DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to electric switching devices, and more particularly, to an arrangement for identifying state of contact and/or contact condition of the electric switching device.

BACKGROUND

[002] In power system protection, electric switching devices such as circuit breakers are used to detect and clear a fault in a monitored circuit according to a relay setting. The relay senses the fault in a circuit and gives command to circuit breaker so as to enable the breaker contacts to separate from each other in response to abnormal conditions or faults.

[003] During abnormal conditions or faults or ever during the switch-on and switch-off operations of the circuit breaker, heavy arc occur during the closing and opening of contacts. The occurrence of arc in circuit breakers causes damage to arcing contacts and also to main contacts over the course of time. The extent of damage depends upon severity of fault which increases based on repetition of fault that occurs for different damage conditions in the contact. An intensity of damage also increases on the basis of repetition of even small level of fault occurs for different damage condition of main contact.

[004] As the circuit breaker includes a spring loaded contacts, occurrence of arcing i.e., erosion of contact, changes compression of the spring and thereby reduces the contact pressure. The reduction in contact pressure further reduces current carrying capacity of the breaker and thereby it affects current carrying &breaking capacity of the product. Thus wanted and/or unwanted switching operation of breakers further increases the occurrence of arc which eventually erodes the contact. Depending upon the stress due to the current or voltage, the erosion of contacts ultimately leads to failure of the switching component. It is therefore important for the operational reliability of an electrics witching device, to identify the contact condition/life periodically and/or after several specified operation, in order to draw conclusions on residual life of the electric switching device.

[005] Several methods and devices for monitoring the erosion of contact using mechanical equipment or by assumed erosion based on electric operations completed by product for identifying the state of contacts are well known in the state of art.

[006] The prior art document US 20050224331 A1 discloses erosion indicator inside the breaker which has erosion display and erosion pointer. The display pointer follows the movement of the on removing contact and, on closing the contacts, and only extends over the display surface or display edge when the value for the erosion of the switch contacts is less than a given maximum value. In order to be able to shorten the display pointer in the unused condition without a special tool to give a separation from the display surface or display edge, the value of which corresponds to the value of the maximum permitted erosion of the switch contacts, at least one marking for the cutting of the display pointer is provided, whereby the marking is separated from the display surface or display edge by the maximum permitted erosion of the switch contacts.

[007] The drawback of the above erosion indicator includes the indication for different status of contact condition by checking the pointer position on erosion display which is very difficult to judge visually from outside the breaker. Also, the erosion display disclosed will no longer be effective due to ash deposition after clearing the fault. The pointer size has to be set by cutting it with proper length for proper indication. This pointer will indicate only erosion of single finger wherein the value of erosion may not be exact.

[008] The prior art document, US 6150625 A discloses an erosion gauge tool for measuring the erosion of a movable contact in a circuit breaker having a stationary contact and movable contact, both of which are sealed in a housing. The movable contact is coupled to a drive insulator. An erosion mark is etched on the housing adjacent to the drive insulator. The erosion gauge tool has a handle, a tab, and a pointer. The tab is adapted to rest on the drive insulator. The pointer is disposed adjacent to erosion mark when said tab is resting on said drive insulator. As the moveable contact erodes, the pointer moves closer to the erosion mark. The erosion gauge is sized to indicate when the moveable contact needs to be replaced, e.g., when the pointer is immediately adjacent to or above the erosion mark.

[009] A current erosion indicator, present in the prior-art, is illustrated in figure 2 wherein the current erosion indicator is positioned within the breaker. During ON operation of the breaker, moving contact travels towards the fixed contact and, the relative distance between the two contacts keeps on decreasing which leads to breakdown of dielectric strength of the medium when gap decreases to a certain minimum value leading to generation of arc. Similarly during OFF operation of the breaker, moving contact travels away from the fixed contact and thus the relative distance between the two contacts keeps on increasing. In this case, due to opening of the contacts arcing occurs and it gets extinguished with the increasing distance as dielectric strength is regained by the medium. The switching operations of the breaker in the abnormal condition like overload/short circuit generates very high temperature and arcing which results into more erosion of contact. In majority of electric switching device, the contact thickness is in the range of 4-5mm which results in minor displacements of spring loaded finger in case of a fault. The ineffective identification of such minor displacement fails to provide true indication of the state of contact. Also as the existing indicator assembly lies inside the breaker with reasonable depth, it is difficult for operator personnel to see indicator slots from outside the breaker and if in an event occurs wherein ash is deposited on the indicator due to arc, the indicator slots becomes completely invisible. This leads to increase possibility of wrong indication of the contacts.

