RFL Electronics GARD 8000, Инструкция по эксплуатации

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Description of Operation
GARD 8000 Distance Relay RFL Electronics Inc.
‘Distance transient block enable’. When transient block is enabled, Zone 4 is forced in the reverse
direction regardless of its directional setting.
9.2.9 WEAK INFEED LOGIC
Weak Infeed logic may be used with the permissive overreach scheme for cases when one of the
terminal units has a weak supply and is not able to transmit the channel signal. An Echo function is
available, which allows the channel signal to be transmitted to the remote-end terminal whenever a
channel signal has been received from the remote-end terminal, and none of the blocking elements is
activated. The Weak Infeed Scheme trip function must also be enabled.
When both terminal units are under normal supply, this scheme behaves like the Permissive Overreach
Scheme. A trip is generated when a fault is detected by the overreach elements (zone 2 or zone 3), the
reverse-looking elements (zone 4) are deactivated, and the remote-end terminal has transmitted the
channel signal. Once the remote-end channel signal has been received (and the overreach elements and
the reverse-looking elements are not activated, indicating that the fault is inside the line), the terminal
will transmit a signal back to the emitter (echo signal) allowing tripping. This signal allows the remote-
end terminal to trip by their overreach elements.
Proper operation of this scheme requires that the measuring element used to activate the channel is
adjusted reverse. Therefore, if Weak Infeed is selected, Zone 4 will be set as reverse, even if the setting
is selected as forward.
As a complement, this scheme includes Weak Infeed Trip logic. A trip by this logic will occur when all
of the following conditions are satisfied:
1. Channel signal is received (trip permitted).
2. Overreach elements (zone 2 or zone 3) and blocking elements (zone 4) are deactivated.
3. Undervoltage elements have picked up.
The channel receive signal is provided with a pick-up delay to prevent operation for spurious carrier
signals. The time is set by ‘Security Time’.
Weak feed trip is blocked by loss-of-potential (fuse fail) if this is set to ‘Enable LOP Block’.
To ensure proper operation for reverse faults (as detected by Zone 4), the weak feed blocking function
provided by these elements is drop-out delayed by the time set on ‘Distance extend time’.
The carrier echo signal will be sent for 100 ms only. This avoids the risk of an echo signal continuing
being sent from one terminal to the other, just to be echoed back.
August 1, 2009 9-26 973.334.3100