Detecting partial discharge using a detection coil and analysis of output signal and noise frequency spectrums

• US 5,469,067 A
• Filed: 12/08/1993
• Issued: 11/21/1995
• Est. Priority Date: 10/25/1989
• Status: Expired due to Fees

• Current Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Endoh, Takeshi, Imai, Tomoaki, Hagiya, Mikio
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): TOBIN, C
• Application Number:
  US08/163,572
• Time in Patent Office: 713 Days
• Field of Search: 324/514, 324/527, 324/529, 324/530, 324/536, 324/541, 324/543, 324/544, 324/6, 324/551, 324/557
• US Class Current: 324/551
• CPC Class Codes: G01R 31/083 in cables, e.g. underground
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

In an electric apparatus such as an electric power cable system, a high frequency pulse is induced on a conductive member such as a metal sheath, where partial discharge occurs in an insulation. The high frequency pulse is detected by means of a bypass lead wire, a metal foil electrode, a detecting coil, and the like provided on the electric apparatus without interrupting a live operation of the electric apparatus.

Claims

1. A method for detecting partial discharge in a plastic solid insulation of a wire shielded electric power cable, comprising the steps of:

providing a single detecting coil wound around said wire shielded electric power cable with a predetermined number of turns;

detecting a frequency spectrum of noise obtained from said wire shielded electric power cable;

supplying a calibration pulse to said wire shielded electric power cable;

detecting a frequency spectrum of an output signal obtained from said wire shielded electric power cable which is supplied with said calibration pulse; and

comparing said frequency spectrums of said noise and said output signal to detect said partial discharge.

2. A method for detecting partial discharge in a plastic solid insulation of wire shielded electric power cable, according to claim 1, and further comprising the step of:

providing a high frequency steel core to cover said detecting coil.

3. A method for detecting partial discharge in a plastic solid insulation of a wire shielded electric power cable according to claim 1, and further comprising the step of:

positioning a high frequency steel core adjacent to said wire shielded electric power cable and winding said detecting coil around said high frequency steel core.