ( ) )CI fL

imag Y C =

+ (1.37)

Assuming a linear system enables the current injection of two frequencies and evaluation of thecorresponding YCI_fnat the same time. This results in very fast measurement possibilities and depends moreor less on the used frequencies and filter algorithms. The duration of the measurement is usually in the rangeof 240 ms.

The following items list the main advantages of this new CIF-algorithm:

Very fast measurement Suitable also for symmetrical networks Determination of the sum of all Petersen-Coils including distributed fixed-coils in the compensated

area Insensitive to the 50 Hz open-delta VT error Suppression of 50 Hz crosstalk

Additional requirements

Depending on the resonance curve and the normal operation philosophy of the network, there arise someadditional requirements for the current injection.

1) The injected current should be variable in the amplitude to enable adaptation to the losses of differentswitching states of the network.

One of the most used criteria for the earthfault detection is the zero-sequence voltage. In small networks


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the losses in the network are smaller, so that only a reduced current should be injected, not to exceed thethreshold level of the earthfault detection system, especially in the resonance point.

On the other side, in case of situations with a large detuning a small injected current will not deliver areliable measurement of the residual voltage UNE_fn .In this case a higher injected current is recommended.

2) The injected frequencies should not include 50 Hz components.

3) Using a current injection with variable frequencies, it is possible to select the injected frequencies in sucha way, that these frequencies are near to the resonance of the network. In this case small injectedcurrents result in large values of the residual voltage. The accuracy of the parameter estimation isincreased, especially for systems with a large standard detuning.

Operation philosophy

Depending on the operation philosophy the current injection can be activated only for a short time after thedetection of an essential relative change of the zero-sequence voltage, to check if a new tuning of thePetersen-Coil is necessary. In symmetrical networks the current injection can be switched on continuously,

to detect any switching operation in the network immediately. Combinations of these two philosophies arepossible, for example to check every 10 min the actual network parameters in symmetrical networks.

More Precise Models

In Fig. 2.25a connection of the Petersen-Coil to the neutral point of the transformer is shown. For a moreaccurate calculation of the network including a Petersen coil, as shown in Fig. 2.25 , it is necessary to use amore precise equivalent circuit as depicted in Fig. 2.28.

Fig. 2.27: Wiring diagram of the Petersen Coil with current injection and wattmetric increase Rp


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ZoTr

YX

LPCRFe

RS2

RS1

Cnet Gnet

Cu

Gu

UU UXZP

ZPC

IPIP

ICI

I2 I0_Tr

IC IG

IX

ICu

IGuIU1

UNS

USE

U0d_TrUP

UNE

IU

I0_Fix

LFixRFix

I0_S

Petersen Coil Transformer

AN

UCI

CCRs CRs

S

ZPC_leakage

ILext

ZFix

Lnet

I0_fix

Fig. 2.28: Simplified zero-sequence equivalent circuit of one transformer, one ASC and one Fix-Coil(red currents and blue voltages can be measured)

Using frequencies unequal to 50 Hz enables now an accurate measurement of the following componentsduring normal operation of the network

Zero-sequence capacity of the network External Petersen Coils existing in the network (distributed Petersen-Coils) Zero-Sequence Impedance of the Transformer Values of the fixed-coils in the substation Detuning Value of additional damping resistors Calculation of the unsymmetry of the network

2.5.3 High Ohmic Earthfault Detection with the DIF-algorithm

The abbreviation DIF is the replacement for: Detection by Injecting Frequencies

The parameter estimation of the network can be extended for each feeder by measuring the injected currents

in each feeder of interest either with the Holmgreen-Circuit (summation CT) or with the core-balancetransformer.

Fig. 2.29: Parameter estimation for each feeder


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As the crosstalk from 50 Hz is suppressed, the measurement of U0Dcan be used for the calculation of theessential parameters for each line.It is possible to calculate the capacitive part BCx, the losses YWxand the size of distributed coils BLxseen onfeeder x, with the same method as explained above. By using additionally the 50 Hz components at thesame time, the actual unbalance of the network can be determined and supervised.The advantage of this algorithm is, that all measurements are made at the same time. The usual problem tocheck for a switching operation is removed. The determination of the network parameter is included in thealgorithm directly.

