Claims:
1. An interlock apparatus positioned between two or more ring switches of a single ring main(RMU) unit panel or between the ring switches of different ring main unit panels, wherein said interlock apparatus controls a state between said two or more ring switches disposed adjacent to each other in a single ring main unit panel or between the ring switches of different ring main unit panels, wherein the interlock apparatus comprising:
a key means (5) detachably arranged to one of said two or more ring switches, wherein said key means rotates freely after one of said two or more ring switches is put to earth state while the other ring switch is put to an operative state using the key (5);
an earth shutter (3) to enable said key means (5) to operate; and
an interlock bracket means (6), rotatably arranged with said key means (5);
wherein said interlock bracket means (6) after rotation actuate at least a limit switch (7) to cut a power supply to said one of said two or more ring switches in earth state, making said ring switch in earth state inactive both electrically and manually.

2. The apparatus as claimed in claim 1, wherein said key means (5) fits within a lock means (4).

3. The apparatus as claimed in claim 2, wherein said key means (5) is free to rotate in anti-clockwise direction when the ring switch is put to earth state, and said key means rotated in a clockwise direction when the ring switch is to be put in operative state.

4. The apparatus as claimed in claim 1, wherein said earth shutter (3) moves from downward position to upward position once the ring switch is in earth state, to enable the key(5) to operate.

5. The apparatus as claimed in claims 1 to 4, wherein said interlock bracket (6) attached to the lock means (4) stop the earth shutter (3) to go downward once the ring switch is in earth state.

6. The apparatus as claimed in claim 2, wherein said key means (5) is detached from the interlock apparatus after its full anti-clockwise rotation, and said key means is attached into interlock apparatus of the same ring switch or some other ring switch to allow operative state of that ring switch.

7. A method for controlling a state of at least two or more ring switches disposed adjacent to each other in a single ring main unit panel or between the ring switches of different ring main unit panels, by using an interlock apparatus, wherein the method comprising:
rotating a key means after one of said two or more ring switches is in earth position while the other ring switch is in operating position using the key;
Enabling rotation of an interlock bracket due to said rotation of said key means;
displacement of a earth shutter from downward position to upward in case said one of two or more ring switches is in earth position;
Actuating, by said interlock bracket, a limit switch for cutting the supply to said ring switch in earth position;
Detaching said key means from said ring switch in case one of said two or more ring switches is in earth position.
, Description:TECHNICAL FIELD OF THE INVENTION
The present subject matter described herein, in general, relates to an interlock apparatus of a ring main unit. More particularly, the invention relates to an interlock apparatus of a ring main unit, which controls a state between a plurality of ring switches disposed either adjacent to each other in a single ring main unit panel or in two different ring main unit panels.

BACKGROUND OF THE INVENTION
In an electrical power distribution system, a ring main unit (RMU) is a factory assembled, metal enclosed set of switchgear used at the load connection points of a ring-type distribution network.

The ring main unit (RMU), which is a type of gas insulated switchgear, is generally used for the distribution of power supply. It has many variants according to its application in power distribution. One main element of RMU is ring switch which helps in switching the power supply. Generally, it has three position i.e.; ON – OFF – EARTH. Some RMU variants consists of ring switches only. The consumer take this variant to take up the power supply from two or more different source. So that in case there is a power supply cut then the second power source can replace the first one.

Generally, the consumer does not use two or more power supply at a time. If accidently it happens then there will be a fatal fault unless the power supplies are synchronized. In ring main unit the synchronization feature is rarely provided. To eliminate this possibility interlock between ring switches is provided.

Reference is made to a US10141129B2 in which an interlock apparatus of a ring main unit is provided. The interlock apparatus may be provided between a plurality of switches which are included in the ring main unit and are adjacent to each other, and when one switch is controlled to a closed state and is connected to a power supply source, the other switch adjacent to the one switch is prevented from being connected to the power supply source, thereby preventing the plurality of switches from being simultaneously connected to the power supply source.

However, the problem with the existing interlock apparatus in the ring main unit is that the present RMU panel does not have any such interlock between the ring switches let alone being electrical or mechanical in nature. It increases the risk of accidents.

