ANSI DEVICE NUMBERS FOR PROTECTION
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 –
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 –