2.5.4 Types of multi-frequency Current Injections (CI)

The most simple way is to use a standard frequency converter (FC) in the mode of a current source asshown in Fig. 2.30. To reduce the disturbances on the 400 V side, a frequency converter with a power factorcorrection module (PFC) is recommended. The coil L1 respectively the parallel circuit L1//L2 is used toconvert the pulsed voltage to an impressed current. The size of L1//L2 defines the maximum availableinjected current. The auxiliary winding of the Petersen-Coil is usually designed for 500 V, which makes

necessary, in these cases, an additional transformer for the adaptation. With this type of current injection twocurrents with individual amplitude, frequency and phase can be injected very easy. On the other side thephysical realisation is not the cheapest one.

Fig. 2.30: Current injection with AC-switch for three frequencies (AC-1)

If the requirement for variable frequencies is cancelled, a much cheaper version to generate a current withmore frequencies is available, as shown in Fig. 2.31

Fig. 2.31: Current injection with AC-switch for three frequencies (AC-1)

The following figure shows one possible pattern of pulses for the current injection.

0 50 100 150 200 250

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

I/A

t / ms

Fig. 2.32: Sample pulse pattern for AC-1


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The corresponding frequency spectrum is shown in Fig. 2.33

0 50 100 150 200 2500

0.1

0.2

0.3

0.4

0.5

0.6

41.67 : 0.34724

50.00 : 0.50000

58.33 : 0.29383

I/A

f / Hz

Fig. 2.33: Frequency spectrum for AC-1

The major disadvantage of this type of current injection is that the main spectrum of the injected current is 50Hz. This can be avoided by the following type of thyristor-switch, where it is possible to invert the direction ofthe current during the previous pause time.

Fig. 2.34: Current injection with AC-switch for two frequencies (AC-2)

The resulting pulse pattern is shown in Fig. 2.35

0 50 100 150 200 250

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

I/A

t / ms

Fig. 2.35: Sample pulse pattern with AC-2

with the corresponding frequency spectrum shown in Fig. 2.36

Depending on the pulse pattern and the number of periods different frequencies are available. The previousfigures show a 100 % phase-firing. The amplitude can be reduced by a reduced phase-firing, as for exampledepicted in Fig. 2.37. This AC-switch (AC-2) can also be used to generate the pattern for three frequencieslike shown in Fig. 2.32.


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0 50 100 150 200 2500

0.1

0.2

0.3

0.4

0.5

0.6

25.00 : 0.28292

41.67 : 0.69448

50.00 : 0.00000

58.33 : 0.58767

I/A

f / Hz

Fig. 2.36: Frequency spectrum for AC-2

0 50 100 150 200 250

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

I/A

t / ms

Fig. 2.37: Sample pulse pattern with AC-2 with phase-firing


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.6 17BSolution for Control with REG-DP(A) 35

2.6 Solution for Control with REG-DP(A)

2.6.1 Without "Current - Injection (CI)"

Tuning of the Petersen Coil only with zero-sequence voltage by changing the coil position Enough zero-sequence voltage must be available Zero-sequence voltage should be used from the Petersen Coil ( With known L0Trthe influence of this

impedance could be taken into account for the display of Cnet)

2.6.2 With " Current - Injection (CI)"

The algorithm uses the measurement according to the simplified schema from Fig. 2.28

In most cases it is sufficient to use the simplified algorithm with ICIand U0Drespectively UNS

The resistors Rs1 and Rs2 normally doesn't exist. In this case UNS= UNE

Measurements for the different algorithms:

MeasurementsAlgorithm

Uod,IciAlgorithm

Uns,IciAlgorithm

Uns,Uod,Ins,IfUsync UNS U0D

ICI I0_S I0_fix

CIF Algorithm ( Control by Injecting Frequencies )

Steps of CIF:

Injection of CI with two frequencies Frequencies are 50 Hz => disturbances of 50 Hz can be suppressed Measurement of U0, UNE and ICI Calculation of the zero-sequence admittance and its components GP, Cnet, ZoTrand LP at this two

frequencies Decision to move the coil or not

Characteristics of CIF:

Up to two frequencies Frequencies near to the resonance frequency Parameters:

o Maximal allowed current injection: |ICI| < 25 Ao Maximal value of u0due to current injection: u0(t) < 5%

Continuous injection with reduced current for supervisory of the network Switch off or reduction of the current injection during coil movement Very fast, as the calculation is within one filter cycle ( 240 ms) For supervision of the network in case of very small U0the current-injection can be selected to be

continuous or periodically During continuous injection switch operation are detected immediately


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Works also in very symmetrical networks No influence of 50 Hz asymmetries or crosstalk of 50 Hz positive sequence components to the zero-

sequence components for the calculation of the detuning.

