Commissioning Test For Power Transformer

Published Date: 02 Nov 2017

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND OF STUDY

Nowadays, transformer is most important equipment in electrical power transmission and power distribution system. The transformers are usually very reliable, with a 20-35 year design life with in practice. The transformer is an electrical device that transfers energy by inductive coupling between two or more of its winding for transforming power from one circuit to another circuit without changing frequency. Transformer works only with varying electric current where the primary winding creates a varying magnetic flux in the transformer ‘s core and thus it have varying magnetic flux through secondary winding or electromotive force (EMF) process will be happen. The transformers are very important in the distribution of electric power because they raise the voltage of electricity generated at the power plant on higher level before transmit the electricity to consumer using transmission network.

The transformers are classified into mainly categories which is power transformer and distribution transformer. The difference between power transformers and distribution transformers is depends on their rated power. Power transformers are used in transmission network of high voltages and are generally their rated power is above 200MVA. For the distribution transformers are usually used for distribution network where the secondary voltage is almost the voltage delivered to the end consumer and generally the rated power is lower than 200MVA.

Commissioning test for power transformer should to be done to verify the technical suitability for the application and check the healthiness or condition of power transformer before energizing by connecting to the power supply system and loading the load. For confirming that power transformer is follow the specification and performances according customer needs based on the specification set by manufacturer of power transformer, some of testing procedures should to be done. The pre commissioning test result should to compare with manufacture test result (basically on transformer name plate or manual guideline) and international standard (IEEE STANDARD or INTERPLANT STANDARD-STEEL INDUSTRY, Code Of Practice For Testing And Commissioning Of Power Transformer And Related Switchgears, IPSS: 1-04-035-08). The INTERPLANT STANDARD covers guidance on testing and commissioning of power and distribution transformer.

In this project, the power transformer on rated 30000KVA, 33KV/11kv, has to be set up on Penang Port Sdn. Bhd. After the installation, pre commissioning test are done to ensure that power transformer has not suffered damage during transit or any inadvertent slips in the factory test result and thus it can loading the load for the port and meet the consumer requirement. The pre commissioning tests performed are insulation resistance test, transformer ratio test, dc winding resistance test and temperature rise test (oil and winding temperature).

1.2 PROBLEM STATEMENT

Transportation of power transformer to site could well have involved a far journey, maybe around of many hundreds of miles, and possibly by sea using ship.

By the long journey when transportation, sometimes the power transformer has a suffered damage.

1.3 OBJECTIVE

The objective of this paper is

To affect the safe and orderly handover of the power transformer from manufacturer to the customer (Penang Port Sdn. Bhd.), guaranteeing its operation in term of performance, reliability, and safety.

To assess the condition of power transformer after installation

To compare the test results of all the low voltage tests with the manufacturer of transformer test reports.

1.4 SCOPE OF WORK

This project describes methods for performing pre-commissioning tests for power transformer at site (Penang Port Sdn. Bhd.) based on IEEE Standard C57.12.01-1998 and INTERPLANT STANDARD-STEEL INDUSTRY IPSS: 1-04-035-08, as a reference and guidelines. This project also to ensure that power transformer is met the customer requirement according the power transformer manufacturer test report. It is intended for use as a basic for performance, safety, and the proper testing for power transformer after installation at site. The standard applied on pre-commissioning test is to all type of power transformer included instrument transformer step-voltage, tap changing, winding resistance, vector group, polarization index and insulation of transformer.

1.5 SIGNIFICANT OF STUDY

To study about pre-commissioning test of power transformer.

To compare the testing result with manufacture test report.

To ensure that the transformer meet the specification and fulfil the customer requirement.

THESIS ORGANIZATION

This thesis is carefully organized in order to explain about the overall research. This thesis consists of six chapters. Below shows the contents of each chapter:

Chapter 1

Chapter one is the introduction chapter. It contains the background of study, problem statement, objective, scope of work and also significant study.

Chapter 2

Chapter two explain about the literature review of the whole research. In this chapter, it consists of explanation about pre-commissioning test such as insulation resistance test, transformer turn ratio test, DC winding test and temperature rise test for oil and winding temperature.

