Sel 751A - Power Measurement Conventions; Metering; Figure 5.1 Complex Power Measurement Conventions

5.2
SEL-751A Relay Instruction Manual Date Code 20100129
Metering and Monitoring
Power Measurement Conventions
Power Measurement Conventions
The SEL-751A uses the IEEE convention for power measurement. The
implications of this convention are depicted in Figure 5.1.
Figure 5.1 Complex Power Measurement Conventions
Metering
The SEL-751A meter data fall into the following categories:
➤ Fundamental metering
➤ Thermal metering: RTD metering (with the external SEL-2600
RTD Module or an internal RTD option)
➤ Energy metering
➤ Maximum and minimum metering
➤ Math variable metering
➤ RMS metering
➤ Analog transducer input metering
➤ Demand and peak demand metering
➤ Synchrophasor metering
➤ Light metering for arc-flash detection (AFD)
Q+ (VAR)
I leads V
W = –
VAR = –
PF = LAG
I lags V
W = –
VAR = +
PF = LEAD
P+ (W)
I leads V
W = +
VAR = –
PF = LEAD
I lags V
W = +
VAR = +
PF = LAG
Feeder
SEL-751A
Relay
Source
Bus
Direction of
Positive Real Power