Secondary electrical power line parameter monitoring apparatus and system

• US 5,426,360 A
• Filed: 02/17/1994
• Issued: 06/20/1995
• Est. Priority Date: 02/17/1994
• Status: Expired due to Fees

• Current Assignee: Niagara Mohawk Power Corporation (National Grid PLC)
• Original Assignee: Niagara Mohawk Power Corporation (National Grid PLC)
• Inventors: Maraio, Robert A., Sieron, Richard L., Crimmins, James W.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): KHOSRAVI, KOURO
• Application Number:
  US08/198,501
• Time in Patent Office: 488 Days
• Field of Search: 324/126, 324/127, 324/117 R, 324/72.5
• US Class Current: 324/126
• CPC Class Codes: G01R 1/22 Tong testers acting as secondary windings of current transformers
• CPC Class Codes: G01R 15/142 Arrangements for simultaneous measurements of several parameters employing techniques covered by groups G01R15/14 - G01R15/26
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

A system for unintrusively determining parameters such as current, voltage and power delivered through a service line to a customer for verifying accuracy of the customer'"'"'s entrance meter. The system includes a sensor apparatus for monitoring voltage and current on the power line. A voltage clamp mechanism is disposed within a sensor housing such that an insulation piercing voltage sensor can be manually actuated to pierce the electrical insulation of the power line and contact the conductor. The sensor apparatus also includes a split-core current transformer fabricated to minimize the air gap between the split-core sections when the apparatus is closed about the power line. A pole unit is electrically connected to each sensor apparatus for monitoring the voltage and current, calculating the power consumed in kilowatt-hours and storing calculated kilowatt-hours in memory with an appropriate date/time stamp, for subsequent retrieval and comparison with the customer'"'"'s entrance meter readings. Data retrieval is accomplished via a hand-held ground unit, such as a palm top computer, which communicates via infrared signals with the pole mounted unit.

Claims

1. Sensor apparatus for monitoring voltage of a power line having a conductor surrounded by electrical insulation, said sensor apparatus comprising:

a sensor housing; and

a voltage clamp mechanism disposed within said sensor housing, said voltage clamp mechanism including an upper support and a lower support sized to cradle the power line there between, and clamping means for forcing said upper support towards said lower support, said lower support being spring biased away from a supporting surface of said sensor housing to which the lower support is affixed and having an insulation piercing voltage sensor disposed in an opening therein, said insulation piercing voltage sensor being fixedly mounted relative to said supporting surface of said sensor housing to which the lower support is affixed and shaped to pierce the electrical insulation surrounding the conductor of the power line when exposed from said lower support, wherein when the power line is cradled between said upper support and said lower support and when the upper support is forced against the power line by said clamping means, the lower support is moved towards the supporting surface of the sensor housing to which the lower support is affixed and the insulation piercing voltage sensor is exposed from the lower support to pierce the electrical insulation and physically contact the conductor of the power line for monitoring voltage thereon.

2. The sensor apparatus of claim 1, wherein the sensor housing has an upper portion pivotally connected to a lower portion, and wherein the upper support of the voltage clamp mechanism resides within the upper portion of the sensor housing and the lower support of the voltage clamp mechanism resides within the lower portion of the sensor housing.

3. The sensor apparatus of claim 1, wherein said voltage clamp mechanism includes limiting means for limiting piercing of the power line by the insulation piercing voltage sensor as the upper support of the voltage clamp mechanism is forced against the power line by said clamping means.

4. The sensor apparatus of claim 3, wherein said clamping means comprises ratcheting clamping means for forcing the upper support towards the lower support and for discontinuing said forcing of the upper support towards the lower support when piercing of the power line by the insulation piercing voltage sensor is limited by said limiting means.

5. Sensor apparatus for monitoring current and voltage of a power line having a conductor surrounded by electrical insulation, said sensor apparatus comprising:

a sensor housing having an upper portion pivotally connected to a lower portion;

a split-core current transformer for monitoring current passing through said power line, an upper half of said split-core current transformer residing within the upper portion of said sensor housing and a lower half of said split-core current transformer residing within the lower portion of said sensor housing; and

a voltage sensor for monitoring voltage of said power line, said voltage sensor having an upper support and a lower support sized to cradle said power line when said sensor housing is closed about said power line, the upper support of said voltage sensor residing in the upper portion of the sensor housing and the lower support of said voltage sensor residing in the lower portion of the sensor housing, said voltage sensor further comprising clamping means for forcing the upper support towards the lower support, said lower support being spring-biased away from a supporting surface of the lower portion of said sensor housing and having an insulation piercing member disposed in an opening therein, said insulation piercing member being fixedly mounted relative to the sensor housing and shaped to pierce the electrical insulation surrounding the conductor of the power line when exposed from said lower support as the upper portion of the sensor housing is forced towards the lower portion of the sensor housing with the power line disposed there between, wherein when the power line is cradled between the upper support and the lower support of the voltage sensor and the upper portion of the sensor housing is forced against the power line by the clamping means, the lower support is moved towards the supporting surface of the sensor housing and the insulation piercing member is exposed from the lower support surface to pierce the electrical insulation of the power line and physically contact the conductor such that the sensor housing can be clamped to the power line to simultaneously establish a voltage connection to the conductor of the power line through the insulation piercing member, to monitor voltage of the conductor, and locate the upper half of the split-core current transformer relative to the lower half of the split-core current transformer, to monitor current through the conductor.

