Protection Functions; Three Phase Current Protection; Earth Fault Protection - ABB REF601 CEI User Manual And Technical Description

1MDU07205-YN rev. F
Section 4
4.1
4.1.1
4.1.2
4.2
4.2.1
REF601 CEI
User's manual

Protection Functions

Three Phase Current Protection

Functionality
The three-phase overcurrent protection is used as one-phase, two-phase or three-
phase non-directional overcurrent and short-circuit protection for feeders.
The function starts when the current exceeds the set limit. The operate time char-
acteristics for low stage is only IDMT (VI) and high stage is defi nite time (DT) defi nite
minimum.The instantaneous stage always operates with the DT characteristic.
In the DT mode, the function operates after a predefi ned operate time and resets
when the fault current disappears. The IDMT mode provides current-dependent timer
characteristics
Principle of Operation
The three-phase overcurrent unit continuously measures the phase currents of the
protected object. On detection of a fault the relay starts, trips the circuit breaker, pro-
vides alarm, records fault data etc. in accordance with the application
REF601 has overcurrent protection with low set, high set and very high set module.
The product support IDMT times (VI Curve) in low set (I>) while high set (I>>) and Very
high set (I>>>) supports to DMT timings. As the fault current exceeds the set value,
trip time counting is started and start LED on front panel of relay glows ON. If fault
current falls down below the drop-off value of set current for 40 ms before trip time
gets complete, start LED will be turned off and trip count will become zero. Trip time
will start from zero for next time when the fault current exceeds the set value again.
After a healthy trip, Start LED will be turned off and again if fault current exceeds
threshold, start LED will be turned ON again.
In case of healthy trip, after trip time get elapsed relay generates the trip command
which operates the Trip relay contacts as per user selected product variant. Two LED
indications on front plate of relay i.e. Trip (common trip indication) and Trip Ip and one
signaling contact (XK2.3 –XK2.4) will also be activated for user as Trip indication.

Earth Fault Protection

Functionality
The earth-fault function is used as non-directional earth-fault protection for feeders.
The function starts and operates when the set current exceeds the set limit.
Protection Functions
25