ANSI DEVICE NUMBERS FOR PROTECTION

Topics: Circuit breaker, Electric motor, Earth Pages: 8 (1426 words) Published: June 9, 2014
CURRENT PROTECTION FUNCTIONS

ANSI 50/51 – Phase over-current
ANSI 50N/51N or 50G/51G – Earth fault or sensitive earth fault ANSI 50BF – Breaker failure
ANSI 46 -Negative sequence / unbalance
ANSI 49RMS – Thermal overload

CURRENT PROTECTION FUNCTIONS
ANSI 50/51 – PHASE OVERCURRENT
Three-phase protection against overloads and phase-to-phase short-circuits. ANSI 50N/51N OR 50G/51G – EARTH FAULT
Earth fault protection based on measured or calculated residual current values: ANSI 50N/51N: Residual current calculated or measured by 3 phase current sensors ANSI 50G/51G: residual current measured directly by a specific sensor ANSI 50BF – BREAKER FAILURE

If a breaker fails to be triggered by a tripping order, as detected by the non-extinction of the fault current, this backup protection sends a tripping order to the upstream or adjacent breakers. ANSI 46 – NEGATIVE SEQUENCE / UNBALANCE

Protection against phase unbalance, detected by the measurement of negative sequence current: Sensitive protection to detect 2-phase faults at the ends of long lines Protection of equipment against temperature build-up, caused by an unbalanced power supply, phase inversion or loss of phase, and against phase current unbalance ANSI 49RMS – THERMAL OVERLOAD

Protection against thermal damage caused by overloads on machines (transformers, motors or generators). The thermal capacity used is calculated according to a mathematical model which takes into account: Current RMS values

Ambient temperature
Negative sequence current, a cause of motor rotor temperature rise

RECLOSER
ANSI 79
Automation device used to limit down time after tripping due to transient or semi-permanent faults on overhead lines. The recloser orders automatic reclosing of the breaking device after the time delay required to restore the insulation has elapsed. Recloser operation is easy to adapt for different operating modes by parameter setting. DIRECTIONAL POWER PROTECTION FUNCTIONS

ANSI 32P – Directional active overpower
ANSI 32Q/40 – Directional reactive overpower

ANSI 32P – DIRECTIONAL ACTIVE OVERPOWER
Two-way protection based on calculated active power, for the following applications: Active overpower protection to detect overloads and allow load shedding Reverse active power protection:
Against generators running like motors when the generators consume Active power Against motors running like generators when the motors supply active power ANSI 32Q/40 – DIRECTIONAL REACTIVE OVERPOWER

Two-way protection based on calculated reactive power to detect field loss on synchronous machines: Reactive overpower protection for motors which consume more reactive Power with field loss Reverse reactive overpower protection for generators which consume Reactive power with field loss.

VOLTAGE PROTECTION FUNCTIONS
ANSI 27D – Positive sequence under-voltage
ANSI 27R – Remanent under-voltage
ANSI 27 – Phase-to-phase under-voltage
ANSI 59 – Phase-to-phase overvoltage
ANSI 59N – Neutral voltage displacement
ANSI 47 – Negative sequence voltage
ANSI 27D – POSITIVE SEQUENCE UNDERVOLTAGE
Protection of motors against faulty operation due to insufficient or unbalanced network voltage, and detection of reverse rotation direction. ANSI 27R – REMANENT UNDERVOLTAGE
Protection used to check that remanent voltage sustained by rotating machines has been cleared before allowing the busbar supplying the machines to be re-energized, to avoid electrical and mechanical transients. ANSI 27 – UNDERVOLTAGE

Protection of motors against voltage sags or detection of abnormally low network voltage to trigger automatic load shedding or source transfer. Works with phase-to-phase voltage. ANSI 59 – OVERVOLTAGE

Detection of abnormally high network voltage or checking for sufficient voltage to enable source transfer. Works with phase-to-phase or phase-to-neutral voltage, each voltage being monitored separately. ANSI 59N – NEUTRAL VOLTAGE DISPLACEMENT

Detection of insulation faults by...
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