GE EPM 5300, EPM 5200, EPM 5350 Consumption, Demand and Poor Power Factor, Delta, 2 Wye

CHAPTER 1: AC POWER MEASUREMENT

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).

A

1) Delta

C B

XEAB IA

P = EAB IA + ECB I C

X

ECB I C

XEAN I A

A

2)Wye

C

B

N

XEBN I B

P = E	I	A	+ E	BN	I	B	+ E	CN	I	C
AN

X

ECN I C

Figure 1.4: Poly Phase System: (1) Delta, (2) Wye

1.3: Consumption, Demand and Poor Power Factor

CONSUMPTION: WH = W ⋅ T W = instantaneous power T = time in hours The total electric energy usage over a time period is the consumption of WH.

Typically, the unit in which consumption is specified is the kilowatt-hour (KWH): one thousand watts consumed over one hour. Utilities use the WH equation to determine the overall consumption in a billing period.

DEMAND: Average energy consumed over a specified time interval. The utility determines the interval, typically 15 or 30 minutes. The utility measures the maximum demand over a billing period. This measurement exhibits a deviation from average consumption, causing the utility to provide generating capacity to satisfy a high maximum consumption demand. The highest average demand is retained in the metering system until the demand level is reset.

POOR POWER FACTOR: Results in reactive power consumption. Transferring reactive power over a distribution network causes energy loss. To force consumers to correct their Power Factor, utilities monitor reactive power consumption and penalize the user for Poor Power Factor.

GE Multilin EPM 5000 series Advanced Power Meters 3