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8.31
Date Code 20070117
Instruction Manual
SEL-351-5, -6, -7 Relay
Breaker Monitor, Metering, and Load Profile Functions
Maximum/Minimum Metering
[The factory default setting is set with time-overcurrent element pickups:
FAULT =
51P + 51G
If there is a fault, 51P or 51G asserts and blocks updating of maximum/
minimum metering values.]
In addition to FAULT being deasserted for at least 3600 cycles, the following
conditions must also be met:
➤
For wye-connected voltage values V
A,B,C,S
, or delta-connected
voltage values V
AB,BC,CA,S
, the voltage is above the
corresponding threshold:
12.5 V secondary (150 V voltage inputs)
25.0 V secondary (300 V voltage inputs)
➤
For current values I
A,B,C,N
the current is above the
corresponding threshold:
0.05 A secondary {5 A nominal current inputs}
0.01 A secondary {1 A nominal current inputs}
2.0 mA secondary {0.2 A nominal channel IN current input}
0.5 mA secondary {0.05 A nominal channel IN current input}
➤
For the residual current value I
G
:
All three phase currents I
A,B,C
are above threshold.
➤
For power values MW
3P
and MVAR
3P
:
All three phase currents I
A,B,C
are above threshold and all three
voltages V
A,B,C
(or V
AB,BC,CA
) are above threshold.
➤
The metering value is above the previous maximum or below
the previous minimum for approximately four seconds.
The SEL-351 stores maximum/minimum values to nonvolatile storage once
per day and overwrites the previous stored value if that is exceeded. If the
relay loses control power, it will restore the maximum/minimum values saved
at 23:50 hours on the previous day.
The values used by the maximum/minimum metering are the same values
used by the regular
MET
command (serial port or instantaneous, front panel),
which are eight-cycle averaged values. The maximum/minimum metering
function updates every two seconds (approximately). These values should be
relatively immune to transient conditions.
In firmware releases R300 to R305, inclusive, the maximum/minimum
metering values were based on high-speed protection voltage values. Because
these values could update after being above the previous maximum or below
the previous minimum for only two cycles, the maximum/minimum recorder
occasionally responded to transient conditions. See
for a list of previous firmware releases.
NOTE:
SEL
OGIC
control equation
setting FAULT also controls other
relay functions; see subsection
Содержание SEL-351-5
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