GE MVAJ 05/10/20 Tripping and Control Relays
MVAJ 10. MVAJ 20
When configured for high burden applications, the burden is
either cut off or is economised to a low figure after a 40-60 ms
time delay. Due to the greater minimum operating current, the
high burden application also permits the use of supervision relays
such as type MVAX 11. where the wiring is at risk. The 40- 60 ms
time delay ensures reliable operation of series elements such as
type MCAA repeat relays.
Type MVAJ 102 relay is specifically designed for applications
requiring a tripping relay which is self-resetting after a nominal
delay of 2.5 seconds. This relay may be used, for example, for
inter-tripping between higher voltage and low voltage circuit
breakers of a large 3-phase power transformer.
This may become necessary when the high voltage circuit
breaker is tripped after a heavy internal fault by protection
which cannot conveniently provide an auxiliary contact with a
dwell time long enough to ensure correct tripping of the low
voltage circuit-breaker.
Typically, the relay is initiated by transformer protection, such as
overall protection, restricted earth fault and Bucholz relays, in
arrangements where both the HV and LV circuit-breakers are to
be tripped simultaneously.
The HV breaker may be expected to trip more quickly than the LV
breaker so the tripping signal is maintained by the delayed reset.
This ensures complete clearance by the LV circuit-breaker, even
though the fault may have been cleared largely by the HV breaker
and the protection has started to reset.