Method for certifying dead cables or conductors by determining current pulse polarity

• US 3,924,179 A
• Filed: 04/24/1974
• Issued: 12/02/1975
• Est. Priority Date: 04/24/1974
• Status: Expired due to Term

• Current Assignee: Multi-Comp Incorporated
• Original Assignee: William A. Dozier
• Inventors: Dozier, William A.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/463,683
• Time in Patent Office: 587 Days
• Field of Search: 324/66,67,133,52,51
• US Class Current: 324/66
• CPC Class Codes: G01R 19/14 Indicating direction of current; Indicating polarity of voltage
• CPC Class Codes: G01R 19/15 Indicating the presence of current
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

Method and apparatus for certifying a dead insulated electrical conductor among a plurality of conductors by determining the polarity of a net DC pulse in the conductor at any desired test point between the ends of the conductor. The conductor to be certified is connected to an electrical return conductor and a periodic DC current pulse between a test point and the return conductor is generated by coupling a pulse transmitter to the conductor. The net DC pulse in the conductor is detected by electro-magnetically coupling a receiver to the conductor without removing the conductor sheathing.

Claims

1. A method for certifying that an insulated electrical conductor is dead at a point remote from the two ends at which end points it is known to be dead and wherein at least one energized and/or AC current carrying conductor is present at the remote point comprising the steps of:

electrically connecting a conductor to be certified to an electrical return path at one of said end points;

supplying a periodic DC current pulse at the other of said end points between said conductor to be certified and said return path to generate therein a net DC current pulse of the same polarity at said remote point along said conductor to be certified, a portion of said current pulse being returned along said electrical return path and the remaining portion of the current pulse being returned through an additional return path;

measuring the vector summation of all the currents in said electrical conductor to be certified and said electrical return path and thereby determining the polarity of the net DC pulse in the conductor to be certified at said remote point; and

determining that said electrical conductor is dead by ensuring that said measured polarity is the same as said same polarity.

2. The method as in claim 1 wherein the step of measuring is carried out by a detector utilizing a radiated electromagnetic field.

3. The method as in claim 1 wherein said step of measuring is carried out with an alternating current flowing in a return conductor.

4. The method as in claim 1 wherein said step of measuring determines the net difference in the radiated outgoing and returning DC current pulse simultaneously with the measurement of the polarity of the net DC pulse using the same receiver.

5. The method as in claim 1 further comprising the step of adding an external parallel return path prior to supplying said periodic DC current pulse for the purpose of certifying that a lone cable is dead.

6. The method as in claim 5 wherein said electrical conductor to be certified is one of multiple conductors having a concentric neutral conductor and further comprising the step of connecting a jumper cable to said neutral conductor on both sides of the receiver used for measuring the polarity of the net DC pulse for bypassing part of the return DC current pulse prior to supplying said periodic DC current pulse to said conductor to be certified.