Chapter 3

Chapter three shows about the background of Penang Port Sdn.Bhd. where power transformer has been set up at there. Therefore, pre-commissioning test carried out there.

Chapter 4

Chapter three shows the methodology in about procedures for each pre-commissioning test. It also shows the guide lines where the tester should be follow before doing the test.

Chapter 5

Chapter four is the result and discussion chapter. It shows and discusses the results that obtained from the each test, and compared the result with international standard and manufacture of power transformer test report.

Chapter 6

Chapter five concludes all the works in this research and also suggests the recommendation for future development for the device enhancement.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

In this chapter the material, device application and testing techniques used in this research was discussed. All low voltage tests are should to be done to assess the condition of power transformer after installation and compare the test results of all the low voltage tests with the manufactures’ test reports before power transformer loading the load. Testing of power transformer is fall into three categories. First test is to ensure that the power transformer has been built correctly according international standard and met the specification (pre-commissioning test). The test usually includes insulation resistance test, transformer turn ratio test, DC winding resistance test, temperature rise test and others. For the second test of power transformer is to prove as guarantees (actual commissioning). The test is after the power transformer has connected the supply and loading the load. The test is to find the losses, impedance, temperature rise and noise level. The third tests is to prove that the power transformer will be satisfactory in service for a long time (preventive and maintenance) where the test includes all the dielectric or overvoltage tests and load current runs. Transportation of power transformer to site could well have involved a far journey. Pre-commission testing which have to be done at site which can demonstrate that it has not suffered damage and the test can be carried out at site should be done as carefully and thoroughly [2]. Before pre commissioning test of power transformer 33KV/11KV performed by tester, the tester should get data about the power transformer from manufacturer. Basically, the manufacture test report is in accordance with the international standard (IEEE STANDARD C57.12.80-1978 or INTERPLANT STANDARD-STEEL INDUSTRY IPSS: 1-04-035-08).

2.2 INSULATION RESISTANCE TEST

Insulation resistance test applied for transformer is to measure the insulation resistance is strongly recommended or not to prevent the electrical shock, assure human and environment safety. This test also to detect the leakage current and to detect deterioration of insulation in order before commissioning of transformer before connecting of the power supply and loading the load. Otherwise the IR test used for an transformer installation requirement to know that their specifications are met and also used for periodic preventive maintenance task There have more common causes on insulation failure such as excessive heat or cold, moisture, dirt, corrosive, oil, aging and internal nicked wiring on transformer.

Figure 2.2: Connection for IR Test on transformer

Transformers are tested at above the rated voltage to be certain there are no excessive leakage paths to ground and to windings. There have two types for insulation resistance test applied for transformer.

2.2.1 Single-Phase Transformer

Include five tests with one minute time duration for each test such as;

Low voltage winding to high voltage winding and to ground.

High voltage winding to low voltage winding and to ground.

High voltage winding to low voltage winding.

Low voltage winding to ground.

High voltage winding to ground.

Figure 2.2.1: Connection IR Test for single phase transformer

2.2.2 Three-Phases Transformer

Include four tests similar with IR Test for single-phase but the connection for ground must to replace for guard and also take around one until ten minutes time duration for each tests such as;

High voltage winding to low voltage winding and to ground.

High voltage winding to ground but low voltage winding to guard.

High voltage winding to low voltage winding.

Low voltage winding to ground and high voltage winding to guard

Figure 2.2.2(a): Internal connection Delta to Wye on transformer

Figure 2.2.2(b): Connection IR Test for three-phase transformer

2.2.3 Insulation Resistance On Pre-Commissioning Of Power Transformer

The insulation resistance test (IR Test) is an insulation test which uses an applied DC voltage (5KV) for electrical part to measure insulation resistance in KΩ, MΩ, or GΩ. The measured insulation resistance is intended to indicate the condition of dielectric or insulation between two parts of conductive, where the higher resistance is the better condition of the resistance [2]. Generally, insulation resistance would be infinite, but as no insulators are perfect where leakage currents through the dielectric will ensure that a finite resistance value is measured. The Table 1 showed the acceptable resistance in IR Test with difference of winding insulation class in KV.

Table 1: Acceptable value of resistance for IR Test.