2.7 Current Injection(CI)

2.7.1 General

Injection and move of the coil at the same time is not required, but possible Size of current injection is changed by the controller. Max of 20 A on the 220 V side

( 10 A on the 500 V side ) Maximal allowed value of u0(t) < 5% caused by Current Injection. The current injection is supervising

u0(t) and limits its actual injection if necessary.

2.8 Influence of the Petersen Coil on the use of CI

2.8.1 Influence of the design of the Petersen coil

higher

lower Imin

Imaxspindle

fixed core

Fig. 2.38: Principal design of a Petersen Coil

The primary winding is connected on one side to the high voltage system and on the other side to ground.According to some specifications also the grounded side must be isolated to ground for the full voltage. Inthis case both bushings on the top of the Petersen-Coils have the same isolation level and the customer canselect which one will be grounded.

The Power-Auxiliary-Winding (PAW) is normally designed for 500 V with variation of 10% over the tuningrange. Due to the variation of the distance dof the air-gap the coupling from the primary winding to the PAW

is not constant. The PAW is normally designed for an additional load-current of about 10% of the specifiedmaximum of the inductive current Ip_max. This current can be ohmic, inductive or capacitive. For the design ofthe Petersen-Coil the maximum duration of this additional current must be specified and depends on the useof this PAW.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.8 19BInfluence of the Petersen Coil on the use of CI 37

In most cases for the measurement of the UNEfew Measurement Windings(MW) are added to deliver about100 V in case of a solid earthfault. Also the accuracy of this winding is only in the range of 10%. Theaccuracy of this measurement depends on the location and distribution of these windings. Sometimes theirarrangement is concentrated and asymmetric as shown in Fig. 2.39: Petersen Coil with PAW. Anothersolution implements the winding on the return limp of the magnetic circuit. There are lot of additional differentsolutions to get better results for the measurement and they can be optimized for a class of coils with anominal power.

Alternative solutions generate the 100 V via a simple autotransformer connected to the PAW. As long thereis not wattmetric-increase connected to the PAW the measurement is relative acceptable.

To improve he accuracy of the voltage measurement some designs uses a small voltage transformer underoil connected directly to the primary voltage. With this solution the accuracy depends only on the accuracy ofthe voltage transformer.

For the current injection the Petersen Coil is not more an ideal transformer. The coupling between the threewindings is a function of the coil position and is nonlinear.

The use of the current injection, as a simple method, can be made more complicate if the current injectionshould be used in combination with an older Petersen-Coil without a PAW.

Petersen Coils with PAW

In this case the Petersen Coil is used as a transformer. The major influence on the accuracy is depending onthe constancy of the transfer-function of the injected current on the secondary side to the resultant current onthe primary side. This transfer-function should be constant over the whole tuning range of the Petersen coil.

Additionally the voltage measurement should reflect the primary voltage and not the voltage on the PAW.

RS

UNE_3

U0d

IS

ICI_3

UNE_2

Fig. 2.39: Petersen Coil with PAW


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The following principal combinations for measurements for the current injection exist:

Parameters for accuracycombinationICI_prim/ICI_3 UNE_2 (Ipos) IS

rating *)

ICI_3 , UNE_2 10% -- 5ICI_3 , UNE_3 3% -- 3ICI_3 , U0d 3% -- 3

IS, UNE_2 10% 3% Bad condition of IS 8IS, UNE_3 3% 3% Bad condition of IS 7IS, U0d 3% 3% Bad condition of IS 7

*) a rating of 1 is the best solution, a rating of 10 is the worst solution

Petersen Coils without PAW

In this case, an additionally small single phase transformer as a replacement of the PAW is necessary,connected parallel to the primary side of the Petersen-Coil. The power rating of this transformer can bedesigned for about 10 A continuous current on the low voltage side. The ratio of the windings is normallydesigned to produce 500 V on the low-voltage side. The short circuit impedance of the transformer shouldbe as small as possible.

