Claims:1. A device for indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member, comprising:
- a plurality of magnets installed on the low voltage end, such that the plurality of magnets are adapted to spread energy of an incident arc plasma from the flashover over the surface of the magnets during the flashover event; and
- a visual indicator attached to the plurality of magnets, the visual indicator is adapted to change color, when plasma from the flashover strikes the plurality of magnets.

2. The device according to claim 1, wherein the low voltage end is connected to a ground voltage potential.

3. The device according to claim 1, wherein the plurality of magnets are mounted at a junction of an insulating part, a conducting part and an air on the low voltage end of the electrical system, such that the plurality of magnets act as a first point of lower potential for occurrence of the flashover event.

4. The device according to claim 3, wherein the device is adapted to take shape corresponding to a shape of the low voltage end of the electrical system at the junction.

5. The device according to claim 3, wherein the conducting part is metallic.

6. The device according to claim 1, wherein the visual indicator is a layer.

7. The device according to claim 6, wherein the layer is at least one from a reflective signage tape, a fluorescent tape, a reflective cloth, a synthetic mastic, a dye, a pigment or a combination thereof.

8. The device according to claim 1, further including a housing to enclose the plurality of magnets and mounting the device on the low voltage end of the electrical system, such that the housing is made from a ferromagnetic and electrical conducting material.

9. The device according to claim 8, wherein the housing is made of mild steel.

10. The device according to claim 1, wherein each of the plurality of magnets are magnetically attached to each other in an end to end fashion to close the magnetic flux path.

11. The device according to claim 1, is used as a retrofit device to be installed on the electrical systems.

12. A method of indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member, comprising steps of:
- installing a plurality of magnets on the low voltage end, such that the plurality of magnets are adapted to spread energy of an incident arc plasma from the flashover over the surface of the magnets during the flashover event;
- attaching a visual indicator to the plurality of magnets, such that the visual indicator is adapted to change color, when arc plasma from the flashover strikes the magnets; and
- indicating the flashover event on observing color change in the visual indicator.

13. The method according to claim 12, wherein the low voltage end is connected to a ground voltage potential.

14. The method according to claim 12, wherein the plurality of magnets are mounted at a junction of an insulating part, a conducting part and an air on the low voltage end of the electrical system, such that the plurality of magnets act as a first point of lower potential for occurrence of the flashover event.

15. The method according to claim 12, wherein each of the plurality of magnets are magnetically attached to each other in an end to end fashion to close the magnetic flux path.

16. A method of indicating a flashover event in an insulator using the device according to claim 1.
, Description:
FIELD OF THE INVENTION

[001] The present invention relates to fault indicator in electrical systems and more particularly, to devices and methods for indicating a flashover event in electrical systems.

BACKGROUND OF THE INVENTION

[002] Flashover (also called arc flash) occurs during a low impedance fault between two conductors or one conductor and the ground. The high current causes to produce an arc flash which results in a high energy plasma. The flashover can expel large amounts of energy causing ionization of the air, and the arc temperatures can reach as high as 35,000 degrees Fahrenheit.

[003] The flashover can be initiated through accidental contact between two conductors, equipment which is underrated for the available short circuit current, contamination or tracking over insulated surfaces, deterioration or corrosion of equipment and, or parts, as well as other causes.

[004] In the case of the generators this energy flashes in the form of a large arc from the positive sets of brushes to the negative sets, or the earthed iron stricture of the machine, through the intervening air space. In insulators, the flashover is a breakdown and conduction of the air around or along the surface of the insulator, causing an arc along the outside of the insulator. Insulators are usually designed to withstand flashover damage. Flashover voltage is the voltage that causes a flash-over arc.

[005] Dirt, pollution, salt, and particularly water on the surface of a high voltage insulator can create a conductive path across it, causing leakage currents and flashovers. The flashover voltage can be reduced by more than 50% when the insulator is wet.

[006] There are multiple signatures associated with a flashover event like increase in the leakage current, partial discharge, rise in electrical conductivity of the surface, rise in surface temperature, flashover arc, conducting plasma etc. There are different devices and methods for measuring these parameters to detect a flashover event in electrical systems; however the leakage current, surface conductivity, surface temperature rise cannot be measured by simple cost-effective means. Further there are methods and sensors which continuously monitor one or more of the above parameter and send the value at a remote location for monitoring the performance and predicting life of the electrical systems. However the monitoring involves complex set of devices including sensors, communication devices, power supply etc.

[007] In view of the limitations inherent in the available devices and methods of detecting flashover event, there exists a need for a device and method for indicating a flashover event, which overcomes the disadvantages of the prior art and which can be used in a simple, cost effective, reliable, secure and environmental friendly manner.

