GE EPM 6000 Multi-function Power Metering System instruction manual Electrical Background

CHAPTER 2: ELECTRICAL BACKGROUND

If we measure the currents in wires A, B and C, we then know the current in wire N by Kirchhoff's Law and it is not necessary to measure it. This fact leads us to the conclusion of Blondell's Theorem that we only need to measure the power in three of the four wires if they are connected by a common node. In the circuit of Figure 1.6 we must measure the power flow in three wires. This will require three voltage coils and three current coils (a three element meter). Similar figures and conclusions could be reached for other circuit configurations involving delta-connected loads.

EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 2–7