Introduction to the History of Selective Protection

Author: Walter Schossig, Germany

Measurement of Power System Values

The conversion of primary power system values to secondary ones are an essential aspect of the protection systems. A measurement technique without iron was proposed by Rogowski and Steinhaus in 1912 however the application of those ideas have only recently been seriously considered and implemented by the power industry.  
In 1926 Arnold proposed a nominal secondary value of 1A however many utilities have continued to use the 5A rating.
Today we speak about the Holmgreen-circuit but in actual fact it was Nicholson who in 1910 proposed and patented a method of measuring zero current.

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