Transformer faults and their protection requirements
Transformer protection is the key to ensure the safe operation of transformers. Simply put, it is a kind of transformers that can quickly cut off the faults and ensure the safe operation of transformers when short-circuit, over-current, over-voltage and some related electrical faults or non-electrical faults occur during operation Electrical equipment, referred to as transformer computer protection device .
The basic requirements for transformer protection:
(1) Transformer should be disconnected from all power supplies in the event of a fault.
(2) The busbar or other components connected to the transformer is faulty, and the faulty component should be separated from the faulty part if its own circuit breaker can not be disconnected due to some reasons (such as protection of refuse or circuit breaker failure) .
(3) When the transformer overload, oil level decreases, the oil temperature is too high, it should send an alarm signal.
Transformer fault and abnormal state:
(1) phase short circuit between windings and their outgoing wires and single-phase to ground short-circuit at the neutral point directly grounded;
(2) winding turn-to-turn short circuit;
(3) external phase short circuit caused by over-current;(4) neutral point directly to the power grid, the external ground short circuit caused by over-current and neutral over-voltage;
(4) neutral point directly to the power grid, the external ground short circuit caused by over-current and neutral over-voltage;
(6) over excitation;
(7) reduce oil level;
(8) Transformer temperature and tank pressure rise and cooling system failure
Transformer protection classification
(1) The main protection of the transformer: Differential instantaneous protection; Proportional differential protection (with second harmonic brake, CT wire breakage);
(2) Transformer backup protection: overcurrent section I (jump section); with low voltage lockout, negative sequence voltage lockout; overcurrent section II (hopping main switch all side switches); with low voltage lockout, negative sequence voltage lockout ; Overcurrent I, II can be selected: phase direction choice; speed limit (speed limit, speed limit breaking direction, low voltage lockout); overload warning; CT disconnection Flow control, zero sequence voltage lockout, zero sequence trip, zero sequence direction selection) PT loss of pressure (alarm) PT breakage (alarm) Busbar ground (alarm)
(3) Transformer non-power protection : ontology light gas-alarm; on-body heavy gas-tripped; on-board light gas-alarm; loaded gas-tripped; pressure release ; High temperature - tripped; high oil level - alarm; low oil level - alarm; high oil temperature - alarm; low oil temperature - alarm; air cooling failure .
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