Schneider Electric iEM3300, iEM3200, iEM3100 Power, energy and power factor, Power PQS, Power flow

iEM3100 / iEM3200 / iEM3300 series user manual Power, energy and power factor

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):

S = P2 + Q2

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.

+Q

(+kVAR)

Quadrant 2 Quadrant 1

Q (+)

-P (-kW)

Q (-)

S	S
P (-)	P (+)
P (-)	P (+)
S	S

Q (+)

+P

(+kW)

Q (-)

Quadrant 3 Quadrant 4

-Q (-kVAR)

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.

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