EP1271591B1 - Optical sensor for accidental arc - Google Patents

Abstract

The sensor has at least one light waveguide with multiple windings in the detection region. Stray light is coupled into the waveguide through the sleeving and passed to a sensor. The waveguide is held or fixed in a base body. At least one optical element (42',52) associated with the base body amplifies the stray light yield. The optical element is a transparent body (42') with fluorescence centers (52) for absorbable radiation.

Description

The invention relates to an optical arc fault sensor.

There are various arc fault sensors, especially for use in switchgear known. An example is in the CH 676 174 A5 shown. In the detection area, an optical waveguide is wound several times; the radiation coupling takes place radially through the sheathing of the optical waveguide. The optical fiber is held in a plastic arm. The arrangement can be covered with a transparent protective cover. This arc fault sensor has a substantially punctiform detection range.

Another example of such sensors is in DE-U-29 513 343 described.

Such sensors are preferably used in electrical switchgear, especially in low-voltage switchgear, but also in medium-voltage and high-voltage switchgear to deliver there as a sensor when an arc fault a shutdown signal.

It is an object of the invention to increase the sensitivity of the sensor with unchanged spatial detection range, without increasing the receiving surface or recording length of the optical waveguide.

The essence of the invention is that the base body is associated with an optical element. This increases the radiation yield or the sensitivity in a certain wavelength range. The optical element can have a ray-enhancing effect, it can be a ray reflector, a beam-bundling element (in the simplest case a lens, also a Fresnel lens) or a body in which fluorescence centers for absorbable radiation are introduced. These alternatives can also be combined as desired.

With a radiation-permeable preferably designed as a shell cover a large detection angle is made possible with simple installation, with proven optical fibers can be used. This allows a universal use of the Störlichtbogensensors. In the base body designed as a carrier element for the optical waveguide in different geometries, the optical waveguide has a defined installation position. One or more arc fault sensors may be located at a suitable point for detecting arcing faults in the substation.

In a first embodiment, the optical element is intended to be a transparent body in which radiation-absorbing, fluorescent dye molecules are present. Such materials have been on the market for some time. The one emitted by the fluorescence centers has a longer wavelength than the absorbed radiation. If the transparent body is chosen to be very thin (as a foil), the radiation remains 'trapped' by total reflection in the foil. At the edges - or on the surface introduced ruffles (scratches or engravings) the radiation emerges and is directed into the main body and into the optical waveguide.

The fluorescence wavelength range of the fluorescence centers is preferably matched to the sensitivity of the Störlichtauswerteschaltung (or the associated receiving diode). Such a range may be approximately between 400 and 600 nm. By tuning for a specific wavelength range light effects can be excluded, which otherwise also fall on the arc fault sensor. Such disturbing influences can come from industrial lighting or from nearby welding units.

An optical reflector used as an optical element (plane mirror, retroreflector, cat's eye) should preferably be arranged on the base body opposite the detection area. The surface of the arc fault sensor (or a transparent cover placed on it) should be within the detection range be provided with a reflection-reducing surface. For this purpose, conventional optical means in question; like lambda quarter anti-reflective coating or microstructured surface (moth or fly-eye structure).

The main body should have optically favorable geometry for optimal detection of an arc fault, which depends essentially on the arrangement, shape or size of the arcs critical contacts. Shown as embodiments are: ball, cylinder, or prism. The optical waveguide is in grooves on the surface of the body spiral or helical. The optical waveguide can also be embedded in the base body made of plastic. It may be provided that in a base body made of cast resin of the optical waveguide is firmly cast, where it hardens together with the plastic in the fabrication. The optical waveguide can be arranged spatially in one plane, or spatially in several planes as a spiral or meander.

The fault arc sensor may preferably have a detection range up to a solid angle of 180 degrees.

Reference to the drawing, are shown in the embodiments, the invention, refinements and improvements and other advantages will be described and explained in more detail.

• Fig. 1 eine erste Ausführungsform des Störlichtbogensensors,
• Fig. 2A, 2B, 2C drei Ansichten des Störlichtbogensensors aus Fig. 1,
• Fig. 3 eine zweite (prismatische) Ausführungsform,
• Fig. 4 eine Ausführungsform in Halbkugel-Form,
• Fig. 5 eine zylindrische Ausführungsform,
• Fig. 6 die Ausführungsform nach Fig. 5 mit Anti-Reflexbeschichtung und
• Fig. 7 eine perspektivische Darstellung nach Fig. 5.

Show it:

• Fig. 1 a first embodiment of the arc fault sensor,
• Fig. 2A, 2B, 2C three views of the arc fault sensor Fig. 1 .
• Fig. 3 a second (prismatic) embodiment,
• Fig. 4 an embodiment in hemisphere shape,
• Fig. 5 a cylindrical embodiment,
• Fig. 6 the embodiment according to Fig. 5 with anti-reflective coating and
• Fig. 7 a perspective view after Fig. 5 ,

An arc fault sensor with a cylindrical geometry (46) of the basic body 5 with a diameter of a few cm is shown in FIG Fig. 1 shown. An optical waveguide 2 is coiled in the interior of the main body 5. The optical waveguide 2 leads the light via fiber optic connector 3 to an interference light detection circuit, not shown. The main body is a transparent plastic in which fluorescent molecules 52 can be incorporated.

