Short Circuit Studies is critical for the safe, economical and efficient operation of all electrical power systems. In case of a short circuit, excessive electric current will flow through the system and could have disastrous consequences including personnel injury, damaged electrical equipment as well as costly downtime. Short circuit calculations provide currents and voltages on a power system during fault conditions. This information is required to design an adequate protective relaying system and to determine interrupting requirements for circuit breakers at each switching location. Fault conditions can be balanced or un-balanced shunt faults or series (open conductor) faults. Often information about contributions to a fault from rotating machines such synchronous machines, large motors would be required as a function of time to determine making and breaking requirements.
Recommendations and guidelines are given in the IEEE Violet Book (IEEE STD 551-2006) as well as North American ANSI C37.5, ANSI C37.010, ANSI C37.13 and International IEC-60909 guidelines. It also supports conventional short-circuit studies without reference to any particular standards.
The results of these studies are provided in tabular form giving details of making and breaking fault currents requirements at each breaker locations (bus locations). Further, plots of peak fault current, dc component of fault current, symmetrical RMS component of fault currents will be provided with respect to time. These calculations will be performed for all types of shunt faults such as 3 phase faults, single line to ground fault, line to line faults and double line to ground faults.
Apart from determining fault levels at various buses, short circuit studies are useful in determining post fault bus voltages in the entire system, post fault network currents in the entire system, and negative and zero sequence currents in various electrical network elements. These calculations generally provide most of the information needed for protection system design, protection setting calculations and relay coordination. These studies may be carried out for various operating scenarios of the plant with existing earthing system and the performance of the plant can be reviewed and remedies can be suggested.The results of these studies will be provided in tabular form and also on single line diagram of the plant. These calculations will be performed for all types of shunt faults.
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Your blog shares valuable explanation about short circuit studies.Your discription is very usefull for analyse the short circuits in faulty conditions. Short circuit study is performed when an electrical system is first designed, and then updated the major modifications or renovation takes place, but no less frequently than every five years. Major changes would be considered a change in feed by the electric utility, in the primary and secondary system configuration or a change in the motors that are energized by the system.
ReplyDeleteThe representation of a short circuit currents is a tremendous amount of destructive energy, which can be released electrical systems under fault conditions. Short circuit current is the flow of electrical energy that results when the insulation barrier fails and allows current to flow in a shorter than the path of intended circuit. We are the one top most consultants of safety hazards. We provide the services like harmonic analysis, Arc flash analysis, Short circuit analysis, etc, …. If you have any queries, Click on