Claims:1. A three position interlocking module (3) for circuit breaker comprising:
a three-position interlock knob (1) adapted to select any one of the three interlock positions;
a three-position interlock socket (2) adaptively coupled to the interlock knob (1) for driving the three-position interlock module (3);
an interlock knob shaft (11) operably coupled to the interlock knob (1) to actuate the three-position interlock socket (2);
wherein the interlock knob (1) can interlock at a first position or a second position or a third position;
wherein at first position, the interlock knob (1) is positioned horizontally such that a circuit breaker locking plate (4) locks an interlock shaft (5);
wherein at second position, the interlock knob (1) is at 60° angle from the horizontal axis; and
wherein at third position, the interlock knob (1) is at 120° angle from the horizontal axis.

2. The interlocking module (3) as claimed in claim 1, further comprising a Low Voltage (LV) plug assembly (6) operatively coupled to interact with the three-position interlock module (3) such that in the first position, the LV plug assembly (6) is not inserted thereby locking a LV socket interlock pin (9) to a LV interlock plate (10).

3. The interlocking module (3) as claimed in claim 2, wherein when the LV plug assembly (6) is inserted and locked into position, the LV plug interlock pin (7) pushes in the LV socket interlock pin (9) such that the LV interlock plate (10) is unlocked and can rotate on a guide slot on a LV plug interlock pin (7).

4. The interlocking module (3) as claimed in claim 2, wherein the LV socket interlock pin (9) is spring loaded.

5. The interlocking module (3) as claimed in claim 1, further comprising a door interlock link assembly (12) to allow or block the rotation of the interlock knob (1).

6. The interlocking module (3) as claimed in claim 1, further comprising an Earthing switch flap assembly (13) to cover an Earthing switch operating shaft.

7. The interlocking module (3) as claimed in claim 1, further comprising an interlock drum (14) and an interlock guide plate (15); wherein the interlock drum (14) is adapted to rotate in all three positions by the interlock knob (1); and wherein the interlock guide plate (15) is adapted to block or allow the movement of the interlock drum (14) based on the position of the circuit breaker.

8. The interlocking module (3) as claimed in claim 1, further comprising an Open/Close interlock flap (16) to cover the circuit breaker close button.

9. The interlocking module (3) as claimed in claim 1, further comprising a racking flap assembly (18) to cover the circuit breaker racking screw.

10. The interlocking module (3) as claimed in claim 1, wherein the first position is TEST, the second position is SEVICE and the third position is TRANSIT.
, Description:FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to circuit breakers and more particularly, pertains to a three position interlocking module for circuit breakers.

BACKGROUND OF INVENTION

[002] Switchgears are essential for the maintenance of social infrastructure, with an important role in delivering electric power directly to the end users. To meet the requirements of the rapidly increasing power demand & need to transmit the power over long distances, many of the new power stations and substations are being installed throughout the world.

[003] The demands on the switchgear for such power stations and substations are very critical. The requirements like reduced maintenance, long life, minimum space requirements, and immunity to weather conditions, occasionally higher altitudes, and sensitivity to seismic zones are the critical factors to be considered during switchgear design and throughout their life cycle.

[004] Significantly, the utmost requirement of any switchgear is its safe operation. Safe operation must be the foremost criteria of any design and it must be given the priority higher than the functional requirements for any design. Medium voltage switchgear being used in supply of enormous electrical energy thus it requires much higher level of safety and reliability in operation.

[005] The switchgear interlocks plays a major role in sustaining the aforesaid critical requirements for smooth and safe operation of the installation and operating personnel.

[006] For some prior art in this technology, reference is made to US Patent No. 2540814 pertains to a removable switchgear interlocking control, more particularly to an inter locking control for metal-enclosed removable self-disconnecting circuit breakers having position-changing mechanism for moving the circuit breaker between the connected and the disconnected positions provided with a removable operating member.