[008] The present invention fulfils this need and provides further advantages as described in the following summary.

SUMMARY OF THE INVENTION

[009] In view of the foregoing disadvantages inherent in the prior arts, the general purpose of the present invention is to provide an improved combination of convenience and utility, to include the advantages of the prior art, and to overcome the drawbacks inherent therein.

[0010] A primary objective of the present invention is to provide a device and method for indicating a flashover event in an electrical system which is simple and cost effective.

[0011] In one aspect, the present invention provides a device for indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member, comprising a plurality of magnets installed on the low voltage end, such that the plurality of magnets are adapted to spread energy of an incident arc plasma from the flashover over the surface of the magnets during the flashover event and a visual indicator attached to the plurality of magnets, the visual indicator is adapted to change color, when plasma from the flashover strikes the plurality of magnets.

[0012] In another aspect of the present invention, the plurality of magnets are mounted at a junction of an insulating part, a conducting part and an air on the low voltage end of the electrical system, such that the plurality of magnets act as a first point of lower potential for occurrence of the flashover event.

[0013] In yet another aspect of the present invention, the device is adapted to take shape corresponding to a shape of the low voltage end of the electrical system at the junction.

[0014] In another aspect of the present invention, the visual indicator is a layer one from a reflective signage tape, a fluorescent tape, a reflective cloth, a synthetic mastic, a dye, a pigment or a combination thereof.

[0015] In a further aspect of the present invention, the device further includes a housing to enclose the plurality of magnets and mounting the device on the low voltage end of the electrical system, such that the housing is made from a ferromagnetic and electrical conducting material. In one preferred embodiment, the housing is made of mild steel.

[0016] In another aspect of the present invention, each of the plurality of magnets is magnetically attached to each other in an end to end fashion to close the magnetic flux path.

[0017] In yet another aspect, the present invention provides a method of indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member. The method comprises installing a plurality of magnets on the low voltage end, attaching a visual indicator to the plurality of magnets, such that the visual indicator is adapted to change color, when arc plasma from the flashover strikes the magnets and indicating the flashover event on observing color change in the visual indicator.

[0018] These together with other aspects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the description annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The advantages and features of the present invention will become better understood with reference to the following more detailed description taken in conjunction with the accompanying drawings in which:

[0020] FIG. 1 illustrates a schematic view of a device for indicating a flashover event, according to one embodiment of the present invention;

[0021] FIG. 2 illustrates a schematic view of the plurality of magnets installed on an insulator, according to one embodiment of the present invention;

[0022] FIG. 3 illustrates a schematic view of the visual indicator of the device installed on an insulator, according to one embodiment of the present invention;

[0023] FIG. 4 illustrates a schematic view of the change in color of the visual indicator after flashover event, according to one embodiment of the present invention;

[0024] FIG. 5 illustrates a schematic view of the device for indicating flashover event installed on a transformer bushing, according to one embodiment of the present invention; and

[0025] FIG. 6 illustrates a flowchart of a method for indicating a flashover event, according to one embodiment of the present invention.

[0026] Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

[0028] As used herein, the term ‘plurality’ refers to the presence of more than one of the referenced item and the terms ‘a’, ‘an’, and ‘at least’ do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0029] Reference herein to “one embodiment” or “another embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention.

[0030] Referring to FIG. 1, which illustrates a schematic view of the device 10 for indicating a flashover event, according to one embodiment of the present invention. The device 10 is for indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member. The device 10 comprises a plurality of magnets 12 installed on the low voltage end of the electrical system and a visual indicator 14 attached to the plurality of magnets 12 (shown separate in FIG. 1). Each of the plurality of magnets 12 is adapted to spread energy of incident arc plasma from the flashover over the surface of the magnets during the flashover event. The visual indicator 14 attached to the magnets is adapted to change color, when plasma from the flashover strikes the plurality of magnets.

[0031] When a flashover happens between a high voltage end and the low voltage end of an electric system, it’s assisted by high energy plasma arc striking the low voltage end. The strike of the plasma energy on the low voltage end happens on the lowest potential point of the low voltage end. Normally the strike of plasma arc is also limited to a small point on the low voltage end connection. The magnets deflect the plasma and spread the point strike location to a significantly larger area on the magnet. Because of the magnetic field created by the magnets, the incident plasma arc strikes and transfers its high energy over a bigger area instead of a single point.

