The operation of distance protection depends on the basic fact that on the occurrence of a fault, the distance between any point in the power system and
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Section 4 Distance Protection
(ii) Errors in the relay, (iii) Errors in the current transformers (CTs) and voltage transformers (VTs), (iv) Errors in the data on which the impedance settings are made.
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Section 4 Distance Protection
discriminative tripping of the circuit breakers controlling the various feeders can be obtained. Usually, a 3-zone distance protection schemes is employed for transmission line protection.
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Section 4 Distance Protection
In many cases, where the consecutive line sections differ very much in length, alterations in the above scheme, in the number of steps or time delays, may be necessary to give optimum selectivity and protection.