Winding Insulation class, kV

Insulation Resistance, MΩ

1.2

600

2.5

1000

5.0

1500

8.7

2000

15

3000

2.3 TRANSFORMER TURN RATIO TEST

The performance of a transformer is depends perfection of specific turns ratio of transformer. Transformer turns ratio test is very important to find out that the power transformers have a ratio corresponding on its rated voltage at primary and secondary follow the specification [1]. Measurements should be within add or mines 0.5 per cent of the ratio value stated on the power transformer nameplate. In an ideal transformer, the induced voltage in the secondary winding (Vs) is proportional to the primary voltage (Vp) and it given by ratio of the number of turns in primary to the number of turn in the secondary [5]. This figure showed the ideal transformer and equation of the proportion;

Figure 2.3(a): Schematic diagram of ideal transformer

Figure 2.3(b): Bridge connection for measuring the turn ratio of transformer

The theoretical turn ratio is adjusted on primary side (transformer turn ratio tested or TTR). The reading on this indicator implies the deviation of measured the turn ratio in percentage.

Deviation in percentage=

For the open turns in primary side winding, it will indicate very low voltage exciting current and no output voltage since open turns in primary winding. It because there have no excitation current or induced voltage. While open turn on secondary side can causes low fluctuating on secondary voltage and maybe affect the winding like figure 2.2 (c).

Figure 2.3 (c): Damaged transformer winding

2.4 DC WINDING RESISTANCE TEST

Measuring the resistance of the winding in transformer is to ensure that the connections winding are correct and good condition and resistance measurements indicates that there are no mismatches or broken. In addition, the test is to ensure Winding resistance measurements in power transformers are of fundamental importance for the following purpose [10];

Calculations of the conductor losses

Measurement of winding temperature at the end of the temperature test cycle

As a base for assessing possible damage in the field

The resistance in the winding should below then 0.5Ω follow the standard from IEEE specification. The tap changes of transformer allow ratio to be increase or decrease by fractions of a per cent and that is involve a mechanical movement of a contact from 1 position to other position [10].

Generally in the dc winding resistance test is impossible to measure the windings temperature which is can affect the result of test. That because windings of transformer usually are immersed in insulation liquid and covered with paper insulation. Therefore the tester should assume that temperature of winding is similar with average temperature of insulating oil in transformer. That because the average temperature of insulating oil should be taken three to eight hours after de-energizing transformer. The winding resistance can be measured by simple voltmeter and ammeter at primary side then applied basic equation (R=V/I) to find the resistance. But the result should be less than 15% of the rated current of the winding. If the result is higher than 15% of the rated current, it may cause inaccuracy by heating the winding and thereby changing their winding temperature and resistance.

Procedure of transformer winding resistance test is;

For the delta connected winding at primary side, the resistance shall be measure between the pairs of line terminals.

The resistance on winding have measure by the calculation on

R = V/I (1)

where voltage and current is measure on high-voltage side by phase to phase on transformer for each tap using multimeter.

2.5 TEMPERATURE RISE (OIL AND WINDING)

Temperature rise test of power transformer is including the pre commissioning test of transformer. The test is shows the tester check whether the temperature rising limit of power transformer winding and oil as per specification or not. If the temperature of transformer is very high, its can cause accelerated aging and their inaccurate measurement limits transformer loading.

Oil temperature can be measured and displayed, but it is more difficult to assess the winding temperature. One method of gauging the temperature of the hottest part is by the use of resistance in the form of thermal models by being immersed in it, and on the other of transformer load current, by caring a current proportional to the load. Using the temperature indicator meter, the tester can get the temperature for oil and primary winding by the setting of thermometer temperature where the thermometer has been immersed in the oil. Indicators operation for alarm and trip contact shall be checked by manual stimulation. Figure 2.5 showed the temperature indicator meter on power transformer.

Figure 2.5: Temperature Indicator Meter

CHAPTER 3

PENANG PORT SDN BHD

3.1 BACKGROUND OF PENANG PORT

Penang Port Sdn. Bhd. (PENANG PORT) is a company where it’s fully owned by the Minister of Finance (Incorporated) on 1 January 1994. That company has a licensed by Penang Port Commission to operate, manage and maintain all port facilities and services. Penang Port provides several services such as container service, cargo service, and transportation service includes ferry and ancillary services (pilotage, towage and ship repair at dockyard). Therefore, Penang Port requires a lot of energy because all the services provided is a heavy industry.

