Schweitzer Engineering Laboratories SEL-787 - Table 4.7 Winding N Residual Overcurrent Settings (N = 1, 2); Table 4.8 Winding N Negative-Sequence Overcurrent Settings (N = 1 or 2)

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 Table 4.12 and Table 4.13). The residual (RES)
overcurrent elements (50Gn1T and 50Gn2T) operate with the current derived
from each winding phase currents (see Figure 4.14).
.
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 Table 4.9
through Table 4.11 for available settings.
You can select from five IEEE and five IEC inverse characteristics. Table 4.14
and Table 4.15 show equations for the curves and Figure 4.19 through
Figure 4.28 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 :=
Facto ry Defa ul t
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.
50Gn1P := OFF
RES IOC DELAY 0.00–5.00 sec 50Gn1D := 0.50
RES IOC TRQCTRL SEL
OGIC 50Gn1TC := 1
RES IOC LEVEL OFF, 0.50–96.00 A
a
,
0.10–19.20 A
b
50Gn2P := OFF
RES IOC DELAY 0.00–5.00 sec 50Gn2D := 0.50
RES IOC TRQCTRL SEL
OGIC 50Gn2TC := 1
Table 4.8 Winding n Negative-Sequence Overcurrent Settings (n = 1 or 2)
Setting Prompt Setting Range
Setting Name :=
Facto ry Defa ul t
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
a
,
0.10–19.20 A
b
50Q2P := OFF
NSEQ IOC DELAY 0.10–120.00 sec 50Q2D := 0.20
NSEQ IOC TRQCTRL SEL
OGIC 50Q2TC := 1