Schweitzer Engineering Laboratories SEL-734 - Figure 4.7 FAULT and DFAULT Meter Word Bit Logic

4.17
Date Code 20090730 Instruction Manual SEL-734 Meter
Metering
Maximum/Minimum Metering
➤ 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.
Figure 4.7 FAULT and DFAULT Meter Word Bit Logic
The meter saves maximum/minimum values to nonvolatile memory once
every minute (it overwrites the previous stored value if it is exceeded). Should
the meter lose control power, it will restore the maximum/minimum values
saved by the meter during the last save to nonvolatile memory.
Maximum/Minimum
Metering Elements
The SEL-734 will not meter certain values during faults to ensure that only
billable quantities are recorded. When asserted, the overcurrent elements
ensure that peak demand, maximum metering, and crest factors are not
recorded. Undervoltage elements will not suspend any meter recording, but
can be used with any SEL
OGIC control equation.
Overcurrent Elements
FAULT: Meter Word bit that asserts if any single-phase current exceeds 21 A
(6.3 A for CL2) or the metered current rises 10 A (3 A for CL2) between any
two power system cycles. Figure 4.7 illustrates when the FAULT and
DFAULT bits assert. Peak demand, maximum/minimum metering, and crest
factor metering are suspended when the FAULT Meter Word bit is asserted
(logical 1).
DFAULT, Delayed Fault: Meter Word bit that asserts identically to the FAULT
bit and suspends the same metering values. The DFAULT Meter Word bit
remains asserted for 60 seconds after the fault condition has been removed.
FLTBLK, Fault Bit Block SEL
OGIC Control Equation: SELOGIC control
equation setting FLTBLK (Fault block) has to be deasserted (logical 0) for the
FAULT Meter Word bit to assert during a fault on the system. Configure
FLTBLK to override, when asserted, the FAULT Meter Word bit. The default
setting for FLTBLK is deasserted.
Undervoltage Elements
27n (n = A, B, or C), Undervoltage Elements: Meter Word bits that assert
when a single-phase voltage drops below the preset threshold defined using
the 27P1P setting. These word bits are commonly referred to as undervoltage
elements.
0
60
sec
FAULT
DFAULT
10
Meter
Word
Bits
21
I1
k
I1
(k-16)
|I1
k
| - |I1
(k-16)
|
SELOGIC Control Equation: FLTBLK
NOTE: Meter Word bit FAULT and
DFAULT also control other Meter
functions.
NOTE: The values used by the
maximum/minimum metering are the
same values used by the regular MET
command (serial port or front panel),
which are one-second averaged
values. The maximum/minimum
metering function updates every
second. These values are relatively
immune to transient conditions.
Courtesy of NationalSwitchgear.com