METHOD AND DEVICE FOR PROTECTION FROM INTERNAL ARCS IN AN ELECTRICAL DISTRIBUTION SYSTEM, AND ELECTRICAL CABINET INCLUDING SUCH A DEVICE

Abstract

A method includes detecting any light beam from 300 nm to 430 nm within the distribution system and, when this beam is detected, generating a signal indicating the presence of an internal arc inside the system; analyzing the characteristics of the light beam based on the signal and, if these characteristics meet required conditions for characterizing an internal arc fault, sending an internal arc fault signal, then; in the presence of an internal arc fault, attenuating its effects in the distribution system. Between the detecting and the analyzing, the visible and infrared portions of this beam are removed, these portions being likely to arise from ionized gases ejected by outlets of a low-voltage circuit breaker interrupting a short-circuit current. A protection device for carrying out this method includes a light detector associated with current-measuring sensors, and protection means including a main circuit breaker, a short-circuiter and a relay.

Claims

1. A method for protection from internal arc faults in an electrical distribution system, comprising: detecting any light beam comprised between 300 and 430 nm within the distribution system and, in the event of the presence of this beam, generating a signal indicating the presence of an internal arc inside the system; analysing the characteristics of said light beam on the basis of said signal and, if these characteristics meet the required conditions for characterizing an internal arc fault, sending an internal arc fault signal, then; in the presence of an internal arc fault, its effects in the distribution system are attenuated, wherein, between said detection step and said analysis step, the visible portion and the infrared portion of this beam are removed, these portions being likely to arise from ionized gases ejected by the outlets of a low-voltage circuit breaker interrupting a short-circuit current.

2. The protection method according to claim 1, wherein, between said detection step and said analysis step, all light waves of the beam having a frequency that is strictly higher than 430 nm are blocked.

3. The protection method according to claim 1, wherein said analysis step comprises a step of measuring the intensity of the light beam.

4. A device for protection from internal arc faults in an electrical distribution system, comprising: a light detector placed inside said distribution system and capable of detecting a light beam comprised between 300 and 430 nm within this system, and of generating a signal indicative of an internal arc inside the system; processing means coupled to said detector and configured to analyse this light beam on the basis of said signal, and to generate a signal indicative of an internal arc fault if the conditions of the internal arc fault are met; and electrical protection means configured to receive the arc fault signal and to attenuate the arc in the distribution system, wherein the detector is capable of removing the visible portion and the infrared portion of this light beam, and of generating a signal indicative of the presence of an internal arc propagating through the system in the presence of a portion of the light beam other than the visible or IR portion, referred to as the remaining portion of the beam, and wherein said processing means are configured to analyse this portion of the beam other than the visible or IR portion, on the basis of said signal, and to generate a signal indicative of an internal arc fault if the conditions of the internal arc fault are met.

5. The protection device according to claim 4, wherein said processing means comprise a means for measuring the intensity of this remaining portion of the light beam.

6. The protection device according to claim 4, wherein this light detector comprises at least one optical sensor or else at least one optical fibre.

7. The protection device according to claim 6, wherein each optical sensor comprises at least one photodiode and/or at least one phototransistor, the or each photodiode or phototransistor being provided with a low-pass filter blocking those beams having a wavelength that is higher than 450 nm (+/20 nm).

8. The protection device according to claim 6, wherein each optical sensor comprises at least one photodiode and/or at least one phototransistor, each photodiode or phototransistor being provided with a 400 nm (+/20 nm) bandpass filter.

9. The protection device according to claim 6, wherein each optical fibre is a UV-transmitting optical fibre, and is associated with a 400 nm (+/20 nm) bandpass filter or with a low-pass optical filter blocking wavelengths that are higher than 450 nm (+/20 nm).

10. An electrical distribution system, comprising: the protection device according to claim 4.

11. An electrical distribution system comprising: a set of busbars J, the protection device according to claim 4, and electrical protection means that are intended to attenuate the effects of a potential internal arc fault inside the system.

12. The electrical distribution system according to claim 11, wherein said protection means comprise a circuit breaker, referred to as the main circuit breaker, supplied with power via said set of busbars J, a relay capable of receiving measurement information relating both to the light inside the system and to the current flowing through the set of busbars J, and a short-circuiter that is electrically linked both to the main circuit breaker and to the relay, said relay being capable of sending, when the threshold value is reached for the two said measurements, two orders in parallel: an order to activate the short-circuiter, and an order to activate the opening of the main circuit breaker, respectively.

13. The electrical distribution system according to claim 10, further comprising at least one low-voltage air circuit breaker located downstream of the light detection device.

14. The electrical distribution system according to claim 13, wherein it is a low voltage electrical cabinet.

Description

[0030] However, other advantages and features of the invention will become more clearly apparent in the detailed description that follows with reference to the appended drawings, which are given solely by way of example and in which:

[0031] FIG. 1 is a partial view illustrating a device for protection from electric arcs according to the invention, shown in an electrical cabinet;

[0032] FIG. 2 is a graphical representation illustrating the intensity of a light beam as a function of its wavelength, this light beam being generated in the electrical cabinet during the simultaneous presence of an internal arc fault and of a short-circuit interrupted by a low-voltage circuit breaker; and

[0033] FIG. 3 is the same graphical representation, illustrating the light beam portion detected by the light detector according to the invention.

