METHOD AND APPARATUS FOR TESTING THE OPERATING CONDITIONS OF AN ELECTRIC NETWORK

US 20090222227A1
Filed: 02/19/2009
Published: 09/03/2009
Est. Priority Date: 02/21/2008
Status: Active Grant

First Claim

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

providing a voltage signal to said the load,measuring the instantaneous current signal circulating in the load,delaying the instantaneous current signal to generate an instantaneous current signal delayed by a predetermined amount of time, the predetermined amount of time being a function of the operating state of said load,calculating, within a predetermined measurement time, an admittance ratio between the mean of the product of the voltage signal and the delayed instantaneous current signal, and the mean of the square of said voltage signal,comparing the value of said admittance ratio with a range of predetermined values to determine the at least one operating state of the electric network.

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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.

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31 Claims

1. A method for testing the operating conditions of an electric network, conditions including at least one operating state, the electric network having at least one load, the method comprising the steps of:
- providing a voltage signal to said the load,measuring the instantaneous current signal circulating in the load,delaying the instantaneous current signal to generate an instantaneous current signal delayed by a predetermined amount of time, the predetermined amount of time being a function of the operating state of said load,calculating, within a predetermined measurement time, an admittance ratio between the mean of the product of the voltage signal and the delayed instantaneous current signal, and the mean of the square of said voltage signal,comparing the value of said admittance ratio with a range of predetermined values to determine the at least one operating state of the electric network.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 21)
- - 2. The method of claim 1, wherein if the operating condition is a short-circuit operating state, the method includes the steps of:
    - delaying the instantaneous current signal by a predetermined amount of time equal to a first time value to generate a first delayed instantaneous current signal (i(t+τ
      
      _sh)),calculating the admittance ratio (G_χ(τ
      
      )) based on the value of the first delayed instantaneous current value (i(t+τ
      
      _sh)) to generate a short-circuit admittance ratio (G_χ(τ
      
      _sh)),comparing the short-circuit admittance ratio (G_χ(τ
      
      _sh)) with the preset value (G_max).
  - 3. The method of claim 1, wherein if the operating condition is an open-circuit operating state (oc), the step of calculating the admittance ratio (G_χ
    - (τ
      
      )) includes the additional steps of;
      
      delaying the instantaneous current signal (i(t)) by a predetermined amount of time (τ
      
      ) equal to a second time value (τ
      
      _n) to generate a second delayed instantaneous current signal (i(t+τ
      
      _n)),calculating the admittance ratio (G_χ(τ
      
      )) based on the value of the second delayed instantaneous current value (i(t+τ
      
      _n)) to generate an open-circuit admittance ratio (G_χ(τ
      
      _n)),comparing the open-circuit admittance ratio (G_χ(τ
      
      _n)) with the preset value (G_min).
  - 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
      
      ), the short-circuit admittance ratio G_χ(τ
      
      _sh) and the open-circuit admittance ratio G_χ(τ
      
      _n) are determined using the following relations;
      
      $G χ (τ) = \frac{\int_{T m} v (t) \cdot i (t + τ) \partial t}{\int_{T m} {v (t)}^{2} \partial t}$ $G χ (τ_{sh}) = \frac{\int_{T m} v (t) \cdot i (t + τ_{sh}) \partial t}{\int_{T m} {v (t)}^{2} \partial t}$ $G χ (τ_{n}) = \frac{\int_{T m} v (t) \cdot i (t + τ_{n}) \partial t}{\int_{T m} {v (t)}^{2} \partial t}$ where (v(t)) is the voltage signal, (i(t+τ
      
      )) is the current signal delayed by the predetermined amount of time (τ
      
      ), (i(t+τ
      
      _sh)) is the first current signal delayed by the first predetermined amount of time (τ
      
      _sh), (i(t+τ
      
      _n)) is the second current signal delayed by the second predetermined amount of time (τ
      
      _n), and (Tm) is the preset measurement time.
  - 5. The method of claim 1, wherein, if the voltage signal (v(t)) and the instantaneous current signal (i(t)) are digital signals, then the admittance ratio G_χ
    - (τ
      
