5.8
SEL-751 Relay Instruction Manual Date Code 20170927
Metering and Monitoring
Metering
All maximum and minimum metering values have the date and time that they
occurred. The analog quantities from Tabl e 5. 4 are checked approximately
every 0.5 seconds and, if a new maximum or minimum value occurs, this
value is saved along with the date and time that the maximum or minimum
value occurred. Maximum and minimum values are only checked if relay
element FAULT is deasserted (no fault condition exists) for at least one
second.
Additionally, the following minimum thresholds must also be met:
➤ Current values I
A
, I
B
, I
C
, and I
N
: 3 percent of the nominal CT
rating.
➤ Current value I
G
: I
A
, I
B
, and I
C
must all be greater than their
thresholds.
➤ Voltage (secondary) values (phase and phase-to-phase): 7.5 V
and 13 V, respectively or 0.2 V and 0.35 V, respectively when
using the 8 Vac rms LEA voltage inputs.
➤ Power values (real, reactive, and apparent): All three currents
(I
A
, I
B
, I
C
) and all three voltages (V
A
, V
B
, V
C
or V
AB
, V
BC
, V
CA
)
must be greater than their thresholds.
Figure 5.6 shows an example device response to the METER M command.
To reset maximum/minimum meter values, issue the METER RM command
as shown in Figure 5.7. The max/min meter values can be reset from the serial
port, Modbus, the front panel, or assertion of the RSTMXMN Relay Word bit.
The date and time of the reset are preserved and shown in the max/min meter
report.
=>>MET M <Enter>
SEL-751 Date: 12/02/2010 Time: 15:46:02
FEEDER RELAY Time Source: External
MAX DATE TIME MIN DATE TIME
IA (A) 1005.8 12/02/2010 15:41:43 19.8 11/09/2010 03:55:41
IB (A) 1097.1 12/02/2010 15:41:26 197.3 11/16/2010 11:41:10
IC (A) 972.7 12/02/2010 15:45:11 206.0 11/16/2010 11:40:47
IN (A) 0.5 11/11/2010 18:20:00 0.4 11/16/2010 11:39:43
IG (A) 155.9 12/02/2010 15:42:32 0.4 11/12/2010 00:31:39
VAB (V) 6650.4 12/02/2010 15:45:45 6647.4 12/02/2010 15:41:14
VBC (V) 6671.9 12/02/2010 15:42:56 6666.8 12/02/2010 15:39:54
VCA (V) 7505.1 12/02/2010 15:41:05 7502.9 12/02/2010 15:45:42
VS (V) 6741.4 12/02/2010 15:45:11 6647.4 12/02/2010 15:41:14
KW3P (kW) 7797.2 11/11/2010 13:45:15 -11108 12/02/2010 15:41:42
KVAR3P (kVAR) 5031.8 12/02/2010 15:42:49 -1396.3 12/02/2010 15:45:24
KVA3P (kVA) 12187 12/02/2010 15:41:42 608.1 11/16/2010 11:42:27
FREQ (Hz) 60.1 11/16/2010 11:36:54 60.0 12/02/2010 15:45:23
LAST RESET = 11/09/2010 03:54:34
=>>
Figure 5.6 METER M Command Response
=>>MET RM <Enter>
Reset Metering Quantities (Y,N)? Y <Enter>
Reset Complete
=>>
Figure 5.7 METER RM Command Response
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