[007] Reference is also made to US Patent No: 3288956 where a draw-out switch gear apparatus is disclosed. Significantly, the apparatus includes an interlock arrangement adapted and disposed to prevent the disconnection of removably engaged main current carrying connectors unless the circuit has been interrupted through the actuation of appropriate switch means operatively engaged with the interlock means.

[008] The drawbacks associated with the existing interlock arrangements being that the prior art are focus mainly on the Test and Service position of the circuit breaker. They do not cover any interlocking with associated equipment’s in the system like low voltage (LV) plug, Earthing switch, panel door or switchgear access.

[009] Accordingly, there is a need to overcome the drawbacks associated with the existing interlock arrangements. In particular, to there is a need to eliminate any chance of malfunction with respect to the circuit breaker operation, i.e., Test, Service And Transit and its associated equipment’s in the system like LV plug, Earthing switch, panel door or switchgear access.

[0010] The above-described need for a three position interlocking module for circuit breaker is merely intended to provide an overview of some of the shortcomings of conventional systems / mechanism / techniques, and is not intended to be exhaustive. Other problems/ shortcomings with conventional systems/ mechanism /techniques and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.

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] An object of the present invention is to alleviate the drawbacks associated with the existing interlock arrangements of circuit breakers.

[0013] Another object of the present invention is to provide a three position (Test, Service & Transit) interlock module for a withdrawable circuit breaker.

[0014] Yet another object of the present invention is to provide an interlock module for a withdrawable circuit breaker with a reliable retrofit option.

[0015] According to a first aspect of the present invention, there is provided a three position interlocking module for circuit breaker. The interlocking module comprising a three-position interlock knob, a three-position interlock socket, an interlock shaft and an interlock knob shaft. The interlock knob is adapted to select any one of the three interlock positions. The interlock socket is adaptively coupled to the interlock knob for driving the three-position interlock module. The interlock knob shaft is operably coupled to the interlock knob to actuate the three-position interlock socket. The interlock knob can interlock at a first position or a second position or a third position. At first position, the interlock knob is positioned horizontally such that a circuit breaker locking plate locks an interlock shaft, at second position, the interlock knob is at 60° angle from the horizontal axis and at third position, the interlock knob is at 120° angle from the horizontal axis.

[0016] In one possible implementation of the interlocking module according to the first aspect, a Low Voltage (LV) plug assembly is operatively coupled to interact with the three-position interlock module such that in the first position, the LV plug assembly is not inserted thereby locking a LV socket interlock pin to a LV interlock plate.

[0017] In another possible implementation of the interlocking module according to the first aspect, when the LV plug assembly is inserted and locked into position, the LV plug interlock pin pushes in the LV socket interlock pin such that the LV interlock plate is unlocked and can rotate on a guide slot provided on a LV plug interlock pin.

[0018] In yet another possible implementation of the interlocking module according to the first aspect, the LV socket interlock pin is spring loaded.

[0019] In yet another possible implementation of the interlocking module according to the first aspect, a door interlock link assembly allows or blocks the rotation of the interlock knob.

[0020] In yet another possible implementation of the interlocking module according to the first aspect, an Earthing switch flap assembly covers an Earthing switch which operates the shaft.

[0021] In yet another possible implementation of the interlocking module according to the first aspect, an interlock drum is adapted to rotate in all three positions by the interlock knob and an interlock guide plate is adapted to block or allow the movement of the interlock drum based on the position of the circuit breaker.

[0022] In yet another possible implementation of the interlocking module according to the first aspect, an Open/Close interlock flap covers the circuit breaker close button.

[0023] In yet another possible implementation of the interlocking module according to the first aspect, a racking flap assembly covers the circuit breaker racking screw.

[0024] In yet another possible implementation of the interlocking module according to the first aspect, the first position is TEST, the second position is SEVICE and the third position is TRANSIT.

[0025] 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

[0026] 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:

[0027] Figure 1 illustrates the isometric view of Circuit breaker (CB) compartment door in closed condition and the 3-position interlock knob on door (CB in test position) in accordance with an aspect of the present invention.

