Commissioning Tests Summary Mobitel

COMMISSIONING PROCEDURE

MOBITEL WELIKADA

Document ref. : DPS188JMM0101

Employer : Mobitel (Pvt) Ltd.

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Tests Included for the Commissioning of 11kV Distribution System

1. HV Switchgear (8BK88 plus 1 ICOG , 1 I/C , 2 O/G)1.1 Current Transformer ( 400 :1 , 200 : 1 ,5P10,CL 1.0 ,10 VA)

1.1.1 Insulation resistance test (with Insulation tester)1.1.2 Winding resistance test (with Omicron CPC 100 primary injection kit)1.1.3 Excitation Curve (with Omicron CPC 100 primary injection kit)1.1.4 Burden test (with Omicron CPC 100 primary injection kit)1.1.5 Ratio & Polarity test (with Omicron CPC 100 primary injection kit)

1.2 Voltage Transformer ( 11/√3 : 0.11/√3 : 0.11/3 , CL1.0 /3P, 50 VA)1.2.1 Insulation Resistance test (with Insulation tester)1.2.2 Ratio & Polarity test (with Omicron CPC 100 primary injection kit)1.2.3 Burden test (with Omicron CPC 100 primary injection kit)

1.3 Busbars and connections (11 kV, 630 A)1.3.1 Insulation resistance at 5kV DC (with Insulation tester)

1.4 Circuit Breaker ( 3AH0, 12 kV, 800 A, 26.3 kA/3 S)1.4.1 Static Contact Resistance test( with Omicron CPC 100 primary injection kit )1.4.2 Insulation Resistance test ( 5 kV Insulation tester )

1.5 Protection relay ( 7SR10,7SR11)

1.5.1 Overcurrent & Earth fault test (with Omicron CMC 356 secondary injection kit)

2 Power Transformer ( 2000 kVA, 11/0.415 kV , Dyn11, LTL Oil Immersed transformer)2.1 Insulation resistance test at 5kV DC (with Insulation Resistance tester)2.2 Winding resistance at central tapping and extremes (with Omicron CPC 100 primary

injection kit)2.3 Turns ratio test at all tap positions (with Omicron CPC 100 primary injection kit)2.4 Vector group test (with Omicron CMC 356 secondary injection kit and multi meter)2.5 Magnetic Balance test ( with Omicron CPC 100 primary injection kit and multi meter)

3 Power Cable ( 11 kV , 3C ×150 mm2 , Cu/XLPE/CTS/PVC/SWA/PVC )3.1 Insulation resistance test at 5 kV DC

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Equipment used for testing & commissioning

Table 1

Ref. No. Equipment Brand Serial No.1 CPC 100 Omicron NJ644U2 5 kV Insulation Resistance tester Kyoritus W03694053 CMC 356 Omicron EB892H4 Digital multimeter Fluke 23030163

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1.1 Current transformer1.1.1 Insulation Resistance test

Earth connection of the CT secondary star point should be removed from the terminal block.

Insulation resistance test is done between primary-earth , primary-secondary (5 kV DC), secondary-earth & among secondary windings (1 kV DC) for a period of 1 minute.

Table 2 : CT IR test Test Insulation Resistance(MΩ) Voltage( kV /min)primary- secondary 5/1primary- earth 5/11S1-2S1 1/11S1-earth 1/12S1-earth 1/1

After conducting the IR test, each terminal should be discharged.

1.1.2 Winding Resistance test A DC current of 1 A is injected to CT secondary terminals & the DC voltage is

measured using DC voltage input of CPC 100. Initially the winding is provided with inductive energy & after saturates the CT

secondary winding, DC current is applied. Winding resistance value is measured at room temperature & the reference

resistance is calculated at 75 ° C according to following formula.

𝑉 235 + 𝑅= (

) × (235 + 𝑎

) : IEC 60076-1

Table 3: Winding resistance test Phase Core Winding Resistance at 25 °C

L1 1S1-1S22S1-2S2

L2 1S1-1S22S1-2S2

L3 1S1-1S22S1-2S2

After conducting this test, CT core should be de-magnetized.1.1.3 xcitation Curve test

This test is carried out to find the knee-point & the linear range of the CT secondary winding.

