Method and apparatus for testing the operating conditions of an electric network

• US 8,483,984 B2
• Filed: 02/19/2009
• Issued: 07/09/2013
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Gonano, Giovanni, Adduci, Pietro Mario, Botti, Edoardo
• Primary Examiner(s): Nghiem, Michael
• Assistant Examiner(s): Lee, Paul D
• Application Number:
  US12/389,173
• Publication Number:
  US 20090222227A1
• Time in Patent Office: 1,601 Days
• Field of Search: 702/57, 702/64, 702/65, 702/66, 702/69, 702/117, 702/118, 702/124, 702/189, 702/190, 702/191, 702/199
• US Class Current: 702/65
• CPC Class Codes: G01R 31/2825 in household appliances or professional audio/video equipment testing LAN's H04L43/50; testing TV systems H04N17/00; testing loudspeakers H04R29/00
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H04R 29/00 Monitoring arrangements; Testing arrangements for hearing aids H04R25/30; detection of loudspeaker connection H04R5/04; sound-field adaptation dependent on speaker detection H04S7/308

Abstract

A method for testing the operating conditions of an electric network, including at least one operating state, including the steps of providing a voltage signal (v(t)) to a network load and measuring the instantaneous current signal (i(t)) circulating in the load, delaying the instantaneous current signal (i(t)) to generate an instantaneous current signal delayed ((i(t+τ)) by a predetermined amount of time (τ), the predetermined amount of time (τ) being a function of the operating state of said load, the method including the steps of calculating, within a predetermined measurement time (Tm), an admittance ratio (G_χ(τ)) between the mean of the product of the voltage signal (v(t)) and the delayed instantaneous current signal (i(t+τ)), and the mean of the square of the voltage signal (v(t)), and to compare the value of the admittance ratio (G_χ(τ)) with a range of predetermined values (Gmin,Gmax) to determine the operating state of the electric network.

Claims

1. A method for testing operating conditions of an electric network, the operating conditions including an operating state, the electric network having a load, the method comprising:

providing a voltage signal to the load and measuring an instantaneous current signal circulating in the load,

generating a delayed instantaneous current signal delayed by an amount of time by delaying the instantaneous current signal with respect to the voltage signal by the amount of time, the amount of time selected as a function of the operating state of said load,

calculating, within a measurement time, an admittance ratio between a mean of a product of the voltage signal and the delayed instantaneous current signal, and a mean of the square of the voltage signal,

comparing a value of the admittance ratio with a range of admittance values and generating an output signal; and

detecting open-circuit and short-circuit operating states of the electric network based on the output signal.

2. The method of claim 1, wherein if the operating condition is a short-circuit operating state:

the generating the delayed instantaneous current signal comprises delaying the instantaneous current signal by an amount of time that is equal to a short-circuit time value,

the calculating includes calculating the admittance ratio as a short-circuit admittance ratio based on a value of the delayed instantaneous current value, and

the comparing includes comparing the short-circuit admittance ratio with a maximum admittance ratio.

3. The method of claim 1, wherein if the operating condition is an open-circuit operating state:

the generating the delayed instantaneous current signal comprises delaying the instantaneous current signal (i(t)) by an amount of time that is equal to an open-circuit time value,

the calculating includes calculating the admittance ratio as an open-circuit admittance ratio based on the value of the delayed instantaneous current value, and

the comparing includes comparing the open-circuit admittance ratio with a minimum admittance ratio.

4. The method of claim 1, wherein, if the voltage signal (v(t)) and the instantaneous current signal i(t) are analog signals, then the admittance ratio G_χ

(τ

), a short-circuit admittance ratio G_χ

(τ

_sh), and an open-circuit admittance ratio G_χ

(τ

_n) are determined using the following relations;

5. The method of claim 4, wherein the voltage signal (v(t)) and the instantaneous current signal (i(t)) are non-sinusoidal signals, the method comprising filtering the voltage signal (v(t)) and delayed current signal (i(t+τ

)) using at least one passband filter.

