thyssenkrupp application of filters for 5th and 7th

THYSSENKRUPP | Case Study

1

CASE STUDY

THYSSENKRUPP Application of filters for 5th and 7th harmonics on 800 VAC

Background:

Even when the application of absorption filters for harmonic currents is well known and experienced by Arteche in low-voltage systems (240V and 480V), on this occasion the challenge was to adjust the standard filter design for their fitting at voltage of 800 Vac. The application took place on the company premises of Thyssenkrupp

Metalúrgica de México S.A. de C.V., devoted to manufacture of rods for motors and located in the township of San Miguel Xoxtla very near the city of Puebla. Among the most important processes carried out in this plant are the casting and treatment of steel for which induction furnaces are operated which use electrical energy through different sub-stations of the plant at 800 Vac. These furnaces are operated by six-pulse rectifier circuits and are coupled electrically to double-secondary transformers, supplied by a general bus of 6200 V, originating from the plant’s main sub-station and provided at 115 kV, 3 Phases, 60 Hz, by a C.F.E. power-line. The plant previously operated with a monthly electrical power requirement of 6MW and PF of 0.83, thus requiring correction of the PF in a secure manner, for prevention of the penalizations received from C.F.E. and reducing the plant’s present outgoing harmonic currents. Development:

Arteche carried out an electrical assessment of the plant’s power system in order to determine the necessary specifications and features for performing the task in a secure and reliable manner. Technical and financial suggestions were submitted for which the company decided to invest in harmonics filters with two stages: the first for prevention of low-PF penalties and the second, once the results were known, toward obtaining the PF-related bonus from C.F.E. and also considering the energy savings attained.

In February of 2005 the first stage of the project was carried out, in which two absorption filters for harmonic filters were installed, with the specifications 800 kVAR, 800 V, each in the secondary sections of the transformer supplying the plant’s 3000 FURNACE. The following diagram shows the electrical lay-out of the harmonics filter location.


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CASE STUDY

Design:

Voltage levels were taken into account for the design of filters, as well as the harmonic distortion levels and traditional merit figures for harmonic filter calculations, in all filters and each of the filters’ components.

Section of the 5th harmonic

Section of the 7th harmonic

Results: *The measurement was carried out on the secondary with star-connection of the transformer. Due to the voltage level between phases, it was not possible to carry out a measurement on the secondary with a delta connection. However, the behavior of both secondaries is expected to be equivalent.

It was observed that when the filter was energized, the value of total RMS current in the transformer’s secondary decreased by 38%, the harmonic distortion in the voltage wave by 39%, harmonic distortion in the current wave fell by 48% and the power factor rose to unit value. These indications constituted an unburdening of the transformer from reactive and harmonic load and reduction of its electrical losses.

The global Power Factor of the plant, once the equipment had been installed was 0.926i, according to the electrical invoice for the month of April 2005. Given the global PF value achieved, the plant has ceased to pay the penalty levied for this reason, besides having already received a bonus for operating at a PF level above 0.90.

The following table shows a summary of electrical values before and after the installation of the filters:

200 600 k V AR k V AR

FURNACE 3000 2000 k V A 6.3 / 0.765 kV Z = 5.4%

6.3 k V , 3 Phases, 60 Hz

1500/5A TC PHASE A

1500/5A TC

PHASE A

RECTIFIER, 6-PULSE

FURNACE 3000

RFP RFP 1250 A 1250 A

5 A 7 A 5 A 7 A

200 600 k V AR k V AR

HARMÓNICS FILTER 800 k V AR, 800 V , 3F 5 ta. y 7 ma. armónicas Inelap S.A. de C. V .


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CASE STUDY

Sub-station

(area)

kVAR

installed

Tension

(Volts)

Demand

kW

HORNO 3000*

800 (2) 780 377

Total Current (Amps) THD (V) %

With filter W/o filter With filter W/o filter

310 500 4.98 8.27

THD (I) % Power Factor

With filter W/o filter With filter W/o filter

19.78 38.4 1.00 0.68

With the above, the plant is no longer paying penalizations relating to PF and with the savings achieved it is estimated that the investment in equipment will be redeemed in 9.5 months.