6. The sensor apparatus of claim 5, wherein said clamping means comprises a ratcheting clamping means having limiting means for limiting piercing of the power line by the insulation piercing member, wherein piercing of the power line is terminated by said limiting means after the insulation piercing member makes physical contact with the conductor of the power line.

7. The sensor apparatus of claim 6, wherein said ratcheting clamping means includes driving means for driving the upper support against the power line and means for disengaging said driving means when the insulation piercing member has pierced the electrical insulation and contacted the conductor of the power line.

8. The sensor apparatus of claim 5, wherein the split-core current transformer includes a magnetic field shield to shield the current transformer from external magnetic fields.

9. The sensor apparatus of claim 8, wherein the split-core current transformer has a tape wound core of eighty (80%) percent nickel and twenty (20%) percent iron with lapped pole faces.

10. The sensor apparatus of claim 5, further comprising a controller electrically connected to the split-core current transformer and to the voltage sensor for monitoring current and voltage of the power line at periodic intervals, and memory means coupled to the controller for storing monitored current and voltage readings.

11. The sensor apparatus of claim 10, wherein said controller includes means for computing power consumption in kilowatt-hours and for date and time stamping each kilowatt-hour computation for storing thereof in said memory means as a history file of kilowatt-hour usage.

12. The sensor apparatus of claim 10, wherein said controller and said memory means are powered through the voltage sensor by the monitored voltage on the power line.

13. The sensor apparatus of claim 12, wherein the sensor housing includes means for indicating a necessary direction of connection of the sensor apparatus to the power line, said necessary direction of connection being such that said split-core current transformer is disposed downstream from the voltage sensor relative to current flow in the power line.

14. The sensor apparatus of claim 10, wherein the controller and the memory means are disposed external to and removed from the sensor housing, and wherein the controller and memory means are electrically coupled to the split-core current transformer and the voltage sensor via at least one electrical cable.

15. The sensor apparatus of claim 10, further comprising means for facilitating calibration of the sensor apparatus.

16. Sensor apparatus for monitoring current of a power line having a conductor surrounded by electrical insulation, said sensor apparatus comprising:

a sensor housing having an upper portion pivotally connected to a lower portion, said upper portion and said lower portion being sized to receive the power line such that the power line passes through the sensor housing when the sensor housing is closed thereabout;

a split-core current transformer for monitoring current passing through said power line, an upper half of said split-core current transformer residing within the upper portion of said sensor housing and a lower half of said split-core current transformer residing within the lower portion of said sensor housing;

a controller disposed external to and removed from the sensor housing and having memory and a tandem current transformer; and

an electrical cable coupling the split-core current transformer to the tandem current transformer of the controller, said split-core current transformer having a secondary winding connected to a primary winding of said tandem current transformer, said split-core current transformer and said tandem current transformer cooperating to monitor current through the power line over a current range of one to at least 200 hundred amperes.

17. The sensor apparatus of claim 16, wherein the split-core current transformer and the tandem current transformer cooperate to monitor current through the power line over a current range of 1 to 800 amperes.

18. The sensor apparatus of claim 17, wherein the electrical cable is greater than two feet in length.

19. The sensor apparatus of claim 16, wherein the split-core current transformer includes a magnetic field shield to shield the split-core current transformer from external magnetic fields.

20. The sensor apparatus of claim 19, wherein the split-core current transformer has a tape wound core of eighty (80%) nickel and twenty (20%) iron with lapped pole faces.

21. A sensor system for monitoring a power line consisting of a conductor surrounded by electrical insulation, said sensor system comprising:

a line-mounted sensor apparatus including

(i) a sensor housing, and

(ii) a voltage clamp mechanism disposed within the sensor housing, the voltage clamp mechanism including an upper support and a lower support sized to cradle the power line there between, and clamping means for forcing the upper support towards the lower support, the lower support being spring-biased away from a supporting surface of the sensor housing to which the lower support is affixed and having an insulation piercing voltage sensor disposed in an opening therein, the insulation piercing voltage sensor being fixedly mounted relative to the supporting surface of the sensor housing to which the lower support is affixed and shaped to pierce the electrical insulation surrounding the conductor of the power line when exposed from said lower support, wherein when the power line is cradled between the upper support and the lower support and the upper support is forced against the power line by the clamping means, the lower support is moved towards the supporting surface of the sensor housing to which the lower support is affixed and the insulation piercing voltage sensor is exposed from the lower support to pierce the electrical insulation and physically contact the conductor of the power line for monitoring voltage thereof;

data memory for storing data representative of monitored voltage of the power line; and

control means, electrically coupled to the insulation piercing voltage sensor of the voltage clamp mechanism and to the data memory, for controlling periodic monitoring of voltage on the conductor of the power line and for storing monitored voltage in said data memory such that a history of voltage on the conductor is compiled.

