ABB REL 301, Инструкция

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I.L. 40-386.4
2-15
The basic operating concepts of a Simplified Unblocking scheme are the same as the POTT
scheme, except for differences in applied pilot channel equipment. In an unblocking scheme, the
pilot channel is a frequency-shift type power line carrier. The transmitter frequency must be dif-
ferent at each terminal. It is normally operated on a blocking frequency and will be shifted to an
unblocking frequency when the pilot relay(s) operate. The carrier receiver should provide logic
for which, in the event of loss-of-channel or low SNR ratio, the pilot trip circuit is automatically
locked out after a short time delay. Pilot trip is provided, however, if the tripping distance relay(s)
operate during this short time period between loss-of-channel and pilot trip lockout. Pulsar
Technologies Inc. type TCF-10B receiver provides this logic; it provides a 150 ms trip window,
then automatic lockout after loss-of-channel. Provision for a second high-speed pilot trip is pro-
vided, for the situation when a permanent fault causes a permanent loss-of-channel and the
breaker closes onto the fault.
The operating concepts of the pilot distance measurement units PLTP and PLTG are the same
as for the non-pilot zone distance measurement units, and are supervised by the same LOPBS,
OSB, IOM, FDOP, and FDOG units, as shown in Figure 2-20. The pilot phase and/or pilot
ground function(s) can be disabled by setting the “Pilot Ø” and/or “Pilot G” to “Disabled”.
The POTT and Simplified Unblocking schemes include the following types of logic:
a. Tripping logic (Figure 2-21)
(1) For a forward external fault, the local pilot distance measurement units PLTP or PLTG de-
tect the fault, operates and keys the pilot channel. The output from OR 40 will satisfy the
first input to AND 30. Assuming that REVERSE BLOCK LOGIC (TBM) does not operate
and PILOT ENABLE (see Figure 2-21 for definition) is set, then three out of four inputs of
AND 30 are satisfied, but pilot trip cannot occur since the remote transmitter is still sending
a guard (or blocking frequency) signal. CR input to AND 30 is not satisfied.
(2) For an internal fault, the pilot relays at both ends PLTP or PLTG, or the zone-1 relays Z1P
or Z1G, detect the internal fault and operate and together with the received trip (or unblock-
ing frequency) signal CR, via AND 44 (Figure 2-22), satisfy AND 30 (Figure 2-21). PT
(Pilot Trip) output of AND 30, will cause high speed tripping via OR 2 (Figure 2-5). Targets
of pilot phase trip or pilot ground trip will result after the breaker trips (TRSL).
b. Carrier Keying Logic (Figure 2-22)
(1) Forward Fault Keying
For a forward internal or external fault, the local pilot relays PLTP or PLTG, or the zone-1
relays Z1P or Z1G, detect the fault operates OR 40 or OR 25, and causes pilot channel
SEND reed relay to operate, via AND 35, if PILOT ENABLE is set. Operation of the SEND
relay will key the local transmitter, shift the transmitting frequency from guard to trip (or from
a blocking to an unblocking), which allow the remote pilot relay system to trip.
(2) Echo Keying
Since the POTT and the Simplified Unblocking schemes require the receiving of a permis-
sive signal from the remote end, for pilot trip, provision is made for the condition when the
remote breaker is opened.
When the breaker is opened, the inputs of AND 34B (Figure 2-22) three of the inputs are
satisfied by the NOT FORWARD (from OR 14), NOT REVERSE (from TBM) and 52b.
Channel receive from either RCVR-1 (2 terminal system configuration) or RCVR-1 and
RCVR-2 (3 terminal system configuration, Figure 2-28) will produce an output from AND