Thursday, May 13, 2010

4/5/10

-To meet protection objectives and requirements,protection systems are required where protective devices or gears are combined together ready to disconnect faulted equipment.
-Protective scheme on the other hand is a coordinated arrangement of several protective systems for protection of equipement bor power system.
-Current and voltagte transformers are the common devices used in protective system.
-Voltage transformer are used for measurement ,directional protection -conventional or reverse power relays -undervoltage/overvoltage protection.
-Two types of voltage transformer constrution in used:
*Electromagnetic type:primary and secondary winding are magnetically coupled via iron core.
*Capacitor voltage transformer -which is connected to main circuit with series of capacitors.

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