[0034] FIG. 1 shows a device P for electrical protection from internal arc faults, intended to be installed within an electrical distribution system, here an electrical cabinet, housing a set of busbars J, said set of busbars being intended to supply power to or else to electrically link control and/or protection members such as circuit breakers or low-voltage contactors.

[0035] This electrical protection device P includes, in a manner known per se, an arc detector including both a light-detecting sensor 1 associated with a current-measuring sensor 6 and electrical protection means 3 that are intended to attenuate the effects of a potential arc fault.

[0036] These electrical protection means 3 include a circuit breaker, referred to as the main circuit breaker 4, supplied with power by the aforementioned set of busbars J, a relay 5 capable of receiving information relating both to the light emitted within the distribution system by means of the light detector 1 and to the current flowing through the set of busbars J by means of current sensors 6 placed on the various busbars, along with a short-circuiter 7. This short-circuiter 7 is electrically linked both to the set of busbars J and to the relay 5. The relay is capable of sending, when the threshold value is reached for the two aforementioned measurements relating to light and current, two orders in parallel, one order to activate the short-circuiter 7, and one order to activate the opening of the main circuit breaker 4, respectively.

[0037] According to the invention, this light detector 1 includes means for removing the visible portions and infrared portions of the emitted light beam. Advantageously, this light detector 1 includes means for blocking all light waves having a frequency that is strictly higher than 430 nm.

[0038] According to the embodiment illustrated in FIG. 1, this light detector 1 is an optical sensor consisting of a photodiode detecting UV, visible and IR light, this photodiode being provided with a filter blocking wavelengths higher than 450 nm (+/20 nm).

[0039] Other types of sensors could be used, such as, for example, phototransistors provided with wavelength-blocking filters or else bandpass filters.

[0040] Thus, for the point sensors, it is possible to envisage providing low-cost standard photodiodes or phototransistors (detecting UV, visible and IR light) with a filter blocking wavelengths that are higher than 450 nm (+/20 nm) or else a 400 nm (+/20 nm) bandpass filter.

[0041] These optical sensors could also be produced using optical fibres. In this case, it is possible to select optical fibres transmitting UV without attenuation associated with 400 nm (+/20 nm) bandpass filters or else low-pass optical filters blocking wavelength that are higher than 450 nm (+/20 nm).

[0042] FIGS. 2 and 3 illustrate the spectrum of the light beam present within the distribution system in the presence of both an internal arc fault and a short-circuit fault, these two figures respectively showing the intensity I of the beam as a function of the wavelength I.

[0043] In FIGS. 2 and 3, the beam portions F correspond to a light beam generated by the emissions of a low-voltage circuit breaker located downstream of the light sensor and interrupting a short-circuit current, while the beam portions D correspond to the light beam generated by the presence of an internal arc fault within the distribution system.

[0044] FIG. 3 illustrates, by means of a box E, the selection made by the light sensor, which takes only those light waves having a wavelength lower than 450 nm into account.

[0045] Thus, the method and the device for protection from internal arcs according to the invention make it possible to detect the light generated by an accidental internal arc arising between two live parts of a (two-phase) electrical installation (or an electrical installation having one phase and the neutral) while remaining inactive when the light is generated by the outlet gases of a low-voltage circuit breaker interrupting an electrical fault outside the cabinet.

[0046] This is made possible by virtue of a device including for example a sensor or optical fibre configured to remove the visible and IR light and to generate a signal indicative of an arc event propagating inside the cabinet, processing means that are coupled to the sensor and configured to analyse a light property on the basis of the signal sent by the sensor and to generate a signal indicative of an internal arc fault. For example, this light property may be the intensity of the light, which, when it is higher than 8000 lux, would result in a change of state of the relay in order to indicate an internal arc fault.

[0047] Lastly, the protection device according to the invention also includes protection means that are configured to receive the internal arc fault signal and to attenuate the effect of the arc in the distribution cabinet.

[0048] In operation, the relay receives two items of information; one relating to light, the other relating to current. However, at this stage, the possibility of light being emitted by a circuit breaker is eliminated. If the threshold value is reached for the two measurements relating to light and current, the relay sends two orders in parallel, one to activate the pyrotechnic short-circuiter, the other to activate the opening of the main circuit breaker. The activation of the short-circuiter and the opening of the circuit breaker take place only when there is an internal arc fault.

[0049] Thus, the invention allows selective tripping between internal arcs and those generated by low-voltage air circuit breakers.

[0050] This method makes it possible both to maintain selectivity of low-voltage protection devices and to protect personnel working in proximity to live conductors.

[0051] Specifically, either the device detects an internal arc fault and this fault is addressed by the disconnection made by the main circuit breaker and the short-circuiter, or the fault is a bolted short-circuit fault, which will not be detected by the internal arc detector, but will be addressed by the low-voltage circuit breaker located downstream of the internal arc detector.

[0052] Of course, the invention is not limited to the embodiments described and illustrated, which have been given only by way of example.

[0053] On the contrary, the invention comprises all technical equivalents of the means described and combinations thereof provided that these are implemented according to the spirit of the invention.