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ΤHE SCIENTIFIC ENERGY SAVING PROJECT OF SEMAN

IN HALYPS CEMENT PLANT

MEMBER OF ITALCEMENTI GROUP

Α. HALYPS CEMENT PLANT OF ITALCEMENTI GROUP.

Italcementi Group, having an annual production capacity of more than 60 million

tons and 46 cement plants, is the world’s fifth largest cement producer. Along with

the cement plants, Italcementi Group’s industrial network includes 12 grinding

centers, 6 terminals, 417 concrete batching units combining the expertise, know-

how and cultures of 22 countries across four continents.

Italcementi Group is operating in Greece through Halyps Building Materials S.A.

company. Halyps Building Materials S.A. is operating in cement activity under the

brand name “Halyps Cement”, in aggregates activity under the brand name "Halyps

Quarries” and in the concrete activity under the brand name "Et Beton", having

three production plants servicing the Attica region.

Picture 1: General Plant View

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Picture 2: General Plant View

Picture 3: Production Line

The total installed electric power of Halyps Cement Plant comes up to 30,5 MW. The

grid is in 50Hz and there are 13 Transformers supplying loads to various voltage

levels (e.g. 6300V, 550V and 400V). The average annual electricity cost is

approximately 7.143.672,79 € in current prices.

Β. The scientific project of SEMAN

The scientific project for electric energy saving and current - voltage quality

improvement has been concluded by SEMAN in March 2010.

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In order to elaborate the scientific study for Halyps Cement Electric Power Grid, the

engineers’ staff of SEMAN performed measurements and recordings of all the

required electrical values at each individual load of the installation (AC & DC motors,

motors operating with Inverters, DC Converters, Star- Delta starters, etc., both in

Low and Medium Voltage).

Picture 4: 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 Halyps Cement plant, transient phenomena occur

not only from the disturbances catering from the Public Power Distribution Network,

but also from its own big electric loads that start and stop sharply during production

days.

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Picture 5: Measurements have been performed also in the core of the electrical installation next to the loads

Moreover, the engineers’ staff of SEMAN proceeded to the collection of all the

essential data regarding the lengths and cross-sections of cables, the number of

cables headed together in canals, the nominal values of motors, the power

transformers and many other data also necessary for the elaboration of the scientific

study for the electric energy saving project.

Picture 6: Measurements with special power quality analyzers

The analysis of measurements and recordings showed that considerable harmonic

sources existed inside the Electric Network of Halyps Cement, producing not only

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harmonic currents (for example, at the ID FAN drive, THD-I% reached 45% of the

fundamental - see Pic. 7), but also considerable voltage harmonics.

Picture 7: Harmonic currents recordings in the electric network

Picture 8: Voltage harmonics distortion % recordings in the electric network

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Picture 9: Portable measurement devices

Running a number of simulations according to SEMAN’s know-how for the Electrical

installation of Halyps Cement plant, the electric energy saving scientific study

concluded that 34 customized interventions should be installed at all voltage levels

(please refer to pictures 10, 11 for low voltage loads and to pictures 12, 13 for

medium voltage loads).

The total installed power of SEMAN’s customized interventions for the voltage-

current quality improvement and electric energy saving project was 10,5MVA.

It should be mentioned that most of the above specialized interventions are

Thyristors switched (please refer to pictures 14 and 15). These Thyristor Switched

interventions have been designed from SEMAN’s engineers especially for the power

system of Halyps Cement plant, which requires instantaneous harmonics absorption

and VAr support to mitigate voltage sags, voltage flicker and high inrush currents

associated with large dynamic loads and motor starting. The answering time could

be as less as 20 milliseconds. Moreover, the inrush currents are the minimum, as the

filter steps of SEMAN’s customized interventions are switched at "zero current cross

over threshold”.

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Picture 10: Low Voltage (LV) SEMAN’s customized interventions

Picture 11: Low Voltage (LV) SEMAN’s customized interventions connected to the motor’s terminal

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Picture 12: Medium Voltage (MV) SEMAN’s customized intervention

Picture 23: Detail of a MV customized intervention of SEMAN

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Picture 34: Thyristor Switched customized intervention of SEMAN

Picture 15: Details of a Thyristor Switch

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The target of the installed customized interventions was to:

maximize the total efficiency of the electrical installation,

improve motors’ efficiencies, through:

the minimization of the counterclockwise electromagnetic torques

caused by harmonics and,

the reduction of voltage drops and the higher constant voltage to

the motors.

improve power transformers’ efficiencies by the reduction of their copper

and iron losses,

reduce the following thermal losses:

Thermal losses of supply.

Contiguity Effect Losses.

