CLIAMS:1. A method for short circuit protection in an electric power distribution system having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other, the method comprising:
receiving, using at least one current circuit breaker from the plurality of circuit breakers, data associated with the downstream breaker;
storing, in the current circuit breaker, data received;
fetching, using the current circuit breaker, data associated with other plurality of circuit breakers;
detecting, based on the availability of data, the current circuit breaker as the upstream breaker or the downstream breaker;
receiving, using the current circuit breaker, at least one setting(s);
detecting, using the current circuit breaker, at least one fault, thereby
tripping, based on the at least one setting(s) received, if the current circuit breaker detected is the downstream breaker, to clear the fault detected; and/or
lasting, if the current circuit breaker detected is the upstream breaker, for the current circuit breaker detected as downstream breaker to clear the fault detected; and
tripping, after lasting, if the downstream breaker does not trip, for short circuit protection.

2. The method as claimed in any of the preceding claims, wherein the data associated with the downstream breaker, in case of short circuit detection or earth fault detection is selected from at least one of trip settings, protection settings, pickup settings, delay setting, curve setting or any combination thereof.

3. The method as claimed in any of the preceding claims, wherein data received is stored in a memory of the current circuit breaker.

4. The method as claimed in any of the preceding claims, wherein data associated with other plurality of circuit breakers or the downstream breaker is stored in non volatile memory (NVM) selected from at least one of Electrically Erasable Programmable Read-Only Memory (EEPROM) or data flash of the upstream breaker.

5. The method as claimed in any of the preceding claims, wherein the setting(s) is/are selected from a group comprising of trip settings, protection settings, pickup settings, delay setting, curve setting or any combination thereof.

6. The method as claimed in any of the preceding claims comprises calculating, using the current circuit breaker, a root mean square value of current flowing through the electric power distribution system.

7. The method as claimed in any of the preceding claims, wherein the at least one fault is selected from a group comprising short circuit fault, earth fault or any combination thereof, and detected using at least one of energy accumulation technique, vector summation of the four phases technique, or any combination thereof.

8. The method as claimed in any of the preceding claims, wherein lasting till delay settings of the downstream breaker detected.

9. An electric power distribution system for short circuit protection, having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other, the electric power distribution system comprising:
at least one circuit breaker configured to
receive data associated with the downstream breaker;
store data received;
fetch data associated with other plurality of circuit breakers;
detect itself as the upstream breaker or the downstream breaker based on the availability of data;
receive at least one setting(s);
detect at least one fault;
trip based on the fault detected; and
thereby providing short circuit protection.

10. The electric power distribution system as claimed in any of the preceding claims wherein if the current circuit breaker detected is downstream breaker and if the fault is detected, downstream breaker trips to clear the fault detected.

11. The electric power distribution system as claimed in any of the preceding claims wherein if the current circuit breaker detected is the upstream breaker it lasts for the current circuit breaker detected as downstream breaker to clear the fault detected, and trips if the downstream breaker does not trip after lasting.
,TagSPECI:TECHNICAL FIELD

The present subject matter described herein, in general relates to circuit breakers, and more particularly, to a zone based short circuit fault protection where an upstream breaker has information about downstream breaker's settings. This technique is based on setting based discrimination between the circuit breakers.

BACKGROUND

Zone Selective Interlocking (ZSI) is a technique which enables two or more circuit breakers to communicate with each other so that a short circuit or ground fault will be cleared by the breaker closest to the fault in the minimum time. The primary goal of ZSI is to switch off the fault current within the shortest possible time under consideration of full selectivity.

There is highly research subject matter and has lot of available work for finding errors, to switch off the fault current within the shortest possible time under consideration of full selectivity. Few of them are mentioned below:

The prior-art document, US8207742 B2 implements ZSI but along with also checks the direction of the current whether it is a forward or reverse and if it is in pick up, give the trip signal accordingly.

The prior-art document, US20090257158A1 discloses ZSI during instantaneous trip Condition. Two threshold signals communication and acknowledgement.

The prior-art document US7570471 B2 discloses circuit breakers in the power distribution system that has a zone-selective-interlocking circuit that includes a zone-selective-interlocking-input circuit and a zone-selective-output circuit. The zone-selective-interlocking system also includes a monitoring device to monitor the voltage sent from the zone-selective-interlocking-output circuit of the at least one downstream breaker to the zone-selective-interlocking-input circuit of the at least one upstream breaker and determine whether there is a proper or improper connection between the upstream and downstream breaker and whether the downstream breaker is sending a restraint signal to the upstream breaker.

