Different operating mechanisms such as solenoid, spring, pneumatic, hydraulic etc. Functional Requirements of Protection Relay Reliability The most important requisite of protective relay is reliability.
At a basic level, protection disconnects equipment which experiences an overload or a short to earth.
If the ratio of voltage to current measured at the relay terminals, which equates to an impedance, lands within a predetermined level the circuit breaker will operate. With more complex systems, it is necessary to detect the point of fault precisely and trip only those sections affected by the fault Electrical protection the rest of the system can continue to function normally.
Both dependability and security are reliability issues. There are two types of overload protection: Instantaneous overcurrent requires that the current exceeds a predetermined level for the circuit breaker to operate.
During fault the protection relay gives trip signal to the associated circuit breaker for opening its contacts. A circuit breaker or protection relay may fail to operate. Additionally, zones possess the following features: Types of protection[ edit ] High-voltage transmission network[ edit ] Protection on the transmission and distribution system serves two functions: If the relay setting is determined to be below the apparent impedance it is determined that the fault is within the zone of Electrical protection.
Some items in substations such as transformers might require additional protection based on temperature or gas pressure, among others. Hence, the battery is another essential item of the power system. You will also learn how to Electrical protection the setting of the relays so that the relays closest to the fault will operate and clear the fault faster than the backup devices.
Relays were initially electro-mechanical devices but static relays and more recently digital relays have become the norm.
Very important equipment may have completely redundant and independent protective systems, while a minor branch distribution line may have very simple low-cost protection.
Devices must provide maximum protection at minimum cost. This relay contact actually closes and completes the DC trip coil circuit and hence the trip coil is energized. Remote back-up protection will generally remove both the affected and unaffected items of plant to clear the fault.
Distance impedance relay [ edit ] Distance protection detects both voltage and current. An electrical substation battery or simply a station battery containing a number of cells accumulate energy during the period of availability of AC supply and discharge at the time when relays operate so that relevant circuit breaker is tripped at the time failure of incoming AC power.
Restricted earth fault protection is a type of earth fault protection which looks for earth fault between two sets of current transformers  hence restricted to that zone. If this imbalance exceeds a pre-determined value, a circuit breaker should operate. Protection coordination is also handled through dividing the power system into protective zones.
Again if relay associated with faulty portion is not operated in proper time due to any defect in it or other reason, then only the next relay associated with the healthy portion of the system must be operated to isolate the fault.
There may be some typical condition during fault for which some relays should not be operated or operated after some definite time delay hence protection relay must be sufficiently capable to select appropriate condition for which it would be operated.
Overlapped regions are created by two sets of instrument transformers and relays for each circuit breaker. Protective relays control the tripping of the circuit breakers surrounding the faulted part of the network Automatic operation, such as auto-re-closing or system restart Monitoring equipment which collects data on the system for post event analysis While the operating quality of these devices, and especially of protective relays, is always critical, different strategies are considered for protecting the different parts of the system.
Such failures are unusual, so the protective relays have to operate very rarely. Zone definitions account for generatorsbuses, transformerstransmission and distribution linesand motors. Devices must minimize protection circuitry and equipment.
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.
There are three parts to protective devices: Sign up for free unlimited access Access to In the picture the basic connection of protection relay has been shown.
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.
They are designed for redundancy to eliminate unprotected areas; however, overlapped regions are devised to remain as small as possible such that when a fault occurs in an overlap region and the two zones which encompass the fault are isolated, the sector of the power system which is lost from service is still small despite two zones being isolated.
Equipment such as generators, transformers and motors also need special forms of protection characterised by their design and operating principles.Sensata is a world leader in the design and production of electrical protection devices for aircraft, home appliances, automotive, and more.
The objective of power system protection is to isolate a faulty section of electrical power system from rest of the live system so that the rest portion can function satisfactorily without any severe damage due to fault current.
Actually circuit breaker isolates the faulty system from rest of the healthy system and these circuit breakers 4/4(8). P&B are specialist design and manufacturers of electrical protection and control technologies - including new and retrofit Switchgear and Protection Relays.
If you have no electrical background, you will struggle with this course. Technological Requirements All you need to participate is a computer with an adequate Internet connection, speakers and, if possible, a microphone.
Basics of Power System Control and Protection A. P. Sakis Meliopoulos Georgia Power Distinguished Professor School of Electrical & Computer Engineering Georgia Institute of Technology.
Protection generators, transformers, lines, motors, capacitors, reactors System Protection. Eaton’s complete line of circuit protection products reflects a long tradition of creating solutions that enhance electrical safety, reliability, code compliance and efficient power distribution in alternative energy, commercial, industrial and mining operations.Download