[0032] In one embodiment of the present invention, the low voltage end is connected to a ground voltage potential. In many electrical systems such as high power lines are insulated by ground or pole by an insulator, a transformer stud and its enclosure surface etc there is one high voltage end and one ground end. The flashover arc, which is of high energy starts from the high voltage end and terminates on the grounded end of the electrical system.

[0033] Referring to FIG. 2, which illustrates a schematic view of the plurality of magnets 12 installed on an insulator 16, according to one embodiment of the present invention. The FIG. 2 shows one application of the device 10 of the present invention to detect flashover event in insulator 16. The insulator 16 is an electric system with a consists of a FRP rod 18, a polymeric shed 20 and a pair of end fittings 22,24 which are used to connect the insulator electrically with other electrical systems. As seen in FIG.2 the top end fitting 22 is connected to a high voltage end and the bottom end fitting 24 is connected to low voltage potential. The top end fitting 22 may be connected to a power line and the bottom end fitting 24 may be connected to ground.

[0034] The flashover will occur as an arc from the top end fitting 22 to the bottom end fitting 24. The device 10 of the present invention is installed to indicate a flashover event, by first mounting the plurality of magnets 12 at a junction of the insulating part 18, a conducting part 24 and air on the low voltage end of the electrical system, such that the plurality of magnets 12 act as a first point of lower potential for occurrence of the flashover event.

[0035] The magnets 12 are installed on the bottom end fitting 24 of the insulator on the junction where the shed on FRP rod 18, air and bottom end fitting 24 meets.

[0036] The junction is the lowest potential point in the insulator for the arc to strike first on the bottom end fitting 24. It is important to mount the device 10 in any electrical system on the point of lowest potential with minimum path for the arc between the high voltage end and the low voltage end of the system. In case of insulator 16, the possible path for arc to start is from the junction part of the top end fitting 22 and the junction part of the bottom end fitting 24 as shown.

[0037] In one embodiment of the present invention, each of the plurality of magnets 12 is magnetically attached to each other in an end to end fashion to close the magnetic flux path. The magnetic field created by the plurality of magnets is strong enough to deflect any incident arc plasma. The plasma arc energy which was striking only on a small point is spread by the plurality of magnets 12 as a whole thereby significantly increasing the striking area over the magnets. Instead of whole energy localized on a single point, the magnets 12 make it delocalized to spread over bigger surface. The magnets 12 used are provided with corrosion prevention coating to sustain external environment during life of its operation.

[0038] In one embodiment of the present invention, the device 10 is adapted to take shape corresponding to the shape of the low voltage end of the electrical system at the junction. The device 12 is analogous to a chain with each magnet acting as its link, providing the flexibility to take shape of the surface where it has to be mounted. As seen in FIGs 2-4 the plurality of magnets 12 mounted on the junction of bottom end fitting 24 forms a ring corresponding to the circular shape of the end fitting 24. If the end fitting(also referred as conducting part 24) is of square cross section then the magnets 12 mounted on the junction will form square ring corresponding to the conducting part shape at the junction.

[0039] In one embodiment of the present invention, the conducting part is metallic. The magnets 12 may be mounted on the conducting part by use of some adhesive. In another embodiment of the present invention, if the conducting part is ferromagnetic then the magnets 12 may be directly mounted on it by the magnetic force.

[0040] The energy of the arc plasma from the flashover is very high and when provided to a polymeric material, it can change its state to visibly change its appearance. Using this concept, in one embodiment of the present invention the visual indicator 14 is a layer. FIG. 3 shows the schematic view of the visual indicator 14 installed on the insulator 16, according to one embodiment of the present invention. The visual indicator 14 is wrapped over the plurality of magnets 12 behind it.

[0041] The layer 14 is located between the magnets and the incident arc plasma of the flashover, so the high energy incident on the magnets 12 also strikes the layer. On exposure to high energy of arc plasma, the layer gets decolorized at some portions, which serves as visual indication that a flashover event has occurred. In one embodiment of the present invention, the layer may be one of reflective signage tape, fluorescent tape, reflective cloth, synthetic mastic, a dye, a pigment or a combination of these. The reflective signage tape is preferred due to it’s very good weathering performance. The layer 14 in the form of tape as mentioned above may be attached to the magnets 12 by any adhesive known in the art. Preferably the tapes are provided with adhesive layer which allows them to be directly stuck on the magnets 12. In another embodiment of the present invention, the layer 14 may be in the form of a coating of dyes, pigment which is directly applied on the magnets 12.

[0042] Initially the layer is given a color such as fluorescent yellow, orange, green etc which is visible from a long distance and when the flashover event occurs it decolorizes some of its portion as seen in FIG. 4. The visual burn type portions indicate occurrence of flashover event.

