# US 9,110,105 B2 · High performance sensor for partial discharge signal-analyzing systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,110,105 B2 - Document ID: US9110105B2 - Status: Granted - Kind: B2 - Application number: 13/667,952 - Filed: 2012-11-02 - Published: 2014-05-08 - Granted: 2015-08-18 - Earliest claimed: 2012-11-02 - Assignees: UTILX Corporation - Applicants: UTILX Corporation - Inventors: Wen Shu; Nelson Hall - Web page: https://patentgrep.com/patent/US9110105B2 ## CPC - G01R 15/16: using capacitive devices - G01R 31/1272: {of cable, line or wire insulation, e.g. using partial discharge measurements (locating faults in cables G01R31/083)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A capacitor component is adapted for capacitive coupling to an electrical power apparatus in which a PD is suspected, such as a shielded power cable; and an impedance transformance device has an input side connected directly to the capacitor component. Together the two components are used as a sensor to pick up and convey PD signals to a PD signal-analyzing system. Although the two components inherently form a classic high-pass RC filter, in accordance with the invention the input impedance at the capacitor side is much greater than the output impedance at the signal-analyzing system side. The effect is to pass much more of the lower frequency components of the PD signal for analysis by the PD signal-analyzing system than if the tranformance device were not included. ## Claims ### Claim 1 A PD sensor for a PD signal-analyzing system having a known coupling, said sensor comprising: a capacitor component having a predetermined capacitance for capacitive coupling to an electrical power apparatus in which a PD is suspected at a location distant from the sensor; and an impedance transformance device including a buffer amplifier having an input side connected directly to the capacitor component and an output side configured for connection to a PD signal-analyzing system having a known coupling impedance, the impedance transformance device being constructed and arranged to convey a PD signal from the input side to the output side, the impedance transformance device having a first effective impedance at the input side and a second effective impedance at the output side, the first effective impedance being much larger than the second effective impedance; whereby the capacitance of the capacitor component in combination with the first effective impedance inherently effects a low frequency filter cutoff much lower than the low frequency cutoff that would be caused by the capacitance of the capacitor component in combination with the known coupling impedance, and said low frequency cutoff includes a bandwidth of low frequencies for indicating the occurrence of a PD at a distance from the sensor. ### Claim 2 (depends on 1) The sensor defined in claim 1, in which the second impedance matches the known coupling impedance. ### Claim 3 (depends on 2) The sensor defined in claim 2, in which the first impedance is 100 to 10,000 times the second impedance. ### Claim 4 (depends on 1) The sensor defined in claim 1, in which the first impedance is at least two orders of magnitude greater than second impedance. ### Claim 5 (depends on 1) The sensor defined in claim 1, in which the capacitance of the capacitor component in combination with the first effective impedance inherently effects a low frequency filter cutoff of at least 4 KHz. ### Claim 6 (depends on 5) The sensor defined in claim 5, in which the capacitance of the capacitor component in combination with the first effective impedance effects a low frequency filter cutoff between 4 KHz and 1 MHz. ### Claim 7 (depends on 1) The sensor defined in claim 1, in which the buffer amplifier has unity gain. ### Claim 8 (depends on 1) The sensor defined in claim 1, in which the impedance transformance device includes a transformer with a winding ratio of at least 5:1. ### Claim 9 (depends on 1) The sensor defined in claim 1, in which the first impedance is 25 to 10,000 times the second impedance. ### Claim 10 (depends on 1) The sensor defined in claim 1, in which the impedance transformance device includes a differential amplifier. ### Claim 11 (depends on 1) The sensor defined in claim 1, in which the output side is adapted for connection to a signal transmission line having a characteristic impedance that determines the coupling impedance. ### Claim 12 (depends on 1) The sensor defined in claim 1, in which the capacitor component has two conductive plates spaced apart and mounted for placement adjacent to an electrical power apparatus in which a PD is suspected for capacitive coupling therewith. ### Claim 13 (depends on 1) The sensor defined in claim 1, in which the capacitor component has a single conductive plate mounted for placement adjacent to an