Schweitzer Engineering Laboratories SEL-701-1, Instruction Manual

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SEL-701-1 Monitor
Date Code 20011009
Metering & Monitoring
Power Measurement Conventions
7.6
Power Measurement Conventions
The SEL-701-1 Monitor uses the IEEE convention for power measurement
assuming motor action. The implications of this convention are described by
Figure 7.1 .
Figure 7.1 Power Measurement Conventions.
In the SEL-701-1 Monitor, reported positive real power and energy are always
into the motor.
Power Plane
S2 = VI
2
*
Q+
Q–
+P P–
S1 = VI
2
*
S4 = VI
4
* S3 = VI
3
*
I
2
Phasor Diagram
Positive Phase Rotation
I
1
I
3
I
4
I leads V
W = –
VAR = –
PF = LAG
+90°
–90°
I lags V
W = –
VAR = +
PF = LEAD
+0° +180°
I leads V
W = +
VAR = –
PF = LEAD
I lags V
W = +
VAR = +
PF = LAG
Bus Voltage, V
M
Source
Bus
Direction of
Positive Real Power
Motor
SEL-701-1
Monitor