CURRENT MEASUREMENT

• US 20130128396A1
• Filed: 11/22/2012
• Published: 05/23/2013
• Est. Priority Date: 11/23/2011
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Metroic Limited (Analog Devices, Inc.)
• Inventors: DANESH, Seyed Amir Ali, HURWITZ, Jonathan Ephraim David
• Granted Patent: US 9,411,003 B2
• Time in Patent Office: Days
• US Class Current: 361/45
• CPC Class Codes: G01R 19/00 Arrangements for measuring currents or voltages or for indicating presence or sign thereof G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24
• CPC Class Codes: G01R 19/16547 voltage or current in AC supplies switching for protection H02H; circuits for emergency power supply H02J9/00
• CPC Class Codes: G01R 19/2506 Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values G01R19/003 takes precedence; Details concerning sampling, digitizing or waveform capturing displaying waveforms G01R13/00; analog sampling G01R19/0053
• CPC Class Codes: G01R 21/06 by measuring current and voltage G01R21/08 - G01R21/133 take precedence
• CPC Class Codes: G01R 23/02 Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/003 Fault detection by injection of an auxiliary voltage same for detection of earth fault currents H02H3/17; for monitoring earth connection H02H5/105
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/32 involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors

Abstract

The present invention relates to current measurement apparatus. The current measurement apparatus comprises first and second measurement devices with each of the first and second measurement devices being operative to measure current in a respective one of a live conductor and a neutral conductor substantially simultaneously. The current measurement apparatus is operative to make plural different determinations in dependence on the substantially simultaneous current measurements.

Claims

1. Current measurement apparatus comprising first and second measurement devices, each of the first and second measurement devices being operative to measure current in a respective one of a live conductor and a neutral conductor substantially simultaneously, the current measurement apparatus being operative to make plural different determinations in dependence on the substantially simultaneous current measurements.

2. Current measurement apparatus according to claim 1 in which at least one of the plural different determinations comprises a measurement relating to operation of an electrical circuit comprising the live and neutral conductors.

3. Current measurement apparatus according to claim 1 in which at least one of the plural different determinations comprises a decision relating to operation of an electrical circuit comprising the live and neutral conductors.

4. Current measurement apparatus according to claim 3 in which the decision comprises determining a fault condition, the current measurement apparatus further comprising a circuit breaker which is operative to break at least one of the live and neutral conductors in dependence on the decision.

5. Current measurement apparatus according to claim 4 operative to perform calibration in respect of measurement paths associated with the first and second measurement devices, the current measurement apparatus being further operative to delay operation of the circuit breaker to reconnect at least one of the live and neutral conductors until completion of the calibration.

6. Current measurement apparatus according to claim 3 in which the decision is one of an over-current decision and an arc fault decision based on at least one of the current measurements.

7. Current measurement apparatus according to claim 1 operative to determine a difference between the currents, one of the plural different determinations being made in dependence on the difference between the currents, whereby the current measurement apparatus is operative to detect a ground fault.

8. Current measurement apparatus according to claim 7 further operative to determine at least one of current consumption, energy consumption and power consumption in dependence on current measurement by at least one of the first and second measurement devices, the ground fault detection and the determination in dependence on current measurement by at least one of the first and second measurement devices being substantially simultaneous.

9. Current measurement apparatus according to claim 1 operative to make at least one determination based on a difference between the current measurements and at least one of the current measurements, whereby the current measurement apparatus is operative to determine plural fault conditions on the basis of the current measurements.

10. Current measurement apparatus according to claim 9 configured to process the current difference by making a decision based on comparison with a changeable threshold value, the threshold value being changed in dependence on a level of a current measurement.

11. Current measurement apparatus according to claim 1 operative to change its configuration in dependence on a self-learning process in which a comparative value and a method of making a determination is changed in dependence on at least one factor comprising:

another measurement;

an analysis of at least one measurement;

a change in load conditions;

a determination; and

at least one past measurement.

12. Current measurement apparatus according to claim 1 configured to make plural different fault decisions, the current measurement apparatus being further configured to respond conditionally in dependence on detection of plural different faults at the same time.