electrical power apparatus in which a PD is suspected for capacitive coupling therewith. ### Claim 14 (depends on 1) The sensor defined in claim 1, in which the capacitor component is adapted for capacitive coupling with a shielded power cable to sense PD signals in the cable and pass the sensed PD signals to the impedance transformance device. ### Claim 15 (depends on 1) The PD sensor of claim 1, further comprising a signal analyzer for identifying the bandwidth of a received PD signal. ### Claim 16 (depends on 1) The PD sensor of claim 1 for sensing a PD at a distance 100 meters or more from the source of the PD. ### Claim 17 (depends on 16) The PD sensor of claim 16 wherein the sensor detects a 20 MHz bandwidth of the PD. ### Claim 18 (depends on 1) The PD sensor of claim 1 for sensing a PD at a distance 500 meters or more from the source of the PD. ### Claim 19 (depends on 18) The PD sensor of claim 18 wherein the sensor detects a 4 MHz bandwidth of the PD. ### Claim 20 (depends on 1) The PD sensor of claim 1 wherein the electrical apparatus comprises one or more of the group consisting of medium voltage (MV) and high voltage (HV) shielded cable systems, transformers, and switch gear. ### Claim 21 (depends on 1) The PD system of claim 1 wherein the electrical apparatus comprises one or more of the group consisting of medium voltage (MV) and high voltage (HV) shielded cable systems, transformers, and switch gear. ### Claim 22 A PD detection system comprising: a signal-analyzing device for analyzing frequencies of a PD signal generated in an electrical power apparatus at a location distant from the PD detection system; a transmission line connected to the signal-analyzing device for conveying the PD signal thereto, the signal-analyzing device and the transmission line forming a signal-analyzing system having a known coupling impedance; and a sensor for detecting the PD signal in the electrical power apparatus and for passing the PD signal to the transmission line, the sensor having a capacitor component having a predetermined capacitance for capacitive coupling to the electrical power apparatus to pick up the PD signal generated in the electrical power apparatus; an impedance transformance device including a buffer amplifier having an inputside connected directly to the capacitor component and an output side configured for connection to the transmission line of the signal-analyzing system, the impedance transformance device being constructed and arranged to convey the PD signal from the input side to the output side, the impedance transformance device having a first effective impedance at the input side and a second effective impedance at the output side, the first effective impedance being much larger than the second effective impedance, and the second effective impedance being selected to match the known coupling impedance; whereby the capacitance of the capacitor component in combination with the first effective impedance inherently effects a low frequency filter cutoff much lower than the low frequency cutoff that would be caused by the capacitance of the capacitor component in combination with the known coupling impedance, and said low frequency cutoff includes a bandwidth of low frequencies for indicating occurrence of a PD at a distance from the PD sensor. ### Claim 23 (depends on 22) The PD detection system defined in claim 22, in which the impedance transformation device has a first effective impedance 100 to 10,000 times the second effective impedance. ### Claim 24 (depends on 22) The PD detection system defined in claim 22, in which the capacitance of the capacitor component in combination with the first effective impedance effects a low frequency filter cutoff between 4 KHz and 1 MHz. ### Claim 25 (depends on 22) The PD detection system defined in claim 22, in which the impedance transformance device includes a differential amplifier. ### Claim 26 (depends on 22) The PD detection system defined in claim 22, in which the impedance transformance device includes a transformer with a winding ratio of at least 5:1. ### Claim 27 (depends on 22) The PD detection system defined in claim 22, in which the first impedance is 25 to 10,000 times the second impedance. ### Claim 28 (depends on 22) The PD sensor of claim 22 wherein the signal-analyzing device identifies the bandwidth of a received PD signal. ### Claim 29 (depends on 22) The PD system of claim 22 for sensing a PD at a distance 100 meters or more from the source of the PD. ### Claim 30 (depends on 29) The PD system of claim 29 wherein the sensor detects a 20 MHz bandwidth of the PD. ### Claim 31 (depends on 22) The PD system of claim 22 for sensing a PD at a distance 500 meters or more from the source of the PD. ### Claim 32 (depends on 31) The PD system of claim 31 wherein the sensor detects a 4 MHz bandwidth of the PD.