Line mounted apparatus for measuring line potential

• US 4,795,973 A
• Filed: 03/29/1988
• Issued: 01/03/1989
• Est. Priority Date: 11/08/1984
• Status: Expired due to Term

• Current Assignee: Undersground Systems, Inc.
• Original Assignee: Niagara Mohawk Power Corporation (National Grid PLC)
• Inventors: Montgomery, John R., Smith-Vaniz, William R.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Urban, Edward
• Application Number:
  US07/174,965
• Time in Patent Office: 280 Days
• Field of Search: 324/126, 324/127, 324/109, 324/123 R, 324/72, 364/492
• US Class Current: 324/126
• CPC Class Codes: G01R 15/144 Measuring arrangements for voltage not covered by other subgroups of G01R15/14
• CPC Class Codes: G01R 15/26 using modulation of waves other than light, e.g. radio or acoustic waves

Abstract

A self contained hot stick mounted radio transmitting module may be permanently mounted on or temporarily pushed against the power conductor of an electrical transmission line. The module is capable of measuring the potential difference between the conductor and ground. The module digitizes and transmits the value of the potential difference to a ground receiver. The module is donut shaped and opens like a pair of jaws. The contact with the power line is accomplished via a resilient conductive elastomer that covers the surfaces in contact with the power conductor. The potential difference between ground and the power conductor is measured with an operational amplifier in an integrating configuration to convert the leakage current from the module to ground into a proportional voltage from a low impedance source. The integrator outputs a voltage proportional to the current flowing into the equivalent capacitance formed by the outer surface of the module and ground. The current is generated by the voltage difference between the power conductor and ground. The power conductor is engaged by a pair of jaws inserts comprising two concentric conducting rings separated by a thin insulating layer forming a large capacitor. The electronic components within the unit are protected by a signal conditioning network to preclude destruction of components in the event of lightning strikes or other overvoltage conditions.

Claims

1. Apparatus for measuring voltage on an above ground power line conductor comprising:

an electrically conductive housing attached to said above ground conductor,

mounting means for attaching said housing to said conductor,

said mounting means including a first conductive portion in electrical contact with said conductor, a second conductive portion in electrical contact with said housing, and electrical insulating means separating said first and second portions,

and low impedance current measuring means, said measuring means electrically connected to said first conductive portion and to said housing whereby said housing acts as a charge collecting plate and said measuring means measures current flowing from said conductor to said housing, said current being proportional to the voltage on said power line conductor.

2. Apparatus as defined in claim 1 wherein said mounting means comprises:

a pair of arcuate nested metal parts including an outer ring and an inner ring fitting within said outer ring; and

a film of insulating material affixed to said inner ring to electrically insulate said inner ring from said outer ring.

3. Apparatus as defined in claim 2 wherein said film is a hard coat ceramic.

4. Apparatus as defined in claim 2 wherein said film is a polymer.

5. Apparatus as defined in claim 4 wherein said film is a fluorocarbon.

6. Apparatus as defined in claim 2 further including a conductive neoprene insert fitting in said inner ring and contacting said conductor when said housing is mounted on said conductor.

7. Apparatus as defined in claim 1 wherein said housing is generally toroidal in shape and surrounds said conductor when mounted on said conductor.

8. Apparatus as defined in claim 1 wherein said measuring means comprises an operational amplifier with first and second inputs.

9. Apparatus as defined in claim 8 further including a surge suppressing network connected between said first amplifier input and said conductor, said second amplifier input connected to said housing.

10. Apparatus as defined in claim 8 wherein said operational amplifier is configured as an integrator.