Fig. 2.40: Petersen Coil without PAW

If figures are shown in the following tables, they assume a 20 kV network, an injection transformer with aratio of 11550/500, a natural unbalance of < 5%, a network with Iceof about 300 A and a maximal injectioncurrent of 10 A on the low voltage side.


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 2.9 20BLiteratur 39

The following principal combinations for measurements for the current injection exist:

Parameters for accuracycombinationZTr ICI_2 /ICI_1 UNE_2 (Ipos) IS

rating *)

ICI_1 , UNE_1 -- -- not applicable 10

ICI_1 , UNE_2 -- 10% -- 8ICI_1 , UNE_3 -- 3% -- 5ICI_1 , U0d -- 3% -- 5

ICI_2 , UNE_1 -- -- -- -ICI_2 , UNE_2 -- 3% 10% -- 2ICI_2 , UNE_3 -- 3% 3% -- 1.5ICI_2 , U0d -- 3% 3% -- 1

IS, UNE_1 -- -- -- --IS, UNE_2 -- -- 10% 3% Bad condition of IS 8IS, UNE_3 -- -- 3% 3% Bad condition of IS 6

IS, U0d -- -- 3% 3% Bad condition of IS 6

*) a rating of 1 is the best solution, a rating of 10 is the worst solution

2.9 Literatur

[1] DIN VDE 0228, Manahmen zur Beeinflussung von Fernmeldeanlagen durch Starkstromanlagen,1987.

[2] Doemeland Wolfgang, Handbuch Schutztechnik, Grundlagen Schutzsysteme Inbetriebsetzung,VDE Verlag GmbH, Berlin-Offenbach, 7.Auflage, 2003

[3] Druml G., Kugi A., Parr B., Control of Petersen Coils, XI. International Symposium on TheoreticalElectrical Engineering, 2001, Linz

[4] Schossig Walter, Netzschutztechnik, VDE Verlag GmbH, Berlin, 2001

[5] Druml G., "EDCSys Operation Manual - Earthfault Detection and Control System", A-Eberle GmbH&CoKG, 2004, Nrnberg, Germany


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 3.1 21BElectrical Data REG-DPA 41

3 Technical Characteristics REG-DPA and CI

3.1 Electrical Data REG-DPA3.1.1 Regulations and standards

IEC 1010 / EN61010 (VDE 0411)CAN / CSA - C 22.2 No. 1010.1 - 92VDE 0110IEC 255-4EN 55011 : 1991EN 50082 - 2 : 1995IEC 688 -1IEC 529EN 50178 / VDE 0160 / 11.94 (currently draft)

VDE0106 PART 100DIN 40050

3.1.2 AC voltage input ( Uneand U12)

Zero-sequence-voltage Une 0,1V ... 120VSynchronisation Usync 0,1V ... 230VWaveform SinusoidalFrequency range 45....50....60....65 HzInternal power consumption Unenn

2/ 20 kOverload capability 120 V *1,2 continuous

3.1.3 Alternating current input I1( and I2)

Current range 1 A / 5 A software selectableWaveform SinusoidalFrequency range 45....50....60....65 HzInternal power consumption 0,5 VAOverload capability 10 A continuous

100 Inennfor 1 s30 Inennfor 10 s500 A for 5 ms

3.1.4 Position signal ( Ipos )

Measurement device PotentiometerNominal values Rn of thePotentiometer

150 bis 3 k

Measurement voltage approx. 5 VDC

Current selectable via jumper( Rin)

1 mA (3 kOhm)5 mA ( 600 Ohm)10 mA ( 300 Ohm)20 mA ( 150 Ohm)

Error message when a break or short circuit occurs in the sensor and/or when the voltage of the slider lies outside the

measurement range.


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42 3 2BTechnical Characteristics REG-DPA and CI Druml: BA_REG-DPA_e_2007_01_01_012.doc

3.1.5 20 mA analogue outputs

Number see ordering informationOutput range (Y1...0...Y2) -20 mA...0...20 mA, Y1 and Y2 are free programmableElectrical isolation Optocoupler

Load range 0 R 8 V / Y2Ripple < 0,5 % of Y2Error limit 0,5 % referred to Y2

The output can be continuously short-circuited or operated open.The output connections are galvanically isolated from all other circuits.

