ABB REU 610 Technical Reference Manual page 26

REU 610
26
Voltage Relay
Technical Reference Manual - ANSI Version
Element 27P-1 has a settable resetting time (both at definite-time and IDMT
characteristics), 27P-1 RESET, for reset coordination with existing
electromechanical relays or for reducing fault clearance times of recurring,
transient faults. If element 27P-1 has picked up and the phase-to-phase
voltages exceed the set pickup value of the element, the pickup of the element
remains active for the set resetting time. If the phase-to-phase voltages fall
below the set pickup value again while the timer is running, the timer is
cleared and the pickup of the element remains active.
Consequently, the set resetting time ensures that when the element picks up
because of voltage drops, it is not immediately reset. If element 27P-1 has
already tripped, the element is reset in 70 ms after the phase-to-phase voltages
have fallen below 0.15 × U
tripped and the phase-to-phase voltages have exceeded the set pickup value of
the element, the element is reset when the set resetting time has expired.
Element 27P-1 tripping can be set to be blocked by the pickup of element
27P-2 or 27D.
Element 27P-1 can also be configured to be used for alarm purposes. When a
trip signal is generated for alarm purposes, the Start/Alarm target LED is lit
and the fault is indicated as an alarm instead of a trip.
When element 27P-1 is configured to be used for alarm purposes:
Pickup signal of element is not generated
*
Trip signal of element is generated, but it is indicated as an alarm
*
Element cannot be used for triggering CBFAIL
*
Number of pickups is increased instead of number of trips
*
When the conventional protection mode is selected and the voltages fall
below the set pickup value of the high-set element, 27P-2, the element
generates a pickup signal after a ~ 50 ms' pickup time. When the set operate
time at definite-time characteristic or the calculated operate time at IDMT
characteristic elapses, the element generates a trip signal. The element is reset
in 70 ms after the phase-to-phase voltages have exceeded the set pickup value
of the element.
The undervoltage elements have a settable drop-off/pick-up ratio, which is
adjustable between 1.01...1.05, the default being 1.03.
Undervoltage protection based on positive phase-sequence
voltage
The undervoltage protection based on calculated positive phase-sequence
voltage can be applied to disconnecting a smaller power plant from the
outside network, for instance in situations where there is a fault in the
network which can be critical for the power plant, such as a short circuit
either at the transmission or distribution network level.
(VT). However, if element 27P-1 has already
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1MRS755972