Communication devices in the relay protection room
Let's start with brief description of seven most known and most used communication medias used in power system communications (in terms of protection and automation):.
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How to connect protection inputs to relay protection
The objective of relay protection is to quickly isolate a faulty section from both ends so that the rest of the system can function satisfactorily.
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The preparedness of relay protection refers to
Relay protection is the discipline of designing schemes that detect faults, coordinate relays, and isolate equipment without outages. Protective relays and devices have been developed over 100 years ago to provide "lastline"of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions.
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Cable trench under relay protection
Cable joint breakdown accidents have occurred frequently in recent years and have gradually become an important concern of the power maintenance department.
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220kV relay protection operating time
For high fault resistance ground faults, the operating time of the protection is usually stepped from m 1–3 seconds and operating times are harmonised with the protection of the main grid. The 110 and 220 kV lines of the main grid are protected by means of two primary protection schemes (two distance relays or a distance and a differential line relay) or a primary protection relay (distance relay) and a backup protection relay (overcurrent and earth fault relay). Time-graded protection is implemented using overcurrent relays with either definite time characteristic or inverse time characteristic. The numerical terminals referred as IED (Intelligent electronic device) contain apart. In case of Long Line, followed by Short Line, the above mentioned Formula may not give us margin against possible underreaching. Inverse time delay, on the other hand, depends on the current magnitude so, the higher the current, the shorter the delay.
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