3.1.6 Binary inputs

Inputs E1 ... E16

Input voltage 48 V...230 V AC/DCWave form, permissible Rectangular, SinusoidalH level >35 VL level < 25 VSignal frequency fs DC fs 60 HzInput resistance 47 kElectrical isolation Optocoupler; all inputs are isolated from each other

3.1.7 Relay outputs

Relay R1 ... R13, including status

max. switching frequency 1 HzElectrical isolation Isolated from all device internal potentialsContact load AC 250 V, 5 A ( cos= 1,0 )

AC 250 V, 3 A ( cos= 0,4 )DC 220 V, 55 W ( L/R = 0 ms)DC 110 V, 55 W ( L/R = 0 ms)DC 60 V, 60 W ( L/R = 0 ms)DC 30 V, 150 W ( L/R = 0 ms)

Number of switches > 105electrical

3.1.8 Reference conditions

Reference temperature 23C 1 KInputs quantities 1 V, 5 V, 20 V, 100VAuxiliary voltage H = Hn 1 %Frequency 50 Hz...60 HzWave form Sinusoidal, form factor 1.1107Load for analogue output Rn = 4 V / Y2 1 %Others IEC 688 - part 1


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3.1.9 Electrical safety

Protection class I

Pollution level 2Overvoltage category II, III

III IIInput circuits of the current and

voltage transformerspower supply

Control circuits(DC),Analogue inputs,

Analogue outputs,ELANs, COMs

Nominal isolation voltages

50 V 150 V 230 VE-LAN,

COM1...COM3,Analogue outputsAnalogue inputs

Voltage inputsCurrent inputs

Power supply,Binary inputs (E1 ... E16),Relay outputs (R1 ...R13)

Test voltageHous.COM1

UhCOM2COM3

BO BI AI AO UE IE

Housing/COM1 Hous./COM1 - 2.2 0.35 1.35 1.35 0.35 0.35 1.35 1.35Auxiliary voltage Uh 2.2 - 3.7 2.9 2.9 3.7 3.7 2.6 2.6COM2/3 /IEC / DNP_ COMx 0.35 3.7 - 2.3 2.3 0.5 0.5 2.8 2.8Binary Outputs BO 2.0 2.9 2.3 - 2.0 2.3 2.3 2.6 2.6Binary Inputs(250V) BI 2.0 2.9 2.3 2.0 - 2.3 2.3 2.6 2.6

Analogue Inputs AI 0.35 3.7 0.5 2.3 2.3 - 0.5 2.8 2.8Analogue Outputs AO 0.35 3.7 0.5 2.3 2.3 0.5 - 2.8 2.8Input voltage UE 1.35 2.6 2.8 2.6 2.6 2.8 2.8 - 2.2Input current IE 2.0 2.6 2.8 2.6 2.6 2.8 2.8 2.2 -

Notes: All test voltages are AC voltages in kV, which may be applied for 1 minute.E-LAN, COM2, COM3 are tested against each other with 0.5 kV.

3.1.10 Electromagnetical compability

EMC requirements EN 61326-1 device class A,Continuous non-monitored operation in industrial applications andEN 61000-6-2 andEN 61000-6-4

Emitted interferenceConducted and EN 61326 Table 3 andradiated emissions EN 61000-6-4

Harmonic currents EN 61000-3-2

Voltage fluctuations EN 61000-3-3and flicker


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Immunity to interference EN 61326 Table A1 andEN 61000-6-2

ESD IEC 61000-4-2 8kV / 15kV contact/air

Electromagnetic fields IEC 61000-4-3 80 2000 MHz: 10 V/m

Fast transients IEC 61000-4-4 4kV / 2kV

Surge voltages IEC 61000-4-5 4kV / 2kV

Conducted IEC 61000-4-6 150 kHz 80 MHz: 10 VHF signals

Magnetic fields with heavy IEC 61000-4-8 100 A/m (50 Hz), continuouselectrical frequencies 1000 A/m (50 Hz), 1 s

Voltage dips IEC 61000-4-11 30 % / 20 ms, 60 % / 1 s

Voltage interruptions IEC 61000-4-11 100 % / 5s

Damped oscillations IEC 61000-4-12 Class 3, 2.5 kV

3.1.11 Power supply

Feature H1 H2AC (intern) - -AC 85 ... 264 V -DC 88 ... 280 V 18 .. 72 VPower consumption 15 VA 10 WattFrequency 50 Hz / 60 HzFuse T2 250V T2 250V

The following applies to all features:Voltage dips at nominal voltage that last 50 ms cause neither a loss of data nor a malfunction.

