ABB MDAR Instruction Manual page 52

I.L. 40-385.5
Z2RI or Z3RI signal via OR-62 and AND-86.
9.13.1 Logic for RB on BF squelch
For a pilot system, the BFI signal can be used to stop
(for a blocking system) or start (for permissive
schemes) the carrier channel to allow far end line ter-
minals to trip in the event a breaker close to an exter-
nal fault fail to open. The problem is how to inhibit it
reclosing on those terminals, to limit damage.
MDAR (REL-300) solves this problem at the far end
terminals by the Reclose Block on Breaker Failure
Squelch logic in the RI/RB software. When the
breaker fails to trip, the BFI logic squelches the chan-
nel to continuous permissive signal, or stops the
blocking signal. This is done after some time delay.
The relay at the far end, having sensed the external
fault in the forward direction, sees the permissive sig-
nal (or stoppage of blocking signal) much later than it
would for a normal pilot trip operation initiated by
relay forward-looking elements at the end closer to
the fault. This time delay is used to differentiate
between a faster normal pilot trip and the slower
problem-related pilot trip initiated by BFI, and to block
reclosing in the later case.
This logic is shown in Figure 24, which includes the
AND-61A and a 132/0 ms timer. The logic at the far
end terminal will initiate RB and inhibit RI) at 132 ms
(about 8 cycles) after the fault is detected by the
overreaching PLTP or PLTG element, if the pilot is
enabled and the TRSL signal is received on any
three-pole trip operation. If the fault is cleared before
the 132 ms expiration of the timer, normal reclosing
will occur.
9.13.2 For Single-pole-trip and pilot applications
The RI1 relay is provided for single-pole trip scheme,
which is controlled by the TTYP setting of SPR and
SR3R. Refer to Chapter X, Operation of MDAR
(REL-300) Optional Functions for the programmable
reclose initiation on single-pole trip or pilot applica-
tions.
9.14 POWER SWING BLOCK SUPERVISION,
OSB
The Out-of-step blocking (OSB) logic in MDAR (REL-
300) is a dual blinder scheme. It contains two blinder
units, providing 4 blinder lines. The nature of the logic
shown in Figure 25 is that the outer blinder 21BO
must operate 50 ms or more ahead of the inner
blinder 21BI, in order for an OS condition to be identi-
fied.
9-6
The OS logic is also supervised by the medium set
phase overcurrent signal (AND-122 on Figure 25).
The OSB signal is a negated input to the AND-131
(Z1P), AND-147 (Z2P), and AND-176 (PLTP) for
supervising the 3-phase distance trip.
The OSB signal is also applied to the reclosing logic
for initiating RB.
The OSB logic as shown in Figure 25 is proposed by
EPRI/China. Its design is based on the power system
operation practices and experiences in China. It
includes the following unique features:
• OSB is not applied to zone-3.
• OSB for zone-1, zone-2 and pilot is selected by
the setting of OSB1, OSB2 and OSBP,
respectively.
• Use separated timers OSOT1 and OSOT2 in
zone-1 and zone-2 logic for out-of-step override
tripping, as shown in Figure 25.
• An selectable OSTM timer setting, range 500 or
1000 ms, is provided for the logic. This timer will
be used for the following features.
• In order to ensure continuously OS block to the
Z-units from tripping on the second and the
following OS cycles where the swing rate may be
faster than the previous cycles, the modified OS
logic provides that once the out-of-step condition
is identified, the reset time of the output signal
from the OS timer will be controlled by the preset
time of OSTM.
• Provide logic for blocking zone-1 and pilot (not
zone-2 and zone-3) 3-phase units on severe
external fault with delay clearing (e.g. breaker
failure condition). This logic included the 21BI
signal, the 200/OSTM timer, and OR-122A, OR-
201A, as shown in Figure 25.
9.15 Communications
Refer to chapter XI for detail.
9.16 Fault Records and Intermediate Targets
Sixteen records and targets are stored. Refer to
chapter XI for detail.