6. The method of claim 1, wherein, if the voltage signal (v(t)) and the instantaneous current signal (i(t)) are digital signals, then calculating the admittance ratio G_χ

(τ

) includes calculating a digital admittance ratio (G_χ

(k)), a short-circuit digital admittance ratio (G_χ

(k_sh)), and an open-circuit digital admittance ratio (G_χ

(k_n)) using the following relations;

7. The method of claim 1, comprising filtering said provided voltage signal and said measured instantaneous current signal.

8. The method of claim 1, wherein the calculating includes calculating the admittance ratio (G_χ

(τ

)) using the following relation;

9. The method of claim 1, wherein the calculating includes calculating the digital admittance ratio (G_χ

(k)) using the following relation;

10. The method of claim 1, wherein voltage signal provided to the load is a sinusoidal signal.

11. The method of claim 1, wherein the load is a passive load.

12. A method for testing operating conditions of an electric network, the operating conditions having an operating state, the electric network including a load, the method comprising:

providing an instantaneous current signal (i(t)) to the load and measuring a voltage signal of the load,

generating a delayed voltage that is delayed with respect to the instantaneous current signal by delaying the voltage signal by an amount of time, the amount of time selected as a function of the operating state of the load from one of a first time to detect a short circuit and a second time to detect an open circuit,

calculating, within a measurement time, an impedance ratio value between a mean of a product of the delayed voltage signal and the instantaneous current signal, and a mean of a square of the instantaneous current signal,

comparing the impedance ratio value with a range of impedance ratio values, and

detecting open-circuit and short-circuit operating states of the electric network using the comparison to.

13. The method of claim 12, wherein if the operating condition is a short-circuit operating state (sc):

the generating the delayed voltage signal includes delaying the voltage signal by an amount of time equal to a short-circuit time value to generate a delayed voltage signal,

the calculating includes calculating the impedance ratio value as a short-circuit impedance ratio value based on the value of the delayed voltage signal, and

the comparing includes comparing the short-circuit impedance ratio value with a minimum impedance value.

14. The method of claim 12, wherein if the operating condition is an open-circuit operating state:

the generating the delayed voltage signal comprises delaying the voltage signal by an amount of time equal to an open-circuit time value to generate the delayed voltage signal,

the calculating includes calculating the impedance ratio value as an open-circuit impedance ratio value based on the value of the delayed voltage signal, and

the comparing includes comparing the open-circuit impedance ratio value with a maximum impedance value.

15. The method of claim 12, wherein, if the instantaneous current signal (i(t)) and the voltage signal (v(t)) are analog signals, then the impedance ratio (Z_χ

(τ

)), a short-circuit impedance ratio (Z_χ

(τ

_n)), and an open-circuit impedance ratio (Z_χ

(τ

_op)) are determined using the following relations;

16. The method of claim 15, wherein the instantaneous current signal (i(t)) and the voltage signal (v(t)) are non-sinusoidal signals, the method including filtering the instantaneous current signal (i(t)) and the delayed voltage signal (v(t+τ

)) using at least one passband filter.

17. The method of claim 12, wherein, if the instantaneous current signal (i(t)) and the voltage signal (v(t)) are digital signals, then a digital impedance ratio (Z_χ

(k)), a digital short-circuit impedance ratio (Z_χ

(k_n)), and a digital open-circuit impedance ratio (Z_χ

(k_op)) are calculated using the following relations;

18. The method of claim 12, the method including filtering the provided instantaneous current signal and the measured voltage signal.

19. The method of claim 12, wherein the calculating includes calculating the impedance ratio (Z_χ

(τ

)) using the following relation;

20. The method of claim 12, wherein the calculating includes calculating the digital impedance ratio using the following relation:

21. The method of claim 12, wherein the instantaneous current signal provided to the load is a sinusoidal signal.

22. A device for testing operating conditions of an electric network having a load, the conditions including an operating state, the device comprising:

a circuit structured to generate a voltage signal to be provided to the load and to measure an instantaneous current signal circulating in the load;

a selector structured to select an amount of time as a function of the operating state to be tested in the load,

a circuit structured to generate a delayed instantaneous current signal delayed with respect to the voltage signal by the amount of time that is selected as a function of the operating state of the load;

a processor structured to operate within a measurement time and configured to calculate an admittance ratio between a mean of a product of the voltage signal and the delayed instantaneous current signal, and a mean of a square of the voltage signal; and

a comparator structured to compare a value of the admittance ratio with a range of admittance values and to generate an output signal to the processor that is structured to detect open-circuit and short-circuit operating states of the electric network.