      ) comprises the calculation of 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;
      
      $G χ (k) = \frac{\sum_{m}^{N} v_{m} \cdot i_{m + k}}{\sum_{m}^{N} v_{m}^{2}}$ $G χ (k_{sh}) = \frac{\sum_{m}^{N} v_{m} \cdot i_{m + ksh}}{\sum_{m}^{N} v_{m}^{2}}$ $G χ (k_{n}) = \frac{\sum_{m}^{N} v_{m} \cdot i_{m + kn}}{\sum_{m}^{N} v_{m}^{2}}$ where (v_m) is the m^thsample of the digital voltage signal, (k, k_sh, k_n) are the numbers of samples whereby current signal (i_m) is to be delayed, (i_m+k) is the m^thsample of the digital instantaneous current signal delayed by the predetermined amount of sampling (k), (i_m+ksh) is the m^thsample of the digital instantaneous current signal delayed by the predetermined sampling amount (k_sh), and (N) are the values sampled within the preset measurement time (Tm).
  - 6. The method of claim 1, comprising the additional step of filtering said provided voltage signal (v(t),v_k) and said measured instantaneous voltage signal i(t).
  - 7. The method of claim 4, wherein the effect of a current noise signal in the electric network corresponds to the calculation of the admittance ratio (G_χ
    - (τ
      
      )) using the following relation;
      
      $G χ (τ) = \frac{\int_{T m} v (t) \cdot i_{real} (t + τ) \partial t}{\int_{T m} v^{2} (t) \partial t} + \frac{\int_{T m} v (t) \cdot i_{noise} (t + τ) \partial t}{\int_{T m} v^{2} (t) \partial t}$ where (v(t)) is the voltage signal, (i_real(t+τ
      
      )) is the current real signal value i(t) delayed by the predetermined time (τ
      
      ), (Tm) is the predetermined measurement time, and (i_noise(t+τ
      
      )) is a current noise signal within the electric network.
  - 8. The method of claim 5, wherein the effect of a current noise signal in the electric network corresponds to the calculation of the digital admittance ratio (G_χ
    - (k)) using the following relation;
      
      $G χ (k) = \frac{\sum_{m}^{N} v_{m} \cdot {i_{real}}_{m + k}}{\sum_{m}^{N} v_{m}^{2}} + \frac{\sum_{m}^{N} v_{m} \cdot {i_{noise}}_{m + k}}{\sum_{m}^{N} v_{m}^{2}}$ where (v_m) is the m^thsample of digital voltage signal, (i_real_—_m+k) is the m^thsample of digital current real signal (i_m+k) delayed by predetermined amount (k), (N) are the values sampled within the preset measurement time (Tm), (i_noise_—_m+k) is the m^thsample of digital current noise signal within the electric network.
  - 9. The method of claim 1, wherein voltage signal v(t) provided to the load is a sinusoidal signal.
  - 10. The method of claim 4, wherein the voltage signal (v(t),v_k) and the instantaneous current signal (i(t),i_k) are non sinusoidal signals, the method comprising the additional step of filtering the measured voltage signal (v(t),v_k) and delayed current signal (i(t+τ
    - ),i_m+k) using passband filter means.
  - 21. The method of claim 1, wherein the load is a passive load.

11. A method for testing the operating conditions of an electric network, the conditions comprising at least one operating state, the electric network comprising at least one load, the method comprising the steps of:
- providing an instantaneous current signal (i(t)) to the load,measuring a voltage signal (v(t)) to the ends of the load,said method being characterized in that it comprises the additional steps of;
  
  delaying the voltage signal (v(t)) by a predetermined amount of time (τ
  
  ) to generate a delayed voltage signal (v(t+τ
  
  )), the predetermined amount of time (τ
  
  ) being a function of the operating state of the load),calculating, within a predetermined measurement time (Tm), an impedance ratio (Z_χ(τ
  
