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iEM3100 / iEM3200 / iEM3300 series user manual Power, energy and power factor
DOCA0005EN-04 105
Chapter 11 Power, energy and power factor
NOTE: The descriptions in this section assume that you are an electrical energy consumer, not a
supplier.
What is in this chapter?
This chapter contains the following sections:
Power (PQS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Energy delivered (imported) / energy received (exported) . . . . . . . . . . . . . . . . . . . . 106
Power factor (PF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Power factor register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Power (PQS)
A typical AC electrical system load has both resistive and reactive (inductive or capacitive)
components. Resistive loads consume real power (P) and reactive loads consume reactive
power (Q).
Apparent power (S) is the vector sum of real power (P) and reactive power (Q):
Real power is measured in watts (W or kW), reactive power is measured in vars (VAR or kVAR) and
apparent power is measured in volt-amps (VA or kVA).
Power and the PQ coordinate system
The meter uses the values of real power (P) and reactive power (Q) on the PQ coordinate system to
calculate apparent power.
Power flow
Positive power flow P(+) and Q(+) means power is flowing from the power source towards the load.
Negative power flow P(-) and Q(-) means power is flowing from the load towards the power source.
SP
2
+ Q
2
=
+Q
(+kVAR)
-P
(-kW)
-Q
(-kVAR)
+P
(+kW)
P (+)
S
P (-)
S
P (+)
S
P (-)
S
Q (-)Q (-)
)+(Q)+(Q
Quadrant 3 Quadrant 4
Quadrant 1
Quadrant 2