GB2265470A

GB2265470A - Thermographic monitoring

Info

Publication number: GB2265470A
Application number: GB9305691A
Authority: GB
Inventors: Gerard Roulot
Original assignee: GEC Alsthom Equipements Basse Tension SA
Current assignee: GEC Alsthom Equipements Basse Tension SA
Priority date: 1992-03-23
Filing date: 1993-03-19
Publication date: 1993-09-29
Anticipated expiration: 2013-03-19
Also published as: FR2688883A1; GB2265470B; GB9305691D0; FR2688883B1

Abstract

Electrical apparatus such as a low-tension circuit breaker which includes a box 4 and connector contacts 5 disposed inside a cabinet fitted with a door or front panel 3, said connector contacts being placed behind the box relative to said door or panel, also includes means such as the mirror 7 enabling an infrared camera 9 situated outside the cabinet to observe the connector contacts, possibly via a porthole 12 which may have a cover 11. <IMAGE>

Description

ELECTRICAL APPARATUS FITTED FOR THERMOGRAPHIC INSPECTION USING INFRARED RAYS The present invention relates to monitoring electrical apparatuses by infrared thermography, and in particular to monitoring low-tension and medium-tension interrupter apparatuses.

When applied to electrical equipment, infrared thermography is a technique of preventative and predictive maintenance. It serves to detect abnormal heating, or drift in heating. Its flexibility enables it to limit and organize periods during which service is interrupted, and to plan maintenance operations.

It is recalled that infrared thermography makes use of a camera that is sensitive to infrared radiation. The operator points the camera at a zone to be monitored, and the light intensity received by the camera provides a value for the temperature of the zone.

A practical difficulty lies in the need to aim at an object that is under tension and that is carrying working current, while nevertheless complying with safety instructiQns and devices. Since all points of electrical circuits cannot be observed simultaneously in a single view, it is of major importance to define strategic points that reveal the state of the circuit in the vicinity of said points.

The Applicant has observed that the semi-fixed resilient contacts, referred to as "connectors", providing a connection between an interrupter member and fixed elements, e.g. sets of bus bars, constitute some of such vital points.

At low tension, because of the high currents that pass through open-type circuit breakers, and because of the way they are often positioned at the head of a network, such circuit breakers constitute elements of primary importance for ensuring continuity of service.

In this type of apparatus, the connector contacts are masked from sight by the circuit breaker itself, and by a door or panel or shield which protects personnel by constituting an obstacle and which protects the equipment by acting as a sealing member.

An object of the present invention is to fit sets of apparatus with means enabling connector engagement to be observed.

Another object of the invention is to make observation possible while the apparatus is under tension and carrying a working current, without interrupting service and under better conditions of safety for personnel and without risk of damaging the equipment.

According to the invention, these objects are achieved by an electrical apparatus such as a low-tension circuit breaker comprising a box and connector contacts disposed in a cabinet provided with a door or a front panel or shield, said connector contacts being placed behind the box relative to said door or panel or shield, wherein the apparatus includes means enabling an infrared camera situated outside the cabinet to observe the connector contacts.

In a preferred embodiment, said means comprise a mirror suitable for reflecting infrared radiation and disposed inside the cabinet above the box and substantially vertically over the connector contacts, said mirror being at an angle close to 45" relative to a vertical plane.

In a variant, said means comprise a mirror suitable for reflecting infrared radiation and disposed on one of the sides of the box, level with the connector contacts and oriented at 45".

In a first embodiment, said mirror is permanently installed in the cabinet.

In a variant, said mirror is removably disposed inside the cabinet on a carriage that slides on horizontal slideways.

Advantageously, said slideways are telescopic.

When the cabinet is closed by a panel, the panel is provided with at least one porthole that is transparent to infrared radiation.

In a variant, the panel includes openings for observation, said openings being of small dimensions and being capable of being closed by shutters that can be moved from the outside.

The invention will be well understood in the light of the following description of an embodiment of the invention, given with reference to the accompanying drawing in which the sole figure is a fragmentary and diagrammatic side view, partially in section, of a cabinet containing a low-tension circuit breaker fitted with the means of the invention.

