GE Multilin EPM 6000 Instruction Manual page 21

CHAPTER 2: ELECTRICAL BACKGROUND
EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
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.
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