GE D90 Plus Instruction Manual page 332

CONTROL ELEMENTS
322
The loss-of-guard operation picks up if all of the following conditions hold:
• The directional comparison unblocking scheme is enabled and not blocked (that is, the
scheme is active)
• Any loss-of-guard signal is received without its associated RX signal
• A fault is seen in the forward zone 2 distance elements or ground directional forward
function (if configured)
• The reverse zone 4 distance elements or ground directional reverse function (if
configured) did not pickup to set the transient blocking
If all of these conditions are met, then the timer specified by the
setting is started. After this timer times out, the trip table is run, operating the
Delay
scheme and asserting the
local phase selector and loss-of-guard signals, determine which tripping operands
operate. The timer specified by the
all channels to transition from guard to permissive before operating due to loss-of-guard in
the presence of a forward fault. The time window of allowing the scheme to operate when
no signal is received when any loss-of-guard was received is the difference
DCUB RX
between the timers specified by the
settings. For the default settings, this value is 150 – 8 = 142 ms. This means the
Delay
scheme is unblocked and can trip during this time window if a forward fault is sensed.
The keying signals, which allows the relay to key the permissive channel during normal
permissive scheme operation by means of the
established when all of the following conditions hold:
• The directional comparison unblocking scheme is enabled and not blocked (that is, the
scheme is active)
• A fault is seen in the forward zone 2 distance elements or ground directional forward
function (if configured)
• The reverse zone 4 distance elements or ground directional reverse function (if
configured) did not pickup to set the transient blocking
If all of these conditions are met, then the directional comparison unblocking scheme keys
the channels by means of asserting transmit signals
aid of the local phase selector or zone 2 distance elements.
The echo signal, which allows the D90
through transmit operands during echo conditions when the local breaker
TX1 DCUB TX4
opened, keys the carrier(s) if all of the following conditions hold:
• The directional comparison unblocking scheme is enabled and not blocked (that is, the
scheme is active)
• The Permissive Echo setting is "Enabled"
• The
LINE PICKUP LEO PKP
the time specified by
Line End Open Pickup Delay
• Any permissive signal
signal is received
DCUB LOG4
• A fault is not seen in the forward zone 2 distance elements or ground directional
forward function (if configured) for at least 100 ms
• The reverse zone 4 distance elements or ground directional reverse function (if
configured) did not pickup to set the transient blocking
If all of these conditions are met, then the directional comparison unblocking scheme
echoes (transmits the
DCUB TX1
RX signals back to the remote relay based on the echo table.
The keying or transmit signals
echo keying conditions.
FlexLogic operand. The trip table, with the aid of the
DCUB OP
Loss Of Guard Pickup Delay
Loss of Guard Trip Window
DCUB TX1
DCUB TX1
Plus
to key the permissive channels through the
operand that detects the local breaker to be open picks up for
through
DCUB RX1 DCUB RX4
through operands) the received permissive DCUB
DCUB TX4
through
DCUB TX1 DCUB TX4
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION
Loss Of Guard Pickup
setting allows for any and
and
Loss Of Guard Pickup
through signals, are
DCUB TX4
through with the
DCUB TX4
setting
is received and any
DCUB LOG1
consist of all normal keying or
DCUB
to