The function of relay and circuit-breakers in the operation of a power system is to prevent or limit damage during fault or overloads and minimize their effect on the remainder of the system. This is accomplished by dividing the system into protective zones separated by circuit breakers, each having its protective relays for determining the existence of a fault in that zone.
Electric power
Thursday, January 12, 2012
Different types of faults in power system
The faults in a power system could be classified as symmetrical or unsymmetrical faults:
· Symmetrical faults:
They involve 3-phase short-circuit. Symmetrical faults are the least probable type of faults. Symmetrical faults represent the most severe type of faults i.e. maximum short-circuit current. Therefore the breaking (rupturing) capacity of circuit-breakers is determined by that type of fault.
· Unsymmetrical faults:
Comprise the following types of faults:
Power System Protection
The large amounts of capital invested in the power systems justify the importance of a reliable protective system. Protection is the art or science of detecting the presence of a fault and initiating the correct tripping of the circuit breakers (C.B). Importance of protection could be understood when a fault (or any other abnormal condition) arises in an electrical power system. That fault must be isolated as quickly as possible from all live supplies in order to:
Single Line Diagram and Layout of the Present 66/11 KV Substation
Studying the figure which presents the single line diagram of the 66/11 KV substation that feeds the residential area in this project shows that the substation consists of a sectionalized double bus bar system fed by eight 66 KV cables, two incoming from the preceding substation in the 66KV ring and two are outgoing to the next substation in the ring and the remaining four 66 KV feeder cells as reserve.
How the Maneuver between Busbars happens
If we want to make maintenance of operating B.B., or to avoid overloading conditions then we have to make maneuver between busbars. This is done by the following procedure:
Essential Civil Structures of an Outdoor Substation
The following civil structures are necessary in a conventional outdoor substation:
§ Towers of incoming and outgoing transmission lines. These are generally located outside the substation boundary, adjacent to the substation.
Substation Equipment
To do its task in a proper way, substations contain much equipment. The most important and common equipment in the transformers substations are the following:
1) Bus Bars
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