Presentation on theme: "POWER SYSTEM PROTECTION"— Presentation transcript:
1 POWER SYSTEM PROTECTION Presented By:Chandra Bhushan SinghElectrical and Electronics Engineering(7th sem)
2 Agenda Introduction Elements of protection system Electrical System fault and system Protection with Protective RelaysConclusion
3 Why A System Needs Protection? There is no ‘fault free’ system.It is neither practical nor economical to build a ‘fault free’ system.Electrical system shall tolerate certain degree of faults.Usually faults are caused by breakdown of insulation due to various reasons: system over current, over voltage, lighting, etc.
4 Element of protection system (1)Current and Voltage Transformers (2)Relays (3)Circuit breakers (4)Batteries (5)Fuses (6)Lighting Arresters
5 Current transformerCurrent transformer consists at least of two secondary windings.The first winding is usually designed for measuring, the second is used for protection.The secondary of current transformers are almost connected in star
6 Voltage transformerVoltage transformer is often consists of two windings.The first winding is connected in star, and the stare point must be earthed.The second winding is connected as open delta.
7 Relay Purpose Isolate controlling circuit from controlled circuit. Control high voltage system with low voltage.Control high current system with low current.Logic Functions
8 Advantages for Using Protective Relays Detect system failures when they occur and isolate the faulted section from the remaining of the system.Mitigating the effects of failures after they occur.Minimize risk of fire, danger to personal and other high voltage systems.
9 CIRCUIT BREAKER Low voltage circuit breaker Magnetic circuit breaker Medium voltage circuit breakerHigh voltage circuit breaker
10 Battery bank Battery bank are called as backbone of protection system Emergency use for power system
11 FuseFuses are selected to allow passage of normal current and of excessive current only for short periods.It is used to protect the low voltage or current rating devices
12 Lighting arresterA lightning arrester is a device used on electrical power system to protect the insulation damaging effect of lightning.All lighting arrester are earthed
14 Protective Devices Comparison Circuit Breaker v/s RelayRelays are like human brain; circuit breakers are like human muscle.Relays ‘make decisions’ based on settings.Relays send signals to circuit breakers. Based the sending signals circuit breakers will open/close.
15 Generator Protection Generator Differential Protection Loss of Field or Loss of Excitation ProtectionNegative Sequence or Current Unbalance ProtectionOver Fluxing or Over Excitation ProtectionOver Current ProtectionStator Earth Fault Protection
16 Rotor Earth Fault Protection Restricted Earth Fault ProtectionBackup Impedance ProtectionLow Forward Power ProtectionReverse Power ProtectionOver Frequency ProtectionUnder Frequency ProtectionOver Voltage Protection
17 Generator Protection Differential and Ground Fault
19 Negative Sequence:The direction of rotation of a negative sequence is opposite to what is obtained when the positive sequence are applied.Negative Sequence Relay will constantly measure and compare the magnitude and direction of the current.
24 Transformer Protection Ground Fault and Differential Relay
25 Thermal Overload Relays Use bimetallic strips to open/close relay contacts when temperature exceeds/drops to certain level.Require certain reaction timeInverse time/current relationship
26 Transmission line protection Distance protectionEarth fault protectionOver current protectionCarrier protection
27 Conclusion Relays control output circuits of a much higher power. Safety is increasedProtective relays are essential for keeping faults in the system isolated and keep equipment from being damaged.Relay is like an insurance against damage due to fault.