They remain inoperative for a long time before a fault occurs; but if a fault occurs, the relays must respond instantly and correctly.
It is quite simple. In this case, the protection levels include the entire plant and also the public too. Sensitivity The relaying equipment must be sufficiently sensitive so that it can be operated reliably when level of fault condition just crosses the predefined limit.
Speed The protective relays must operate at the required speed. The main purpose of these devices is to keep the power distribution network as simple as possible.
The cost of protection is directly dependent on the kind of device in use. Backup Relay Reset Time of Relay: Without this reliability, systems may cause costly damages. They may be installed locally, that is, in the same substation as the primary relays, or remotely.
Historically, protective device coordination was done on translucent log—log paper. A level detector can be used to detect the magnitude of this comparison or a special relay such as a percentage differential or harmonic restrained relay is applicable.
Very important equipment may have completely redundant and independent protective systems, while a minor branch distribution line may have very simple low-cost protection. Secondly it has to investigate any possible occurrence of disturbance.
Fault current may flow through a part of healthy portion since they are electrically connected but relays associated with that healthy portion should not be operated faster than the relays of faulty portion otherwise undesired interruption of healthy system may occur.
Reliability, Dependability, and Security Reliability is generally understood to measure the degree of certainty that a piece of equipment will perform as intended. Protection Aspects of Multi-Terminal Lines.
The equation is to protect the remaining operating network besides clearing the fault. Normally the three phase currents are in balance, i. Both dependability and security are reliability issues.
Solid-State Relays All of the functions and characteristics of electro-mechanical relays can be performed by solid-state devices, either as discrete components or as integrated circuits.
Figure 1 shows the zones of protection in a typical system. The most important parameter in this regard is the operating quality. Distance impedance relay [ edit ] Distance protection detects both voltage and current.
It is installed in series with the equipment being protected, and it operates by melting a fusible element in response to the current flow. The intention of the protective control is to cater to the affected area and not the entire system. Devices must minimize protection circuitry and equipment. Their purpose is to limit, to the extent possible, further damage to equipment, to minimize danger to people, to reduce stress on other equipment, and above all, to remove the faulted equipment from the power system as quickly as possible so the integrity and stability of the remaining system is maintained.
The secondary of current transformer is connected to the current coil of relay and secondary of voltage transformer is connected to the voltage coil of the relay.Power System Protection is the epergne of any power system network & its reliability is of critical importance.
Fast, reliable & accurate protection techniques will always be needed to ensure the integrity of the power system. The actuating impedance in the relay is the function of distance in a distance protection relay.
This impedance or corresponding distance is called the reach of relay. Power system protection relays can be categorized into different types of relays/5(16).
Power System Studies. Today’s competitive electric power market puts a premium on reliability, efficiency and low cost. POWER Engineers provides essential analysis and planning services that help you meet those goals.
POWER SYSTEM PROTECTION Introduction Below Fig. 1 is an typical example of power system sections with their protection systems. Where: G1 is a generator. FUNCTIONS OF EQUIPMENTPROTECTIONProtection schemes are generally divided into equipmentprotection and system mint-body.com main function of equipment protection.
Purpose of POWER System protection The purpose of any power system is to generate, transmit, and distribute electricity to the consumer in a manner that is safe, reliable, and economical; both in the short and long term.
NSF/ECEDHA Education Workshop Georgia Tech GLC, Atlanta, Georgia, JulyBasics of Power System Control and Protection A. P. Sakis Meliopoulos.Download