Figure 3.1: Penang Port Sdn. Bhd.

3.2 PENANG PORT ELECTRICAL INSTALLATION

The Penang Port electrical distribution systems begin from the incoming source from Pencawang Masuk Utama (PMU) Chain Ferry 132KV/33KV through underground cable to the main substation of Penang Port. The main substation (PPU) for Penang Port has used two power transformers 30MVA, 33KV/11KV and type of power transformer is DOTW 30000/30 from SGB Sdn. Bhd. The rated power for each transformer is around 30000KVA. From the PPU, the electric has distributes to ten substation in North Butterworth Container Terminal. To meet the needs of heavy industry, Penang Port Sdn. Bhd. decided to build a new substation.

Figure 3.2: North Butterworth Container Terminal

3.3 SUBSTATION

Substation is part of electrical where it has transformer and switchgear. The substation has included transformers to change voltage levels between high transmission voltages and lower distribution voltages like substation at Penang Port. The input for the each distribution substation at Penang Port is around 11KV. They used underground cable to connect the substation with main substation (PPU).

Figure 3.3(a): Substation no 3 at Penang Port

Figure 3.4(b): Switchgear in substation

3.4 POWER TRANSFORMER

Power transformer is used for the transmission purpose at heavy load at least around 33KV above. Power transformer is used in transmission network and usually they are not directly connected to the consumers because they transmit the high voltage. But, for the power transformer where is used in distribution network like at substation of Penang Port. The new power transformer has been installed at substation on Penang Port. The type of new power transformer is DOTW 30000/30 and the rated power is around 30MVA. Therefore, after the power transformer installation complete, pre-commissioning should be done to ensure that power transformer is in good condition.

Figure 3.4: Power transformer 30MVA, 33KV/11KV.

CHAPTER 4

METHODOLOGY

4.1 INTRODUCTION

Before do the testing, the testers must be following the guideline to avoid the most accident because testing work on transformer need to be done carefully and cautiously. The study of pre-commissioning test is done based on the data from primer source including observation at site and data from secondary source which is includes books, journals, internet searching, information from the Institute of Electrical and Electronic Engineering (IEEE) and Qifays Enterprise (PKK Class II & MOF Registered Bumiputra Contractor. The observation of pre-commissioning test has been done at Penang Port Sdn. Bhd. Pulau Pinang. The observation for installation of power transformer on site is done before the power transformer connect the supply and loading the load. Some reading and photograph was taken as additional data.

Figure 4.1(a): Manufacture of power transformer

Figure 4.1 (b): Installation of power transformer on site

Figure 4.1 (c) showed the flow chart when doing overall of the testing on power transformer for pre-commissioning.

Start

Data acquire and data collect

Testing work

Required equipments and materials

Literature review (studied about previous project of pre-commissioning)

Expected result No

Data analysis Yes

End

Figure 4.1 (c): Methodology for pre-commissioning testing

4.1.1 Site Visit

The initial site survey should be design to obtain as much information as possible about the condition and the problem experience. Site surveys are generally performed to evaluate the site where the power transformers have been installed. In addition, the tester should be study about the manufacture test report of power transformer before pre-commissioning test begins.

4.1.2 Data Collection

The data should be taken after every pre-commissioning test and compare the result with manufacture test report. After that, all result has been analysed. The manufacture’s test report can be referring to transformer nameplate like Table 2 on page 37. For the international standard can be referring on appendix in page……..

4.2 INSULATION RESISTANCE TEST

This test is carried out to ensure the healthiness of over insulation system of an electrical part of power transformer. Before measure the insulation resistance, the tester should be ensuring that all connection in the test circuit is tight. Then before testing, the tester should test the "finger" of this equipment must show INFINITY value when not connected, and ZERO when the two terminals are connected together (short circuit). During testing, the tester should to connect one terminal in to earth, and the other terminal must connect to electrical part [3].

The tester should inject the DC voltage using IR Test equipment (5KV) on electrical part such as primary side to earth, secondary side to earth, and primary to secondary. Time duration of the insulation resistance test shall be one minute minimum for the first test and ten minute minimum for the second test.