In the figure, reference 1 designates the front face of a cabinet having a rear face 2 and a front panel or shield 3. Inside the cabinet, there is a circuit breaker box 4 connected by its electrical connection contacts 5 to bus bars 6. In a variant, the panel is replaced by a door.

As can be seen in the figure, the connector contacts are disposed behind the circuit breaker box 4 relative to the panel 3, and therefore cannot be seen from the outside, even if the panel is removed or if the door is opened.

That is why, according to a feature of the invention, a mirror 7 is placed substantially in the vertical plane that contains the connector contacts, in that portion of the cabinet which lies above the circuit breaker. The mirror 7 may be made of any material having a low coefficient of absorption for infrared radiation, e.g. a stainless steel, or a metal mirror whose optical qualities are obtained by polishing or by an electrolytic coating. Tests have shown that certain insulating plastics such as melamines are quite suitable.

The mirror 7 which is capable of reflecting infrared radiation, slopes at substantially 45" relative to a vertical plane so as to reflect an image of the connector contacts 5 through an opening 8 formed in the panel 3.

The image is received by an infrared camera 9 placed outside the cabinet.

In a variant, the mirror may be disposed on one of the sides of the box, level with the connector contacts 5, and oriented at 45".

The mirror may be installed permanently inside the cabinet.

In a variant and as shown in the figure, the mirror is fixed on a carriage 7A that is movable on slideways 10, e.g. telescopic slideways. At the end of its stroke, appropriately directed grooves (not shown) enable the mirror to be positioned accurately. When using a removable mirror, it is possible to use either a metal mirror or a glass mirror having a reflecting surface on the front of the glass.

It is mentioned above that the panel 3 includes openings 8 for observation purposes. For reasons of safety, the openings are small in size; for example they may prevent insertion of a ball having a diameter equal to or greater than 50 mm; the opening can be closed by flaps 11 that can be maneuvered from outside the cabinet and that protect the equipment against foreign bodies being inserted, with the index of protection provided complying with the general index of protection for the front face of the cabinet.

A variant embodiment consists in providing the panel 3 with portholes of a material that is transparent to infrared radiation. One such porthole 12 is shown in the figure by means of dashed lines.

When the cabinet is closed by a door rather than by a panel or by a shield, then observation takes place via the mirror after the door has been opened by an appropriately qualified operator.

The invention is not limited to its application to low-tension circuit breakers which is given purely by way of example. The invention can be used in thermography in association with any electrical apparatus that includes sensitive zones or points that are not directly visible.

Claims

1/ Electrical apparatus such as a low-tension circuit breaker comprising a box and connector contacts disposed in a cabinet provided with a door or a front panel or shield, said connector contacts being placed behind the box relative to said door or panel or shield, wherein the apparatus includes means enabling an infrared camera situated outside the cabinet to observe the connector contacts.

2/ Electrical apparatus according to claim 1, wherein said means comprise a mirror suitable for reflecting infrared radiation and disposed inside the cabinet above the box and substantially vertically over the connector contacts, said mirror being at an angle close to 45" relative to a vertical plane.

3/ Electrical apparatus according to claim 1, wherein said means comprise a mirror suitable for reflecting infrared radiation and disposed on one of the sides of the box, level with the connector contacts and oriented at 45".

4/ Apparatus according to claim 2 or 3, wherein said mirror is permanently installed in the cabinet.

5/ Apparatus according to claim 2 or 3, wherein said mirror is removably disposed inside the cabinet on a carriage that slides on horizontal slideways.

6/ Apparatus according to claim 5, wherein the slideways are telescopic.

7/ Apparatus according to any one of claims 1 to 6, wherein when the cabinet is closed by a panel, the panel is provided with at least one porthole that is transparent to infrared radiation.

8/ Apparatus according to any one of claims 1 to 6, wherein when the cabinet is closed by a panel or shield the panel or shield includes openings for observation purposes, said openings being of small dimensions and being capable of being closed by flaps that can be maneuvered from outside the cabinet.

9/ Electrical apparatus including a cabinet, contacts inside the cabinet and means enabling an infred camera situated outside the cabinet to observe the contacts, the apparatus being substantially as herein described with reference to and as illustrated in the sole figure of the accompanying drawing.