CHAPTER 7: PROTECTION
CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
291
Figure 249: DUTT scheme logic
Permissive under-reaching transfer trip
The permissive under-reaching transfer trip (PUTT) scheme uses an under-reaching zone 1
distance element to key transfer trip signal to the remote terminals where they are
supervised by an over-reaching zone 2 distance element. For proper operation, the zone 1
and 2 phase and ground distance elements must be enabled, configured, and set as per
the principles of distance relaying.
In single-pole tripping applications, the PUTT scheme uses local fault type identification
provided by the phase selector together with information received from the remote
terminals. The scheme generates output operands (
PUTT TX1
through
PUTT TX4
) that are
used to transmit the signal to the remote ends. Choices of communications channel
include remote inputs, remote outputs, and telecommunications interfaces. When used
with telecommunications facilities the output operands should be assigned to operate
output contacts connected to assert the individual bits at the interface.
To make the PUTT scheme a fully operational stand-alone feature, the scheme output
operands must be configured to interface with other relay functions, in particular the
output contacts. The output operands are typically programmed to initiate a trip, breaker
fail, and autoreclose, and drive an annunciator indication as per user requirements. When
used in conjunction with the trip output element, the scheme is pre-configured to initiate
trip, breaker fail and single-pole autoreclose actions.
Select the
Settings > Protection > Control > Pilot Schemes > PUTT Scheme
menu item to
access the permissive under-reaching transfer trip settings.
Figure 250: PUTT scheme configuration settings
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