Claims:1. An electronic trip unit, ETU for use in a circuit breaker comprising:

a protection function controller (1) communicably coupled to a display controller (2) and a communication module (4), said display controller (2) is coupled to display means (5) to display data to a user;

characterized in that memory means (3), communicably coupled to the display controller (2) and the protection function controller (1), is adapted to store ETU settings to be sent to either the protection function controller or the display controller if the other controller fails to operate.

2. The trip unit as claimed in claim 1, wherein the memory means (3) is a non-volatile ferroelectric random access memory (FRAM).

3. The trip unit as claimed in claim 2, wherein the FRAM has dual ports to communicably couple the protection function controller (1) and the display controller (2).

4. The trip unit as claimed in claim 3, wherein the FRAM is communicably coupled by SPI/I2C protocol.

5. The trip unit as claimed in claim 2, wherein the FRAM has a single port and a handshaking pin operably couples the protection function controller (1) and the display controller (2), said pin is adapted to avoid simultaneous access to both the controllers.

6. The trip unit as claimed in claim 1, wherein ETU settings are modified by a user.

7. The trip unit as claimed in claim 1, wherein ETU settings are modified from Human Machine Interface, HMI, by different communication protocols.

8. The trip unit as claimed in claim 1, wherein the display controller (2) is communicably coupled to a zone selective interlocking, ZSI module (7), said ZSI module operably coupled to an upstream breaker (8).

9. The trip unit as claimed in claim 1, wherein the display controller (2) is coupled to the communication module by a hardware switch (9).

10. A method for detecting failure in an Electronic Trip Unit, as claimed in any of the preceding claims.

11. The method as claimed in claim 10, wherein the protection controller is adapted to receive ETU settings stored in the FRAM, if the display controller fails.

12. The method as claimed in claim 10, wherein the display controller is adapted to drive a zone selective interlocking (ZSI) module to indicate an upstream breaker of the unavailability of a downstream breaker to trip in case of fault, if the protection function controller fails.

13. The method as claimed in claim 10, wherein display controller is adapted to receive ETU settings from the FRAM and send to the communication module, if the protection function controller fails, said module being operably coupled to the display control.

14. The method as claimed in claim 10, wherein during power down, the protection function controller and the display controller can save a copy of latest settings in their data flash memory.

15. The method as claimed in claim 10, wherein the latest settings data can be acquired from the communication module to configure settings of upstream breaker, if both the protection function controller and the display controller fail.
, Description:FIELD OF INVENTION
The present invention pertains to an electronic trip unit in circuit breakers in general, and, more particularly, to an electronic trip unit and a method of detecting microcontroller failure in dual microcontroller based electronic trip units.

BACKGROUND

Circuit breakers are used to break the current passing through it in case the current goes above a certain threshold value. Microcontroller based electronic trip units (ETU) are the brain of the circuit breakers. These ETU provide a variety of protections such as current protection, voltage protection, frequency protection, power protection etc. Circuit breakers are also capable of providing current, voltage, frequency, energy and power metering and logging various types of records such as alarm, pickup, trip, maintenance etc. Breaker related data such as fault counters, breaker counters, breaker status etc. can be stored and displayed. Modern day electronic trip units also communicate to the external world devices such as mobile phones, cloud based systems and with other devices such as relay module, temperature module etc. Since the ETU need to perform a wide variety of functions they are designed with two or more controllers. Two controllers are in general used to share the processing load such that one controller performs the metering and protection function whereas the other controller provides user interface for viewing metering, records, settings etc. and communicating with external world.
The microcontroller responsible for protection function reads the current and voltage values sampled by ADC, calculates the per cycle RMS value and issues a trip command if the current or voltage goes above the threshold set by user. It also computes the average current and voltage metering parameters. The protection function controller also generates the trip record, alarm record, pickup record etc. whenever the condition occurs. Using on-board protocols such as SPI or I2C or any other communication protocol the data can be communicated between the protection function controller and display controller. The display controller on the other hand is responsible for driving the display for providing navigation.
Data such as settings or records or metering etc. can be stored in the non-volatile memory of protection function controller or display controller. If the data needs to be available to the user even after the self-power supply is not present, then the data is usually stored in the data flash memory of display controller. This is because; when self-power is not present display controller can be turned ON using battery power. At that time, we don’t need to turn ON the protection function controller as it will cause faster drainage of the battery by consuming more power. In the same way, settings can be modified by the user when self-power is not present that is in battery only mode. So settings can also be saved in the data flash memory of the display controller and communicated to main controller when self-power is detected. At power up once the settings are communicated to protection function controller, a copy can also be stored in the data flash memory of main controller.
The technical problem with this scheme is that in case the protection function controller fails, the trip unit will not provide the required protection and this will be a hazardous situation.
Reference has been made to WO2015047123A1, disclosing fault detection in dual microprocessor electronic trip unit, wherein one of the microprocessors is for performing only protection function and other controller is for performing metering functions. So both of the controllers are getting the current and voltage signals from the common hardware circuitry. Both protection function controller and metering function controller compute current and voltage data and timestamp them. Ideally, for the same instant the current and voltage values computed by the two controllers should be same. The data calculated is communicated to other controller using communication protocol. If there is large deviation between the values computed by the two controllers beyond a certain threshold, then it is assumed that there is some problem in the circuitry or controller itself. In this case indication is given to the user.
Although the fault condition is efficiently detected, it doesn’t provide a mechanism to clear the fault condition or switching the functionality from failed controller to healthy controller in case of microcontroller failure. In case of hardware circuitry failure, only indication is given to the user.
Thus there is a need to provide an electronic trip unit and a method thereof for detecting controller failure and provide redundancy using another healthy controller and communication to indicate the user of the controller failure.