  )) between the mean of the product of the delayed voltage signal (v(t+τ
  
  )) and the instantaneous current signal (i(t)), and the mean of the square of the instantaneous current signal (i(t)),comparing the value of the impedance ratio (Z_χ(τ
  
  )) with a range of predetermined values (Z_min,Z_max) to determine the at least one operating state of the electric network.
- View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
- - 12. The method of claim 11, wherein if the operating condition is a short-circuit operating state (sc), the method includes the steps of:
    - delaying the voltage signal (v(t)) by a predetermined amount of time (τ
      
      ) equal to a second time value (τ
      
      _n) to generate a first delayed voltage signal (v(t+τ
      
      _n)),calculating the impedance ratio (Z_χ(τ
      
      )) based on the value of the first delayed voltage signal (v(t+τ
      
      _n)) to generate a short-circuit impedance ratio (Z_χ(τ
      
      _n)),comparing the short-circuit impedance ratio (Z_χ(τ
      
      _n)) with the preset value (Z_min).
  - 13. The method of claim 11, wherein if the operating condition is an open-circuit operating state (oc), the step of calculating the impedance ratio (Z_χ
    - (τ
      
      )) includes the additional steps of;
      
      delaying the voltage signal (v(t)) by a predetermined amount of time (τ
      
      ) equal to a third time value (τ
      
      _op) to generate a second delayed voltage signal (v(t+τ
      
      _op)),calculating the impedance ratio (Z_χ(τ
      
      )) based on the value of the second delayed voltage signal (v(t+τ
      
      _op)) to generate an open-circuit impedance ratio (Z_χ(τ
      
      _op)),comparing the open-circuit impedance ratio (Z_χ(τ
      
      _op)) with the preset value (Z_max).
  - 14. The method of claim 11, wherein, if the current signal (i(t)) and the instantaneous voltage signal (v(t)) are analog signals, then the impedance ratio (Z_χ
    - (τ
      
      )), the short-circuit impedance ratio (Z_χ(τ
      
      _n)), the open-circuit impedance ratio (Z_χ(τ
      
      _op)) are determined using the following relations;
      
      $Z χ (τ) = \frac{\int_{T m} v (t + τ) \cdot i (t) \partial t}{\int_{T m} {i (t)}^{2} \partial t}$ $Z χ (τ_{n}) = \frac{\int_{T m} v (t + τ_{n}) \cdot i (t) \partial t}{\int_{T m} {i (t)}^{2} \partial t}$ $Z χ (τ_{op}) = \frac{\int_{T m} v (t + τ_{op}) \cdot i (t) \partial t}{\int_{T m} {i (t)}^{2} \partial t}$ where (v(t+τ
      
      )) is the voltage signal delayed by the predetermined amount of time (τ
      
      ), (v(t+τ
      
      _n)) is the first voltage signal delayed by the second predetermined amount of time (τ
      
      _n), (v(t+τ
      
      _op)) is the second voltage signal delayed by the third predetermined amount of time (τ
      
      _op), (i(t)) is the current signal, and (Tm) is the preset measurement time.
  - 15. The method of claim 11, wherein, if the current signal (i(t)) and the instantaneous 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)), a digital open-circuit impedance ratio (Z_χ(k_op)) are defined, which are determined using the following relations;
      
      $Z χ (k) = \frac{\sum_{m}^{N} v_{m + k} \cdot i_{m}}{\sum_{m}^{N} i_{m}^{2}}$ $Z χ (k_{n}) = \frac{\sum_{m}^{N} v_{m + kn} \cdot i_{m}}{\sum_{m}^{N} i_{m}^{2}}$ $Z χ (k_{op}) = \frac{\sum_{m}^{N} v_{m + kop} \cdot i_{m}}{\sum_{m}^{N} i_{m}^{2}}$ where (k, k_n, k_op) are the numbers of samples whereby the voltage signal (v_m) is to be delayed, (v_m+k) is the m^thsample of the digital voltage signal delayed by the predetermined amount of sampling (k), (v_m+kn) is the m^thsample of the first digital voltage signal delayed by the second predetermined sampling amount (k), (v_m+kop) is the m^thsample of the second digital voltage signal delayed by the third predetermined amount of sampling (k_op), (i_m) is the m^thsample of the digital instantaneous current signal, and (N) are the values sampled within the preset measurement time (Tm).
  - 16. The method of claim 11, the method comprising the additional step of filtering the provided current signal (i(t),i_k) and the measured voltage signal (i(t)).
  - 17. The method of claim 14, wherein the effect of a voltage noise signal in the electric network corresponds to the calculation of the impedance ratio (Z_χ
    - (τ
      
