Method for measuring insulation resistance and device therefor

Claim 1

A method for the measuring insulation resistance of a grounded supply line, in which one end of a secondary circuit, to which a main frequency f 0 is fed, is grounded via a ground wire, comprising the steps of applying a low voltage of a frequency f 1 , different from the main frequency f 0 , into the ground wire through a transformer coupled thereto, detecting separately the leakage current of the frequency f 0 and the leakage current of the frequency f 1 , both said current leakages being included in the output of a zero phase transformer coupled with said ground wire, obtaining a component of the leakage current of the frequency f 0 and a component of the leakage current of the frequency f 1 , and deriving an amount in inverse proporytion to the insulation resistance of each non-grounded line by using an arithmetic operation of said components while the line is in active condition.

Claim 2

A method for the measuring insulation resistance of a grounded supply line, in which one end of a secondary circuit, to which a main frequency f 0 is fed, is grounded via a ground wire, comprising the steps of applying a low voltage of a frequency f 1 , different from the main frequency f 0 , into the ground wire through a transformer coupled thereto, detecting separately the leakage current of the frequency f 0 and the leakage current of the frequency f 1 , both said current leakages being included in the output of a zero phase transformer coupled with said ground wire, obtaining a component of the leakage current of the frequency f 0 and a component of the leakage current of the frequency f 1 , and deriving an amount in inverse proporytion to the insulation resistance of each non-grounded line by using an arithmetic operation of said components while the line is in active condition.

Claim 3

A method for measuring insulation resistance as claimed in caim 1, wherein the transformer injecting the frequency f 1 into the ground wire is an oscillation transformer having said frequency f 1 .

Claim 6

A method for measuring insulation resistance of a grounded supply line, in which one end of a secondary circuit, to which a main frequency f 0 is fed, is grounded via a ground wire, comprising the steps of applying a voltage of a frequency f 1 , different from main frequency f 0 , into the ground wire through a transformer coupled thereto, detecting separately of a leakage current of the frequency f 0 the leakage current of the frequency f 1 , both said current leakages being included in output of a zero phase transformer coupled with said ground wire, obtaining an effective component of the leakage current of said frequency f 0 and an effective component of the leakage current of said frequency f 1 , and deriving an amount in inverse proportion to parallel composite value of insulation resistances of the non-grounded line from only one of said effective components.

Claim 7

A method for measuring insulation resistance of a grounded supply line, in which one end of a secondary circuit, to which a main frequency f 0 is fed, is grounded via a ground wire, comprising the steps of applying a voltage of a frequency f 1 , different from main frequency f 0 , into the ground wire through a transformer coupled thereto, detecting separately of a leakage current of the frequency f 0 the leakage current of the frequency f 1 , both said current leakages being included in output of a zero phase transformer coupled with said ground wire, obtaining an effective component of the leakage current of said frequency f 0 and an effective component of the leakage current of said frequency f 1 , and deriving an amount in inverse proportion to parallel composite value of insulation resistances of the non-grounded line from only one of said effective components.

Claim 11

A device for measuring insulation resistance of a grounded supply line, in which one end of secondary circuit is grounded via a ground wire comprising; an oscillator for generating a low frequency f 1 which is different from a main frequency f 0 to be fed to the line, a coupling transformer for coupling said frequency f 1 generated from the oscillator to the ground wire of the line, a zero phase current transformer coupled with said ground wire for deriving leakage current having frequency components of f 0 and f 1 , a band-pass-filter for passing said main frequency f 0 coupled with an output of the zero phase transformer, a multiplier fed with an output of the band-pass-filter for the frequency f 0 at one of its input and fed with a voltage in proportion to the line voltage of frequency f 0 and for producing multiplied product thereof, a low-pass-filter fed with an output of said multiplier to derive a dc component of the leakage current having frequency f 0 therefrom, a band-pass-filter for passing said frequency f 1 also coupled with said output of the zero phase transformer, a multiplier fed with an output of the band-pass-filter for the frequency f 1 at one of its input and fed with the oscillator voltage having frequency f 1 for producing multiplied product thereof, a low-pass-filter fed with an output of said multiplier to derive a dc component of the leakage current having frequency f 1 therefrom, and arithmetic units for applying operation for the derived dc components to obtain an amount in counter proportion to the desired insulation resistance of the individual line.

Claim 12

A device for measuring insulation resistance of a grounded supply line, in which one end of secondary circuit is grounded via a ground wire comprising; an oscillator for generating a low frequency f 1 which is different from a main frequency f 0 to be fed to the line, a coupling transformer for coupling said frequency f 1 generated from the oscillator to the ground wire of the line, a zero phase current transformer coupled with said ground wire for deriving leakage current having frequency components of f 0 and f 1 , a band-pass-filter for passing said main frequency f 0 coupled with an output of the zero phase transformer, a multiplier fed with an output of the band-pass-filter for the frequency f 0 at one of its input and fed with a voltage in proportion to the line voltage of frequency f 0 and for producing multiplied product thereof, a low-pass-filter fed with an output of said multiplier to derive a dc component of the leakage current having frequency f 0 therefrom, a band-pass-filter for passing said frequency f 1 also coupled with said output of the zero phase transformer, a multiplier fed with an output of the band-pass-filter for the frequency f 1 at one of its input and fed with the oscillator voltage having frequency f 1 for producing multiplied product thereof, a low-pass-filter fed with an output of said multiplier to derive a dc component of the leakage current having frequency f 1 therefrom, and arithmetic units for applying operation for the derived dc components to obtain an amount in counter proportion to the desired insulation resistance of the individual line.