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Figure 4.2 (a): Insulation resistance test equipment

The voltage injection by IR test equipment shall be applied between;

Primary to secondary plus ground (covered during switchgear test).

Secondary to primary plus ground.

Secondary core to core.

Insulation resistance test procedure shall be applied between;

Isolate the equipment, apply working ground to all incoming and outgoing cable (disconnect) from the transformer bushing terminals connections.

Ensure the transformer tank and core must be grounded

Disconnect fan system, meter control and all lightning arresters.

Short circuit all winding terminal of the same voltage level together.

Perform IR test until one minute for each circuit for first test and 10 minute for the second test.

Remove all shorting leads after test complete and discharge the electrical part.

4.2.1 Flow Chart For Insulation Resistance Test

Start

Data acquire and data collect

Study about insulation resistance of power transformer

Required insulation resistance test equipment

Setup the circuit and testing work begin

Expected result No

Data analysis Yes

End

Figure 4.2 (b): flow chart for insulation resistance test

4.3 TRANSFORMER TURN RATIO TEST

Ratio between all the three corresponding primary and secondary phases is to be measured on all each taps. Disconnect all the line and neutral terminal on transformer. The tap changer of transformer is kept in the lowest position and secondary terminals are kept open.

Transformer turn ratio test procedure shall be applied between;

The tap changer of power transformer must keep in the lowest position and the secondary side terminals are kept open.

Apply 3-phase 415V supply on primary terminals.

Measure the voltages applied on each phase at primary (phase to phase) and induced voltages at secondary terminals simultaneously.

Repeat the same for each of the tap position separately.

Figure 4.3 (a): transformer turn ratio test of power transformer

4.3.1 Flow Chart For Transformer Turn Ratio Test

Start

Study about turn ratio of power transformer

Required multimeter (Voltmeter and ammeter)

Setup the circuit and applied 415V on HV side

Data acquire and data collect

Expected result and compare with nameplate

No

Data analysis Yes

End

Figure 4.3 (b): Flow chart for transformer turn ratio test.

4.4 DC WINDING RESISTANCE TEST

By the configuration transformer delta-wye, the measurement is made phase to phase and comparisons are made to determine for each tap, if readings are comparable [8]. The tester has to apply dc current through the winding and internal standard current shunt. The resistance on winding have measure by the calculation on;

R+ (Ldi/dt) = Vdc/I (2)

Where;

Vdc = voltage across transformer winding

I = DC current through transformer winding

R =resistance of the tranformer winding

L = inductance of the trancformer winding

di/dt= changing value of current - riple

where voltage and current is measure on primary side by phase to phase on transformer for each tap using multimeter. From that, we can calculate the winding resistance on primary side using equation (2). Inject for example 5V on dc voltage on primary side before get the actual data (voltage and current) in the winding. The acceptable of windings resistance usually from 0.1ohm until 0.5ohm. For the secondary side, dc winding resistance test must to do but if the winding resistance at high-voltage side is acceptable, the tester just measure on one taps only.

DC winding resistance test procedure shall be applied between;

The power transformer should be kept in off condition without excitation.

Applied dc supply (variable voltage, example 5V) to primary side.

Measure the voltage and current at primary side for each phase.

To minimize observation error, polarity of the core magnetization shall be kept constant during all resistance readings.

The voltmeter shall be independent of the current leads.

The reading have be taken after the voltage and current have reached steady state values.

The primary side of transformer is delta connection, so that the resistance per phase would be 0.67 times of measured resistance between two line terminals of the transformer.

Figure 4.4 (a): Current and voltage of delta winding resistance

measurement for one phase.

4.4.1 Flow Chart For DC Winding Resistance Test

Start

Study about winding resistance and connection the test

Required multimeter (Voltmeter and ammeter)

Setup the circuit and applied variable voltage on HV side

Data acquire and data collect

Expected result and compare with International standard (IEEE)

No

Data analysis Yes

End

Figure 4.4.1(a): Flow chart for DC winding resistance test

Figure 4.4.1(b): analog multimeter

4.5 TEMPERATURE RISE TEST (OIL AND WINDING)

A temperature indicator calibration system including a well including a well for receiving a temperature sensor such as thermometer and thermocouple, and a heater for heating the well to desired and adjustable temperature[4]. Setting temperature at range 40celcius to 120celcius using thermometer like figure 4.5 (a) and data for temperature for oil and winding have been recorded.

