Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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4.145
Date Code 20170814 Instruction Manual SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Set 81RmnTRN Trend to INC or DEC to limit the operation of the element to
increasing or decreasing frequency, respectively. Also, when set to INC or
DEC, the element is supervised by nominal frequency, FNOM. Set the trend to
ABS if you want the element to disregard the frequency trend.
Voltage supervision: A minimum positive-sequence voltage is necessary for
the operation of the 81R element when the 81RmVSUP setting specifies the
level. Set 81RmVSUP := OFF if no voltage supervision is necessary. In any
case, the element is also supervised by Relay Word FREQTRKm, which
ensures that the relay is tracking and measuring the system frequency.
Use the Relay Word bits 81RXnT and 81RYnT to operate output contacts that
open the appropriate breaker(s) necessary for your load-shedding scheme.
Over- and
Undervoltage
Elements
The SEL-700G Relay provides two levels of phase-to-phase overvoltage and
undervoltage elements irrespective of the delta or wye VT connections. Six
levels of positive-sequence overvoltage and undervoltage elements are also
provided to comply with NERC standard PRC-024-1.
When you connect the SEL-700G voltage inputs to phase-to-neutral
connected VTs, as in Figure 2.16, the relay provides two levels of phase-to-
neutral overvoltage and undervoltage elements. When a synchronism voltage
input is present (for example, VS input shown in Figure 2.23), the SEL-700G
provides two levels of VS under- and overvoltage elements.
When an open-delta PT is connected to the SEL-700G voltage inputs, the
relay allows you to connect external zero-sequence voltage to
VS-NS
or
VN-NN
inputs (EXT3V0_X := VS or VN), as in Figure 2.16 (e) and (f), respectively.
In either case, when EXT3V0_X := VS or VN, the relay routs the external
3V0 to 3V0X for use with X-side residual-ground overvoltage elements
(59GX1 and 59GX2), as shown in Figure 4.103. Note that when EXT3V0_X
:= VS, the two levels of
VS undervoltage and overvoltage are not available for
setting. The voltage magnitude calculation block in Figure 4.102 (a)
calculates the zero-sequence voltage (3V0m) as follows for different PT
configurations and the EXT3V0_X setting.
➤
If DELTAY_m := WYE, then 3V0m = VAm + VBm + VCm
(Applies to both X and Y sides, m = X or Y)
➤
If DELTAY_X := DELTA, EXT3V0_X = VS, then 3V0X := VS
(Applies to X side only)
➤
If DELTAY_X := DELTA, EXT3V0_X = VN, then 3V0X := VN
(Applies to X side only).
You can use these elements for protection and/or control actions, as necessary.
Each of the elements, except the three-phase under- and overvoltage elements, 3P27
and 3P59, has an associated time delay. You can use these elements as you choose
for tripping, warning, and control. Figure 4.101
to Figure 4.104 show the logic
diagram for the undervoltage and overvoltage elements, respectively. To disable any
of these elements, set the level settings equal to OFF.
0.28–0.26 27
< 0.25 30
a
(m = X or Y; n = 1–4).
Table 4.42 Time Window Versus 81RmnTP Setting
a
(Sheet 2 of 2)
81RmnTP
Setting (Hz/s) Time-Window (Cycles)