Blondel's Theorem And Three Phase Measurement - GE Multilin EPM 2200 Instruction Manual

BLONDEL'S THEOREM AND THREE PHASE MEASUREMENT

1.4 Blondel's Theorem and Three Phase Measurement
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Figure 1-4: Phasor Diagram, Three-Phase Voltages and Currents, Delta-Connected
Another common delta connection is the four-wire, grounded delta used for lighting
loads. In this connection the center point of one winding is grounded. On a 120/240
volt, four-wire, grounded delta service the phase-to-ground voltage would be 120
volts on two phases and 208 volts on the third phase. Figure 1.5 shows the phasor
diagram for the voltages in a three-phase, four-wire delta system.
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Figure 1-5: Phasor Diagram Showing Three-phase Four-Wire Delta-Connected System
In 1893 an engineer and mathematician named Andre E. Blondel set forth the first
scientific basis for polyphase metering. His theorem states:
If energy is supplied to any system of conductors through N wires, the total power in
the system is given by the algebraic sum of the readings of N wattmeters so arranged
that each of the N wires contains one current coil, the corresponding potential coil
being connected between that wire and some common point. If this common point is
on one of the N wires, the measurement may be made by the use of N-1 Wattmeters.
CHAPTER 1: THREE-PHASE POWER MEASUREMENT
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EPM 2200 POWER METER – INSTRUCTION MANUAL
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