Τhe scientific energy saving project of scientific …
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ΤHE SCIENTIFIC ENERGY SAVING PROJECT OF
SCIENTIFIC ENERGY MANAGEMENT DMCC (SEMAN DMCC)
IN AL-ASSEMAH STEEL BILLETS FACTORY IN JEDDAH, KSA,
OF RAJHI STEEL INDUSTRIES CO.
Α. AL-ASSEMAH STEEL BILLETS FACTORY OF RAJHI STEEL INDUSTRIES CO.
Al-Assemah Steel Billets Factory (Rajhi Steel in brief, pictures 1 - 4) is based in the city
of Jeddah – Saudi Arabia and it is one of the leading national companies in iron and
steel industry and one of the Middle East & North Africa’s largest steel manufacturers,
especially in rebar and commercial steel. Some Rajhi Steel products include:
Rebars/Reinforcement Steel
Plain wire rod
Rebar coils
Rectangular and Square Tube
Hot Rolled Steel Sheets
Cold Rolled Steel Sheets
Zincor /Electro-Galvanized Sheets
Checkered Sheets
Galvanized Steel Sheets
Ordinary and Insulated Corrugated Sheets
Black Pipes
Galvanized Pipes
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Picture 1: Part of the plant in Jeddah
Picture 2: Production Line
Picture 3: Production Line
Picture 4: Production Line
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The total installed electric power of Rajhi Steel comes up to 55 MW. The grid is in 60Hz
and there are more than 10 Transformers that supply loads to various voltage levels
(e.g. 6300V, 3300V, 480V, 380-400V). The average annual cost of electricity is
approximately 4.430.000 € in current prices.
Β. The scientific project of SEMAN DMCC
The scientific project for energy saving and current - voltage quality improvement has
been concluded by SEMAN DMCC at the end of July 2013.
In order to elaborate the scientific study for Rajhi Steel’s Electric Power Grid, the
engineers’ staff of SEMAN DMCC performed measurements and recordings (Pictures 5,
6, 7 & 10) – of all the required electrical values – in each individual load of the
installation (AC & DC motors, motors operating with Inverters, inductive furnaces, DC
Converters, Star- Delta switches etc. both in Low and Medium Voltage).
Picture 5: Laptops used for measurements and recordings
Measurements and recordings concerned the basic electric values (power, reactive
power, voltage, current, frequency) as well as current & voltage harmonics (up to the
35th class) and transient phenomena.
Inside the Electric Power Grid of Rajhi Steel Industry, transient phenomena occur not
only from the disturbances catering from Public Power Distribution Network, but also
from their own big electric loads that start and stop sharply during production days.
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Picture 6: Measurements have been performed also in the core of the electrical installation next to the loads
Moreover the engineers’ staff of SEMAN DMCC proceeded to the collection of all the
essential data that had to do with lengths and cross-sections of cables, number of
cables headed together in canals, nominal values of motors, power transformers and
many others also necessary for elaborating the scientific study for the energy saving
project.
Picture 7: Measurements with special power quality analyzers and laptops
Based on the above, the engineers of SEMAN DMCC were able to simulate the
behavior of Rajhi Steel’s Electric Power Grid and detect all the problems that were
causing bad quality of voltage and current, low electric loads and power transformers
efficiency, harmonic resonances and multiple other energy losses. The simulations
conducted are based on SEMAN DMCC’s know-how, which has been awarded by the
university of Cambridge and USA institutes. More particularly, models based on the
Finite Elements Method (FEM) in combination with load flow analysis were used to
complete all the required simulations (more information concerning SEMAN DMCC’s
simulation models can be found at http://www.seman.gr/F7FF7B13.en.aspx.
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The analysis of measurements and recordings showed that considerable harmonic
sources existed inside Rajhi Steel’s Electric Network, producing not only harmonic
currents (in some cases THD-I% reached 70% of the load),
Picture 8: Harmonic currents recordings in the electric network
but also considerable voltage harmonics.
Picture 9: Voltage harmonics recordings in the electric network
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Picture 10: Portable measurement devices
Moreover, a number of energy saving scenarios, for the specific Electrical Power Grid –
all based on the know-how of SEMAN DMCC – carried out by the use of simulations
and finally the scientific study concluded 38 customized interventions (please refer to
pictures 11, 12, 13, 14 & 15 for low voltage loads interventions and to pictures 16 & 17
for medium voltage loads interventions) that had been installed inside the Electric
Power Network of Rajhi Steel.
More specific:
12 interventions installed in LV 380V
20 interventions installed in LV 480V
2 interventions installed in LV 600V
4 interventions installed in MV 3,3kV.
The total installed power of the customized interventions for the voltage-current
quality improvement and energy saving project was 7,8MVA.