3.1.12 Environmental requirements

Dry, cold IEC 60068-2-1 - 15 C / 16 h

Dry, hot IEC 60068-2-2 + 65 C / 16 h

Constant humid heat IEC 60068-2-78 + 40 C / 93 % / 2 days

Cyclical humid heat IEC 60068-2-30 12+12 h ,6 cycles +55 C / 93 %

Toppling IEC 60068-2-31 100 mm drop, unwrapped

Vibration IEC 60255-21-1 class 1

Shock IEC 60255-21-2 class 1

Resistance to earthquakes IEC 60255-21-3 class 1


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3.1.13 Data Storage

Device settings Serial EEPROM with 1000 k read/write cycles

RAM data Li battery laser welded(recorder functionFeature S1)

3.1.14 Display, Status

Display LC - Display 128 x 128 with graphics capabilities

Function supervision (Status) In each controller, the battery, the operation of the process (Watchdog) andthe operation voltage are supervised.

Status indication LED - green


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3.2 Optical Interface of REG-DPA

The REG-DPA regulator can also be directly connected via a fibre optic cable interface.

Sending and receiving devices are available for glass and plastic fibre optic cables.

In addition, it can be choose between various mechanical connection possibilities (ST or FSMA connection).Features V13 to V19 give an overview of the various possibilities

3.2.1 Electrical logical interface

Logic level of receiving output: CMOS (Uhmin: > 0.9VCC, Ulmax< 0.1VCC @ Io = 1mA)

Logic level of transmitting input: CMOS (Uhmin: > 0.7VCC, Ulmax< 0.3VCC), Schmitt trigger

3.2.2 Optical transmitter

Product Type Fibre PmindBm1)

PmaxdBm1)

50/125 m, NA=0.2 -19.8 -12.862.5/125 m, NA=0.275 -16.0 -9.0100/140 m, NA=0.3 -10.5 -3.5

Glass STGlass SMA

HFBR 1414-THFBR 1404= 820 nm

200 m HCS, NA=0.37 -6.2 +1.81 mm POF -7.5 -3.5POF_ST HFBR 1515B

= 650 nm 200 m HCS -18.0 -8.51 mm POF -6.2 0.0POF_SMA HFBR 1505C

= 650 nm 200 m HCS -16.9 -8.51) TA = 0..70 C, IF = 60 mA, measured in 1 m fibre optic cable

3.2.3 Optical receiver

Product Type Fibre PmindBm2)

PmaxdBm2)

-24.0 -10.0Glass STGlass SMA

HFBR 2412-THFBR 2402

0...5 MBd= 820 nm

100/140 m, NA=0.3

1 mm POF -20.0 0.0POF_ST HFBR 1515B= 650 nm 200 m HCS -22.0 -2.0

1 mm POF -21.6 -2.0POF_SMA HFBR 1505C= 650 nm 200 m HCS -23.0 -3.4

2) TA= 0..70 C, VCC = 5 V 5 %, output level LOW (active)


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3.3 Mechanical design of REG-DPA

Housing Sheet steel, RAL 7035 gray

Height 288 mm / Width 216 mm / Total depth 114 mmMounting depth 87 mm

Mass 3 kg

Housing doors with silica glass

Front panel plastic, RAL 7035 gray on aluminium supports

Control panel cutout Height 282 mm / Width 210 mm

Degree of protection IP 54

Rain test 3R UL50

F3

F2

F1

F4

F5

AUTO REMOTE

LOCAL

ACK

MENUESC

REG-DPA

SERVICE

BLOCKED

REGSys www.regsys.de

12

18 87 250

281x209

307

Fig. 3.41: Mechanical dimensions, front view


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Panel mountingRear view

Cutout

282 x 210 mm

Panel

Fig. 3.42: Mechanical dimensions, panel-mounting version

Standard DIN- railRear viev

mounting

127

65

Fig. 3.43: Mechanical dimensions, standard DIN-rail assembling


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Druml: BA_REG-DPA_e_2007_01_01_012.doc 3.3 23BMechanical design of REG-DPA 49

surface / wall-mountingRear view

252

270

200

328

6.5

5.5

Fig. 3.44: Mechanical di

reglaj bobinei de stingere_reg dpa

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