Method and device for detecting and locating fault and/or partial discharges in a gas-insulated electrical equipment

• US 4,446,420 A
• Filed: 01/28/1982
• Issued: 05/01/1984
• Est. Priority Date: 01/28/1982
• Status: Expired due to Fees

• Current Assignee: Hydro-Quebec (Province of Québec)
• Original Assignee: Hydro-Quebec (Province of Québec)
• Inventors: Drouet, Michel G.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US06/461,870
• Time in Patent Office: 824 Days
• Field of Search: 324/52, 324/51
• US Class Current: 324/522
• CPC Class Codes: G01R 31/08 Locating faults in cables, transmission lines, or networks
• CPC Class Codes: G01R 31/1254 of gas-insulated power appliances or vacuum gaps testing switches G01R31/327; detecting electrical or mechanical defects in encased switchgear H02B13/065

Abstract

A device and a method for detecting and locating faults and/or partial discharges in a gas-insulated electrical equipment, such as gas-insulated bus or cable, a gas-insulated substation or a gas-insulated switchgear. The detecting device comprises a plurality of field coupled current sensors located at given intervals inside the housing of the equipment for detecting any variation of the current flowing through the conducting element extending inside this housing. Each sensor consists of a toroidal helix pick up coil, preferably a differentiating Rogowski coil, located in an annular cavity machined in the wall of the equipment housing and extending all around the conducting element. Each cavity is connected along its entire length to the inner surface of the housing wall by a slit having opposed side walls sufficiently spaced apart to be insulated from each other. Each sensor gives a signal which is proportional to the detected variation of the current. A control circuit is connected to each of the sensors for comparing their signals and measuring the time interval between all the signals given by the sensors of a given variation current, and thereby determining where is located the fault or partial discharge having caused this given variation of current. The main advantages of this device are that it is not electrically connected to the circuit carrying the main current and it is not influenced by the voltage drop associated with the flow of current on the inside surface of the annular cavities. Moreover, the sensitivity of the device is a function of the number of turns in the pick up coil, and therefore can be very high.

Claims

1. In a device for detecting and locating faults and partial discharges in a gas-insulated electrical equipment of the type comprising a closed wall housing containing an insulating gas for electrically insulating at least one conducting element centrally extending inside said housing, said device comprising:

a plurality of field coupled current sensors located at given intervals inside the housing for detecting any variation of the current flowing through the conducting element, each of said sensors giving a signal in correlation with said detected variation; and

a control circuit connected to each of the sensors for comparing their signals and measuring the time interval between all the signals given by the sensors of a given variation of current, and thereby determining where is located the fault and/or partial discharge causing said given variation of current

the improvement wherein;

each of said sensors comprises a toroidal helix pick up coil located in an annular cavity machined in the housing wall and extending all around the conducting element,

each of said annular cavities being connected along its entire length to the inner surface of the housing wall by a slit having opposed side walls sufficiently spaced apart to be insulated from each other.

2. The improved device of claim 1, wherein each toroidal helix pick up coil is a differentiating Rogowski coil giving an output voltage signal proportional to the derivative of the current flowing through the conducting element with respect to the time.

3. The improved device of claim 2 for use in a gas-insulated electrical equipment comprising a plurality of housing sections attached end to end by pairs of flanges having opposing surfaces, wherein the coil receiving cavities are machined in the opposing surfaces of different pairs of flanges.

4. The improved device of claim 3, wherein each coil receiving cavity is machined in the surface of one flange of one of said pairs of flanges, and the opposed side walls of the slit connecting said cavity to the inner surface of the housing wall are portions of opposing surfaces of said one pair of flanges.

5. The improved device of claim 4, further comprising a high-pass filter connected between each coil and the control circuit, for discriminating high frequency signals that correspond to a fault and/or partial discharge, from low frequency signals caused by any current flowing in, or induced in the conducting element.

6. The improved device of claim 5, wherein the gas-insulated electrical equipment is a gas-insulated bus or cable, a gas-insulated substation or a gas-insulated switchgear.

7. The improved device of claim 2 for use in a gas-insulated electrical equipment comprising a plurality of housing sections attached end to end by means of welding-ring inserts, wherein the coil receiving cavities are all machined in different welding-ring inserts.

8. The improved device of claim 7, further comprising a high-pass filter connected between each coil and the control circuit, for discriminating high frequency signals that correspond to a fault and/or partial discharge, from low frequency signals caused by any current flowing in, or induced in the conducting element.

9. The improved device of claim 8, wherein the gas-insulated electrical equipment is a gas-insulated bus or cable.

10. In a method for detecting and locating faults and/or partial discharges in a gas-insulated electrical equipment of the type comprising a closed wall housing containing an insulating gas for electrically insulating at least one conducting element centrally extending inside said housing, said method comprising the steps of:

providing field coupled sensors at given intervals inside the housing;

detecting the current induced in each sensor by the current flowing through the conducting element;

measuring the time interval between detections by all the sensors of a given variation of current, and

thereby determining where is located the fault and/or partial discharge having caused said given variation of current,

the improvement wherein;

use is made as sensors, of toroidal helix pick-up coils each located in an annular cavity machined in the housing wall and extending all around the conducting element, each of said cavities being connected along its entire length to the inner surface of the housing wall by a slit having opposed side walls sufficiently spaced apart to be insulated from each other.

11. The improved method of claim 10, wherein the toroidal helix pick-up coils are differentiating Rogowski coils giving an output voltage signal proportional to the derivative of the current flowing through the conducting element with respect to the time.

12. The improved method of claim 11, applied to the detection and location of faults and/or partial discharges in a gas-insulated bus or cable, gas insulated substation or gas-insulated switchgear wherein the coil receiving cavities are machined in opposing surfaces of different pairs of flanges used for attaching together sections of the housing wall of the equipment.

13. The improved method of claim 12, comprising the additional step of filtering high frequency current variations that correspond to a fault and/or partial discharge, from low frequency current variations that are caused by the current flowing in, or induced in the conducting element.

14. The improved method of claim 11 applied to the detection and location of faults and/or partial discharges in a gas-insulated bus or cable, wherein the coil receiving cavities are machined in different welding-ring inserts used for attaching together sections of the housing wall of the equipment.

15. The improved method of claim 14, comprising the additional step of filtering high frequency current variations that correspond to a fault and or partial discharge, from low frequency current variations that are caused by the current flowing in, or induced in the conducting element.