Blondel's theorem

Blondel's theorem, named after its discoverer, French electrical engineer André Blondel, is the result of his attempt to simplify both the measurement of electrical energy and the validation of such measurements.

The result is a simple rule that specifies the minimum number of watt-hour meters required to measure the consumption of energy in any system of electrical conductors.

[1] Blondel wrote a paper on his results that was delivered to the International Electric Congress held in Chicago in 1893.

Blondel's Theorem simplifies the work of an electrical utility worker by specifying that an N wire service will be correctly measured by a N-1 element meter.

Unfortunately, confusion arises for such workers due to the existence of meters that don't contain tidy pairings of single potential measuring units with single current measuring units.

Electric energy meters that meet the requirement of N-1 elements for an N wire service are often said to be Blondel Compliant.

The non compliance of the meter occurs in measuring line to neutral loads.

[1] Since the industry typically maintains five percent accuracy in potential, the error will be acceptably low if the loads aren't heavily unbalanced.