The prior-art document, US20120014026 A1 discloses modifying of ZSI settings for short circuit fault. It talks about having two sets of reading for ZSI tripping.

The prior-art document, US8280653 B2 discloses the trip mechanism that includes a zone selective interlocking input and a zone selective interlocking output. The device includes a first input electrically interconnected with the zone selective interlocking input, a second input electrically interconnected with the zone selective interlocking output, and an indicator circuit structured to indicate that the zone selective interlocking input occurred at the first input or that the zone selective interlocking output occurred at the second input.

For understanding the drawbacks in the existing ZSI techniques, assume Circuit Breaker 1 is upstream and circuit breaker 2,3,4 are downstream. If a short circuit fault is detected by breaker 4, then it should trip and clear the fault. But the same short circuit fault will also be detected by Breaker 1. If breaker 1 clears the fault before breaker 4, then even beaker 2 and 3 will be de energized. In order to avoid this in prior art either the breaker 4 used to communicate to breaker 1 that it is going to clear the fault or breaker 1 would have higher delays.

Further, according to the prior-art there is the requirement of any communication means like ZSI circuitry required between an upstream and downstream breaker for fault analysis. In prior art a ZSI circuitry would include an input and output circuitry where output circuitry is required to send information to an upstream breaker about detection of fault by a downstream breaker and the ZSI input circuitry would be present in upstream breaker for receiving signals and recalculating its settings. Another method used assigning higher pickup and delay settings for an upstream breaker. But this could put the safety of devices and personnel in danger as these settings are kept just to avoid multiple fault clearings.

Thus due to above mentioned drawbacks, there is a need for an improved and efficient zone based short circuit fault protection mechanism where an upstream breaker has information about downstream breaker's settings. Further, the proposed mechanism must reduce the hardware complexity as well as software complexities of the existing ZSI techniques.

SUMMARY

This summary is provided to introduce concepts related to zone based short circuit protection. This summary is not intended to identify essential features of the subject matter nor is it intended for use in determining or limiting the scope of the subject matter.

In accordance with one aspect, a method for short circuit protection in an electric power distribution system having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other is a disclosed. The method comprises of receiving, using at least one current circuit breaker from the plurality of circuit breakers, data associated with the downstream breaker; storing, in the current circuit breaker, data received; fetching, using the current circuit breaker, data associated with other plurality of circuit breakers; detecting, based on the availability of data, the current circuit breaker as the upstream breaker or the downstream breaker; receiving, using the current circuit breaker, at least one setting(s);detecting, using the current circuit breaker, at least one fault, thereby tripping, based on the at least one setting(s) received, if the current circuit breaker detected is the downstream breaker, to clear the fault detected; and/or lasting, if the current circuit breaker detected is the upstream breaker, for the current circuit breaker detected as downstream breaker to clear the fault detected; and tripping, after lasting, if the downstream breaker does not trip, for short circuit protection.

In accordance with another aspect, an electric power distribution system for short circuit protection, having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other is disclosed. The electric power distribution system comprises of at least one circuit breaker configured to receive data associated with the downstream breaker; store data received; fetch data associated with other plurality of circuit breakers; detect itself as the upstream breaker or the downstream breaker based on the availability of data; receive at least one setting(s);detect at least one fault; trip based on the fault detected; and thereby providing short circuit protection.

In accordance with another aspect, a breaker 1 asks the user about settings of all its downstream breakers and stores it in its internal memory. It then assigns its own pickup and delay settings based on pickup and delay settings of downstream breakers. So any breaker just checks its internal memory for presence of any downstream breaker data. If any settings are present the breaker declares itself as upstream and recalculates its own pickup and delay settings. If no information is present it assumes that it is a downstream breaker and works with the actual settings. In an embodiment, the breakers may include/provided with, a setting to declare it as upstream or downstream. If declared as upstream then the user can enter the details of downstream breaker. This method hence eliminates need of additional communication lines for data transfer.

In accordance with another aspect, a breaker 1 asks the user about settings of all its downstream breakers and stores the information in its internal memory. Circuit breaker 1 then assigns its own pickup and delay settings based on pickup and delay settings of downstream breakers. For example an upstream breaker is 630A breaker and a downstream breaker is 250A. So the user sets the downstream breaker for 250A for 100ms. The upstream breaker is set at 400A at 300ms. The settings of downstream breaker are set in upstream breaker as well. So in case of a short circuit fault, the upstream breaker knows that any current greater than 250A will be cleared by the downstream breaker in 100ms. If the short circuit fault is not cleared in 100ms plus some tolerance time then the upstream breaker issues a trip at 300ms. Also the upstream breaker can be configured to trip immediately as it knows that the downstream breaker can withstand 250A for only 100ms.If the delays set of both upstream and downstream breaker are same, then the upstream breaker depending on the settings of downstream breakers, recalculates its own higher pickup and delay settings for short circuit protection. This recalculation causes selective discrimination.

