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Why Normal time-overcurrent relays are not adequate for generator backup protection?
Wiki User
∙ 15y ago
Setting the time-overcurrent relays high enough to prevent tripping for normal overloads may result in them not tripping at all due to the decaying characteristic of the generator fault current. Using the system voltage to control the overcurrent characteristic resolves this problem, since the voltage should drop very little for overloads, but will collapse to a small value for external faults. The 51V protection function uses the system voltage to adapt the operation of a time overcurrent element, using either voltage-restraint (51VR) or voltage-control (51VC).
Wiki User
∙ 15y ago
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