5.8
SEL-787 Relay Instruction Manual Date Code 20081022
Metering and Monitoring
Metering
Math Variable
Metering
The SEL-787 includes 32 math variables. When you receive your SEL-787,
no math variables are enabled. To use math variables, enable the number of
math variables (between 1 and 32) you require, using the EMV setting in the
Logic setting category. Figure 5.9 shows the device response to the METER
MV M(ath) V(ariable) command with 8 of the 32 math variables enabled.
=>>MET MV <Enter>
SEL-787 Date: 03/11/2008 Time: 12:32:10
TRNSFRMR RELAY Time Source: Internal
MV01 1.00
MV02 -32767.00
MV03 -1.00
MV04 0.00
MV05 1000.59
MV06 -1000.61
MV07 2411.01
MV08 2410.99
=>>
Figure 5.9 MET MV Command Report
RMS Metering
The SEL-787 includes root mean squared (rms) metering. Use rms metering
to measure the entire signal (including harmonics). You can measure the rms
quantities shown in Table 5.6.
RMS quantities contain the total signal, including harmonics. This differs
from the fundamental meter (METER command) in that the fundamental
meter quantities only contain the fundamental frequency (60 Hz for a 60-Hz
system). Figure 5.10 shows the METER RMS command report.
=>MET RMS <Enter>
SEL-787 Date: 01/23/2008 Time: 13:44:57
TRNSFRMR RELAY Time Source: Internal
IAW1 IBW1 ICW1
RMS (A pri.) 118.0 122.5 120.7
IAW2 IBW2 ICW2
RMS (A pri.) 2351.7 2461.3 2401.1
IN
RMS (A pri.) 146.6
VAB VBC VCA
RMS (V pri.) 12090 11893 21180
=>
Figure 5.10 METER RMS Command Report
Ta b l e 5 . 6 R M S M eter Va l u e s
Relay Option RMS Meter Values
Base Model RMS current IAW1, IBW1, ICW1, IAW2, IBW2, and ICW2
magnitudes (A primary)
With Neutral Current
(IN) Option
RMS current IN magnitude (A primary)
With Voltage Option VAB, VBC, VCA or VAN, VBN, VCN, and VG magnitudes
(V primary)
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