INTERLOCKING

FIELD OF THE INVENTION

The present invention generally relates to electrical interlock system in an Automatic Transfer Switch (ATS) system. In particular, the present invention relates to an ATS system having an electrical interlock system using a token exchange method.

BACKGROUND OF THE INVENTION

Typically there are two types of architecture for source-change over system with electrical interlock.

Architecture type 1 : Separate equipment for Source change over functionality and electrical interlock (shown in FIG. 1 ).

In this architecture, electrical interlocking between two breaker systems is achieved by dedicated electrical equipment. This equipment takes the full control for the two breaker systems and allows ATS (Automatic Transfer Switch) to control breaker system based on the predefined logic. Normally dedicated actuators are used to open and close circuit breaker/ switch dis-connector. Full control of these actuators is taken by electrical interlocking device to ensure electrical interlocking between two systems. This also ensures not to allow any other interface in the system to control the breaker/switch dis-connector.

However, the disadvantages of the Architecture type 1 are:

1 ) Complexity of installation and wiring due to separate electrical interlocking device

2) Cost of overall solution

3) Less flexibility in the system to control breaker or switch dis-connector

4) Configuration difficulties

5) Actuator of the breaker system is controlled by an external device making it a less reliable system Architecture 2: Source change over equipment with embedded Electrical interlock intelligence.

In this architecture, electrical interlocking between two breaker systems is achieved by intelligence embedded in ATS equipment. ATS with embedded electrical interlocking mechanism takes the full control for the two breaker systems and controls breaker system based on the predefined logic. Normally dedicated actuators are used to open and close circuit breaker/ switch dis-connector. Full control of these actuators is taken by ATS device to ensure electrical interlocking between two systems and preventing any other interface in the system to control the breaker/switch dis-connector.

Architecture type 2 also has several disadvantages such as:

1 ) Less flexibility in the system to control breaker or switch dis-connector

2) Configuration difficulties

3) Actuator of the breaker system is controlled by an external device making it a less reliable system

In view of the above discussion, it may be realized that there exists a need to provide a source change over system with improved distributed electrical interlocking.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method.

Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which reduces the complexity of installation and wiring.

Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which reduces the cost of overall solution. Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which gives more flexibility to user for accessing electrical parameters and controlling Breaker/Switch disconnector even if it is used for source change over application.

Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which simplifies configuration difficulties.

Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which improves performance and reliability of source change over system.

Another object of the present invention is to provide an improved distributed electrical interlocking for source change over system with token exchange method which is very flexible to adopt to achieve electrical interlocking for more number of breaker systems.

In order to achieve the above mentioned objects, the present invention discloses a source change over system having distributed electrical interlocking. The source change over system includes an automatic transfer switch (ATS) for issuing control commands, a plurality of switch disconnectors/ circuit breakers communicatively coupled with the automatic transfer switch for tripping actuators for break operation based on the control commands, a plurality of Human Machine Interfaces (HMIs) , field bus communication interfaces and input output interfaces connected with each of the plurality of switch disconnectors/ circuit breakers, wherein the plurality of switch disconnectors/ circuit breakers are interconnected by one or more communication channels and are embedded with the electrical interlock intelligence with token exchange method.

In one embodiment, the plurality of switch disconnectors/ circuit breakers take decisions of token exchange based on: the switch disconnector/ circuit breaker that intends to close the breaker requires to possess an electrical interlocking token therewith, the interlocking token is possessed by only one switch disconnector/ circuit breaker at a time or the interlocking token is possessed by none of the switch disconnectors/ circuit breakers, if a switch disconnector/ circuit breaker intends to close the breaker and does not possess the electrical interlocking token therewith a request is sent to other switch disconnectors/ circuit breaker to release the interlocking token thereto that requires the token for closing the breaker, and a switch disconnector/ circuit breaker releases the token to other switch disconnector/ circuit breaker if and only if the breaker of the releasing switch disconnector/ circuit breaker is in open and not in trip state and no other token request is pending.

In one embodiment, the communication channels interconnecting the plurality of switch disconnectors/ circuit breaker may be a physical media, a communication bus, a RS485 bus, a CAN channel, an Ethernet channel or an input output interface.

In one embodiment, the automatic transfer switch may be a programmable logic.

It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and other advantages of the invention will be better understood and will become more apparent by referring to the exemplary embodiments of the invention, as illustrated in the accompanying drawings, wherein

FIG. 1 illustrates one existing architecture of source-change over system with electrical interlock as prior art;

FIG. 2 illustrates another existing architecture of source-change over system with electrical interlock as prior art; FIG. 3 illustrates a source change-over equipment with embedded electrical interlock with distributed intelligence according to one embodiment of the present invention; and

FIG. 4 is a flowchart illustrating how two system exchange interlocking token according to one embodiment of the present invention.

DETAIL DESCRIPTION OF THE INVENTION

Reference will now be made to the exemplary embodiments of the invention, as illustrated in the accompanying drawings. Where ever possible same numerals will be used to refer to the same or like parts.

