5.4
SEL-749M Relay
Instruction Manual
Date Code 20080918
Metering and Monitoring
Power Measurement Conventions
Power Measurement Conventions
The SEL-749M uses the IEEE convention for power measurement assuming
motor action. The implications of this convention are depicted in
Figure 5.3
Complex Power Measurement Conventions—Motor Action
In the SEL-749M, reported positive real power is always into the motor.
Power Into Motor
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
M
SEL-749M
Relay
Source
Bus
Direction of
Positive Real Power
Motor
Содержание SEL-749M
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