# US 2014/0125353 A1 · 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 2014/0125353 A1 - Document ID: US20140125353A1 - Status: Published application - Kind: A1 - Application number: 13/667,952 - Filed: 2012-11-02 - Published: 2014-05-08 - Earliest claimed: 2012-11-02 - Assignees: UTILX Corporation - Inventors: Wen Shu; Nelson Hall - Web page: https://patentgrep.com/patent/US20140125353A1 ## 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 impedance, said sensor comprising: a capacitor component having a predetermined capacitance for capacitive coupling to an electrical power apparatus in which a PD is suspected; and an impedance transformance device 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. ### 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 1) The sensor defined in claim 1, in which the first impedance is at least two orders of magnitude greater than second impedance. ### Claim 4 (depends on 2) The sensor defined in claim 2, in which the first impedance is 100 to 10,000 times the 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 impedance transformance device includes an IC buffer. ### Claim 8 (depends on 7) The sensor defined in claim 7, in which the IC buffer has unity gain. ### Claim 9 (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 10 (depends on 1) The sensor defined in claim 1, in which the first impedance is 25 to 10,000 times the second impedance. ### Claim 11 (depends on 1) The sensor defined in claim 1, in which the impedance transformance device includes a differential amplifier. ### Claim 12 (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 13 (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 14 (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 15 (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 16 A PD detection system comprising: a signal-analyzing device for analyzing a PD signal generated in an electrical power apparatus; 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; and an impedance transformance device having an input side 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 ### Claim 17 (depends on 16) The sensor defined in claim 16, in which the first effective impedance is 100 to 10,000 times the second effective impedance. ### Claim 18 (depends on 16) The sensor defined in claim 16, 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 19 (depends on 16) The sensor defined in claim 16, in which the impedance transformance device includes an IC buffer. ### Claim 20 (depends on 16) The sensor defined in claim 16, in which the impedance transformance device includes a differential amplifier. ### Claim 21 (depends on 16) The sensor defined in claim 16, in which the impedance transformance device includes a transformer with a winding ratio of at least 5:1. ### Claim 22 (depends on 16) The sensor defined in claim 16, in which the first impedance is 25 to 10,000 times the second impedance.