Appendices
24
5.2.3
Voltage Ratio Test
a) Apply 3-Phase, 433V AC supply on the HV side and the Voltage Ratio
at all tap positions can be derived using suitable precision voltmeter
connected to the LV side. A ratio meter, if available can be used for a
more accurate measurement.
b) The Ratio values obtained should be similar to those indicated in the
manufacturers’ test report, furnished with the handing-over documents.
5.2.4
Winding Resistance Measurement Test
a) Winding Resistance of every phase of each winding should be
measured using suitable DC Resistive Bridge or similar.
b) Winding Resistance values obtained should be similar to those
indicated in the manufacturers’ test report, furnished with the handing-
over documents.
5.2.5
Marshalling Box Scheme Check
a) All the auxiliary wiring from various accessories to marshalling box
shall be checked with marshalling box scheme drawing furnished with
the handing-over documents.
b) During testing of accessories like buchholz relay, etc., operation of all
the alarm / trip contacts shall be checked at marshalling box terminal
blocks ensuring both operation and wiring are checked correct.
5.2.6
Buchholz Relay Test
a) Relay operation for alarm and trip contact shall be checked by injecting
air inside the relay through test petcock. Injected air collected inside
the relay allow the alarm float / flap & trip float / flap to fall thereby
operating their respective switch.
5.2.7
Temperature Indicator Test
a) Indicators operation for alarm and trip contact shall be checked by
manual stimulation.
5.2.8
Off-Circuit Tap Selector (OCS)
a) During shipment, the OCS has not been separated from the
transformer so it is not necessary to recheck the internal connections of
tapping and internal mechanism.
b) Means of protecting the OCS from unauthorised operation is provided
by using pad locking arrangement at designated tap position.
A - 6