Upon irradiation of the body, the molecules absorb the radiation and emit radiation in a specific wavelength range, so that the embedded optical waveguide receives the radiation twice, once as direct radiation from the detection area, which may preferably be a top surface of the cylinder and the other by Radiation emitted by the molecules.

The coupled into the optical waveguide radiation enters a receiving diode and is evaluated in a Störlichterfassungsschaltung. The receiving diode is preferably designed for a narrow-band wavelength range. With a narrow-band receiving diode, it is possible to switch off stray light in other wavelength ranges and thus make the detection of an arc-fault safer. Fault arcs usually burn on copper contacts, so that in this case excited green spectral lines - ie in the range 400 to 600 nm - are particularly suitable for detecting an arc fault.

The three FIGS. 2A, 2B and 2C (Section AA off Fig. 2A ) indicate a possible position of the optical waveguide 2 in the main body. Thereafter, the optical waveguide is tightly wound in a spiral substantially in a plane E of the main body 5. Another embodiment with a meander arrangement of the optical waveguide also in a plane shows the Fig. 3 in a prismatic base body 42. Not shown are possible layers in the base body, in which the optical waveguide is arranged in more than one plane. It is essential that the optical waveguide in the base body occupies a good space filling. As the FIGS. 2B, 2C and 3 identify, are the entry routes 3 'of the optical waveguide coming from the fiber optic plugs 3 not in the previously mentioned main layer plane E of the optical waveguide 2. The entrance sections 3', however, can also lie in the same plane as one of the main layer levels E.

The Fig. 4 shows a base body 44, in which an optical waveguide 2 is inserted spirally in a groove-shaped groove 8. In the Figures 2 and 4 an optical waveguide 2 is shown, which is also wrapped around the main body in grooves 8 several times. As a result, the optical waveguide is accurately positioned. The radiation coupling takes place radially through the sheathing of the optical waveguide. The detection range of the optical waveguide is the upper surface of the main body. The detection area is relatively punctiform, as compared to rod or line-shaped sensors, which are arranged along busbar in a panel.

Opposite the detection area - ie below the body - a beam reflector (20) is arranged. The in Fig. 7 shown beam reflector 22 is one of a plurality of angular mirrors (cat's eye) formed reflector. In the FIGS. 5 and 7 is also drawn this type of beam reflector.

The arc fault sensor can be covered with a radiation-transmissive element (hood or shell) which rests on or abuts the base body 5. The covering element is not shown. The radiation of the arc fault, e.g. in the spectral range of the UV radiation, enters through the cover in the body.

For attachment to a cabinet wall or other attachment point, the cover may be provided with a radially outwardly directed mounting collar. The radiation-permeable cover member may be bolted to or otherwise secured to a cover member disposed on the bottom side. On the cover part mounting holes may be present in a mounting collar.

The main body 44 in Fig. 4 is hemispherical and the main body 46 in FIGS. 5, 6 and 7 is cylindrical designed as a disc.

The shape of the body is not limited to the geometries described above, but may have other shapes such as cones or domes.

Claims (11)

1. An optical accidental arc sensor for use in switchgears, which comprises at least one optical waveguide (2), the optical waveguide (2) being disposed in multiply wound arrangement in the sensing area and stray light being coupled in radially through the cladding of the optical waveguide and passed on to a sensor, the optical waveguide (2) being held or secured in a base member (5), characterised in that at least one optical element (20, 30, 52), with which the stray light efficiency is enhanced, is associated with the base member (5).
2. An optical accidental arc sensor according to claim 1, characterised in that the optical element (20, 30, 52) is a transparent body (42), in which centres of fluorescence (52) for absorbable radiation are present.
3. An optical accidental arc sensor according to claim 2, characterised in that the transparent body (42) is a sheet.
4. An optical accidental arc sensor according to one of claims 2 to 3, characterised in that the fluorescent wavelength range of the centres of fluorescence (52) is matched to the sensitivity of a stray light evaluation circuit.
5. An optical accidental arc sensor according to one of claims 2 to 4, characterised in that the transparent body (42) comprises surface roughening for radiation decoupling into the base member (46).
6. An optical accidental arc sensor according to claim 1, characterised in that the optical element (20) is a beam reflector (22).
7. An optical accidental arc sensor according to claim 6, characterised in that the beam reflector (20) is arranged on the base member (5) opposite the sensing area.
8. An optical accidental arc sensor according to claim 6 or claim 7, characterised in that the beam reflector (20) is a corner reflector (22) or a retroreflector.
9. An optical accidental arc sensor according to claim 1, characterised in that the optical element (20) takes the form of a radiation-concentrating means (30).
10. An optical accidental arc sensor according to any of the preceding claims, characterised in that the surface of the optical element is provided with a reflection-reducing surface.
11. An optical accidental arc sensor according to any of the preceding claims, characterised in that the base member (5) is of an optically favourable geometric shape and the optical waveguide (2) is arranged in spiral or helical manner in grooves (8) on the surface of the base member (5).

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