[0028] Figure 2 illustrates the isometric view of door interlock link assembly with the CB compartment door in open condition and the 3-position interlock socket on CB racking assembly (CB in test position), in accordance with another aspect of the present invention.

[0029] Figure 3 illustrates the isometric view of CB locking plate and interlock shaft with 3-position interlock mechanism at position no.1 (CB in test position), in accordance with another aspect of the present invention.

[0030] Figure 4 illustrates the isometric view of door interlock link assembly with interacting parts of 3-position interlock mechanism (CB in test position), in accordance with another aspect of the present invention.

[0031] Figure 5 illustrates the isometric view of LV plug and socket assembly with interacting parts of 3-position interlock mechanism (CB in test position), in accordance with another aspect of the present invention.

[0032] Figure 6 illustrates the isometric view of Earthing switch flap assembly with interacting parts of 3-position interlock mechanism (CB in test position), in accordance with another aspect of the present invention.

[0033] Figure 7 illustrates the isometric view of CB open/close interlock flap assembly with interacting parts of 3-position interlock mechanism (CB in test position), in accordance with another aspect of the present invention.

[0034] Figure 8 illustrates the isometric view of Interlock drum, interlock guide plate and CB racking flap assembly (CB in transit position), in accordance with another aspect of the present invention.

[0035] Figure 9 illustrates the isometric view of CB open/close interlock flap assembly with interacting parts of 3-position interlock mechanism (CB in service position), in accordance with another aspect of the present invention.

[0036] 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

[0037] 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.

[0038] 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.

[0039] 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.

[0040] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0041] 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.

[0042] 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.

[0043] 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 component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0044] The present invention lies in providing a three position interlocking module for circuit breaker.

[0045] The existing interlock arrangements focus mainly on the Test and Service position of the circuit breaker. They do not cover any interlocking with associated equipment’s in the system like low voltage (LV) plug, Earthing switch, panel door or switchgear access. To overcome said shortcomings of the prior art, the present invention describes an interlock module for a withdrawable circuit breaker with a reliable retrofit option to eliminating any chance of malfunction with respect to the circuit breakers operation and its associated equipment’s in the system like low voltage plug, Earthing switch, panel door or switchgear access.

[0046] An exemplary embodiment of present invention to demonstrate the different states of the three position interlock mechanism along with its related parts is illustrated in Fig. 1. The manner of achieving the interlock conditions are discussed hereinbelow. In particular, the mandatory interlock conditions for a withdrawable circuit breaker are as follows:

Cond. No CB locked to panel CB Position CB Earthing switch LV plug CB Compartment door Operation / Interlock
1 No Test Open OFF Connected Closed CB cannot be racked in
2 Yes Test Open OFF Disconnected Closed CB cannot be racked in
3 Yes Test Open OFF Connected Open CB cannot be racked in
4 Yes Test Open ON Connected Closed CB cannot be racked in
5 Yes Test Closed OFF Connected Closed CB cannot be racked in
6 Yes Transit Open OFF Connected Closed CB cannot be closed
7 Yes Transit/ Service Open OFF Connected Closed CB compartment door cannot be opened
8 Yes Transit/ Service Open OFF Connected Closed Earthing switch operation access is barred
9 Yes Transit/ Service Open OFF Connected Closed LV plug cannot be disconnected
10 Yes Service Closed OFF Connected Closed CB cannot be racked out

Table 1 tabulates the mandatory interlock conditions for withdrawable circuit breaker

[0047] Interlock Condition No.1: Initially CB locking plate (4) locks the Interlock shaft (5). This results in the three-position interlock mechanism being locked in first position of three-position interlock knob (1). There by not allowing the CB to be racked in.

[0048] To lock CB to the panel, CB locking plate (4) is moved horizontally as shown in Fig. 3. Hence the three-position interlock knob (1) is free to rotate to second or third position (provided LV plug is inserted, CB compartment door is closed, Earthing switch is OFF, CB is open). Thus, allowing the CB to be racked in. This fulfils interlock condition no. 1 as per Table 1.