[0010] Thus, in view of the drawback of existing contact erosion indicator arrangement, there exists a need to provide an improved arrangement for identifying the state of contact indication that is inexpensive and easy to use and thus provide a desired result when displacement of the contact is very small.

SUMMARY OF THE INVENTION

[0011] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0012] The main object of the present invention is to provide a switching contact erosion indication device/ apparatus for monitoring the contact condition so that lifetime of contact parts is predicted without interrupting the operation of the switch or having to open the switch housing.

[0013] Another object of the present invention is to provide a suitable mechanism that provides information regarding the state of contact by detecting moving contact surface position and comparing it with indicator slots by indicator part so as to decide in what range (GOOD/MEDIUM/BAD) the finger surface lies.

[0014] Yet another object of the present invention is to provide exact condition of contact providing a magnified output so that a minor displacement of contacts is also predicted.

[0015] Still another object of the invention is to provide a contact erosion indication arrangement that results in a magnified clear true indication of contact condition outside the breaker wherein the contact condition indication arrangement is used in multiple breakers having same window size.

[0016] Yet another object of the present invention is to provide a device arrangement for determining the condition of contacts wherein the device fixing arrangement is same as that of arc chute arrangement and thus no extra fixing arrangement is required.

[0017] Yet another object of the present invention is to provide an indication window for indicating the contact condition wherein the indication window is placed outside of the breaker and in front of the user.

[0018] Still another object of the present invention is to provide a device that indicates contact spring compression/contact pressure in addition to detection of contact erosion.

[0019] In one implementation, the present invention provides a switching contact condition indication apparatus mounted in at least one circuit breaker, to determine at least one main contact condition, said switching contact condition indication apparatus comprises at least one indicator section having a top portion/pointer operable coupled to at least one indicator window and a bottom portion moveably affixed to at least one moving contact surface, wherein said indicator section adapted to measure at least one relative distance of said moving contact surface with respect to a steady reference surface based on at least one displacement of at least one moving contact toward at least one fixed contact, wherein said relative distance changes with respect to at least one thickness of said main contact; and at least one holding section adapted to hold said indicator section by means of at least one hinge arrangement having a predefined hinge ratio corresponds to said thickness of said main contact; wherein, said top portion/pointer obtains, by means of said predefined hinge ratio and measured said relative distance, at least one magnified output corresponding to said main contact condition, and thereby said top portion/pointer activates said indicator window to display said magnified output indicating said main contact condition.

[0020] In one implementation, there is provide a method for measuring at least one main contact condition using a switching contact condition indication apparatus, wherein said method comprising:
· determining, by means at least one indicator section, at least one displacement of at least one moving contact towards at least one fixed contact;
· measuring, by means of bottom portion of said indicator section, at least one relative distance of said moving contact surface with respect to a steady reference surface based on said displacement of said moving contact towards said fixed contact;
· obtaining, by means of a measured relative distance and a predetermined hinge ratio, at least one magnified output corresponding to said main contact condition;
· displaying, by means of at least indicator window, said magnified output indicating said main contact good condition or medium condition or bad condition.

[0021] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0022] Figure 1 illustrates breaker window to which invented indicating device has to be fixed to identify contact erosion, in accordance with an embodiment of the present subject matter.

[0023] Figure 2 illustrates an existing method (prior-art) of deciding erosion of contact in the breaker using an indicator device, in accordance with an embodiment of the present subject matter.

[0024] Figure 3 illustrates a top view of breaker window when Contact Condition Indicator device assembled to measure contact erosion, in accordance with an embodiment of the present subject matter.

[0025] Figure 4 illustrates a side view of breaker assembled with contact condition indicator device, in accordance with an embodiment of the present subject matter.

[0026] Figure 5 illustrates a contact condition indicator device indicating GOOD indication in contact GOOD condition, in accordance with an embodiment of the present subject matter.

