Patent ID: 6184725
Filing Date: 2001-02-06
Classification: G01R

Abstract:
A circuit arrangement for making isolated measurements on a current of a transmission line with a go conductor and a return conductor for supplying power to electrical apparatus, wherein the go conductor contains a-first resistor (R2) connected in series therewith for producing a voltage drop across the first resistor which is shunted by a series combination of a transformer (T) having a primary winding and a secondary winding and a first optically controllable clocked switching element (OS2) for chopping the voltage across the first resistor and providing the chopped voltage to the primary winding of the transformer (T), and wherein said isolated measurements are made by measuring an isolated voltage on the secondary winding of the transformer (T), and wherein said circuit arrangement also allows for making isolated measurements on a voltage of the transmission line characterized in that said circuit arrangement further comprises a shunt branch between the go conductor (+) and the return conductor (-) containing a series combination of the transformer (T), a second optically controllable, clocked switching element (OS1) for chopping the line voltage and providing the chopped line voltage to the primary winding of the transformer (T), and a second resistor (R1) connected in series with the shunt branch for limiting a current drawn through the shunt branch.