The target of the installed interventions is to minimize the current-voltage harmonics,
to improve the current-voltage quality of the electric installation of Rajhi Steel plant
and finally to achieve electrical energy saving. The Current – Voltage Quality
improvement will lead to energy saving due to the:
Maximization of the total efficiency of the Electrical Installation,
Improvement of motors’ efficiencies, due to:
the minimization of the counterclockwise electromagnetic torques
caused by harmonics and,
the reduction of voltage drops and the higher constant voltage to
the motors.
Improvement of power transformers’ efficiencies by the reduction of their
copper and iron losses,
Reduction of the following thermal losses:
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Thermal losses of supply.
Contiguity Effect Losses.
Skin Effect Losses.
Eddy Current Losses.
It should be mentioned that the design of each customized intervention for every
electrical load took into consideration not only the interactions with all the other
electrical loads of the network, but also the resonance frequencies of every electrical
power cable of the grid.
Picture 11: Customized SEMAN DMCC Energy Saving Intervention for Low Voltage (LV) load in Rajhi Steel plant
Picture 12: Customized Reactor of a SEMAN DMCC LV Energy Saving Intervention in Rajhi Steel plant
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Picture 13: Customized SEMAN DMCC Energy Saving Intervention for a rapidly variable Low Voltage (LV) load in Rajhi Steel plant
The customized interventions for voltage-current quality improvement and energy
saving are connected in parallel to the electric loads and lead to harmonics absorption
and their important reduction inside the electric installation of the factory.
Furthermore, resonance frequencies that could lead to dangerous tuning are being cut
off. PLC with special software design from Seman DMCC’s engineers, based on the
results of the scientific study, control the dynamic operation of each intervention
according to the fluctuations of every electric load and ensure the cutting of all
dangerous interactions between the loads.
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Picture 14: Customized SEMAN DMCC Energy Saving LV Harmonic Filter in Rajhi Steel plant
Picture 15: Details of a customized SEMAN DMCC energy saving intervention - Active LV Harmonic Filter in Rajhi Steel
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Picture 16: Medium Voltage (MV) customized SEMAN DMCC Energy Saving Intervention in Rajhi Steel.
Picture 17: Details of a MV customized SEMAN DMCC energy saving intervention in Rajhi Steel
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C. Results – Benefits
For the evaluation of the Power Quality Improvement and Energy Saving Project in
Rajhi Steel plant, measurements and recordings were taken place in two time periods
(July and October) with and without the interventions into operation. The
measurements and recordings were realized in presence of Rajhi Steel’s staff of
engineers.
Applying these measurements - recordings to the electricity invoices, by the use of a
specific algorithm – created in collaboration with Rajhi Steel’s Industry staff of
engineers & Rajhi Steel Managers, the results presented in Table 1 are concluded.
Table 1. Synoptic Results of the Power Quality Improvement and Energy Saving Project accomplished for the Rajhi Steel Industry
Value
Results
Guaranteed saving according to the contract (%) -10,15%
Saving achieved (%)
(according also to the attached Reference Letter by
Rajhi Steel Company Management) -15,74%
Guaranteed Pay Back Period of the project (years)
3,2
Real Pay Back Period of the project (years) 2,06
Annual Money Saving(€) 697.282,00 €
In addition, SEMAN DMCC’s scientific project inside the electrical installation of Rajhi
Steel plant in Jeddah, Saudi Arabia, had some extra benefits, confirmed also by the
recordings before and after the installation of the energy saving equipment and the
ascertainments of Rajhi Steel responsible Managers.
These extra benefits are the following:
1. Reduction of current & voltage harmonics up to 80%.
This significant harmonics reduction is easily notable by viewing the four Graphs
representing the comparison of the Currents and Voltage Harmonics before SEMAN
DMCC’s project in operation (Pictures 8 and 9) and after SEMAN DMCC’s project in
operation (Pictures 18 & 19)
2. Optimization of the voltage & current quality of the electrical power grid of the
factory.
3. Maximization of the efficiency ratio of the electric power grid, motors and power
transformers.
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4. Reduction of undesirable stopping of production lines because of the reduction of
sensitivity of load voltage supply to immersions of the voltage supplied by the
electricity provider’s Power Distribution Network.
5. Increase of the reserve and capacity charge of the electrical installation, which is a
positive factor for the future plant’s expansions.
6. Reduction of the maintenance cost concerning all the components of the electrical
installation, which according to the plant’s technical department led to an additional
reduction of the pay back period.
Based on all above, the Power Quality Improvement & Energy Saving Project of SEMAN
DMCC in Rajhi Steel plant was proven to be absolutely successful, as it is also
confirmed at Rajhi Steel’s Reference letter delivered to SEMAN DMCC.
(please refer to the attached file “Reference Letter by Rajhi Steel.pdf”)
Picture 18: Harmonic currents recordings in the electric network after Seman DMCC’s project
Picture 19: Voltage harmonics recordings in the electric network after Seman DMCC’s project