Temperature rise test procedure for oil transformer shall be applied between;

Low voltages winding of the transformer have to be short circuit.

Using three thermometers, first thermometer is placed in transformer top cover, second thermometer at inlet and outlet of the cooler transformer.

During the test, hourly reading of top oil temperature are taken using temperature indicator meter from the thermometer already placed in top cover

Temperature rise test for oil should be continuing until the top oil temperature has reached an approximate steady value.

Temperature rise test procedure for winding transformer shall be applied between;

The current is reduced to its rated value for power transformer after temperature rise for oil test completed

After one hour, switch off the supply and short circuit connection to the low voltage side are opened.

The temperature of winding transformer have be recorded by increasing the temperature of thermometer

Figure 4.5 (a): thermometer for temperature rise test

4.5.1 Flow Chart Of Temperature Rise Test

Start

Study about temperature rise for oil and primary winding

Required thermometer

Setup the circuit and adjusted the temperature of thermometer and immersed into the oil transformer tank

Data acquire and data collect by temperature indicator meter

Expected result and compare with International standard (IEEE)

No

Data analysis Yes

End

Figure 4.5.1 (b): Flow chart of temperature rise test

CHAPTER 5

RESULT AND DISCUSSION

5.1 TRANSFORMER NAME PLATE DETAIL

Table 2: Transformer name plate

Make

SGB

Year Of Manufactured

2009

Rated Power

30000KVA

S/Number

716471

Type

DOTW 30000/30

Total Weight

48500kgs

Vector Group

DYN 11

Total Mass

-

Rated Impedance at 75°C Tap 7 = 13.12

Min. Tap = 1

Centre Tap = 7

Max. Tap = 16

Tap

HV

LV

Oil Raise Temp.

50°C

Volts

Amp

Volts

Amps

Ratio

1

36300

477.2

11000

1575

3.3

Winding. Temp. Raise

55°C

2

35750

482.5

3.25

3

35200

492.5

3.2

Rated Freq.

50Hz

4

34650

500

3.15

5

34100

507.2

3.1

HV Winding. CT

(CT1)

Ratio: 1575/1.5

10VA

Class: 5

6

33550

516.4

3.05

7

33000

525

3

8a

LV Winding. CT

(CT2)

Ratio:1575/1

10VA

Class: 5

8b

32450

533.8

2.95

8c

9

31900

543.0

2.9

10

31350

552.6

2.85

11

30800

562.4

2.8

12

30250

572.6

2.85

13

29700

583.2

2.7

14

29150

594.2

2.65

15

28050

605.8

2.6

16

28050

617.6

2.55

The minimum information to be shown on transformer nameplate depends on the KVA rating of the transformer as specified in the standard like figure 5.1. The nameplate of transformer shown that a value as a reference of pre-commissioning test such as ratio, rated power, vector group, oil raise temperature and winding raise temperature. The nameplate details is prepared by manufacture of power transformers where it also refer to the international standard like (IEEE STANDARD or INTERPLANT STANDARD-STEEL INDUSTRY, Code Of Practice For Testing And Commissioning Of Power Transformer And Related Switchgears, IPSS: 1-04-035-08).

5.2 INSULATION RESISTANCE TEST

Table 3: Insulation Resistance Test Result.

Between

Insulation Resistance Measured (MΩ)

1 minutes

10 minutes

HV - E

6000

10000

LV - E

6500

11500

HV - LV

6000

11000

The results shown in Figure 5.2 (a) shows the experiment conducted in 1 minute and 10 minutes using insulation tester. The difference between duration one minutes and ten minutes is because for the first test, the power transformer have charge, and need to be discharge. For the second test around ten minute duration is after discharge, then the value of insulation also higher than first test. So the testing is successful. Therefore, the result is up to the standard of IEEE. Figure 5.2 (b) showed the IR Test equipment.

