In this article we will discuss about:- 1. Faults in Power System 2. Fault Statistics 3. Kinds. Faults in Power System: A fault in an electrical equipment/apparatus is defined as a defect in the electrical circuit due to which current is diverted from the intended path. The nature of a fault simply implies any abnormal condition which causes a reduction [...]
Mainly there are three sources which can feed into the short circuit of motors in the power system. The sources are:- 1. Generators. 2. Synchronous Motors and Synchronous Condensers. 3. Induction Motors. Source # 1. Generators as a Source of Fault Power: The generators are driven by prime movers and when the short circuit occurs, the generators continue to run [...]
Resistance and reactance (and consequently impedance) may be expressed in percentage or ohmic terms. In the case of rotating machines and transformers, manufacturer values are always in percentage terms while tables for cables and overhead lines are always in ohmic terms. Calculations can be made using either but not a mixture. For short circuit calculations, generally the percentage values are [...]
The short circuit may have any of the following consequences: 1. The heavy currents due to short circuit cause excessive heating which may result in fire or explosion. 2. Sometimes the short circuit takes the form of an arc that may cause considerable damage to the elements of the power system. For example, an arc on an overhead power line, [...]
Symmetrical (L-L-L) fault occurs infrequently, as for example, when a line, which has been made safe for maintenance and/or repairs by clamping all the three phases to earth, is accidently made alive or when, due to slow fault clearance, an earth fault spreads across to the other two phases or when a mechanical excavator cuts quickly through a whole cable. [...]
The results obtained from the faults at the terminals of an unloaded synchronous generator can also be used in the analysis of faults in power systems. Consider a short section of a transmission line in which phase is grounded. Only for theoretical purpose (for convenience of representation of fault currents), think of the fault as occurring on a short stub [...]
The synchronous generators may be subjected to different types of faults at its terminals and they are as follows- 1. Symmetrical Three-Phase (L-L-L or L-L-L-G) Fault 2. Single Line-to-Ground (L-G) Fault 3. Line-to-Line (L-L) Fault 4. Double Line-to-Ground (L-L-G) Fault. These are listed in increasing order of severity, and the symmetrical fault follows these as the most severe. If the [...]
The faults, involve power conductor or conductors-to-ground or short circuit between conductors and are termed as shunt faults. Such faults are characterized by increase in current and fall in voltage and frequency. On the other hand, a plain break in one or two conductors in a 3-phase circuit leads to an open-conductor or series fault. When fuses are used in [...]