In yet another aspect, the present invention provides higher delay for the upstream devices.

In yet another aspect, the present invention enables entering the setting details of downstream breaker in an upstream breaker.

In yet another aspect, the present invention the upstream breaker stores the settings of downstream breaker in its memory.

In yet another aspect, the present invention the upstream breaker reads the memory to fetch details of downstream breaker settings. The upstream breaker then assigns its settings based on downstream breaker settings.

In yet another aspect, the present invention enhances the life of upstream breaker increased. As upstream breaker's pickup and delay settings will always be recalculated based on the downstream breaker's settings, the chances of nuisance tripping of breaker reduce. The electrical and mechanical life of a breaker is fixed. So by reducing the chances of nuisance tripping we increase the life of breaker.

In yet another aspect, the present invention the upstream breaker does not trip because of a fault that can be cleared by a downstream breaker. So other downstream breakers are not de energized.

In yet another aspect, the present invention no or no separate communication lines required between the upstream and downstream breakers.

In yet another aspect, the present invention reduces the cost as ZSI hardware is not required.

In still another aspect, the present invention reduces the code size as ZSI code is not required.

In still another aspect of the present invention no communication or signal interface is required between 2 breakers specifically for communicating the status of each breaker and tripping for clearing the same fault.

In still another aspect of the present invention settings based discrimination between upstream and downstream breakers where downstream breaker's settings are entered in upstream breaker.

In still another aspect of the present invention No nuisance tripping of other downstream breakers, as upstream breaker trips and clears the fault, due to fault in path of one downstream breaker.

In still another aspect of the present invention No communication lines required between the upstream and downstream breakers.

Additional features, benefits or advantages of the present invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 illustrates a block diagram of an electric power distribution system for short circuit protection is shown, in accordance with an embodiment of the present subject matter.

Figure 2 (a) and (b) illustrates a method for short circuit protection in an electric power distribution system is shown, in accordance with an embodiment of the present subject matter.

The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings that form a part of the specification.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Preferred embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. 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.

Accordingly, the present invention relates to a zone based short circuit protection.

The present invention relates zone based short circuit fault protection where an upstream breaker has information about downstream breaker's settings. This technique is based on Setting based discrimination between the circuit breakers.

Referring now to figure 1, illustrates a block diagram of an electric power distribution system for short circuit protection is shown, in accordance with an embodiment of the present subject matter.

In one implementation, an electric power distribution system for short circuit protection, having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other is disclosed. The electric power distribution system comprises of at least one circuit breaker configured to receive data associated with the downstream breaker; store data received; fetch data associated with other plurality of circuit breakers; detect itself as the upstream breaker or the downstream breaker based on the availability of data; receive at least one setting(s); detect at least one fault; trip based on the fault detected; and thereby providing short circuit protection.

In one implementation, if the current circuit breaker detected is downstream breaker and if the fault is detected, downstream breaker trips to clear the fault detected.

In one implementation, if the current circuit breaker detected is the upstream breaker it lasts for the current circuit breaker detected as downstream breaker to clear the fault detected, and trips if the downstream breaker does not trip after lasting.

In one implementation, figure 1 explains the general breaker, load positioning in a network. Circuit breaker 2, 3 and 4 are downstream to breaker 1. So their setting details are present in Breaker 1. Circuit breaker 5 and 6 are downstream to breaker 2 and hence breaker 2 contains their details. Breaker 3, 4, 5 and 6 are connected to load. Now assume the maximum load requirement of load 1 is 100A. So following are the short circuit settings for each breaker:-
· Breaker 5 is set at 150A for 100ms
· Breaker 2 is kept at 250A at 100ms.
· Breaker 1 is at 500A at 100ms.

All the upstream breakers have information about their corresponding downstream breakers. If a short circuit fault of 1000A occurs at load 1, then breaker 1, 2, 5 all detect the fault. But breaker 1 knows the settings of breaker 2 and knows that breaker 2 will clear this fault in 100ms. So it waits for breaker 2 to clear the fault. Similarly breaker 2 knows the settings of breaker 5 and knows that breaker 5 will clear this fault in 100ms. So it waits for breaker 5 to clear the fault. No communication between the breakers is required as they all know the status of their downstream breaker. So if breaker 5 does not clear the fault, breaker 2 will do the clearing in 100ms plus some tolerance time and so on.

