Differential Relay:
Principle of Differential Protection
scheme is one simple conceptual technique. The differential relay actually
compares between primary current and secondary current of power transformer, if any unbalance found in
between primary and secondary currents the relay will actuate and inter trip
both the primary and secondary circuit breaker of the transformer.
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| Differential Relay Scheme |
What is the advantages and disadvantages of a differential relay.
Advantage:
Fully digital signal handling with a powerful 16-microprocessor and high measuring accuracy on all the setting ranges due to an accurate 16-bit A/D conversion technique.
Easily adaptable to various substation and alarm system with flexible signal grouping marix in the relay.
Disadvantage:
There may be a probability of mismatching in cable impedance from CT secondary to the remote relay panel.
These pilot cables capacitance causes incorrect operation of the relay when large through fault occurs external to the equipment’s.
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