[0043] In case of insulators which are installed on poles, the advantage is that the lineman can inspect the insulator by looking at it from the ground level. During inspection, if someone finds presence of different decolorized portions on the layer as seen in FIG.4, the inspector can conclude that the insulator has gone through at least one flashover event and can suggest replacing the insulator if needed.

[0044] In one embodiment of the present invention, the device further includes a housing (not shown) to enclose the plurality of magnets 12 and mounting the device 10 on the low voltage end of the electrical system. The housing encloses the magnets 12 preventing any disconnection or falling of any magnet 12. The magnets 12 are arranged in the housing and the visual indicator 14 in the form of a layer is installed on the outer surface of the housing, such that the magnets inside the housing spread the incident arc plasma and it strikes the housing surface. The housing has to be made from a ferromagnetic and electrical conducting material, so it does not shield the magnetic field created by the magnets and it also allows the electric current of flashover to reach the magnets enclosed within. The housing is coated with corrosion prevention coating to sustain external environment during life of the device.

[0045] The shape of the housing is adapted to enclose the corresponding shape of the magnets 12 and its size is as per the requirement of the number of magnets used and the shape of the junction of lower voltage end in the electrical system where the device 10 has to be installed. The shape and size of the housing should be such that it encloses all the magnets tightly within it, preventing any disconnection of magnets from each other and breaking the magnetic flux path. When the housing is used, the housing may be installed on the conducting part 24 by adhesive.

[0046] In one preferred embodiment of the present invention, the housing is made of mild steel. It may be noted that the housing may also be made from a non-metallic material with added material powder, which provides the ferromagnetic and electrically conducting properties.

[0047] In one embodiment of the present invention, the device 10 is used as a retrofit device to be installed on the electrical systems. The device may be provided as a strip which can be cut or connected with another strip to be mounted on the electrical system where flashover event has to be detected. As seen in FIGs. 2-4 the device 10 can be mounted on existing insulators.

[0048] Similarly the device may also be installed on the base of a transformer bushing as shown in FIG. 5 that shows a schematic view of the device 10 installed on a transformer bushing. The transformer stud is the part which is connected to high voltage and the enclosure of the transformer is connected to ground voltage. The stud is enclosed inside the bushing which is insulating part between the stud and the enclosure. The device 10 is installed on the base of the bushing and on the transformer enclosure wall as it is the junction between the insulating part (bushing), air and the conducting part (transformer enclosure wall). The flashover occurs between the stud and enclosure wall and the device 10 takes energy from incident arc plasma to decolorize its visual indicator 14 to show occurrence of flashover event in the transformer.

[0049] It is to be noted that the device 10 of the present invention is shown and described to be used in insulator and transformer for explanation purpose and is not limited to be used in these two applications only. The device 10 may be used in other electrical systems where there is chance of occurrence of a flashover event. The device may undergo engineering changes in terms of shape, size, design, installation method and location as per the needs of the electrical system where it has to be used.

[0050] Referring to FIG.6, which shows a flowchart of a method 100 of indicating a flashover event between a high voltage end and a low voltage end of an electrical system separated by an insulating member. The method 100 starts with step 110 of installing a plurality of magnets 12 on the low voltage end, such that the plurality of magnets are adapted to spread energy of an incident arc plasma from the flashover over the surface of the magnets during the flashover event.

[0051] In next step 120 the visual indicator 14 is attached to the plurality of magnets 12. The visual indicator 14 is adapted to change color, when arc plasma from the flashover strikes the magnets. Now when color change in the visual indicator is observed, the flashover event is indicated in step 130.

[0052] In one embodiment of the present invention, the low voltage end is connected to a ground voltage potential. The plurality of magnets are mounted at a junction of an insulating part, a conducting part and an air on the low voltage end of the electrical system, such that the plurality of magnets act as a first point of lower potential for occurrence of the flashover event. Each of the plurality of magnets are magnetically attached to each other in an end to end fashion to close the magnetic flux path.

[0053] The device 10 of the present invention is very much suited for manual inspection to detect any flashover event in the electrical systems, however the device 10 may be combined with sensors to detect the color change and convert it into a digital signal and transferred to a remote location via communication means to remotely inspect the electrical system for flashover event occurrence. The device 10 may also be supplemented with other sensors for measuring the leakage current, partial discharge, rise in electrical conductivity of the surface, rise in surface temperature etc to monitor the working and predicting life of the electrical system.

[0054] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized to those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement in the configurations of the parts, changes in steps and their sequences may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as may fall within the spirit and scope of the present invention.

[0055] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.

[0056] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.