An AC voltage up to 2 kV is injected using CPC 100 & the magnetizing current is continuously measured and plotted.

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According to IEC 60044-1, knee point is defined as the point where a voltage increment of 10 % will cause magnetizing current increment of 50 %.

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1.1.4 Burden test The secondary resistive burden comprises of relay or metering burden along with

leading wires is measured in this test. The CT rated secondary current ( i.e. 1 A) is injected & the AC voltage is measured. In this test, CT winding is separated from the burden. Burden is calculated according to following formula. This test is carried out to verify

the actual Accuracy Limit Factor of the CT.

𝐼 𝑐 , 𝑟 𝑛( 𝑉 ) = 𝐼𝑐, × 𝑉𝑐,𝑎𝑐 × ( ) 𝑐,𝑎 𝑐

1.1.5 atio & Polarity Test CT ratio is done by injecting 5% , 20 % , 50% , 80% of rated primary current. Care should be taken to short circuit the unused CT cores to avoid hazardous voltages. Usually, the ratio is measured when 25 % of rated primary current is flowing through

primary terminals. Polarity test is automatically done in CPC 100 while conducting the ratio test.

Table 4: CT ratio & polarity test Phase Core Primary

current (A)Secondary current ( mA)

Rated ratio

Measured ratio

Polarity

L1 1S1-1S22S1-2S2

L2 1S1-1S22S1-2S2

L3 1S1-1S22S1-2S2

1.2 Voltage Transformer1.2.1 Insulation Resistance test

Remove earth connection from the VT primary & secondary star point. And 5 kV DC voltage is applied between primary & earth terminals for 1 minute , thus

IR can be measured. Similarly, Insulation resistance is measured between secondary-earth & among

secondary cores. After conducting the IR test, discharging must be done.

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Table 5: VT IR test

Test L1 L2 L3 Voltage ( kV / min )

primary – Earth 5/1primary – sec 5/1secondary – Earth 1/11a – a1 1/1

1.2.2 atio & Polarity test AC voltage of 2 kV is applied between primary terminal & neutral point from the 2

kV output port & the secondary voltage is measured using V1 AC input port. Same ratio test is carried out for broken-delta winding. Polarity is automatically conducted by CPC100 while doing the ratio test.

Table 6 : VT ratio & polarity test

Phase CorePrimary Voltage (V)

Secondary Voltage (V)

Rated Ratio Measured Ratio

Phase (deg) Polarity

L11a – 1n 11/√3:

0.11/√3a1 – n1 11/√3: 0.11/3

L21a – 1n 11/√3:

0.11/√3a1 – n1 11/√3: 0.11/3

L31a – 1n 11/√3:

0.11/√3a1 – n1 11/√3: 0.11/3

1.2.3 Burden test Secondary side resistive burden is calculated by applying AC voltage of 63.51 V from 130 V

AC output of the CPC 100. The AC current is measured using I AC input port. VT burden is calculated according to the

following formula.

𝑉 𝑐 , 𝑟 𝑛 (𝑉 ) = 𝑉𝑐, × 𝐼𝑐,𝑎𝑐 ( ) 𝑐,𝑎 𝑐

1.3 Bus bars & Connections1.3.1 Insulation Resistance test

Insulation resistance between phases & earth is measured by applying 5 kV DC voltage for 1 minute.

After conducting the IR test, discharging must be done.

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Table 8 : IR test for Busbars Phase Insulation Resistance/ MΩ Voltage( kV/min)L1 5/1L2 5/1L3 5/1

1.4 Circuit Breaker ( 3AH0)1.4.1 Static Contact Resistance test

Contact resistance of the closed circuit breaker is done by applying DC current of 80 A between phase terminals & voltage drop is measured.

If the mV drop value is less than 4 mV, the contact resistance is satisfactory.Table 9: Static Contact Resistance test for 3AH0

Phase Applied current/ A Voltage drop / mV Contact resistance/ μΩL1L2L3

1.4.2 Insulation Resistance test Insulation resistance is measured between phases as well as between phase & earth

while circuit breaker is open. Further, insulation resistance is measured between phase & earth while the circuit

breaker contacts are closed. CB open

Table 10 : Across phase

Phase Insulation Resistance (GΩ) Voltage (kV/min)L1 5/1L2 5/1L3 5/1

Table 11: Phase to Earth


CB closedTable 12 : Phase to Earth


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Phase Insulation Resistance (GΩ) Voltage (kV/min)L1- L2 5/1L2- L3 5/1L3- L1 5/1

1.5 Protection relay ( 7SR11,7SR10) Pick-up time & trip time of the 7SJ62 & 7SJ80 relay for several secondary currents (

varying between the set value ) are injected to relay CT terminal inputs from CMC 356 secondary injection kit.

