Energy Measurement of Three Phase Unbalanced load

[tsknan]

in 3ph 3wire meter whether exact energy measurement of Three Phase Unbalanced load is possible?the supply side is star grounded and load side is star grounded,but there is no neutral wire running between supply and load.if Y ph load is more than the R&Y loads what happen to energy measurement?any referance available for this?

 

[rcw retired EE]

Search Blondel's theorem onthis website.

 

[stevenal]

With the source wye grounded, consider the earth as a conductor when applying Blondel. While loads are not normally connected line to ground, they could be. If this is revenue metering for a load beyond your control, consider running a neutral as far as the meter to avoid any lost revenue.

 

[waross]

What is the Form number of the meter? There are many three phase meters.
There is a circuit for metering unbalanced three phase currents with a two element meter. The meter measures "A" phase and "C" phase directly and uses a third CT in delta to meter the current in "B" phase. "A" phase is metered correctly, "C" phase is metered correctly, but "B" phase is metered with a weighted average of the voltages on "A" and "C" phases.
This works OK with balanced voltages but errors develop if the voltages are not balanced.
With a unity power factor "B" phase will be measured with a true average of the voltages on "A" and "C" phases. As the power factor changes, the voltage of one or the other phase will have more influence.

Bill
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