GE EPM 5200, EPM 5300, EPM 5350 instruction manual Three-Phase System, Delta Wye

CHAPTER 1: AC POWER MEASUREMENT THREE-PHASE SYSTEM

1.2Three-Phase System

A three-phase system delivers higher levels of power for industrial and commercial applications; the three phases correspond to three potential lines. A 120° phase shift exists between the three potential lines.

A typical configuration has either a Delta connection or a Wye connection (see Figure 1.3, below).

In a three-phase system, the voltage levels between the phases and the neutral are uniform and defined by:

Ean = Ebn = Ecn = Eab = Ebc = Eac

3 3 3

C

A

A

1) Delta

B

B

2) Wye

N

C

FIGURE 1–3: Three-Phase System: (1) Delta, (2) Wye

Voltages between the phases vary depending on loading factors and the quality of distribution transformers. The three-phase system is distributed in different voltage levels: 208V AC, 480V AC, 2400V AC, 4160V AC, 6900V AC, 13800V AC, and so on.

Power measurement in a poly phase system is governed by Blondel's Theorem. Blondel’s Theorem states that in a power distribution network which has N conductors, the number of measurement elements required to determine power is N-1. A typical configuration of poly phase system has either a Delta connection or a Wye connection (see Figure 1.4, below).

EPM 5300 SERIES ADVANCED POWER METERS – INSTRUCTION MANUAL 1–3