And trip time ( from binary output 3) is compared with theoretical operating time depending on the curve selected. For Normal Inverse curve,

= 0.14 𝑀

(𝑃 𝑀 0.02−1)

(IEC 60255-3)

Table 14 : 7SJ62,7SJ80 operating time characteristics for O/C & E/F

TestPhase Current (A) Trip

Time (s)

Expected Trip Time (s)

Deviation In Trip Time (%)

RemarkL1 L2 L3

Over current pickup ( A set value)

L1

L2

L3

Over current trip ( A)

L1

L2

L3

Earth fault Protection

Pickup

Table 13 : Phase to

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EF

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2. Power transformer ( Dyn11 , LTL Oil Immersed transformer) Before the commencement of the test, the transformer should be at ambient

temperature for at least 3 hours. ( IEC 60076-1)

2.1 Insulation Resistance test

The insulation resistance test is measured between HV terminals-earth, HV – LV terminals by applying 5 kV DC for 1 minute.

Also IR test is conducted between LV – earth by applying 1 kV for 1 minute.

Table 15: Power transformer IR test

Test Insulation Resistance/ MΩ Test Voltage (kV/min)Pri. – Earth 5/1Sec. – Earth 1/1Pri. – Sec. 5/1

2.2 2 Winding resistance test

A constant DC current of 1 A is injected between each winding of HV winding for each tap position.

The DC voltage is measured from the 10 V DC input port.

Table 16 : Pr imary w inding r esistance (Ω) Tap Phase 1U-1W Phase 1V-1U Phase 1W-1V

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Further, for secondary windings , 1 A DC current is applied between LV terminals. Winding resistance is also calculated at reference temperature (75 °C)

Table 17 : Secondary winding resistance ( m Ω) Phase 2U-N Phase 2V-N Phase 2W-N

2.3 Turns ratio test A sinusoidal voltage of 500 V is applied to each HV terminal from 2 kV AC output of the CPC

100. The secondary induced voltage is measured from V1 AC input.

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2v

2w

Table 18 : Turns ratio test for phase 1U

Phase 1UTap Nom.Ratio V Prim I Prim I Phase V Sec V Phase TTR Ratio

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2.4 Vector Group test A connection should be made between 1U and 2u terminals. A three phase sinusoidal voltage of 50 V is applied using CMC 356 to HV terminals & the

voltage is measured using a multi meter according to following table.Table 19: Vector group test

Measurement Voltage (V)IU-IV

1V-1W1W-1U1V-2v1V-2w1W-2v1W-2w2u-2v2v-2w2w-2u

For a Dyn11 transformer,

1U, 2u

1W1V

2.5Magnetic Balance test

Tap changer position is kept at nominal position(i.e. tap no. 3)

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Single phase 200 V AC is applied using CMC 356 between HV terminals & the other HVterminal voltages are measured.

Table 20: Magnetic Balance test 1U-1V 1U-1W 1V-1W

Applied/ Measured voltage

200 X0 Y0

X1 200 Y1

X2 Y2 200

If there is no problem with magnetic path of the transformer circuit, X0 + Y0 = 200X1 + Y1 = 200 X2 + Y2 = 200

For the center limb, induced voltage is higher than the limb situated at the corner.

3. Power Cable3.1 Insulation Resistance test

The connections from either end of the power cable is removed. A DC voltage of 5 kV is applied from the Insulation tester for a period of 1 minute, between

each phase & copper screen.

Table 21: IR between phase-Cu screen Phase Insulation resistance (GΩ) Test voltage ( kV/min)L1 5/1L2 5/1L3 5/1

Table 22 : IR across phases Phase Insulation Resistance (GΩ) Test voltage ( kV/min)L1-L2 5/1L1-L3 5/1L2-L3 5/1

Commissioning Tests Summary Mobitel

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