22. The sensor system of claim 21, wherein said data memory and said control means reside within a data processing unit, said data processing unit being external to and remote from said line-mounted sensor apparatus and being coupled to said line-mounted sensor apparatus via at least one electrical cable.

23. The sensor system of claim 22, wherein said data processing unit includes means for mounting said data processing unit to a pole supporting the power line.

24. The sensor system of claim 22, wherein the data processing unit is powered through the insulation piercing voltage sensor by voltage on the conductor of the power line.

25. The sensor system of claim 22, wherein the line-mounted sensor apparatus further comprises a split-core current transformer for monitoring current passing through the power line, and wherein the sensor housing has an upper portion pivotally connected to a lower portion, an upper half of the split-core current transformer residing within the upper portion of the sensor housing and a lower half of the split-core current transformer residing within the lower portion of the sensor housing.

26. The sensor system of claim 25, wherein the control means includes means for periodically monitoring voltage and current of the power line and for computing kilowatt-hours based thereon, and for saving each kilowatt-hour computation in the data memory such that a history of kilowatt-hour usage is compiled.

27. The sensor system of claim 25, wherein the data processing unit includes a tandem current transformer coupled and sized to cooperate with the split-core current transformer to measure current on the conductor of the power line over a range of current from 1 ampere to greater than 200 hundred amperes.

28. The sensor system of claim 21, wherein the sensor system is capable of monitoring multiple power lines each consisting of a conductor surrounded by electrical insulation, said sensor system including multiple line-mounted sensor apparatus, each line-mounted sensor apparatus being coupled to a different one of the multiple power lines.

29. The sensor system of claim 26, further comprising a hand-held ground unit capable of communicating remotely with the data processing unit such that the history of voltage on the conductor can be downloaded to the hand-held ground unit for transfer to a central computer for comparison of the kilowatt-hour usage history from the sensor system with kilowatt-hour usage from an entrance meter connected to the power line.

30. The sensor system of claim 29, wherein the hand-held ground unit communicates with the data processing unit via infrared signals, said hand-held ground unit and said data processing unit each having an infrared transceiver.

31. Sensor apparatus for monitoring current and voltage of a power line having a conductor surrounded by electrical insulation, said sensor apparatus comprising:

a sensor housing having an upper portion pivotally connected to a lower portion;

a split-core current transformer for monitoring current passing through said power line, an upper half of said split-core current transformer residing within the upper portion of said sensor housing and a lower half of said split-core current transformer residing within the lower portion of said sensor housing;

a voltage sensor for monitoring voltage of said power line, said voltage sensor having an upper support and a lower support sized to cradle said power line when said sensor housing is closed about said power line, the upper support of said voltage sensor residing in the upper portion of the sensor housing and the lower support of said voltage sensor residing in the lower portion of said sensor housing, said voltage sensor further including an insulation piercing member capable of piercing the electrical insulation of the power line as the upper portion of the sensor housing is forced towards the lower portion of the sensor housing with the power line disposed therebetween;

a controller electrically coupled to the split-core current transformer and to the voltage sensor for monitoring current and voltage of the power line at periodic intervals, and memory means coupled to the controller for storing monitored current and voltage readings, said controller and said memory means being disposed external to and removed from the sensor housing, said controller and said memory means being electrically coupled to the split-core current transformer and the voltage sensor via at least one electrical cable;

a tandem current transformer connected to the controller and the memory means, said tandem current transformer also being disposed external to and removed from the sensor housing, said tandem current transformer being coupled to said split-core current transformer via the at least one electrical cable such that a secondary winding of the split-core current transformer is connected to a primary winding of the tandem current transformer, said split-core current transformer and said tandem current transformer cooperating to monitor a wide range of potential current in the power line, said wide range of potential current being from approximately 1 ampere to at least 200 amperes; and

wherein when the power line is cradled between the upper support and the lower support of the voltage sensor and the upper portion Of the sensor housing is in opposing relation with the lower portion of the sensor housing, the sensor housing can be clamped to the power line to simultaneously establish a voltage connection to the conductor of the power line through the insulation piercing member, such that voltage of the conductor can be monitored, and to locate the upper half of the split-core current transformer relative to the lower half of the split-core current transformer, such that current through the conductor can be monitored.