Protection
18
One definite time overcurrent stage
One definite time earth fault protection
stage
Inrush restraint can be selected
Cross blocking for inrush detection
Settable maximum inrush current
Manual closing binary input detection
Overload protection
(50OL)
The IED supervises load flow in real time.
If each phase current is greater than the
dedicated setting for a set delay time, the
protection will issue alarm.
Overvoltage protection
(59)
The
overvoltage
protection
detects
abnormally
network
high
voltage
conditions. Overvoltage conditions may
occur possibly in the power system during
abnormal conditions such as no-load,
lightly load, or open line end on long line.
The protection can be used as open line
end detector or as system voltage
supervision normally.
The protection provides following features:
Two definite time stages
Each stage can be set to alarm or trip
Measuring voltage between phase-
-earth
voltage
and
phase-phase
(selectable)
Settable dropout ratio
Undervoltage
protection (27)
One voltage reduction can occur in the
power system during faults or abnormal
conditions.
The protection provides following features:
Two definite time stages
Each stage can be set to alarm or trip
Measuring voltage between phase-
-earth
voltage
and
phase-phase
selectable
Current criteria supervision
Circuit
breaker
aux.
contact
supervision
VT secondary circuit supervision, the
Undervoltage function will be blocked
when VT failure happens
Settable dropout ratio
Breaker failure
protection (50BF)
The circuit breaker failure protection is
designed to detect failure of the circuit
breaker during a fault clearance. It ensures
fast back-up tripping of surrounding
breakers by tripping relevant bus sections.
The protection can be three phase started
to allow use with single or three-phase
tripping applications.
Once a circuit breaker operating failure
occurs on a feeder/transformer, the bus
section which the feeder/transformer is
connected with can be selectively isolated
by the protection. In addition a transfer trip