Dcb Logic - Sel -300 Series Application Manual

DCB L
OGIC
When you have enabled each relay for a DCB scheme, program the elements that qualify a
communications-assisted trip. To program the logic, consider the following:
➤
In the SEL-421-5 and SEL-311C-1, the setting for the communications-assisted trip is
TRCOMM, and in the SEL-321-1, the setting is MTCS. SEL recommends setting
TRCOMM and MTCS by using the same elements so that each terminal responds simi-
larly to fault conditions.
➤
Note the polarization choices for the directional element in the relays. The
SEL-321-0, -1, -2, -3, -4 only have negative-sequence voltage (Q) polarization; the
SEL-321-5 has both negative-sequence voltage (Q) and zero-sequence voltage (V)
polarization; and the SEL-421-5, SEL-311L, and SEL-311C-1 allow you to choose a
combination of negative-sequence voltage (Q), zero-sequence voltage (V), or zero-
sequence current (I) polarization in any order. To prevent miscoordination, set the
SEL-421-5 to use the same directional elements used by the SEL-300 series relay on
the other end of the line.
➤
The calculation of the negative-sequence directional element thresholds (Z2F and Z2R)
is different in the SEL-300 series and SEL-400 series relay instruction manuals. When
coordinating the SEL-300 series relays with the SEL-400 series relays, coordinate the
Z2F and Z2R settings on both line terminals. Calculate (manually or by using the
AUTO or AUTO2 settings) these thresholds for the SEL-400 series relays, and replicate
the same thresholds for the SEL-300 series relays.
➤
Each relay must be able to transmit a block signal. In the SEL-421-5 and SEL-311C-1,
send the block via TMB1A, and in the SEL-321-1, send it via TMB1.
➤
The relays must be programmed to map the BLOCK element from the remote end into
the DCB logic. Map the BLOCK element to the received Mirrored Bit. In the
SEL-421-5 and SEL-311C-1, program BT to RMB1A, and in the SEL-321-1, program
RMB1 to BT.
➤
The SEL-421-4, -5 supports quadrilateral phase elements. If these elements are enabled
on one end, the distance elements in these relays may have different sensitivities than
the SEL-311C-1 and SEL-321-1. Ensure the distance elements coordinate on both line
terminals.
➤
A tripping output must be assigned to trip the respective circuit breaker of each relay. In
the SEL-421-5, set OUT201 to TRIP; in the SEL-311C-1, set OUT101 to TRIP; and in
the SEL-321-1, set OUT1 to 3PT, as shown in Figure 14 and Figure 15.
➤
Wire a breaker contact status to each relay. In the SEL-421-5, wire 52A to IN201; in the
SEL-311C-1, wire 52A to IN101; and in the SEL-321-1, wire 52A to IN1. It is not
required to wire the 52A contact status for DCB and POTT schemes, but it is beneficial
to wire the 52A contact for other elements in the relay.
Table 14 SEL-421-5 DCB Logic Settings (Sheet 1 of 2)
Setting Setting Description
TRCOMM Communications-Assisted Trip Conditions
TMB1A Transmit Channel A Mirrored Bit 1
BT Block Trip Equation
OUT201 Output Contact 101 Equation
Date Code 20200326
Setting Value Comment
Z2PGS OR Elements that allow high-speed
a
67QG2S communications-assisted tripping.
DSTRT Send a block signal to the remote end.
RMB1A Receive a block signal from the remote
end.
TRIP Trip the output to the circuit breaker.
13
SEL Application Guide 2020-04