[0049] Interlock Condition No.2: When the LV plug assembly (6) is not inserted, the spring-loaded LV socket interlock pin (9) locks the LV interlock plate (10). This locks the three-position interlock mechanism (3) in First position of three-position interlock knob (1). When the LV plug assembly (6) is inserted and locked into position the LV plug interlock pin (7) pushes in the LV socket interlock pin (9). The LV interlock plate (10) being free to rotate on a guide slot on LV plug interlock pin (7) as shown in Fig. 5. Hence the three-position interlock knob (1) is free to rotate to second or third position (provided CB compartment door is closed, Earthing switch is OFF, CB is open, CB locked to panel). Thus, allowing CB to be racked in. This fulfils interlock condition no. 2 as per Table 1.

[0050] Interlock Condition No.3: The three-position interlock socket (2) can only be actuated by the Interlock knob shaft (11) as shown in Fig. 2. Once the CB Compartment door is closed, the three-position interlock knob shaft (11) engages with three-position interlock socket (2). Hence the three-position interlock knob (1) is free to rotate to second or third position (provided LV plug is inserted, Earthing switch is OFF, CB is open, CB locked to panel). Thus, allowing CB to be racked in and closed. This fulfils interlock condition no. 3 as per Table 1.

[0051] Interlock Condition No.4: When the Earthing switch is ON, the Earthing switch flap assembly (13) locks the Interlock shaft (5) in First position of the three-position interlock knob (1). When the Earthing switch is OFF, the Earthing switch flap assembly (13) releases the Interlock shaft (5) as shown by the arrow in Fig. 6. Hence the three-position interlock knob (1) is free to rotate to second or third position (provided LV plug is inserted, CB compartment door is closed, CB is open, CB locked to panel). Thus, allowing CB to be racked in. This fulfils interlock condition no. 4 as per Table 1.

[0052] Interlock Condition No.5: When the CB is closed, CB Open/Close interlock stopper (17) as shown in Fig. 7 locks the three-position interlock mechanism (3) in third position of the three-position interlock knob (1). When the CB is open CB Open/Close interlock stopper (17) will moves downwards as shown by the arrow as shown in Fig. 7, thereby releasing three-position interlock mechanism (3). Hence the three-position interlock knob (1) is free to rotate to second or first position (provided LV plug is inserted, CB compartment door is closed, CB locked to panel, Earthing switch OFF). Thus, allowing CB to be racked in. This fulfils interlock condition no. 5 as per Table 1.

[0053] Interlock Condition No.6: When the CB is racked into transit condition, the interlock drum (14) is locked by the interlock guide plate (15) in second position of 3-position interlock knob (1), as shown in Fig. 8. The interlock drum (14) also releases the limit switch of CB closed electrical circuit. Hence the CB cannot be closed by any electrical means.

[0054] Transit is only possible in second position of three-position interlock knob (1). In this condition CB closed push button access is barred by CB Open/Close interlock flap (16), thereby not allowing CB to be closed. This fulfils interlock condition no. 6 as per Table 1.

[0055] Interlock Condition No.7: When the CB is racked into transit or service condition. The interlock drum (14) is locked by the interlock guide plate (15) in second or third position of three-position interlock knob (1), as shown in Fig. 8 & Fig. 9. Thus, first position of three-position interlock knob (1) cannot be achieved. Thus, not allowing CB Compartment door to be opened as it can be opened only in First position of three-position interlock knob (1) as shown in Fig. 4.

[0056] In first position of 3-position interlock knob (1) interlock knob shaft (11) releases door interlock link assembly (12). Thereby, allowing the CB Compartment door to be opened. This fulfils interlock condition no. 7 as per Table 1.