Figure 5.2(a): IR Test equipment

5.3 TRANSFORMER TURN RATIO TEST

Transformer turn ratio test result injected by AC voltage (415V) at primary side and measure voltage at LV site has showed by graph. Figure 5.3(a) until figure 5.3(c) showed the comparison between voltage at primary side and secondary side for each phase and tap changing to calculate the ratio for each tap.

Table 4: Result for transformer turn ratio test

Tap

HV –Injected Voltage

LV – Measured Voltage

Cal.

Ratio

Rated

Ratio

A-B

B-C

C-A

a-b

b-c

c-a

a-n

b-n

c-n

1

404

406

404

123.4

123.6

123.2

71.0

71.2

71.0

3.3

3.3

2

404

405

403

125.1

125.3

124.4

72.1

72.3

71.8

3.23

3.25

3

402

406

403

128.0

128.3

127.9

74.0

74.5

73.5

3.2

3.2

4

403

407

406

129.2

130.0

128.6

74.7

75.3

74.4

3.14

3.15

5

403

407

408

132.4

132.1

131.2

75.6

75.9

75.6

3.1

3.1

6

407

406

406

134.3

134.6

132.8

76.9

77.4

76.4

3.04

3.05

7

404

407

402

136.2

136.4

135.5

77.8

78.7

77.9

3

3

8b

404

403

404

138.4

137.4

138.0

79.0

79.6

79.8

2.93

2.95

9

405

408

407

140.7

140.5

139.9

80.5

81.3

80.8

2.9

2.9

10

407

405

406

142.5

143.0

141.3

82.0

82.6

81.7

2.85

2.85

11

406

406

404

145.1

146.0

144.2

83.3

84.0

83.4

2.8

2.8

12

402

405

402

147.5

147.4

146.8

85.2

85.2

84.8

2.74

2.75

13

408

410

407

151.7

152.0

150.4

87.2

88.0

87.3

2.7

2.7

14

408

409

406

154.3

154.2

153.2

88.6

89.0

88.8

2.65

2.65

15

408

410

405

157.3

157.2

156.6

90.6

90.8

90.5

2.6

2.6

16

407

408

405

159.8

159.4

158.8

91.9

92.2

91.2

2.55

2.55

Figure 5.3(a): Graph voltage measurement at phase A-B for HV side and phase a-b for LV side vs tap changing

Figure 5.3(b): Graph voltage measurement at phase B-C for HV side and phase b-c for LV side vs tap changing

Figure 5.3(c): Graph voltage measurement at phase C-A for HV side and phase c-a for LV side vs tap changing

Based on figure 5.3(a) until figure 5.3(c), we can see that voltage on HV side is propotional with LV side (at phase to phase) for each tap changer. Thats means the calculation ratio based on voltage and current measurement at HV side and LV side depending on phase shown almost the same for each taps.

Figure 5.3(d): Graph calculation ratio and rated ratio vs tap changing

Based on figure 5.3(d), the graph shown that the calculation ratio is almost the similar with rated ratio for each taps where it refer on the power transformer nameplate details. The transformer turn ratio test is succesful.

5.4 DC WINDING RESISTANCE TEST

DC winding resistance test result injected by DC voltage (5V) at primary side and measure voltage also at primary side has showed by graph. Figure 5.4 until figure 5.5 showed the voltage and current at primary side for each tap measured by multimeter. The calculation to find the resistance is

R=V/I

Table 5: Result for DC winding resistance test

Tap

DC - Voltage (volt)

DC – Current (Amp)

Calculated Ohm ()