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 object of the present invention is to provide an electronic trip unit, ETU for use in a circuit breaker.
An object of the present invention is to provide a method for detecting failure in the ETU.
In accordance with an aspect of the present disclosure, is to provide an electronic trip unit, ETU for use in a circuit breaker comprising a protection function controller communicably coupled to a display controller and a communication module. The display controller is coupled to display means to display data to a user and a non-volatile memory communicably coupled to the display controller and the protection function controller, is adapted to store ETU settings to be sent to either the protection function controller or the display controller if the other controller fails to operate.
In accordance with another aspect of the present disclosure, is to provide a method for detecting failure in the ETU, and provide redundancy using another healthy controller and communication to indicate the user of the controller failure.
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, disclose exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 illustrates the connection of various controllers in accordance to the invention.
Figure 2 illustrates indication based on ZSI module to upstream breaker in case of protection function controller failure in accordance to the invention.
Figure 3 illustrates indication based on communication module to SCADA system in case of protection function controller failure in accordance to the 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
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure 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 various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be 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 present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure 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. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense, but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.
The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.
The subject invention lies in providing an electronic trip unit, ETU for use in a circuit breaker and a method for detecting failure in the ETU thereof.
An embodiment of the invention describes an electronic trip unit, ETU for use in a circuit breaker comprising a protection function controller (1) communicably coupled to a display controller (2) and a communication module (4); said display controller (2) is coupled to display means (5) to display data to a user. A non-volatile memory (3), communicably coupled to the display controller (2) and the protection function controller (1), is adapted to store ETU settings to be sent to either the protection function controller or the display controller if the other controller fails to operate.
Another embodiment of the invention describes a method for detecting failure in the ETU.
Another embodiment of the invention describes electronic trip unit with dual microcontroller. One microcontroller provides protection function and other which mainly provides user interface. Metering, events, records etc. are generated by protection function controller whereas display controller displays the data to user as and when queried. A FRAM which is a type of non-volatile memory is interfaced with both protection function controller (1) and the display controller (2) via SPI/I2C protocol. It is used for storing a copy of latest settings whenever modified from local display or Human Machine Interface, HMI.
Another embodiment of the invention describes when the protection function controller (1) fails; the failure can be detected by the display controller (2). Detection process may involve polling a status line from the protection controller (1) or monitoring communication frame between the two controllers. When failure is detected, the display controller can drive a zone selective interlocking, ZSI module (7) to indicate an upstream breaker (8) of the unavailability of a downstream breaker to trip in case of fault. So in case a fault condition being detected by the upstream breaker, it can trip immediately if ZSI signal is present. If ZSI signal is not present, then upstream breaker will trip as per its selectivity settings.
Another embodiment of the invention describes the display controller (2) being connected to the communication module (4) via a hardware switch (9), wherein the hardware switch (9) is driven by the display controller (2). When the switch is ON, SPI/I2C or CAN lines of both the display controller (2) and the communication module (4) gets connected. When protection function controller (1) fails, the display controller (2) will detect the failure and will turn ON the switch (9), so that communication channel between the communication module (4) and the display controller (2) is set up. Once the communication is set up, the communication module (4) is adapted to receive the ETU settings from the display controller (2). The display controller (2) in turn will read the settings from FRAM. In this way ETU setting is communicated to the SCADA (6) system using the communication module (4). Now SCADA (6) system can decide the settings of other breakers in the installation such as to overcome the failure of this circuit breaker or may be change the coordination settings of breakers.
In another embodiment of the invention, during power down, the protection function controller (1) as well as the display controller (2) saves a copy of latest settings in their data flash memory. On powering up, if FRAM is found to be not working then protection function controller (1) still have the latest settings to work with.
