GE D90 Plus Instruction Manual page 327

CHAPTER 7: PROTECTION
Pilot-aided scheme application guidelines
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 264: Directional comparison unblocking scheme logic, sheet 2 of 2
This section provides guidelines for implementing pilot-aided schemes with the D90
Direct underreaching transfer trip (DUTT) application guidelines
The direct underreaching transfer trip (DUTT) scheme uses an under-reaching zone 1
distance element to key a transfer trip signal to the remote end or ends, where on receipt,
the DUTT pilot scheme operates without any additional supervision.
For proper operation of the scheme, the zone 1 phase and ground distance elements must
be enabled and configured per the standard rules of distance relaying.
The DUTT scheme generates an output operand
to the remote end. Choices of communications channel include remote inputs and outputs
and telecommunications interfaces. When used with telecommunications facilities, assign
the output operand to operate an output contact connected to key the transmitter at the
interface.
Note that the same protection signaling can be used by a breaker failure scheme, in which
case the signal can be sealed in by breaker failure for a time longer than the autoreclose
"reclaim" time that then prevents autoreclose when not required.
A provision for an optional seal-in of the send signal is made to cover those situations
where power line carrier (PLC) signaling is used and the signal must be transmitted in a
potentially noisy situation due to the fault.
The scheme output operand
Plus
D90 functions (output contacts in particular) to make the scheme fully operational.
Typically, program the output operand to initiate a trip, breaker fail, and autoreclose, and
to drive a user-programmable LED as per user requirements.
Permissive underreaching transfer trip (PUTT) application guidelines
The permissive underreaching transfer trip (PUTT) scheme uses an underreaching zone 1
distance element to key a transfer trip signal to the remote end where it is supervised by
the overreaching zone 2 distance elements.
For proper operation of the scheme the zone 1 and 2 phase and ground distance elements
must be enabled and configured per the standard rules of distance relaying.
(DUTT TX) that is used to transmit the signal
(DUTT OP) must be configured to interface with other
CONTROL ELEMENTS
Plus
.
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