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A method and a device for monitoring instantaneous electrical parameters of a power distribution system under load utilizing digital control means. An analog signal equivalent to such a parameter is sensed and rated down for processing by solid state components. This signal is converted into a binar

A method and a device for monitoring instantaneous electrical parameters of a power distribution system under load utilizing digital control means. An analog signal equivalent to such a parameter is sensed and rated down for processing by solid state components. This signal is converted into a binary coded digital signal having n digits. A plurality of digital signals is sampled and squared values with a format of 2n digits are derived from each sample. The squared values of one sampling period are accumulated to a sum value composed of 2n+m digits and the square root comprising n+k digits of the sum is taken. This value is rescaled to a true root mean square value by performing k left shifts as an accurate measurement result. The core of such device is represented by a microcomputer with built-in analog-to-digital converter.

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A method for monitoring instantaneous electrical parameters being present in a circuit of a power distribution system under load, the method utilizing digital control means adapted to be connected to said circuit and including the steps of: (a) sensing the present load condition of the circuit and d

A method for monitoring instantaneous electrical parameters being present in a circuit of a power distribution system under load, the method utilizing digital control means adapted to be connected to said circuit and including the steps of: (a) sensing the present load condition of the circuit and deriving an equivalent analog signal constituting one electrical characteristic of the electro-motive power present in said circuit; (b) rating down said analog signal to a range suitable for processing by an integrated electronic circuit; (c) converting the rated analog signal into a binary coded digital signal comprising a value of n digits; (d) sampling a plurality of subsequent binary digital signals during a sampling period; (e) deriving from each of the sampled digital signals a respective squared value with a format of 2n digits and accumulating each respective squared value obtained during one sampling period of a sum value composed of 2n+m digits; (f) forming a square root value of said sum value, said square root value comprising n+k digits; and (g) rescaling said square root value to a true root means square value by performing k left shifts on the square root value and storing said true root mean square value, whereby the rescaled value represents an accurate measurement of said electrical characteristic.