4.70
SEL-787 Relay Instruction Manual Date Code 20081022
Protection and Logic Functions
Trip/Close Logic
ULTRm is asserted. The TR1 and TR2 are intended for breaker 1 and 2
respectively and the TRXFMR for the transformer lockout relay. The output of
the logic is Relay Word bit TRIPm.
The relay controls the tripping output contact(s) when the Relay Word bit
TRIPm appears in an output contact SEL
OGIC control equation. Default relay
settings have output OUT103 set to TRIPXFMR (see Table 4.32). Assign Relay
Word bits TRIP1 and TRIP2 to other available outputs as required by your
application. See Figure 2.19 for typical trip circuit connection.
Set the TRm SEL
OGIC control equations to include an OR-combination of all
the Relay Word bits that you want to cause the associated trip bits to assert.
The factory default setting already includes all commonly required Relay
Word bits.
REMTRIP Remote Trip Conditions SELOGIC Control Equation
You can map any Relay Word bit or SELOGIC equation to the REMTRIP to
trip a breaker or the transformer. For example, you can map a control input to
REMTRIP and map the REMTRIP to appropriate TRm equation.
Unlatch Trip Logic
Each of the three trip logic equations has an associated unlatch trip SELOGIC
equation. Following a fault, the appropriate trip signal is maintained until all
of the following conditions are true:
NOTE: Factory default setting of the
ULTRIP provides an automatic reset of
the trip when breaker opens and
selected 50/51 elements are not
picked up.
➤ Minimum trip duration time (TDURD) passes.
➤ The TRm (m =1,2, XFMR) SELOGIC control equation result
deasserts to logical 0.
➤ One of the following occurs:
➢ Unlatch Trip SELOGIC control equation setting
ULTRIP asserts to logical 1.
➢ Target Re set SELOGIC control equation setting
RSTTRGT asserts to logical 1.
➢ Target Reset Relay Word TRGTR asserts. The TRGTR
is asserted when the front-panel {TARGET RESET}
pushbutton is pressed or a target reset serial port
command is executed (ASCII, Modbus, or DeviceNet).
52A Breaker Status Conditions SELOGIC Control Equations
You can connect an auxiliary contact of the high and low side breaker to the
relay. The
SELOGIC control equations 52A1 and 52A2 allow you to configure
the relay for either 52b or 52a contact input (or other contact that indicates a
closed breaker). The factory default setting assumes no auxiliary contact
connection (both 52A1 and 52A2 := 0).
If you connect the breaker auxiliary contact to a digital input, you must change
the factory default logic equation. For example, set 52A1 := IN101 if you
connect the 52a contact of breaker 52-1 to input IN101.
Figure 4.45 shows a close logic diagram of the breaker 52-1, logic of the
breaker 52-2 is similar.
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