Mention the initial commissioning checks on CT’s, PT’s and relays.

Mention the initial commissioning checks on CT’s, PT’s and relays.
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1 Answer

Answer :

Commissioning checks on

CT

a) Terminal marking correctness.

b) Polarity of terminals.

c) Insulation resistance between primary and secondary.

d) Insulation resistance between primary to earth and secondary to earth.

e) Magnetization characteristic and knee point voltage test.

f) Ratio test.

PT

a) Terminal markings.

b) Polarity checks of terminals.

c) Insulation resistance between primary and secondary.

d) Insulation resistance between primary to earth and secondary to earth.

e) Ratio test.

f) Whether PT can supply as per the burden of load check.

RELAYS

a) Pickup and dropout value check.

b) Insulation resistance of contacts and relay coil.

c) Time delay (if relay is not instantaneous), operating time value check of relay.

d) See that the correct circuit breaker trips on energisation of the particular relay.

e) Continuity checks of contacts after energisation of relay.

f) See if plug-shorting contacts are correct.

g) See if CT’s and PT’s are corrected in correct polarity.

h) Burden check of relay.

i) Primary injection test.

j) Secondary injection test. 
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