Branch current monitor with calibration

• US 8,421,443 B2
• Filed: 11/20/2009
• Issued: 04/16/2013
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: Veris Industries LLC (Schneider Electric SE)
• Original Assignee: Veris Industries LLC (Schneider Electric SE)
• Inventors: Bitsch, Michael, Cook, Martin, Rupert, Matthew
• Primary Examiner(s): Benitez Rosario, Joshua
• Application Number:
  US12/592,211
• Publication Number:
  US 20100207604A1
• Time in Patent Office: 1,243 Days
• Field of Search: 324/117.R, 324/126, 324/127, 324140 T-142, 324/706, 324/764.01, 324/648
• US Class Current: 324/127
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

A meter for measuring electric power consumed by a plurality of branch circuits includes interchangeable current transformers including respective transformer memories for storage of transformer characterization data and enables self-discovery of a phase shift induced by respective current transformers and the phase of current conducted by each branch circuit.

Claims

1. An electricity meter comprising:

(a) a current sensor having a sensor output datum quantitatively representing an electric current;

(b) a current sensor memory affixed to said current sensor and arranged to store at least one current sensor characterization datum defining at least one of;

(i) a sensor type for said current sensor;

(ii) a magnetization error correction datum for said current sensor; and

(iii) a sensor position of said current sensor and a sensor position of at least one other sensor; and

(c) a data processing unit remote from said current sensor and said current sensor memory and including a selectively detachable conductive connection to said current sensor and said current sensor memory, said data processing unit arranged for communication with said current sensor and said current sensor memory and to calculate an electric current from said sensor output datum and at least one current sensor characterization datum.

2. The electrical meter of claim 1 where said current sensor comprises a current transformer.

3. The electrical meter of claim 1 wherein said current sensor comprises:

(a) a support arranged for detachable securement to a mounting surface; and

(b) a current transformer detachably connectable to said support.

4. The electrical meter of claim 1 wherein said current sensor comprises:

(a) a support arranged for detachable securement to a supporting structure; and

(b) a current transformer including a housing detachably connectable to said support, said housing enclosing said current sensor memory.

5. A meter comprising:

(a) a mounting structure arranged to support a plurality of current sensors and securable to a supporting structure;

(b) plural current sensors supported by said mounting structure, at least one current sensor detachably securable to said mounting structure and operable to output a sensor output datum quantitatively representing an electric current;

(c) a memory affixed to said at least one current sensor and arranged to store a current sensor characterization datum, said memory conductively connectable to a conductor supported by said mounting structure; and

(d) a data processing unit remote from said mounting structure, said at least one current sensor and said affixed memory and including a selectively detachable conductive connection to said at least one current sensor and said memory, said data processing unit arranged to communicate with said current sensor and said memory and to determine an electric current from said sensor output datum and said current sensor characterization datum.

6. The meter of claim 5 wherein said sensor characterization datum defines a sensor type of said current sensor.

7. The meter of claim 5 wherein meter further comprises a plurality of sensor positions, said sensor characterization datum defining a sensor position of said current sensor.

8. The meter of claim 5 wherein said sensor characterization datum defines a turns ratio of said current sensor.

9. The meter of claim 5 wherein said sensor characterization datum defines a phase shift of said current sensor.

10. A method for determining a shift between a phase of an electric current to be measured by one of a plurality of current transformers and a phase of an output signal of said current transformer, said method comprising the step of:

(a) passing a conductor through an aperture defined by portions of a toroidal core of one of said plural current transformers;

(b) energizing said conductor with a temporally varying signal;

(c) with a data processing device arranged to detect and compare said temporally varying signal and an output signal of respective ones of said plural current transformers determining if an output signal is detectable at one current transformer;

(d) if an output signal is detected at said one current transformer, measuring with said data processing device a temporal shift between a temporal reference in said temporally varying signal and a corresponding temporal reference in said output signal;

(e) in a memory accessible to said data processing device storing said temporal shift in association with an identification of said one current transformer; and

(f) if an output signal is not detected at said one current transformer repeating steps (c)-(f) for another current transformer; and

(h) if a temporal shift associated with said one current transformer has been stored in said memory, repeating steps (a)-(h) for another of said plural current transformers.

11. A method for determining a phase of electric power conducted by the ones of a plurality of branch circuit conductors, each branch circuit conductor connected to at least one source of electric power having one of a plurality of phases, said method comprising the steps of:

(a) installing a current sensor for each branch circuit conductor, each current sensor having an output quantitatively responsive to a current in said branch circuit conductor associated with said current sensor;

(b) energizing a first source of electric power with a temporally varying signal;

(c) with a data processing device arranged for selectively detecting an output by respective current sensors, determining if an output of a first current sensor quantitatively responds to said temporally varying signal;

(d) if said output of said first current sensor quantitatively responds to said temporally varying signal, storing an association of said first current sensor and a first phase of said electric power in a memory accessible by said data processing device;

(e) repeating steps (c) and (d) for each of said plurality of current sensors;

(f) removing said temporally varying signal from said first source of said electric power;

(g) energizing a second source of electric power with a temporally varying signal; and

(h) repeating steps (c) and (d) for each of said plurality of current sensors.

12. A method for determining a phase of electric power conducted by the ones of a plurality of branch circuit conductors, each branch circuit conductor connected to at least one source of electric power having one of a plurality of phases, said method comprising the steps of:

(a) energizing a first branch circuit conductor with a first signal;

(b) energizing a second branch circuit conductor with a second signal, said second signal distinguishable from said first signal;

(c) arranging a data processing device to detect a signal in a conductor arranged for conducting a first phase of electric power and a conductor arranged for conducting a second phase of electric power;

(d) if said first signal is detectable by said data processing device at said conductor arranged for conducting said first phase of electric power, storing an identification of said first phase in association with an identification of said first branch circuit conductor in a memory accessible by said data processing device;

(e) if said second signal is detectable by said data processing device at said conductor arranged for conducting said first phase of electric power, storing an identification of said first phase in association with an identification of said second branch circuit conductor in said memory accessible by said data processing device;

(f) if said first signal is detectable by said data processing device at said conductor arranged for conducting said second phase of electric power, storing an identification of said second phase in association with an identification of said first branch circuit conductor in said memory accessible by said data processing device; and

(g) if said second signal is detectable by said data processing device at said conductor arranged for conducting said second phase of electric power, storing an identification of said second phase in association with an identification of said second branch circuit conductor in said memory accessible by said data processing device.