Referring to figure 1, illustrating the schematic of an embodiment of ETU, describes one microcontroller providing protection function and the other controller mainly providing user interface. Metering, events, records etc. are generated by the protection function controller (1) whereas the display controller (2) displays the data to user as and when queried. A FRAM which is a type of non-volatile memory is interfaced with both the protection function controller (1) and the display controller (2) for storage of any data such as settings, records, metering etc. Settings data is very crucial because it defines the operational configurations of the trip unit along with tripping characteristics of various protection algorithms.
In another embodiment of the invention, the FRAM can be a dual port one where both protection function controller (1) and the display controller (2) are interfaced via SPI/I2C protocol with FRAM.
In another embodiment of the invention, a single port FRAM is used. In case of single port FRAM, a handshaking pin is used between protection function controller (1) and the display controller (2). Handshaking pin will be used to avoid simultaneous access by two controllers.
In another embodiment of the invention, when the ETU settings are modified by a user from local display, the modified ETU settings are first updated in the FRAM using SPI/I2C communication between the display controller and FRAM. Then the new settings are applied to the protections.
In another embodiment of the invention, ETU settings can also be modified from HMI, herein Supervisory Control And Data Acquisition, SCADA using communication protocols such as Modbus, Profibus, TCP-IP, or different wireless protocols. The communication interface can be inbuilt in the trip unit or can be altogether a separate module. Generally, in circuit breakers, a separate communication module acts as an interface to facilitate communication between the HMI and a main controller of the trip unit.
When settings are modified from the HMI, protection function controller communicates the same settings to FRAM using SPI/I2C communication. Then the new settings are applied to protections.
In another embodiment of the invention, if the display controller fails due to any reason, user interface will not work. But the main functionality of the electronic trip unit which is to provide protection to the load will be working as the main controller can take the latest settings from FRAM. Protection function controller can also drive an LED indication to indicate the same.
In another embodiment of the invention, referring to figure 2, when protection function controller (1) fails, the same can be detected by the display controller (2). The detection process may involve frequently polling a status line from protection controller or monitoring communication frame between two controllers. When failure is detected, the display controller (2) is adapted to drive a zone selective interlocking, ZSI module (7), to indicate the upstream breaker (8) of the unavailability of the downstream breaker to trip in case of fault. So in case a fault condition is detected by the upstream breaker, it can trip immediately if ZSI signal is present. If ZSI signal is not present, then upstream breaker will trip as per its selectivity settings.
In another embodiment of the invention, referring to figure 3, the display controller (2) is coupled to the communication module via a hardware switch (9), which is driven by the display controller (2). When the switch (9) is ON, SPI/I2C lines of both the display controller (2) and the communication module (4) gets connected. SPI/I2C communication protocols can work well for a distance such as 1-2 meter. Usually the communication module (4) is mounted near to the electronic release and SPI/I2C communication is selected because these protocols are readily available on all the controllers these days.
In another embodiment of the invention, if the communication module (4) needs to be mounted at a longer distance, then instead of SPI/I2C protocol CAN protocol can be used for communication between display controller (2) and the communication module (4). When switch (9) is ON, CAN lines of both the display controller (2) and the communication module (4) gets connected. When switch (9) is OFF, the communication module (4) can only communicate with protection function controller (1). When protection function controller (1) fails, display controller (2) will detect the same. It will turn ON the switch (9), so that communication channel between the communication module (4) and display controller (2) is set up. Once the communication is set up, the communication module can query the ETU settings from display controller. Display controller in turn will read the settings from FRAM. In this way ETU settings can be communicated to the SCADA system using the communication module. Now SCADA system can decide the settings of other breakers in the installation such as to overcome the failure of this circuit breaker or may be changed the coordination settings of breakers.
In this way, reliability is added to the circuitry by storing settings in FRAM and communicating the same in case of any of the controller failure.
In another embodiment of the invention, in case of failure of both the protection controller and the display controller, the SCADA system (6) can use the settings data acquired through the communication module prior to the failure, to configure settings of upstream breaker to compensate for the loss of protection and indicate the respective authorities about the failure condition so that appropriate action can be taken.
Some of the non-limiting advantages of the present invention are:
a) It provides a method for detecting failure in the ETU, and provide redundancy using another healthy controller and communication to indicate the user of the controller failure.

Although an electronic trip unit, ETU for use in a circuit breaker and a method for detecting failure in the ETU have been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of an electronic trip unit, ETU for use in a circuit breaker and a method for detecting failure in the ETU.