Skin Effect Losses.

Eddy Current Losses.

According to SEMAN’s scientific tools for the simulation of electrical installations,

such as the finite elements method along with load flow analysis, all interferences

between the electrical loads of the plant and all possible resonance frequencies of

current harmonics at cables, subpanels and power transformers were calculated. The

results of the above simulations led to the final design of the customized

interventions, which can operate in any operation scenario of the installation.

Furthermore, an extensive spread Power Quality Measuring System has been

developed at the Electrical Installation of Halyps Cement Plant. 37 Power Quality

analyzers (please refer to pictures 16 and 17) have been installed at different places

of the plant, measuring all the electrical values of certain electric loads. All the 37

devices are interconnected using fiber optics, profibus and network cables. The

purpose of the established network is to transfer the measured values to a central

SCADA system (please refer to pictures 18 and 19). The operation and control with

this center’s interface is being made via Programmable Logic Controller (PLC). PLC is

running the well-known WinCC Premium software by SIEMENS. The SIMATIC WinCC

Powerrate add-on provides transparency for energy consumption from the power

supply to the user. Energy data is continuously collected, archived and further

processed. Exact knowledge of the consumption profile and detailed information

about the costs involved allow the user to identify savings potential, optimize the

energy import, and thus, lower the energy costs. This transparency enables energy

consumption to be optimized while being fully integrated into the WinCC

environment.

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Picture 15: Power Quality Measuring Systems

Picture 16: Power Quality Analyzer

Picture 17: General View of SCADA system visualization

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Picture 48: Detail of SCADA system visualization

C. Results – Benefits – Conclusions

After the completion of the project, measurements and recordings were performed

that demonstrated significant reductions in rms consumption currents, improvement

of voltage levels, reduction up to eradication of the requested reactive power. The

evaluation of SEMAN’s energy saving project result was realized according to the

methodology described in the relative International Bibliography:

[1] Council Regulation (EEC) No 1836/93 of 29 June 1993 allowing voluntary

participation by companies in the industrial sector in a Community eco-management

and audit scheme.

[2] International Performance Measurement & Verification Protocol. Concepts and

Options for Determining Energy and Water Savings, Volume 1, Revised March 2002.

[3] North American energy M&V protocol, version 1March 1996.

Specifically, by using historical data of the electric energy consumption and

operation of the several sections of the plant before the electric energy saving

project, a mathematical model was developed, based on regression analysis,

correlating the monthly electric energy consumption with the monthly operational

data of the plant (such as production data of the various plant departments,

operational hours, etc). The correlation accuracy of the mathematical model was

very good, as the average prediction error for the historical data was only 0,73%.

By applying this accurate mathematical model to the months followed project

implementation, it was calculated with great accuracy the energy consumption of

each month if SEMAN’s saving project had not been carried out. By comparing each

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month these calculations with the real energy consumption (extracted by the

monthly electricity bills of the plant) in the presence of SEMAN’s customized

interventions, the final electric energy saving and also the cost saving result in the

electricity bills was calculated. The aggregated results are analytically presented in

the following Table 1.

Table 1. Synoptic Results of SEMAN’s Electric Energy Saving Project accomplished for Halyps Cement Plant

Value Results

Guaranteed Electric Energy Saving according to the contract (%) -5,32%

Real Electric Energy Saving finally achieved (%)

(according also to the Reference Letter by Halyps Cement Company

Management)

-9,00%

Guaranteed Pay Back Period of the project (years) 3

Real Pay Back Period of the project (years) 1,8

Annual Money Saving (€) 642.930,00 €

Picture 19: Harmonic currents recordings in the electric network after SEMAN’s project

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Picture 20: Voltage harmonics distortion % recordings in the electric network after SEMAN’s project

In conclusion, SEMAN’s scientific project in the electrical installation of Halyps

Cement plant had some extra benefits, as confirmed also by Halyps Cement staff.

Some of these extra benefits are the following:

1. Reduction of current & voltage harmonics up to 40%. Before (See Pic 8 & 9)

and After (See Pic 19 & 20) SEMAN’s interventions.

2. Optimization of the voltage & current quality in the electric installation of

the plant.

3. Increase of the efficiency of the electric power grid, motors and power

transformers.

4. Reduction of production lines’ undesirable halts, due to the decrease of load

supply voltage sensitivity, caused by voltage dips and the instability of the

electricity provider’s Power Distribution Network in general.

5. Increase of electrical installation’s reserve.

6. Reduction of the maintenance cost concerning all components of the

electrical installation.

Taking everything into account, SEMAN’s project was considered totally successful y

Halyps Cement staff, which, also, sent a congratulatory reference letter.