Download Protective Relays in Power Systems: Functions, Types, and Causes of Faults and more Study notes Engineering in PDF only on Docsity! What are function of protective relay? The function of protective relaying is to cause the prompt removal from service of any element of a power system when it suffers a short circuit, or when it starts to operate in any abnormal manner that might cause damage or otherwise interfere with the effective operation of the rest of the system. How the electrical power system protection is divided? 1.Transmission Line Protection and feeder protection 2.Transformer Protection 3.Generator Protection 4.Motor Protection 5.Bus bar Protection What do you mean by zone protection? Protection zone is defined as the part of the power system which is protected by a certain protective scheme. It is established around each power system equipment. When the fault occurs on any of the protection zones then only the circuit breakers within that zone will be opened. How many types of fault are there in 3 phase system? Symmetrical Faults Unsymmetrical Faults Why does the adjacent zone of protection overlap? Draw single line diagram of power station? What is meant by busbar protection? Busbar protection is a protection scheme meant to protect the busbar from electrical fault. Various feeders are connected to a busbar through circuit breaker in any of the bus configuration viz. Double Busbar arrangement or one and half breaker scheme. What are the effect of electrical fault? Over current flow: When fault occurs it creates a very low impedance path for the current flow. This results in a very high current being drawn from the supply, causing tripping of relays, damaging insulation and components of the equipments. Danger to operating personnel: Fault occurrence can also cause shocks to individuals. Severity of the shock depends on the current and voltage at fault location and even may lead to death. Loss of equipment: Heavy current due to short circuit faults result in the components being burnt completely which leads to improper working of equipment or device. Sometimes heavy fire causes complete burnout of the equipments. Disturbs interconnected active circuits: Faults not only affect the location at which they occur but also disturbs the active interconnected circuits to the faulted line. Electrical fires: Short circuit causes flashovers and sparks due to the ionization of air between two conducting paths which further leads to fire as we often observe in news such as building and shopping complex fires. Give some example of fault limiting device? Fuse: It is the primary protecting device. It is a thin wire enclosed in a casing or glass which connects two metal parts. This wire melts when excessive current flows in circuit. Type of fuse depends on the voltage at which it is to operate. Manual replacement of wire is necessary once it blowout. Circuit breaker: It makes the circuit at normal as well as breaks at abnormal conditions. It causes automatic tripping of the circuit when fault occurs. It can be electromechanical circuit breaker like vacuum / oil circuit breakers etc, or ultrafast electronic circuit breaker. Relay:
