Wednesday, March 11, 2009

Generator Electrical Protective Relay Devices base on ANSI


Over excitation protection Volt/Hertz relay (ANSI No.24)

Relay ini harus di-set untuk meng-counter high induction
proporsional dengan V/f, yang mengakibatkan thermal
overloading. These may occur during starting and shut


Picture :
ABB-product series-compact and integrated with multi protectiondown under full load condition




Under voltage relay (ANSI No.27)
This relay prevents generator/motor to operate below normal voltage/frequency operating system cause by AVR or internal faults. Time delay must be set slower than transient system voltage dip and must be faster than too much slowing down generator and make re accelerate to meet proper plant recovery

Reverse power relay (ANSI No. 32)
This device protects generator to receive power from system in case of failing prime mover to drive generator. Turn back power may damage generator.

Lost of excitation relay (ANSI No. 40)
Faulty in generator field excitation circuitry causes generator loss of excitation. In this case generator will act as induction generator which received reactive power from system. This condition will make instability in power system and over heating on damper rotor windings

Negative sequence relay (ANSI No.46)
These are included to detect phase unbalance, phase reversal, and phase sequence fault. These abnormal condition will heat machine windings. This kind of relay is more independent to do close/open power system

Inadvertent energizing relay (ANSI No. 50/27)
Due to unintentionally energizing will make generator damage. This relay will limit down possibility of generator damage. Actually this relay is combination of over current relay and under voltage relay with controlling electronic digital logic.

Breaker failure relay (ANSI No.50BF)
In the event of a downtimes or faulty in generator, generator can remain online if the breaker is defective or substantial damage. This protection will measure minimum breaker current and thru auxiliary contact. It can be activated via internal protective tripping or externally via binary input

Sensitive earth fault relay (ANSI No.50/51G)
This device is for Limiting damage of generator in the event of rotor earth fault. The sensitive earth fault can be use as separate earth fault protection

Definite time over current relay (ANSI No.50/51)
This is short circuit protective device

Inverse time over current relay (ANSI No 51V)
This is also short circuit protective device with ANSI and IEC curve characteristic respond. This can be selected base on system requirement

Over voltage relay (ANSI No.81U)
This protect generator voltage regulator that could be damaged in an over voltage condition due to AVR failure or manual voltage control errors. A time delay is provided to prevent tripping under transient voltage spikes

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