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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) Fusing of bulb
(b) Loose connection in trip D.C. circuit
(c) Resistance found open circuit in trip ckt.
(d) Alignment of Aux. contacts of C.B. getting
(e) Trip coil open.
3.  Non Working of O.L.T.C Control  (a) Failure of A.C. supply
(b) Failure of Aux. Transformer 220/110V
(c) Putting Remote /Local switch on local/ Non
operation from remote
(d) Contact problem in lower rase button
(e) Tripping of miniature ckt. breaker of A.C. motor
(f) Phase sequence is reverse.
4.  Non auto start of compressors  (a) Pressure switch faulty
(b) Loose connection
5.  Non tripping of feeder breaker  (a) Loose connection
(b) Open circuit of trip coil
(c) Mechanical trouble
(d) Alignment of Aux. contacts of C.B. getting
6.  Noise in CT  (a) Open circuit of CT secondary circuit
(b) Loose connection in C.T. secondary ckt.
7.  Spring changing motor does not start  (a) Failure of A.C. Supply
(b) Failure of limit switch
(c) Defective motor
(d) Failure of AC to DC convenor
8.  Non closing of breaker  (a) Loose connection
(b) Open circuit in closing coil
(c) Mechanical trouble
(d) Alignment of Aux contacts of C.B. getting
(e) Spring was not charged or low air pressure
(f) Non resetting of master relay
(g) Non closing from remote and if local remote
switch is on local.
9.  Flash covers and damage to the wiring  (a) Failure of insulator
(b) Short circuit due to lizards, rates etc.


10.   Tripping of Transformer on differential  (a) Failure of L.A.
(b) Loose connection in CT ckt.
(c) Providing improper class for CT secondary
(d) Failure of L.V. cable box
(e) Failure of insulators within differential zone
(f) Failure of C.T.
(g) Magnetising inrush current in case of DDT
relay or faulty cords in DTH 31, DTH 32.
D.C. leakage
11.   Tripping of Transformer on buchhoz  (a) Due to oil surge
(b) Due to moisture/water inside the connection box
(c) Improper operation of buchhoz relay
(d) Shorting of terminal due to failure of bakelite plates
(e) Low oil level
12.  Low oil level indication on panel appearing   continuously  (a) D.C. leakage
(b) Sticking of low oil level pointer
(c) Rain water inside the connection box
13.  Flag not resetting  (a) Mechanical defect
14.  Non resetting of bell  (a) Accept switch faulty
(b) D.C. leakage
(c) Aux. relay faulty
15.  Non resetting of indication  (a) D.C. leakage
(b) Push button faulty
16.  Non tripping of CB from remote  (a) The local/remote switch on local position
(b) Loose connection
(c) Trip/close switch faulty
(d) Alignment of Aux. contact of C.B. getting disturbed
17.  Capacitor Bank tripping  (a) Faulty capacitor unit
(b) Blowing of H.T. fuse of capacitor unit
18.  Tripping of breaker without indication  (a) Due to shorting of DC (+) ve
(b) Leakage of DC.
(c) Due to low pressure
19.  Continuous ringing of bell  (a) D.C leakage
(b) Adjustment of Aux Relay-contact is disturbed


20.  Abnormal noise in current transformer  (a) Winding is open
21.  Mal-Operation of relay  (a) Defects in relay
(b) D.C. leakage
22.  Battery charge not working  (a) Failure of transformer
(b) Failure of diode
(c) Failure of A.C. supply
(d) Switch faulty
23.  Transformer cooling fans auto start not working  (a) Defects in temp. indicator
(b) Defects in contactor
(c) Loose connection
24.  Indication lamp not indicating  (a) Fusing of lamp
(b) Defects in Aux. switch
(c) Loose connections
25.  Semaphore not working  (a) Defects in Aux. switch
(b) Loose connections
(c) Semaphore coil burnt
26.  SF6 Breaker trip circuit faulty  (a) Loose connections
(b) Low air presser
(c) Low gas pressure
27.  VCB trips but fault not cleared  (a) Check push-rod connection
(b) Failure of vacuum
28. Breaker Tripping without fault

Also Read : SUB-STATIONS Operational concepts


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