13. Current measurement apparatus according to claim 1 configured to determine a frequency characteristic of at least one measurement, the current measurement apparatus being operative to respond in dependence on a determined frequency characteristic.

14. Current measurement apparatus according to claim 1 in which the plural different determinations comprise at least two of:

series arc fault detection;

parallel arc fault detection;

ground fault detection;

current measurement; and

over-current detection.

15. Current measurement apparatus according to claim 1 in which at least one of the first and second measurement devices comprises one of:

an electrical component in series with a load which is electrically connected to the conductor; and

an electrical circuit disposed in relation to the conductor, the electrical circuit being configured such that a current signal in the conductor induces an electrical signal in the electrical circuit.

16. Current measurement apparatus according to claim 1 further comprising voltage measurement apparatus which is configured to measure a voltage between the live and neutral conductors, the current measurement apparatus being operative to determine power consumption in dependence on current measurement and voltage measurement.

17. Current measurement apparatus according to claim 1 further comprising voltage measurement apparatus which is configured to measure a voltage between the live and neutral conductors and in which the current measurement apparatus is operative to respond conditionally in dependence in part on a voltage measurement.

18. Current measurement apparatus according to claim 1 configured to apply a calibration signal to the first and second measurement devices and in which the first and second measurement devices are operative to measure the applied calibration signal and the current measurement apparatus is operative to calibrate the first and second measurement devices in dependence on measurement of the applied calibration signal.

19. Current measurement apparatus according to claim 18 further configured such that first current measurements are made with a measurement device in each of the live and neutral conductors, the first current measurements comprising the applied calibration signal and second current measurements are made with a measurement device in each of the live and neutral conductors, the second current measurements lacking the applied calibration signal, the current measurement apparatus being operative to determine a signal common to the calibration signal and the live and neutral conductors in dependence on differences between the first and second current measurements.

20. Current measurement apparatus according to claim 19 configured such that the first and second measurements on each of the live and neutral conductors are made with the first and second measurement devices, the current measurement apparatus being configured such that the first measurements are made during an interval when the calibration signal is applied and the second measurements are made during an interval when no calibration signal is applied.

21. Current measurement apparatus according to claim 19 further comprising a third measurement device in the live conductor and a fourth measurement device in the neutral conductor, the current measurement apparatus being configured such that the calibration signal is applied to the first and second measurement devices but not the third and fourth measurement devices at a particular time and the first current measurements are made with the first and second measurement devices and the second current measurements are made with the third and fourth measurement devices.

22. Current measurement apparatus according to claim 1 configured:

to operate the first and second measurement devices to measure current in the live and neutral conductors;

to store the measured currents; and

to adjust subsequent current measurements in dependence on the stored measured currents to thereby provide for calibration of the measurement devices.

23. Current measurement apparatus according to claim 1 further comprising at least one acquisition circuit, the at least one acquisition circuit being configured:

to have at least one of plural different dynamic ranges and plural different frequency characteristics; and

to be operative to acquire a signal from a measurement device within each of the at least one plural different dynamic ranges and plural different frequency characteristics.

24. Current measurement apparatus according to claim 1 further comprising a differential measurement device which is configured to measure of itself a sum of current in the live and neutral conductors

25. A current measurement arrangement comprising plural current measurement apparatus according to claim 1, each of the plural current measurement apparatus being configured to measure current in a different one of plural live conductors and a neutral conductor.

26. Electrical apparatus comprising current measurement apparatus according to claim 1, the electrical apparatus being configured such that the current measurement apparatus measures current passing through a part of the electrical apparatus.

27. Current measurement apparatus comprising first and second measurement devices, each of the first and second measurement devices being operative to measure current in a respective one of a live conductor and a neutral conductor, the current measurement apparatus being operative to determine a difference between the measured currents and to make a determination in dependence on the current difference.

28. Current measurement apparatus according to claim 27 operative to make solely one fault determination in dependence on the current difference, the fault determination being a ground fault determination.

29. A current measurement method comprising:

operating first and second measurement devices to measure current in a respective one of a live conductor and a neutral conductor substantially simultaneously; and

operating current measurement apparatus to make plural different determinations in dependence on the substantially simultaneous current measurements.