So, an interlock is needed which can fulfill the need both electrically and manually. This interlock eliminates the manual error. Currently there is no such invention which claims to provide mechanical & electrical interlock between multiple adjoining ring switches of a single ring main unit panel or between the ring switches of different ring main unit panels.

SUMMARY OF THE INVENTION
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.

An objective of the present invention is to provide an interlock apparatus between multiple adjoining ring switches of a single ring main unit panel or between the ring switches of different ring main unit panels, so that the desirable ring switch can be operated while all the other ring switches will remain in earth condition.

Accordingly, in one aspect, in one implementation, the present invention discloses an interlock apparatus positioned between two or more ring switches of a single ring main unit panel or between the ring switches of different ring main unit panels, wherein said interlock apparatus controls a state between said two or more ring switches disposed adjacent to each other or between ring switches of different ring main unit panels, wherein the interlock apparatus comprising:
a key means detachably arranged to one of said two or more ring switches, wherein said key means rotates freely and taken out after one of said two or more ring switches is put to earth state while the other ring switch is put to an operative state using the key;
an earth shutter to enable said key means to operate; and
an interlock bracket means, rotatably arranged with said key means;
wherein said interlock bracket means after rotation actuate a limit switch to cut a power supply to said one of said two or more ring switches in earth state, making said ring switch in earth state inactive electrically and manually.

In one aspect, in second implementation the key means fits within a lock means.

In one aspect, in third implementation the key means is free to rotate in anti-clockwise direction when the ring switch is put to earth state and said key means rotated in a clockwise direction when the ring switch is to be put in operation state.

In one aspect, in fourth implementation, the earth shutter moves from downward position to upward position once the ring switch is in earth state, to enable the key to operate.

In one aspect, in fifth implementation, the interlock bracket attached to the lock means stop the earth shutter to go downward once the ring switch is in earth state.

In one aspect, in sixth implementation, the key means is detached from the interlock apparatus after its full anti-clockwise rotation, and said key means is attached into said interlock apparatus to allow operative position of said ring switch or can be attached to the interlock apparatus of other ring switches to allow operative position.

In another aspect, in one implementation, the present invention discloses a method for controlling a state of at least two or more ring switches disposed adjacent to each other in a single ring main unit panel or between the ring switches of different ring main unit panels, by using an interlock apparatus, wherein the method comprising:

Attaching and rotating a key means after one of said two or more ring switches is in earth position while the other ring switch is also in earth position. The other ring switches can be made operative using the key;
Enabling rotation of an interlock bracket due to said rotation of said key means;
displacement of a earth shutter from upward position to downward in case said one of two or more ring switches is in earth position;
Actuating, by said interlock bracket, a limit switch for starting the supply to said ring switch in earth position;
Detaching said key means from said ring switch in case one of said two or more ring switches is in earth position.

Thus, to eliminate manual error and to increase human safety, the interlock apparatus doesn’t allow the operation of more than one ring switch at a time. If there is a requirement of operating another ring switch than the first ring switch in operation should be earth first. Thus, making it safe for the operator to change the supply whenever required.

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:

Figure 1 shows the ring main unit (RMU) with four ring switches, according to one implementation of the present invention. The Figure 1(a) shows the detailed view of the ring switches; the figure 1(b) shows the RMU with four ring switches; and the figure 1(c) shows the circuit diagram of RMU, according to one implementation of the present invention.

Figure 2 shows the ring switch fascia assembly, wherein figure 2(a) shows the front view and the figure 2(b) shows the rear view, according to one implementation of the present invention.

Figure 3 shows the detailed view of the interlock apparatus, according to one implementation of the present invention.

Figure 4.1 shows the position of the interlock apparatus according to the step 1 of one implementation of the present invention.

Figure 4.2 shows the position of the interlock apparatus according to the step 2 of one implementation of the present invention.

Figure 4.3 shows the position of the interlock apparatus according to the step 3 of one implementation of the present invention.

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
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.

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.

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.

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

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.

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.

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.

In one implementation, the present invention discloses an electrical cum mechanical interlock apparatus between multiple adjoining ring switches in ring main unit of a single ring main unit panel or between the ring switches of different ring main unit panels.

