Transformer Sat Addc & Aadc

Standard Technical Specifications for Electric Works

SITE ACCEPTANCE TESTS (SAT) AFTER INSTALLATION

(SPECIFICATIONS)

TRANSFORMER / REACTORS / RESISTORS

AUXILIARY/DISTRIBUTION TRANSFORMERS EPOXY-RESIN DRY TYPE

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SITE ACCEPTANCE TESTS (SATS) AFTER INSTALLATION

Auxiliary/Distribution Transformers – Epoxy-Resin Dry Type

ADDC/AADC STANDARD : DOCUMENT.DOC

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CONTENTS

1 PHYSICAL SITE INSPECTION...............................................................3

2 SITE TESTS (MINIMUM REQUIREMENTS)........................................32.1 Measurement of Winding Ratio on all tap positions (for OFF-LOAD and LOAD tap

changing transformer) by voltmeter method..............................................................32.2 Checking of Vector Group (the voltmeter method shall be applied).........................32.3 Measurement of Winding Resistance at principal tapping and extreme position.......42.4 Measurement of Winding Insulation Resistance (R15s, R60s, R180s, R600s). The

absorption ratio R60/R15 shall not exceed 3.0 (R10/R1 shall not exceed 1.1 according to American Standards) after oil-treatment. Results shall be compared with factory test results...................................................................................................................5

2.5 Measurement of the insulation resistances (R60) on auxiliary wiring at 1,000Vdc...52.6 Over-Voltage test at 1,000 VAC on control and supervisory equipment...................52.7 Measurement of Impedance (short-circuit voltage)....................................................52.8 Checking of Transformer Protection Schemes...........................................................52.9 Measurement of Capacitance and Insulation power factor........................................5

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Auxiliary/Distribution TransformersEpoxy-Resin Dry Type

1 PHYSICAL SITE INSPECTION

a. Check level and alignment of installed transformer;

b. Check tightness of connections and fastenings;

c. Check proper grounding;

d. Check wire and cable connections;

e. Check cable glands and entrance;.

2 SITE TESTS (MINIMUM REQUIREMENTS)

After the transformer has been installed, the following tests shall be executed as a minimum requirement. The transformer shall be OUT of SERVICE:

2.1 Measurement of Winding Ratio on all tap positions (for OFF-LOAD and LOAD tap changing transformer) by voltmeter method.

The test must be carried out by applying voltage (low voltage 380 Vac or 220 Vac) to H.V. winding at rated frequency.

The test must be carried out by using two voltmeters, one to read voltage of H.V. winding and the other to read L.V. winding.

The two voltmeters must be read at the same time.

The test must be carried out on all phases and for each position of the tap changer.

Example:

OLTC Position

Theoretical Ratio K

Voltmeter H.V., V1

Voltmeter L.V., V2

Measured RatioKM=V1/V2

VAB= 376 Vab= 39.21 9.68 VBC= 376 Vbc= 39.2 9.592

VCA= 376 Vca= 39.2 (diff - 0.9%)

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2.2 Checking of Vector Group (the voltmeter method shall be applied)

The test must be carried out in accordance with BS 171.

The test will be carried out by applying low voltage (415V or 240V) A.C.) three phases clock wise on the primary side. H.V. side phase (A) must be connected with the L.V. side phase (a). Check that the relation of the vector groups are satisfied by using one voltmeter.

Different combinations of voltage between H.V. terminals must be measured.

Example:

Aa 0 V AB 380 VBb 345 V Bc 380 VCc 345 V Cb 345 V

According to BS 171 - Vector Diagram Table:

If Bb = CcBb < ABBb < Bc

for an Star / Delta connected transformer, the vector group must by YND1.

2.3 Measurement of Winding Resistance at principal tapping and extreme position

The tests have to be carried out in accordance with IEC 76.1.

In measuring the cold resistance for the purpose of temperature rise determination, special effort shall be made to determine the average winding temperature accurately.

In all resistance measurements, all the precautions shall be taken in order to minimise the effect of the self induction.

Record the resistance value, when the measuring current value become steady.

Use D.C. source and resistor to limit the current, within the range of 10 A. Use one Voltmeter class +/- 0.1 %, shunt 15 A, 75 mV.

Calculate the resistance measured at the ambient temperature.

REF = (VOLT)/2 * (AMP) (Resistance at ambient temperature)

REQ = REF * (234.5 + Tq) / 234.5 + Tf) (Resistance at reference temperature)

Tq = Reference temperature (750 C)

Tf = Test temperature (0 C)

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Example:

Phase Amb.Temp. AMP VOLT REF () REQ ()1 350 C 13 1.883 0.0724 0.08312 350 C 12.5 1.909 0.0764 0.08773 350 C 12.5 1.869 0.0748 0.0859

2.4 Measurement of Winding Insulation Resistance (R15s, R60s, R180s, R600s). The absorption ratio R60/R15 shall not exceed 3.0 (R10/R1 shall not exceed 1.1 according to American Standards) after oil-treatment. Results shall be compared with factory test results.

5000 or 10000 VDC between primary H.V. winding and ground (secondary grounded)

1000 or 5000 VDC between secondary L:V: winding and ground with other secondary L.V. and primary H.V. windings grounded..

2.5 Measurement of the insulation resistances (R60) on auxiliary wiring at 1,000Vdc

2.6 Over-Voltage test at 1,000 VAC on control and supervisory equipment

2.7 Measurement of Impedance (short-circuit voltage)

Apply about 0.4 kV or higher ACV to the transformer high-voltage (primary) bushing

Transformer low-voltage (secondary) bushings are shortened

Tap changer at principal, highest and lowest taps (three measurements)

Measurements:

U1 = U - V Voltage between phase U and V

U2 = W - V Voltage between phase W and V

U3 = U - W Voltage between phase U and W

Um = (U1+U2+U3) / 3

I1 = Current of phase U

I2 = Current of phase V

I3 = Current of phase W

Im = (I1+2+I3) / 3

IT = Rated tap current

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UT = Rated tap voltage

Impedance: Z = (Um * IT * 100%) / (UT * Im)

2.8 Checking of Transformer Protection Schemes

2.9 Measurement of Capacitance and Insulation power factor

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Transformer Sat Addc & Aadc

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