Methods and systems for identifying a malfunctioning current sensor

1. A method for identifying a malfunctioning current sensor in an electrical apparatus, in which an electrical power supply of the electrical apparatus is at least partly supplied by a switch-mode electrical power supply circuit connected to at least one current sensor which samples an electrical current in a phase conductor of an electrical installation, the power supply circuit delivering a regulated electrical voltage, the method comprising:

determining a switching duty cycle of a power switch of the switch-mode electrical power supply;

analysing the switching duty cycle determined; and

identifying a failure condition if the behaviour of the switching duty cycle is representative of a failure of at least one of the current sensors.

2. The method according to claim 1 , wherein analysing the switching duty cycle comprises comparing the switching duty cycle determined with a predetermined reference value.

3. The method according to claim 2 , wherein the predetermined reference value is chosen as a function of an amplitude of current flowing in the phase conductors.

4. The method according to claim 1 , wherein analysing the switching duty cycle comprises analysing a variation of the duty cycle over time with respect to a history of past values.

5. The method according to claim 4 , wherein analysing the variation over time is carried out by an infinite pulse response filter.

6. The method according to claim 1 , wherein analysing the switching duty cycle comprises comparing the switching duty cycle determined with a theoretical value of the comparison duty cycle calculated based on values of current measured by one or more additional current sensors.

7. The method according to claim 1 , wherein the duty cycle determined is an average value of the switching duty cycle averaged over a predefined period of time.

8. The method according to claim 1 , wherein an alarm is automatically raised if a failure condition is identified.

9. The method according to claim 1 , wherein the electrical apparatus is an electrical protection apparatus, and wherein the apparatus is automatically triggered if a failure condition is identified.

10. The method according to claim 1 , wherein the method for identifying a malfunctioning current sensor further comprises:

measuring a value of a total current flowing in the phase conductor or conductors of the electrical installation, by one or more additional current sensors;

measuring a total current coming from said at least one current sensor, then comparing values of the total current measured with the values of current measured by the additional sensor or sensors; and

identifying a failure condition if a difference between the values of total current coming from said at least one current sensor and the values of current measured by the additional sensor or sensors is greater than a predefined threshold.

11. The method according to claim 7 , wherein the predefined period of time is a period of time corresponding to several periods of current flowing in the phase conductors.

12. The method claim 9 , wherein the electrical protection apparatus is a circuit breaker.

13. An electrical apparatus, comprising:

at least one current sensor configured to sample an electrical current in a phase conductor of an electrical installation, and

a switch-mode electrical power supply circuit connected to said at least one current sensor and configured for delivering a regulated electrical voltage for powering the electrical apparatus,

wherein the electrical apparatus comprises a diagnostic device configured to implement:

determining a switching duty cycle of a power switch of the switch-mode electrical power supply;

analysing the switching duty cycle determined; and

identifying a failure condition if the behaviour of the switching duty cycle is representative of a failure of at least one of the current sensors.