A - B

B - C

C - A

A - B

B - C

C - A

A - B

B - C

C - A

1

1.40

1.03

0.83

4.38

3.20

2.59

0.3196

0.3219

0.3204

2

1.40

1.00

0.80

4.43

3.13

2.52

0.3160

0.3195

0.3175

3

1.38

0.97

0.78

4.42

3.07

2.48

0.3122

0.3160

0.3145

4

1.36

0.94

0.77

4.39

3.01

2.45

0.3097

0.3123

0.3142

5

1.30

0.92

0.75

4.31

2.96

2.43

0.3063

0.3108

0.3086

6

1.30

0.90

0.73

4.27

2.92

2.38

0.3044

0.3082

0.3067

7

1.27

0.88

0.72

4.24

2.89

2.35

0.2995

0.3044

0.3063

8b

1.28

0.85

0.70

4.17

2.82

2.31

0.3069

0.3014

0.3030

9

1.22

0.83

0.69

4.12

2.76

2.29

0.2961

0.3007

0.3013

10

1.19

0.81

0.67

4.05

2.37

2.27

0.2938

0.2967

0.2951

11

1.15

0.79

0.66

3.93

2.68

2.25

0.2926

0.2948

0.2933

12

1.12

0.76

0.65

3.91

2.62

2.24

0.2864

0.2901

0.2902

13

1.10

0.75

0.64

3.86

2.60

2.23

0.2849

0.2885

0.2869

14

1.07

0.73

0.63

3.82

2.56

2.22

0.2801

0.2852

0.2838

15

1.04

0.71

0.62

3.74

2.53

2.21

0.2781

02806

0.2805

16

1.02

0.70

0.61

3.71

2.51

2.20

0.2749

0.2789

0.2772

Figure 5.4(a): Graph voltage at HV side vs tap changing

Figure 5.4(b): Graph current at HV side vs tap changing

For the DC-current (Amp) B-C at tap changing ten is maybe because mistake connection on tap changing adjusted by tester but it is not serious. After the tap changing ten, the graph showed that constant value for each tap until last tap.

Figure 5.4(c): Graph winding resistance at HV side vs tap changing

Based on figure 5.4(a) to figure 5.4(c), the graph shown the relationship between voltage and current to find the winding resistance. All the result have displayed follow IEEE standard where the winding resistance is must below than 0.5Ω.

5.5 TEMPERATURE RISE (OIL AND WINDING)

Table 6: Temperature for oil and winding

Temperature

Setting (ºC)

Temperature Indication Meter (ºC)

Difference

Oil

HV – Winding.

Oil

HV – Winding.

120

122

120

2

0

110

110

117

0

7

100

102

105

2

5

90

90

90

0

0

80

80

80

0

0

70

70

70

0

0

60

60

60

0

0

50

50

50

0

0

40

40

40

0

0

30

-

-

-

-

Figure 5.5: Comparison between oil and winding temperature

with temperature reference.

Based on the result in Table 2, the temperature for oil have increase 2°C when the tester increase the temperature setting up 120°C while temperature of winding maintain 120°C. For the setting temperature 110°C, temperature indication meter for oil shown constant but for HV winding increase up to 117°C. The difference between temperature indication meter and temperature setting maybe caused by condition of transformer have not stable, but eventually it will good soon.

CHAPTER 6

CONCLUSION AND FUTURE DEVELOPMENT

6.1 CONCLUSION

To ensure that power transformer was no subjected any damage during transportation and in good condition when operation and according of customer needs, and follow the specification from manufacturer test, most of testing need to be done. This project has shown that the power transformer has been installed correctly and each equipment was working in co-ordination with other equipment as desired. All the protection and control schemes are working in accordance with relevent specification and protection requirements. For the insulation resistance test, it can be conclude that the power transformer has a high insulation to prevent any leakage current. For the transformer turn ratio test, it can be deduced that calculation ratio for each phase is similar with rated ratio represent by manufacture test report. For the third test is DC winding resistance test, it can conclude that the winding has a low resistance which is the potential to conductor losses can be minimize. For the last test is temperature rise for oil and winding transformer, it can sum up that the temperature for them is in good condition especially for ambient temperature. Indicators operations for alarm and trip contact have shown in good condition when tester adjusts the thermometer temperature to increase the temperature of oil and high voltage winding. Based on the all result, it can be concluded that all of the tests done on the transformer power is follow the specification of manufacturer and able to meet the needs of the industry in Penang Port.

6.2 FUTURE DEVELOPMENT

There are many approaches that could be done in order to enhance the quality of pre commissioning test such as used the digital equipment test to get accurate reading about testing on power transformer. In addition, using Supervisory Control and Data Acquisition (SCADA) Systems to monitoring the testing work for prevent any accident involved human. The others recommendation for future research is study detail about relay on transformer, current ratio, pilot cable, and dissolved gas analysis of transformer. Most recommendation is including on preventive or maintenance of transformer to improve their long live in service.