      )) using the following relation;
      
      $Z χ (τ) = \frac{\int_{T m} v_{real} (t + τ) \cdot i (t) \partial t}{\int_{T m} i^{2} (t) \partial t} + \frac{\int_{T m} v_{noise} (t + τ) \cdot i (t) \partial t}{\int_{T m} i^{2} (t) \partial t}$ where (v_real(t+τ
      
      )) is the voltage real signal delayed by the predetermined time (τ
      
      ), (i(t)) is the current signal i(t), (Tm) is the predetermined measurement time, and (v_noise(t+τ
      
      )) is a voltage noise signal within the electric network.
  - 18. The method of claim 15, wherein the effect of a voltage noise signal in the electric network corresponds to the calculation of the digital impedance ratio (Z_χ
    - (τ
      
      )) using the following relation;
      
      $Z χ (k) = \frac{\sum_{m}^{N} v_{{real}_{m + k}} \cdot i_{m}}{\sum_{m}^{N} i_{m}^{2}} + \frac{\sum_{m}^{N} v_{{noise}_{m + k}} \cdot i_{m}}{\sum_{m}^{N} i_{m}^{2}}$ where (v_actual_—_m+k) is the m^thsample of the digital current real signal (v_m+k) delayed by the predetermined amount (k), (i_m) is the m^thsample of the digital current signal, (N) are the values sampled within the preset measurement time (Tm), (v_noise_—_m+k) is the m^thsample of the digital voltage noise signal within the electric network.
  - 19. The method of claim 11, wherein the current signal (i(t)) provided to the load is a sinusoidal signal.
  - 20. The method of claim 14, wherein the instantaneous current signal (i(t),i_k) and the voltage signal (v(t),v_k) are non sinusoidal signals, the method comprising the additional step of filtering the measured voltage signal (i(t),i_k) and the delayed voltage signal (v(t+τ
    - ),v_m+k) using passband filter means.

22. A device (10A) for testing the operating conditions of an electric network, the conditions including at least one operating state, the electric network having at least one load, the device comprising:
- a circuit (11) for generating a voltage signal (v(t)) to be provided to the load, measuring the instantaneous current signal (i(t)) circulating in the load;
  
  a selector for selecting a predetermined amount of time (τ
  
  ) as a function of the operating state to be tested,a circuit for generating an instantaneous current signal delayed (i(t+τ
  
  )) by the predetermined amount of time (τ
  
  ) as a function of the selected operating state,a processor operating within a predetermined measurement time (Tm) and configured to process 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
  
  )), andthe mean of the square of the voltage signal (v(t)); and
  
  a comparator for comparing the value of the admittance ratio (G_χ(τ
  
  )) with a range of predetermined values (G_min,G_max) to determine the at least one operating state of said electric network.
- View Dependent Claims (23)
- - 23. The apparatus for testing the operating conditions of an electric network of claim 22, comprising a filter for filtering out signal noises in the electric network.

