TESTING AND COMMISSIONING : TESTING OF CIRCUIT BREAKERS  1 . Insulation Resistance Measurement :- By 1KV to 5 KV (DC) Megger. Measure IR value between pole to Earth (when CB is open). IR value of HV CB is very high above 1000 Meg ohm. IR value of control, circuit, trip circuit, relay circuit, and secondary … Read more

Relay : Types of Relay

Relay Preliminary examination & checks Damage like dents, broken glass covers, loose parts etc. Iron filings in air gaps of magnets. Moving parts getting jammed etc. Confirming to rating, correct auxiliary supply voltage etc. Types of Relay 1. Over current, Instantaneous / Time 2. Over/under voltage 3. Differential 4. Reverse power 5. Over/under frequency 6. … Read more


CAPACITIVE VOLTAGE TRANSFORMER (CVT) Capacitive Voltage Transformer Polarity Test Same as in CT or PT. Ratio Test – Apply voltage to primary with secondary open. Measure secondary voltage and determine ratio. In case of star/star configuration care has to be taken to ensure that primary & secondary neutral points are not connected together. Measurement of … Read more


CURRENT TRANSFORMER (CT) Polarity check Each CT should be individually tested to verify that primary and secondary polarity marking are correct. The ammeter should be center zero type. The connection arrangement of CT terminals, battery and ammeter is shown. Show push button in closed – If should give a +ve flick. Show push button is … Read more


TESTING AND COMMISSIONING 1. TRANSFORMERS. Pre-commissioning Test — The objective of the pre-commissioning tests is to confirm that the transformer has not suffered any damage during transit and also check any inadvertent slips in the factory tests. (Measurement of Insulation Resistance) The IR values are measured between the following. HV to LV and earth connected … Read more

Battery Trouble Shooting

Battery Trouble Shooting Battery Trouble Symptoms Remedies Over Charging (a) Excessive gas sing (b) Falling of active materials from positive plates (c) Buckling of plates (d) Increased temperature (e) Building of container (1) Reduce the charging rate till the specific gravity attains value 1.2 (2) Add distilled water Under Charging (a) Low specific gravity (b) … Read more

General Problems in Transformers

In Transformers 13 General Problems and Possible Causes : General Problems in Transformers Nature of Problems Possible Causes Low IR value (a) Ageing (b) Ingress of moisture through breather. (c) Sludge formation within transformer (d) Error in measurement such as measuring leads falling on the transformer itself. Oil Leakage in bushing (a) Crack in porcelain (b) … Read more


ELECTRICAL FAULT FINDING : Trouble Shooting Works No  Nature of Trouble  Work to be Attended 1.  Non Working of bell  (a) Loose connection (b) Disturbing of bell adjustment (c) Burning of bell coil (d) Alarm D.C. Fuse blown (e) Relay self sealing not proper (i.e. Aux, relay fault) 2.  Failure of trip healthy indication  (a) … Read more



 DATA ON SUB-STATIONS 1. Sub-Station Operational concepts:- a. Equi-Potential Concept :- This concept is an important tool for the power system for the operation of Isolator (air break switch). The terminals in the system need to be connected by isolator are charged to the same potential. Then the isolator /air break switch is operated smoothly … Read more

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