The present invention discloses a source change over system with an improved distributed electrical interlocking using token exchange method. The main inventive feature of the present invention compared to the earlier architectures is electrical interlocking intelligence of the system is with switch dis-connector or the breaker system. The intelligence is distributed in the breaker systems. The present invention allows any number of breakers to be connected with the ATS system. However, the ATS system of the present embodiment includes two breakers for easiness of explanation.

Advantage of the present invention is the flexibility in the breaker system. The ATS system according to the present invention can be controlled by any means of interface such as local HMI, field bus communication interface, 10 interface and so forth. Still electrical interlock is ensured by additional intelligence embedded in the breaker system itself.

The present invention is more reliable compared to other architectures since end decision of controlling breaker/switch dis-connector is taken by mechanism in-built breaker/switch dis-connector. To achieve complete closed loop control system, actuator for controlling breaker/switch dis-connector and sensor for breaker /switch dis-connector are accessed through a single mechanism or intelligence. Mechanical latency is well managed in this solution, time delay between actual actuator activation and status change in the breaker /switch dis-connector can be easily manageable with the in-build mechanism. FIG. 3 illustrates a typical source change over system with two switch dis-connector/ breaker systems (304, 306) according to the one embodiment of the present invention. From here onwards system 1 (304) may be referred as normal source breaker system and system 2 (306) may be referred as replacement breaker system. Both the system has multiple interfaces for monitoring and controlling breaker system, for example, interface such as local HMI (308, 312), field bus communication interface (310, 314), IO interface and so forth.

The ATS system (302) can control this system via any of the preferred interface (316) of the user choice, normally IO interface or field bus communication. Since, the intelligence of the electrical interlock is distributed in both the systems. It is mandatory for the both breaker systems to communicate with each other.

In the present invention, it is achieved by two channels such as channel 1 (318) and channel 2 (320). Channel 1 sends information from breaker system 1 to breaker system 2 and channel 2 exchanges information from breaker system 2 to breaker system 1. These channels can be of any type of physical media, communication bus such as RS485, CAN, Ethernet and so forth or an input output interface. The appropriate channel may be selected by the user based on the requirement.

The present invention requires two channels only if channel 1 and 2 are managed using digital Input/output. If the present invention is implemented using communication bus, channel 1 and channel 2 may be considered as same channel.

Electrical interlocking between breaker systems is achieved by a token mechanism. Based on the availability of token, the breaker system takes decision to control breaker. In general, the token exchange follows the below rules:

1 ) The breaker system which wants to close the breaker need electrical interlocking token with it.

2) At a time, only one breaker system can have token or there can be a condition both does not have token. 3) If any breaker system want to close the breaker and does not have electrical interlocking token with it. One breaker system can request other breaker system to release the token to breaker system which requires the token if all the required conditions are met.

4) One breaker system can release the token to other breaker system if and only if breaker is open and not in trip state (for breaker with trip unit) or no other token request is in- progress from its own system.

Tokens are exchanged between two breaker systems via channel 1 and channel 2.

If breaker system 1 requires a token, then breaker system 1 sends a message 1 (Request for Token) via channel 1 to breaker system 2 requesting for the token. If all conditions of releasing token are met, the breaker system 2 sends a message 2 (Positive Acknowledgement for Token) through channel 2 to breaker system 1 confirming the release of the token. Otherwise if all conditions of releasing token are not met, the breaker system 2 sends a message 3 (Negative Acknowledgement for Token) through channel 2 for not releasing the token.

The below table explains the possible use cases (shown in FIG. 4) and token exchanges:

token (424)

5 Simultaneous Close cmd on To close breaker , breaker system needs token

both BREAKER SYSTEM So both breaker systems will initiate request for token by systems sending Message 1 on channel 1 and channel 2.

Both the system will lose token and both BREAKER SYSTEMS will go to initial state.

6 Token is with BREAKER To close breaker, breaker system needs token

SYSTEM1 and BREAKER • So BREAKER SYSTEM 2 will initiate request for token SYSTEM 1 is closed/ by sending Message 1 (420) via channel 2 if BREAKER

SYSTEM 2 receives Message 3 after 100ms BREAKER Tripped state and

SYSTEM 2 will not acquire token

BREAKER SYSTEM 2 gets • BREAKER SYSTEM 2 will reject close command since a close command BREAKER SYSTEM2 does not get token (422)

7 Token is with BREAKER To close breaker, breaker system needs token

SYSTEM1 and BREAKER • So BREAKER SYSTEM 2 will initiate request for token SYSTEM 1 's breaker state by sending Message 1 via channel 2 if BREAKER

SYSTEM 2 receives Message 2 after 100ms BREAKER is open state and BREAKER

SYSTEM 2 will acquire token

SYSTEM 2 gets a close • BREAKER SYSTEM 2 can close breaker after getting command token

It is to be understood by a person of ordinary skill in the art that various modifications and variations may be made without departing from the scope and spirit of the present invention. Therefore, it is intended that the present invention covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.