24. A device for testing the operating conditions of an electric network, including at least one operating state, the electric network having at least one load, the device comprising:
- a circuit for generating an instantaneous current signal (i(t)) to be provided to the load and measuring a voltage signal (v(t)) to the ends of the loada selector for selecting the at least one operating state of the load (L),a generator for generating a voltage signal delayed (v(t+τ
  
  )) by a predetermined amount of time (τ
  
  ) as a function of the selected operating state,a processor for calculating, within a predetermined measurement time (Tm), an impedance ratio (Z_χ(τ
  
  )) between the mean of the product of the delayed voltage signal (v(t+τ
  
  )) and the instantaneous current signal (i(t)), and the mean of the square of the instantaneous current signal (i(t)),a comparator for comparing the value of the impedance ratio (Z_χ(τ
  
  )) with a range of predetermined values (Z_min,Z_max) to determine the at least one operating state of the electric network.
- View Dependent Claims (25)
- - 25. The apparatus for testing the operating conditions of an electric network of claim 24, comprising a filter (16A) for filtering out signal noises in the electric network.

26. A method, comprising:
- providing a voltage signal to an electric network having at least one operating state, the electric network including at least one load;
  
  measuring the instantaneous current signal circulating in the load as a result of providing the voltage signal;
  
  generating a delayed instantaneous current signal that is delayed by a predetermined amount of time that is a function of an operating state of the load;
  
  calculating within a predetermined measurement time an impedance or admittance ratio; and
  
  comparing the value of the impedance or admittance ratio with a range of predetermined values to determine at least one operating state of the electric network.
- View Dependent Claims (27, 28)
- - 27. The method of claim 26, wherein calculating the impedance or admittance ratio comprises calculating the impedance or admittance ratio between the mean of a product of the voltage signal and the delayed instantaneous current signal, and the mean of the 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 the steps of delaying the instantaneous current signal by a predetermined amount of time equal to a first time value to generate a first delayed instantaneous current signal, calculating the impedance or admittance ratio based on the value of the first delayed instantaneous current value to generate a short-circuit impedance or admittance ratio, and comparing the short-circuit impedance or admittance ratio with a preset value;
    - andif the operating condition is an open-circuit operating state, the step of calculating the impedance or admittance ratio includes the additional steps of delaying the instantaneous current signal by a predetermined amount of time equal to a second time value to generate a second delayed instantaneous current signal, calculating the impedance or admittance ratio based on the value of the second delayed instantaneous current value to generate an open-circuit impedance or admittance ratio, and comparing the open-circuit impedance or admittance ratio with a preset value.

29. A circuit for testing operating conditions of an electric network having at least one operating state and coupled to at least one 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 a predetermined amount of time;
  
  a second circuit adapted to generate an instantaneous current signal that is delayed by the predetermined amount of time;
  
  a processor operating within a predetermined measurement time and adapted to process an impedance or admittance ratio; and
  
  a comparator adapted to compare the value of the impedance or admittance ratio with a range of predetermined values to determine the at least one operating state of the electric network.
- View Dependent Claims (30, 31)
- - 30. The circuit of claim 29, wherein the selector is adapted to select the predetermined amount of time as a function of the operating state to be tested of the electric network, and the second circuit is adapted to generate the instantaneous current signal by the predetermined amount of time as a function of the selected operating state by the selector.
  - 31. The circuit of claim 30, wherein the processor is configured to process the impedance or admittance ratio between the mean of the product of the voltage signal generated by the first circuit and the delayed instantaneous current signal generated by the second circuit and the mean of the square of the voltage signal generated by the first circuit.

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Current Assignee
STMicroelectronics SRL (STMicroelectronics NV)
Original Assignee
STMicroelectronics SRL (STMicroelectronics NV)
Inventors
Adduci, Pietro Mario, Gonano, Giovanni, Botti, Edoardo

Granted Patent

US 8,483,984 B2
Time in Patent Office

Days
Field of Search
US Class Current

702/66
CPC Class Codes

G01R 31/2825   in household appliances or ...

G01R 31/52   Testing for short-circuits,...

H04R 29/00   Monitoring arrangements; Te...

METHOD AND APPARATUS FOR TESTING THE OPERATING CONDITIONS OF AN ELECTRIC NETWORK

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METHOD AND APPARATUS FOR TESTING THE OPERATING CONDITIONS OF AN ELECTRIC NETWORK

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