[0027] Figure 6 illustrates a contact erosion indicator device indicating MED indication in contact MEDIUM condition, in accordance with an embodiment of the present subject matter.

[0028] Figure 7 illustrates contact condition indicator device showing BAD indication in contact BAD condition, in accordance with an embodiment of the present subject matter.

[0029] Figure 8 illustrates a side view of contact condition indication device with predefined hinge ratio, in accordance with an embodiment of the present subject matter.

[0030] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0031] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0032] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0033] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0034] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0035] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0036] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0037] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0038] In one implementation, the present invention provides an independent device to give clear, magnified and true indication of contact condition. The independent device comprises an indicator part and a holding part arrangement, wherein the indicator part includes an indicator device, for measuring the displacement of contact in breaker, and an indication window, for displaying a contact condition. The indicator part is further hinged on the holding part arrangement so as to magnify an output. In one example the magnified output is equal to multiplication of hinge ratio and actual displacement.

[0039] In one implementation the indication window in the indicator part is provided but not limited to, outside the breaker so as to provide visual information of contact condition. As the display window for the independent device is located outside the breaker and in front of the user, it is easy to operate and interpret by operator personnel.

[0040] In one implementation, the present invention provides a switching contact condition indication device which indicates the state of contact condition in the breaker. In one example the switching contact indication device provides information regarding spring compression/contact pressure and erosion of contact.

[0041] In one implementation, the present invention provides switching contact condition indication device that provides exact contact erosion indication with magnified output so as to capture minor displacements of contacts. In one example minor displacement will result in times displacement of a pointer (in case of hinge ratio 4 indication is 4 times the actual displacement).

[0042] Referring now to figure 1,a breaker window (1) is illustrated wherein a switching contact condition indication device is fixed. In one implementation the switching contact condition indication device is used for multiple breakers having same window size.

[0043] Referring now to figure 2, a conventional method for indicating state of contact in the breaker is illustrated wherein a current erosion indicator (12) is positioned within the breaker. In ON condition of the breaker, moving contact surface (6) occupied position according to erosion of contact. The surface (6) has to match with indicator slots as shown in figure. The slots are difficult to see from outside of the breaker as indicator is inside the breaker with reasonable depth. Also 1-2 mm displacement is very difficult to judge from outside of the breaker in this method.

[0044] Referring now to figure 3, a top view of breaker window when contact condition indicator device assembled to measure contact erosion is illustrated. In one implementation, a switching contact condition indication device comprises an indicator part (10) and a holding part (9) arrangement, wherein the indicator part includes an indicator device/indicator window (11), for measuring the displacement of contact in breaker, and an indication window, for displaying a contact condition. The indicator part (10) is further hinged on the holding part (9) arrangement so as to magnify an output. The holding part (9) has guiding wings at bottom which guides the indicator part (10) while measuring the displacement of contact. In one example the magnified output is equal to multiplication of hinge ratio and actual displacement.

[0045] Referring now to figure 4, a side view of breaker assembled with a switching contact condition indication device is illustrated. In one implementation, the switching contact condition indication device is used in a disconnected position of breaker and in breaker ON condition. In ON condition of circuit breaker, the switching contact condition indication device is mounted in place of arc chute so that the indicator part (10)moves in a manner that a bottom end (7) of the indicator part rests on a finger surface (6). The switching contact condition indication device is measuring relative distance of the finger surface (6) from a steady reference surface (14) of breaker housing. The indicator part (10) is hinged (8) on the holding part (9) such that its bottom part (7) can easily move towards contact surface (6)as moving contact (5) moves towards fix contact (2) due to erosion. The indicator part (10) hinged on holding part (9) with predefined hinge ratio so as to give a magnified output equal to multiplication of hinge ratio and actual displacement.

[0046] In one implementation the main contact (3) has an optimum thickness to make and/or break the fault current as designed; such a contact condition is called a contact “GOOD” condition. In case the erosion of contact is such that the circuit breaker can carry the rated current in case of a fault and thus fails to break the current, the condition is called contact “MEDIUM” condition. This indicates maintenance of contact (3). Further in case the erosion of contact is very high such that the circuit breaker fails to carry even the rated current then the condition is called contact “BAD” condition. The contact (3) has to be replaced at this stage.