The following charts show the waveforms and harmonic spectrums for the result of the application of filters in the plant’s power system.

Measurements without filter

1000 750

500

250 0

-250

-500

-750 -1000

1000 750 500

250 0

-250

10:52:59:835 10:52:59:840 10:52:59:845 10:52:59:85 0 10:52:59:855 10:52:59:860 10:52:59:865

-500 -750

-1000 CH A V olt s CH A V olts

Amps V olts Waveforms for Voltage and Current

Harmonic voltage spectrum

CH A Amps T otal RMS: 444.52 V olts

DC Level: 0.55 V olts

Even contribution (H02- H30): 1.28% of FND Odd contribution (H03-H-29): 8.17% of FND

Fundamental (H1) RMS: 438.35 V olts T otal Harmonic Distortion (H02-H30): 8.27% of FND

% of FND 9 8 7 6 5 4 2 1 0 Thd H05 H30 H10 H15 H20 H25

Harmonic current spectrum

CH A Amps DC Level: 7.46 V olts

T otal RMS: 301.98 V olts

Even contribution (H02- H30): 15.43 % of FND Odd contribution (H03-H-29): 30.74 % of FND

Fundamental (H1) RMS: 261.33 V olts T otal Harmonic Distortion (H02-H30): 34.40 % of FND

% of FND 35 30 25 20 15 10 5 0 Thd H05 H10 H15 H20 H30 H25


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CASE STUDY

Measurements with filter

Avg

CHTOT PF (arit) avg -0.25

CHA VThdavg 9.74

CHA IThdavg 26.11

Avg

CHA VHarm (300Hz) 13.44

CHA VHarm (420Hz) 10.29

25

20

Volts Performance of voltage in 5th and 7th harmonics

15

10

5

10:55 10:50 10:45 10:40 0 10:2 0 10:2 5 10:3 0 10:35

CH A VHarm (300 Hz) 17/05/2005 10:24:59.79 - 17/05/2005 10:54:00.00

CH A VHarm (420 Hz)

% 0.75

Performance of THD, V, THDI and FP

0.50

0.25

0.00

-0.25

-0.50

-0.75

-1.00 10:55 10:50 10:45 10:40 10:35

CH A VThdavg 10:2 0 10:25 10:30

CH T O T PF (arith) avg

30

CH A IThdavg

25

20

15

10

5

17/05/2005 10:24:59.79 - 17/05/2005 10:54:00.00

1000 750 500 250

0 -250 -500 -750

-1000 10:52:59:850 10:52:59:855 10:52:59:835 10:52:59:840 10:52:59:845 10:52:59:860

1000 750 500 250 0 -250 -500 -750 -1000

CH A V olts CH A V olts

V olts Waveforms for Voltage and Current Amps

CH A Amps T otal RMS: 451.33 V olts

DC Level: -0.86 V olts



H05 H30 H10 H15 H20 H25 Thd

Harmonic voltage spectrum 5 % of FND 4

2 1 0

Harmonic spectrum of current % of FND 20.0 17.5 15.0 12.5 10.0

7.5 5.0

Thd H05 H10 H15 H20 CH A Amps

T otal RMS: 3 1 1.10 V olts DC Level: -1.93 V olts



H30 H25 0.0 2.5


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CASE STUDY

Avg

CHA IHarm (300Hz) 76.66

CHA IHarm (420Hz) 42.91

Performance of voltage in 5th and 7th harmonics

120 Amps

1 10

100

90

80

70

60

50

40

30

20 10:20 10:25 10:30 10:35 10:4 0 10:45 10:50 10:55

17/05/2005 10:24:59.79 - 17/05/2005 10:54:00.00

CH A IHarm(300Hz ) CH A IHarm(420Hz)

thyssenkrupp application of filters for 5th and 7th

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