GE D60 Instruction Manual page 547

CHAPTER 5: SETTINGS
This menu allows selecting and setting up protection signaling of the directional comparison unblocking scheme. This
scheme is available for single-pole tripping applications and can be used with one, two, or four bit communications
channels. Choices of communications channel include remote inputs/outputs and telecommunications interfaces.
Generally, this scheme uses an over-reaching zone 2 distance element to compare the direction to a fault at all terminals
of the line. Ground directional overcurrent functions available in the relay can be used in conjunction with the zone 2
distance element to key the scheme and initiate its operation. This increases the coverage for high-resistance faults.
The scheme is for two or three-terminal applications. As a long reach of the overreaching distance element can be
required for three-terminal applications, transient blocking logic is provided for both distance and ground directional
overcurrent elements. An echo feature is made available to cope with line open conditions.
By default, the scheme uses the reverse-looking zone 4 distance element to identify reverse faults. Additionally, reverse-
looking ground directional overcurrent functions can be used in conjunction with the zone 4.
For proper operation of the scheme, the zone 2 and 4 phase and ground distance elements must be enabled, configured,
and set per rules of distance relaying. Enable the line pickup element, configure it, and set it to detect line-end-open
conditions. If used by this scheme, the selected ground directional overcurrent function(s) must be enabled, configured,
and set accordingly.
In single-pole tripping applications, the scheme uses local fault type identification provided by the phase selector together
with information received from the remote terminal. The scheme generates output operands
that are used to transmit the signal to the remote terminal(s). The directional comparison unblocking scheme was
developed for use with frequency shift keying communications channels, though different telecommunications interfaces
can be used (for example, digital communication channels utilizing the D60 teleprotection input/outputs).
To make the scheme fully operational as a stand-alone feature, the scheme output operands must be configured to
interface with other relay functions, output contacts in particular. Typically, you program the output operands to initiate a
trip, breaker fail, and autoreclose, and drive a user-programmable LED as per the intended application.
When used in conjunction with the trip output element, the scheme is pre-configured to initiate trip, breaker fail, and
autoreclose actions.
— This setting allows the user to assign any FlexLogic operand to block the scheme. Contact inputs from a
DCUB BLOCK
pilot cut-out switch are typically used for this purpose.
— Enabling this setting sends a permissive echo signal to the remote end(s) under certain
DCUB PERMISSIVE ECHO
conditions (see the logic diagram for details). If set to "Custom", the echo signal is sent if a condition selected with the
setting is satisfied. The echo is sent only once and then the echo logic locks out for the time specified by the
ECHO COND
setting. The duration of the echo pulse is programmable by the
ECHO LOCKOUT
returned only if no overreaching and reverse protection elements operate.
— This setting specifies a user-selected echo condition and applies if the
DCUB ECHO COND
"Custom".
— This setting defines the FlexLogic operand (if any) of a protection element used in addition to zone 2 for
GND DIR O/C FWD
identifying faults on the protected line, and thus, for keying the communication channel(s) and initiating operation of the
scheme (both through the transient blocking logic).
Good directional integrity is the key requirement for an over-reaching forward-looking protection element set as
. Even though any FlexLogic operand can be set as
O/C FWD
responses of various protection elements or to apply extra conditions through FlexLogic equations, this extra signal is
primarily meant to be the output operand from either the negative-sequence directional or neutral directional overcurrent
elements. As both these elements have separate forward and reverse output operands, use the forward indication (that is,
or
NEG SEQ DIR OC1 FWD NEUTRAL DIR OC1
D60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
DCUB LOG4:

Off
DCUB SCHEME TARGET:

Self-Reset
DCUB SCHEME EVENTS:

Disabled
GND DIR O/C FWD
FWD).
Range: FlexLogic operand
Range: Self-Reset, Latched, Disabled
Range: Disabled, Enabled
(DCUB TX1
setting. The echo is
ECHO DURATION
DCUB PERMISSIVE ECHO
, thereby enabling the user to combine
CONTROL ELEMENTS
5
through
DCUB TX4)
DCUB
setting is
GND DIR
5-369