[0047] Referring now to figure 5,a contact erosion indicator device indicating GOOD indication in contact GOOD condition is illustrated.

[0048] Referring now to figure 6, a contact erosion indicator device indicating MED indication in contact MEDIUM condition is illustrated.

[0049] Referring now to figure 7, contact erosion indicator device showing BAD indication in contact BAD condition is illustrated.

[0050] In one implementation, as the main contact (3) erodes, moving contact surface (6) moves towards fixed contact (2) which means it also moves towards steady reference surface(1). So the distance between moving contact surface (6) and steady reference surface (1) reduces as the main contact (3) erodes. The indicator part bottom portion (7) will rest on moving contact surface (6) for measurement and so indicator part will measure relative distance with steady reference surface(1). Thus, the moving contact (5) may be displaced towards fix contact (2)because of erosion because of spring loading on it, and accordingly the moving contact (5) position changes compare to GOOD contact condition. The indicator bottom end (7) rests on the moving contact surface (6) and accordingly the bottom end (7) position also changes according to moving contact (5)compare to GOOD contact condition which reflect on the indication window (11).

[0051] In one implementation, in contact GOOD condition, the distance of finger surface (6) to steady reference surface (14) is maximum. As contact (3) erodes the distance reduces because of spring loaded contact (5) and according to it pointer (10) will move towards BAD from GOOD on indication window (11).

[0052] Referring now to figure 8, a side view of contact erosion indicator device with predefined hinge ratio is illustrated. In one implementation, as erosion takes place the contact (3) thickness reduces and so spring loaded finger (5) travels towards fix contact (2) compare to fresh (GOOD) contact. The indicator part (10) measures the displacement with respect to steady reference surface and magnifies it with the help of hinge arrangement. The magnified displacement is indicated clearly on the indication window (11).

[0053] In one implementation, due to hinge arrangement, small movement of indicator bottom end (7) results in large movement of pointer (10) and magnified output is displayed on the indication window (11). The indication window (11) is accessible from outside and so indication is very clear. The indication on window (11) is multiplication of hinge ratio and displacement that results in a magnified output.

[0054] In one implementation, device hinge ratio is 4, the contact (3) thickness reduced to 2 mm due to erosion; the switching contact condition indication device displays 8mm displacement on indication window (11). This gives a clear visibility as indication window (11) is outside and in front of user.

[0055] In one implementation, for 4mm contact thickness, 2 to 6 hinge-ratio range can be used for clear indication of the contact thickness on the indication window. The hinge ratio can be decided on application point of view and it may depend on main contact thickness also. The hinge ratio can be increased to achieve more magnified indication on the indication window. In one example, if manufacturer wants to give indication of 0.5mm contact erosion by 2mm pointer deflection on indication window; then hinge-ratio will be 4. If manufacturer use hinge-ratio equals to 6; then 0.5mm erosion will reflect as 3mm pointer deflection on indication window. This will give more magnified output. Therefore, higher the hinge-ratio, indication of the contact erosion will be more precise and even it can indicate small erosion that may be in the range 0.3-0.4mm.

[0056] In one implementation, indication can also be formed in terms of the percentage like (10%, 20%, of contact thickness). Any indication can be marked by paint or sticker on indication window (11).

[0057] In one implementation, as the switching contact condition indication device also indicates the contact spring compression of the breaker by same method because contact spring compression is inversely proportional to erosion of contact. If contact erodes by 2 mm then contact spring compression reduced by 2mm in breaker closed condition compare to GOOD contact condition. Inverse scale can calibrate on indication window (11). Contact pressure is proportional to contact spring compression. So the switching contact condition indication device can indicate contact pressure also and for that scale has to calibrate according to that.

[0058] In one implementation, as contact (3) erodes spring loaded moving contact (5) starts moving towards fix contact (2) and according to that the indicator part (10) showing higher percentage of erosion on indication window (11).Manufacturer may decide optimum contact (3) thickness for GOOD, MEDIUM and BAD condition based on breaker rating, breaker capacity of clearing the faults and contact (3) properties. And according to that calibration of indication window (11) is undertaken.