[0057] Interlock Condition No.8: When the CB is racked into transit or service condition. The interlock drum (14) is locked by the interlock guide plate (15) in second or third position of three-position interlock knob (1), as shown in Fig. 8 & Fig. 9. Thus first position of three-position interlock knob (1) cannot be achieved. Thus, not allowing Earthing switch operation access as it can be only accessed in first position of three-position interlock knob (1) as shown in Fig. 6.

[0058] In first position of three-position interlock knob (1) the interlock shaft (5) allows the Earthing switch flap assembly (13) to be lifted thereby, allowing access for the Earthing switch operation. This fulfils interlock condition no. 8 as per Table 1.

[0059] Interlock Condition No.9: When the CB is racked into transit or service condition. The interlock drum (14) is locked by the interlock guide plate (15) in second or third position of three-position interlock knob (1), as shown in Fig. 8 & Fig. 9. Thus first position of three-position interlock knob (1) cannot be achieved. Thus, not allowing Low Voltage plug assembly (6) to be disconnected as it can be disconnected only in first position of three-position interlock knob (1) as shown in Fig. 5.

[0060] In first position of three-position interlock knob (1) Low Voltage interlock plate (10) release Low Voltage plug interlock pin (7) thereby, allowing the Low Voltage plug assembly (6) to be disconnected. This fulfils interlock condition no. 9 as per Table 1.

[0061] Interlock Condition No. 10: When the CB is closed, CB Open/Close interlock stopper (17) as shown in Fig. 9 locks the three-position interlock mechanism (3) in third position of the three-position interlock knob (1). When the CB is open CB Open/Close interlock stopper (17) will moves downwards as shown by the arrow shown in Fig. 9, thereby releasing three-position interlock mechanism (3). Hence the three-position interlock mechanism (3) is free to rotate to second position of three-position interlock knob (1). Thus, allowing CB to be racked out. This fulfils interlock condition no. 10 as per Table 1.

[0062] According to an embodiment of the present invention, a three position interlocking module for circuit breaker is disclosed. The interlock mechanism of the present invention is fitted on the stationary body of the circuit breaker. The interlocking module (3) comprising a three-position interlock knob (1), a three-position interlock socket (2), an interlock shaft (5) and an interlock knob shaft (11). The interlock knob (1) is adapted to select any one of the three interlock positions. The interlock socket (2) is adaptively coupled to the interlock knob (1) for driving the three-position interlock module (3). The interlock knob shaft (11) is operably coupled to the interlock knob (1) to actuate the three-position interlock socket (2). The interlock knob (1) can interlock at a first position or a second position or a third position.

[0063] At first position, the interlock knob (1) is positioned horizontally such that the circuit breaker locking plate (4) locks the interlock shaft (5), at second position, the interlock knob (1) is at 60° angle from the horizontal axis and at third position, the interlock knob (1) is at 120° angle from the horizontal axis.

[0064] The present invention finds its application in any industry where medium voltage withdrawable circuit breakers are used.

[0065] Some of the non-limiting advantages of the present invention are mentioned hereinbelow:
a) It can be fitted with both new and existing withdrawable circuit breakers;
b) It provides a flexible/adjustable add-on or pre-assembled module arrangement for various variants of withdrawable circuit breakers;
c) It provides complete isolation and ingress protection;
d) It provides a safe, positive and fool-proof interlock mechanism thereby ensuring complete safety of the operator;
e) It offers highest level of operational reliability through mechanical repeatability, lesser components in linkages, minimal degradation of performance with time;
f) It is compact with respect to the space constraints offered.
g) It optimizes the components of the circuit breaker to provide an economical and cost effective product;
h) It offers mechanical indication and direct visibility of electrical isolation;
i) It is easily replaceable on site thereby providing a reliable retrofit option and
j) It provides ample high voltage clearance, i.e., the interlock does not hamper the dielectric performance of the switchgear.

[0066] Although a three position interlocking module for circuit breaker has been described in language specific to structural features and/or methods as indicated, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or components or devices or methods described therein. Rather, the specific features are disclosed as examples of implementations of a three position interlock module with retrofit capability for a medium voltage withdrawable circuit breaker.