Referring now to figure 2 illustrates a method for short circuit protection in an electric power distribution system is shown, in accordance with an embodiment of the present subject matter. The method may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, functions, etc., that perform particular functions or implement particular abstract data types. The method may also be practiced in a distributed computing environment where functions are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, computer executable instructions may be located in both local and remote computer storage media, including memory storage devices.

The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method or alternate methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof. However, for ease of explanation, in the embodiments described below, the method may be considered to be implemented in the above described system.

In one implementation a method for short circuit protection in an electric power distribution system having a plurality of circuit breakers with at least one upstream breaker and at least one downstream breaker electrically coupled to each other is a disclosed. The method comprises of:
· receiving, using at least one current circuit breaker from the plurality of circuit breakers, data associated with the downstream breaker;
· storing, in the current circuit breaker, data received;
· fetching, using the current circuit breaker, data associated with other plurality of circuit breakers;
· detecting, based on the availability of data, the current circuit breaker as the upstream breaker or the downstream breaker; receiving, using the current circuit breaker, at least one setting(s);
· detecting, using the current circuit breaker, at least one fault, thereby
· tripping, based on the at least one setting(s) received, if the current circuit breaker detected is the downstream breaker, to clear the fault detected; and/or
· lasting, if the current circuit breaker detected is the upstream breaker, for the current circuit breaker detected as downstream breaker to clear the fault detected; and tripping, after lasting, if the downstream breaker does not trip, for short circuit protection.

In one implementation, the data related to downstream circuit breaker settings (other circuit breakers) is stored in non volatile memory (NVM) like EEPROM or data flash of current circuit breaker (upstream breaker). The data is stored in known location of the NVM. This data when requested is read from the memory.

In one implementation, the data associated with the downstream breaker, in case of short circuit detection or earth fault detection is selected from at least one of trip settings, protection settings, pickup settings, delay setting, curve setting or any combination thereof.

In one implementation, the data received is stored in a memory of the current circuit breaker.

In one implementation, as shown in figure 3, the setting(s) is/are selected from a group comprising of trip settings, protection settings, pickup settings, delay setting, curve setting or any combination thereof.

In one implementation, the method further comprises of calculating, using the current circuit breaker, a root mean square value of current flowing through the electric power distribution system.

In one implementation, the at least one fault is selected from a group comprising short circuit fault, earth fault or any combination thereof, and detected using at least one of energy accumulation technique, vector summation of the four phases technique, or any combination thereof.

In one implementation, the upstream breaker lasts till delay settings of the downstream breaker detected.

In one implementation, as show in figure 2(a) and (b), the following flow chart explains the working of software algorithm to be used.
1. The current breaker firsts ask the user to enter downstream breaker data through HMI or by any other means that may include but not limited to enter by user through various means like HMI, DIP switch, Panel display and the like, as in step 1.
2. In step 2, the present breaker stores the downstream breaker data in its non volatile memory (NVM). If the breaker is upstream, it will get the data. If no data is entered, it is assumed that the current breaker does not have any downstream breakers. A setting may also be provided in the breaker for it to be configured as upstream or downstream.
3. Breaker might/ might not reset after setting. (Step 3)
4. Read the downstream breaker data from NVM of current breaker as in step 4.
5. In step 5, it is checked whether downstream breaker data is present. If data is present, in step 6, the breaker is declared as upstream breaker. If data is absent, in step 7, the breaker is declared as downstream breaker.
6. The user is then asked to enter the Short Circuit or any other protection setting as in step 8.
7. Calculate the RMS of current flowing through the conductor. (Step 9, Optional - depends on short circuit detection method) as in step 9.
8. In step 10, it is checked whether short circuit fault is detected. If no, the breaker again repeats the procedure. If yes, in step 11, it is checked whether the breaker is declared as upstream or downstream to decide on the tripping time.
9. If the breaker is upstream breaker then, in step 12, the upstream breaker waits for the downstream breaker to clear the fault. In step 13, the breaker checks whether after the delay specified by downstream breaker to clear the fault, does the fault still exist. If the fault still exists then in step 14, the breaker trips immediately or as stated by the user setting. If the fault is cleared by the downstream breaker then in step 15, the breaker does not trip.
10. If the breaker is declared as downstream breaker in step 11, then the breaker trips according to its delay settings set by the user.

Although implementations for a zone based short circuit protection have been described in language specific to structural features and/or the methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features are disclosed as examples of, zone based short circuit protection.

It is intended that the disclosure and examples above be considered as exemplary only, with a true scope of the disclosed embodiments being indicated by the following claims.