4.33
Date Code 20081022
Instruction Manual
SEL-787 Relay
Protection and Logic Functions
Basic Protection
The relay offers two types of ground fault detecting overcurrent elements. The
neutral overcurrent elements (50N11T and 50N12T) operate with current
measured by the
IN1
input (see
and
). The residual (RES)
overcurrent elements (50G
n
1T and 50G
n
2T) operate with the current derived
from each winding phase currents (see
).
.
The relay offers two negative-sequence overcurrent elements per winding to
detect phase-to-phase faults, phase reversal, single phasing, and unbalance
load.
Time-Overcurrent
Elements
One level of inverse time element is available for maximum phase, residual,
and negative-sequence overcurrent per transformer winding. See
for available settings.
You can select from five IEEE and five IEC inverse characteristics.
and
show equations for the curves and
through
show the curves. The curves and equations shown do not account
for constant time adder and minimum response time (settings 51_CT and
51_MR respectively, each assumed equal to zero). Use the 51_CT if you want
to raise the curves by a constant time. Also, you can use the 51_MR if you
want to ensure the curve times no faster than a minimum response time.
Each element can be torque controlled using appropriate SEL
OGIC
equations
(e.g., when 51P1TC := IN401 the 51P1P element will be operational only if
IN401 is asserted).
Table 4.7
Winding n Residual Overcurrent Settings (n = 1, 2)
Setting Prompt
Setting Range
Setting Name :=
Factory Default
RES IOC LEVEL
OFF, 0.50–96.00 A
a
,
0.10–19.20 A
b
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
50G
n
1P := OFF
RES IOC DELAY
0.00–5.00 sec
50G
n
1D := 0.50
RES IOC TRQCTRL
SEL
OGIC
50G
n
1TC := 1
RES IOC LEVEL
OFF, 0.50–96.00 A
,
0.10–19.20 A
50G
n
2P := OFF
RES IOC DELAY
0.00–5.00 sec
50G
n
2D := 0.50
RES IOC TRQCTRL
SEL
OGIC
50G
n
2TC := 1
Table 4.8
Winding n Negative-Sequence Overcurrent Settings (n = 1 or 2)
Setting Prompt
Setting Range
Setting Name :=
Factory Default
NSEQ IOC LEVEL
OFF, 0.50–96.00 A
a
,
0.10–19.20 A
b
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
50Q1P := OFF
NSEQ IOC DELAY
0.10–120.00 sec
50Q1D := 0.20
NSEQ IOC TRQCTRL
SEL
OGIC
50Q1TC := 1
NSEQ IOC LEVEL
OFF, 0.50–96.00 A
,
0.10–19.20 A
50Q2P := OFF
NSEQ IOC DELAY
0.10–120.00 sec
50Q2D := 0.20
NSEQ IOC TRQCTRL
SEL
OGIC
50Q2TC := 1
Summary of Contents for SEL-787
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