GE EPM 5350, EPM 5200, EPM 5300 Chapter Ac Power Measurement, Single Phase System, W 2 + VAR

CHAPTER 1: AC POWER MEASUREMENT

CHAPTER 1

AC POWER MEASUREMENT

The economics of electric power distribution networking dictate several configurations of AC power transmission. The number of phases and voltage levels characterize these configurations.

1.1: Single Phase System

A single phase system is a basic two-wire system used in low power distribution applications, such as residential communities or offices. Typically, the voltage is 120V AC. For higher power requirements, such as small commercial facilities, the typical power configuration is two lines of 120V AC opposite in phase (see Figure 1.1 B, below).

This system produces 120 volts from line to neutral for lighting and small appliance use. The line-to-line voltage is 240V AC, used for higher loads such as water heaters, electric dryers, ranges and machinery.

Line

A)

Single Phase

2 Wires

Neutral

Line 1

B)
Single Phase	Neutral
3 Wires

Line 2

Figure 1.1: Single Phase System: (A) Two-Wire, (B) Three-Wire

The power (W) in a single phase system is: W =E • I • cosΘ

E = potential, I = current, and cosΘ = phase difference between the potential and the current. Power in a 120/240V AC system is: W = (ELine 1 • ILine 1 • cosΘ) + (ELine 2 • ILine 2 • cosΘ)

Phase differential between the potential and the current results from a non-resistive load, either reactive or capacitive.

Reactive power (VAR): The additional power consumed that does not produce any work but must be

delivered to the load: VAR = E ⋅ I ⋅sinΘ . This is a measure of the inefficiency of the electrical system.

Apparent power (VA): The total power delivered to the load, and the vector sum of real power and reactive power.

Power Factor (PF): The ratio between real power and apparent power: PF =	W	=	W
	VA		W 2 + VAR2

GE Multilin EPM 5000 series Advanced Power Meters 1