In one implementation, reference is made to figures 1 to 4, in which major components & assemblies which this interlock is comprised of are :
1) Ring main unit
2) Ring switch fascia assembly (front & rear view)
3) Earth shutter
4) Lock
5) Key
6) Interlock bracket
7) Limit switch
8) Limit switch mounting bracket

In one implementation, reference is made to figure 1(a) to (c). In this interlock apparatus, for the operation of any other ring switches then the ring switch in operation should be put to earth. There is a single key between all the ring switches (Fig 1(a)) which comes under this interlock. All the ring switches have a lock (4) in which this key(5) fits.

In one implementation, reference is made to figure 2 which shows the ring switch fascia assembly, wherein figure 2(a) shows the front view and the figure 2(b) shows the rear view.

In one implementation, reference is made to figure 3 which shows the detailed view of the interlock apparatus.

According to various implementations of the present invention, the key (5) can be removed from the ring switch in operation after it is put to earth. When the ring switch is put to earth, the key (5) is free to rotate in anti-clockwise direction. Once the ring switch is in earth position, the earth shutter (3) from downward position can go up. After this the key (5) is free to operate. The interlock bracket (6) attached to the lock(4) rotates along with the key. The interlock bracket (6) after rotation then actuate a limit switch (7) which cut of the motor supply hence making the ring switch electrically inactive. The interlock bracket (6) attached to the lock(4) stop the earth shutter(3) to go downward. As the earth shutter (3) remain in upward position, the manual operation cannot be performed. The key (5) is free to be removed from the operational ring switch after its full designated anti-clockwise rotation. Now this ring switch is in earth position and it cannot be put to operation through electrical and mechanical means until the key (5) is inserted again and the above procedure is performed in reverse direction.

The key(5) removed the earthed ring switch now can be put to any of the desired ring switch to make that ring switch operational both electrically and manually. The key(5) should be inserted and rotated in clockwise direction. After the key (5) is rotated fully in its designated clockwise rotation, the earth shutter of the current ring switch can go downward hence allowing the manual operation. Also as soon as the key(5) is rotated the limit switch is released which allow the electrical operation of the ring switch.

By the above process, the operator can easily and safely switch between rings switches which they want to operate.

In one implementation, reference is made to figure 4, which shows various position of the interlock apparatus according to the following steps:

STEP 1: The earth shutter is in downward position. The key is trapped in the lock. The limit switch is not pressed. (shown in Figure 4.1)

STEP 2: The ring switch is put to earth. The earth shutter is slide to upward direction, so the manual operation of the ring switch is blocked. The key remains in its original position. Electrical operation of ring switch is possible as the limit switch is not pressed. (Shown in figure 4.2)

STEP 3: The key rotated in anti-clock wise direction, so the key is free to remove from lock. The interlock bracket attached to the lock press the limit switch hence cutting the supply for the electrical operation of ring switch. Now the ring switch cannot be operated in electrical or mechanical means. (Shown in figure 4.3)

According to various implementations of the present invention, the interlock apparatus allows only one ring switch to go to ON position while all the other adjoining ring switches will be in EARTH position. The interlock is both electrical and mechanical in nature. This interlock hold true for infinite numbers ring switches.

Some of the unique features of this invention are:
1) It is an electrical as well as mechanical interlock. (For this purpose, electrical interlock is never designed before neither the combination of electrical & mechanical interlock)
2) It can be used between ring switches of same RMU panel or between the ring switches of Different RMU panels. No need to place ring switches adjacent to each other.
3) It can be used between infinite numbers of ring switches.

Some of the non-limiting advantages of the present invention are as follows:
• Use a completely new and innovative way to achieve the interlock.
• Interlock can be applied to infinite number of ring switches.
• Comprises of both electrical & mechanical interlock.
• Increased safety of personnel and switchgear.
• Chance of manual error eliminated.
• Reliability is impeccable.
• Easy of assembly.
• Low cost impact.

Although an interlock apparatus between multiple adjoining ring switches of a single ring main unit panel or between the ring switches of different ring main unit panels is provided, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or apparatus described herein. Rather, the specific features are disclosed as examples of implementations of the interlock apparatus between multiple adjoining ring switches of a single ring main unit panel or between the ring switches of different ring main unit panels.