Filter circuit for corona detection

Claim 2

Apparatus for providing substantially optimum resolution of high frequency corona discharge in an insulated cable comprising: a high pass filter for substantially rejecting the low frequency line signal and its harmonics present in a resultant corona discharge; and a low pass lossy transformer electrically coupled to said high pass filter for introducing a bucking voltage to balance out any residual low frequency signals resulting from the broad tuning characteristics of the high pass filter to provide optimum resolution and sensitivity of pulse response in the detection of high frequency corona discharge.

Claim 3

Apparatus for providing substantially optimum resolution of high frequency corona discharge in response to a line signal applied to an insulated cable comprising: a high pass filter arranged to shunt the line signal and its harmonics to ground; means for coupling said high pass filter to a low pass lossy transformer to transmit the high frequency corona discharge and any residual low frequency signals thereto; said low pass lossy transformer including primary and secondary windings, said primary winding having one terminal connected to said coupling means and the other terminal connected to ground; and a potentiometer connected in parallel across said secondary winding, to provide a variable output voltage pulse representative of high frequency corona discharge between ground and the adjustable potentiometer setting.

Claim 4

Apparatus for providing substantially optimum resolution of high frequency corona discharge in response to a line signal applied to an insulated cable comprising: a high pass filter arranged to shunt the line signal and its harmonics to ground; means for coupling said high pass filter to a low pass lossy transformer to transmit the high frequency corona discharge and any residual low frequency signals thereto; said low pass lossy transformer including primary and secondary windings, said primary winding having one terminal connected to said coupling means and the other terminal connected to ground; and a potentiometer connected in parallel across said secondary winding, to provide a variable output voltage pulse representative of high frequency corona discharge between ground and the adjustable potentiometer setting.

Claim 5

Apparatus for detection of corona discharge in an insulated cable comprising: a high pass filter; a high voltage blocking capacitor connected in series with said high pass filter; said high pass filter and said blocking capacitor capable of being arranged in parallel with the insulated cable being tested, said high pass filter adapted to substantially remove the low frequency line signal and its harmonics present in the resultant corona discharge; a coupling capacitor connecting said high pass filter to a low pass lossy transformer to transmit the high frequency corona discharge and any residual low frequency signalS thereto; said low pass lossy transformer having a secondary winding with a limited frequency response to introduce a bucking voltage to balance out any residual low frequency signals, thereby providing substantially optimum resolution of the high frequency corona discharge.

Claim 6

Apparatus for detection of corona discharge in an insulated cable comprising: a high pass filter; a high voltage blocking capacitor connected in series with said high pass filter; said high pass filter and said blocking capacitor capable of being arranged in parallel with the insulated cable being tested, said high pass filter adapted to substantially remove the low frequency line signal and its harmonics present in the resultant corona discharge; a coupling capacitor connecting said high pass filter to a low pass lossy transformer to transmit the high frequency corona discharge and any residual low frequency signalS thereto; said low pass lossy transformer having a secondary winding with a limited frequency response to introduce a bucking voltage to balance out any residual low frequency signals, thereby providing substantially optimum resolution of the high frequency corona discharge.

Claim 7

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating corona discharge, wherein the improvement comprises: a low pass lossy transformer electrically coupled to the high pass filter for introducing a bucking voltage to balance out any residual low frequency signals to provide optimum resolution of the pulse response representative of high frequency corona discharge which is transmitted to the detector.

Claim 8

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating corona discharge, wherein the improvement comprises: a low pass lossy transformer electrically coupled to the high pass filter for introducing a bucking voltage to balance out any residual low frequency signals to provide optimum resolution of the pulse response representative of high frequency corona discharge which is transmitted to the detector.

Claim 9

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating corona discharge as claimed in claim 4 including: a plurality of said low pass lossy transformers connected in cascade.

Claim 10

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter means for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating a corona discharge as claimed in claim 4 wherein: said low pass lossy transformer includes a tertiary winding for more selective transmission of the desired high frequency corona discharge band to eliminate the effects of phase shift while improving the efficiency, resolution and frequency response.

Claim 11

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating a corona discharge as claimed in claim 6 including: a plurality of said low pass lossy transformers connected in cascade.

Claim 12

Apparatus for corona detection of the type having means for applying a high voltage signal to a length of insulated cable which is to be tested for corona discharge, a high pass filter for rejecting low frequency signals present in a resultant corona discharge, and a detector capable of indicating a corona discharge as claimed in claim 4 including: amplifier means electrically coupled to the output of said low pass lossy transformer, adapted to match the output impedance thereof, providing substantially distortionless transmission of the pulse response representative of the high frequency corona discharge band to the detector.