23. The device for testing the operating conditions of the electric network of claim 22, comprising a filter structured to filter out signal noises in the electric network.

24. A device for testing operating conditions of an electric network, including an operating state, the electric network having a load, the device comprising:

a circuit structured to generate an instantaneous current signal to be provided to the load and measuring a voltage signal at the ends of the load;

a selector structured to select the operating state of the load;

a generator structured to generate a delayed voltage signal that is delayed with respect to the instantaneous current signal by an amount of time that is selected as a function of the operating state of the load;

a processor structured to calculate, within a measurement time, an impedance ratio between a mean of a product of the delayed voltage signal and the instantaneous current signal, and a mean of a square of the instantaneous current signal; and

a comparator structured to compare a value of the impedance ratio with a range of impedance values and to generate an output signal to the processor, the processor further structured to detect open-circuit and short-circuit operating states of the electric network.

25. The device for testing the operating conditions of an electric network of claim 24, comprising a filter structured to filter out signal noises in the electric network.

26. A method, comprising:

providing a voltage signal to an electric network having an operating state, the electric network including a load;

measuring a resulting instantaneous current signal circulating in the load;

generating a delayed instantaneous current signal that is delayed with respect to the voltage signal by an amount of time selected as a function of an operating state of the load;

calculating within a measurement time an admittance ratio; and

comparing a value of the admittance ratio with a range of admittance values to detect open-circuit and short-circuit operating states of the electric network.

27. The method of claim 26, wherein calculating the admittance ratio includes calculating the admittance ratio between a mean of a product of the voltage signal and the delayed instantaneous current signal, and a mean of a square of the voltage signal.

28. The method of claim 27, wherein if the operating condition of the electric network is a short-circuit operating state, the method includes delaying the instantaneous current signal by an amount of time equal to a short-circuit time value to generate a first delayed instantaneous current signal, calculating the admittance ratio based on a value of the delayed instantaneous current value to generate a short-circuit admittance ratio, and comparing the short-circuit admittance ratio with an admittance value;

and

if the operating condition is an open-circuit operating state, the method further includes calculating an impedance ratio by delaying the instantaneous current signal by an amount of time equal to an open-circuit time value to generate a second delayed instantaneous current signal, calculating the impedance ratio based on the value of the second delayed instantaneous current value to generate an open-circuit impedance ratio, and comparing the open-circuit impedance ratio with an impedance value.

29. A circuit for testing operating conditions of an electric network having an operating state and coupled to a load, the circuit comprising:

a first circuit adapted to generate a voltage signal to be provided to the load and to measure an instantaneous current signal circulating in the load as a result of the generating of the voltage signal;

a selector circuit adapted to select an amount of time;

a second circuit adapted to generate a delayed instantaneous current signal that is delayed with respect to the voltage signal by the amount of time selected by the selector;

a processor operating within a measurement time and adapted to process an admittance ratio within a measurement time; and

a comparator adapted to compare the value of the admittance ratio with a range of values and generating an output signal to the processor that is further structured to detect open-circuit and short-circuit operating states of the electric network.

30. The circuit of claim 29, wherein the selector is adapted to select the amount of time as a function of the at least one operating state to be tested of the electric network, and the second circuit is adapted to generate the instantaneous current signal by the amount of time as a function of the operating state selected by the selector.

31. The circuit of claim 30, wherein the processor is configured to process the admittance ratio between a mean of a product of the voltage signal generated by the first circuit and the delayed instantaneous current signal generated by the second circuit and a mean of a square of the voltage signal generated by the first circuit.