[0059] In one implementation, the main contact thickness in GOOD, MEDIUM and BAD condition may be decided based on the circuit breaker capacity. In case of a GOOD condition, the breaker can make and break fault current equal to short circuit capacity. In case of a MEDIUM condition, the breaker can carry rated current but may fail in breaking and make fault current. And in case of BAD condition of breaker, means breaker fails to carry even rated current.

[0060] In one example, the main contact (3) thickness 2.9 to 4mm can be considered as GOOD condition; contact thickness 1.5 to 2.9mm can be considered as MEDIUM condition and contact thickness less than 1.5 mm can be considered as contact in BAD condition. Total thickness of the main contact can be 4mm.

[0061] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. Clear, true and magnified indication on outside of breaker.
2. Indication is outside of the breaker and in front of user so easy to operate and easy in interpretation.
3. Multiple number of contact erosion indication is possible between GOOD to BAD i.e., 20% erosion, 40% erosion, etc.
4. Fixed and steady reference.
5. No specific material requirements; can be made by any material.
6. No electronic circuit require for indication.
7. Used existing fixing arrangement of arc chute hence indicator can be used in existing product range i.e. no retrofit issue. It is independent than breaker & so it can be used for currently installed breakers on site also.
8. Device can also be calibrated for indication of contact pressure and contact spring compression i.e., THREE-IN-ONE device.
,CLAIMS:1. A switching contact condition indication apparatus mounted in at least one circuit breaker, to determine at least one main contact (3) condition, said switching contact condition indication apparatus comprising:
at least one indicator section having a top portion/pointer (10) operable coupled to at least one indicator window (11) and a bottom portion (7) moveably affixed to at least one moving contact surface (6), wherein said indicator section adapted to measure at least one relative distance of said moving contact surface (6) with respect to a steady reference surface (14) based on at least one displacement of at least one moving contact (5) toward at least one fixed contact (2), wherein said relative distance changes with respect to at least one thickness of said main contact (3); and
at least one holding section (9) adapted to hold said indicator section by means of at least one hinge arrangement having a predefined hinge ratio (8), wherein said hinge ratio (8) corresponds to said thickness of said main contact (8);
wherein, said top portion/pointer (10) obtains, by means of said predefined hinge ratio and measured said relative distance, at least one magnified output corresponding to said main contact condition, and thereby said top portion/pointer (10) activates said indicator window (11) to display said magnified output indicating said main contact condition.

2. The switching contact condition indication apparatus as claimed in claim 1, wherein said holding section comprises at least one guiding wings to guide said bottom portion of said indicator section during displacement of said moving contact.

3. The switching contact condition indication apparatus as claimed in claim 2, wherein due to said displacement of said bottom portion, said top portion/pointer adapted to enable said indicator window to display said magnified output corresponding to said main contact condition.

4. The switching contact condition indication apparatus as claimed in claim 3, wherein said magnified output corresponds to multiplication of said hinge ratio and said relative distance.

5. The switching contact condition indication apparatus as claimed in claim 1, wherein during said main contact good condition, the said relative distance between said moving contact surface to steady reference surface is maximum.

6. The switching contact condition indication apparatus as claimed in claim 5, wherein as the said main contact condition erodes, the said relative distance reduces with respect to the reduction in thickness of said main contact.

7. The switching contact condition indication apparatus as claimed in claim 1, wherein said indicator window calibrated with at least one contact good condition or at least one medium condition or at least one bad condition with respect to predetermined said thickness of said main contact.

8. The switching contact condition indication apparatus as claimed in claim 7, wherein said indicator window is provided outside said circuit breaker for visible indication of said contact condition.

9. The switching contact condition indication apparatus as claimed in claim 1, measures spring compression/contact pressure of said main contact, wherein said spring compression inversely proportional to said thickness of said main contact.

10. A method for measuring at least one main contact condition using a switching contact condition indication apparatus as claimed in claim 1-9, wherein said method comprising:
determining, by means at least one indicator section, at least one displacement of at least one moving contact towards at least one fixed contact;
measuring, by means of bottom portion of said indicator section, at least one relative distance of said moving contact surface with respect to a steady reference surface based on said displacement of said moving contact towards said fixed contact;
obtaining, by means of a measured relative distance and a predetermined hinge ratio, at least one magnified output corresponding to said main contact condition;
displaying, by means of at least indicator window, said magnified output indicating said main contact good condition or medium condition or bad condition.