Claims:1. An assembly for sensing and monitoring temperature of a circuit breaker, said circuit breaker comprising a moving compartment (9) housed within a fixed compartment (3), and an electronic trip unit (8), said fix compartment (3) comprising:
an external terminal connection (1) comprising a plurality of thermistors (10) for sensing temperature mounted therein,
a secondary isolation contact cross piece (11) comprising a fixing plate (5); and
a plurality of secondary isolating contacts (4);
said assembly is characterized by:
a temperature module (2) mounted on the fixing plate (5) and comprising a plurality of input terminals (6) and a plurality of output terminals (7);
said input terminals (6) of the temperature module (2) are operably coupled to the thermistors (10) to receive the temperature sensed therein;
wherein said temperature module (2) is adapted to process the temperature received from the thermistors and generate a signal;
said output terminals (7) of the temperature module (2) are operably coupled to the secondary isolating contacts (4) to send the signal generated by the temperature module (2);
an electronic trip unit (8) mounted on the moving compartment (9) and operably coupled to the secondary isolating contacts (4) to receive the signal generated by the temperature module (2);
wherein the electronic trip unit (8) is adapted to process the signal received therein and generate temperature value;
said electronic trip unit (8) comprises: a display unit to display the temperature value generated by the electronic trip unit (8), and an indicator (12);
wherein the electronic trip unit (8) compares the signal with a pre-set ALARM temperature limit and a TRIPPING temperature limit set for protection of the circuit breakers;
said electronic trip unit (8) is adaptively configured to:
power the indicator (12) as ALARM when the temperature value sensed by the thermistors reaches the pre-set ALARM temperature limit;
trip the circuit breaker when the temperature value sensed by the thermistors goes beyond the TRIPPING temperature limit to isolate said circuit breaker.

2. The assembly as claimed in claim 1, comprising an external relay, bulb or hooter operably coupled to the indicator (12) of the electronic trip unit (8).

3. The assembly as claimed in claim 1, wherein the electronic trip unit (8) comprises a flux shift device to trip the circuit breaker.

4. The assembly as claimed in claim 1, wherein the ALARM and TRIPPING temperature limit for protection is set by a user.

5. The assembly as claimed in claim 1, wherein the indicator (12) is an LED or LCD.

6. A method for sensing and monitoring temperature of a circuit breaker, said method comprising the steps of:
sensing (S1), by a thermistor (10), temperature of external terminal connection (1) of the circuit breaker;
receiving (S2), by a temperature module (2), the temperature sensed by the thermistor (10) on the external terminal connection (1);
processing (S3), by the temperature module (2), the temperature sensed on the external terminal connection (1) to generate a signal;
receiving (S4), by an electronic trip unit (8), the signal generated by the temperature module (2);
processing (S5), by the electronic trip unit (8), the signal generated by the temperature module (2); and
displaying (S6), by the electronic trip unit (8), real-time continuous temperature value of the circuit breaker.

7. The method as claimed in claim 6, wherein output terminal (7) of the temperature module (2) is operably coupled to secondary isolating contacts (4) of the circuit breaker to send the signal generated by the temperature module (2).

8. The method as claimed in claim 7, wherein the electronic trip unit (8) is operably coupled to the secondary isolating contacts (4) of the circuit breaker to receive the signal generated by the temperature module (2).

9. The method as claimed in claim 7, wherein the electronic trip unit (8) is adaptively configured to:
power an indicator (12) as ALARM when the temperature value sensed by the thermistors reaches the pre-set ALARM temperature limit;
trip the circuit breaker when the temperature value sensed by the thermistors goes beyond the TRIPPING temperature limit to isolate said circuit breaker.
, Description:FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to temperature monitoring of protection devices and more particularly, pertains to an assembly for sensing and monitoring temperature of circuit breakers and a method thereof.

BACKGROUND OF INVENTION

[002] Electrical transmission and distribution systems employ a circuit breaker, which is an automatically operated electrical switch, to protect an electrical circuit from damage caused by overcurrent, typically resulting from an overload or short circuit.

[003] The circuit breaker is a switching device designed to make, carry and break the circuit. The main contact system or current path of the circuit breaker involves a moving terminal and a fixed terminal. Mechanism is the part of the circuit breaker that is used for driving power contact system of the circuit breaker to close and open. Energy stored in the mechanism by means of springs is utilized to join the moving terminal with the fixed terminal to thereby close the circuit. Under normal operating conditions i.e. in electrical current carrying state; the circuit remains closed. The aforementioned mechanism is also associated with tripping linkages to open the circuit. Opening of circuit is achieved by separation of attached fixed and moving contacts to form air space (air as a dielectric medium). Notably, opening of a circuit can be intentional, as performed by an operator or automatic, during abnormal electrical conditions such as overload, under voltage or short circuit.

[004] The moving terminal and fixed terminal carry maximum up to rated operational current for which it is designed; during normal operating conditions. During operation of the switching device, heat will be generated due to the inherent conduction losses. The cross section of the terminals limit the temperature rise in switching device and are not limited to the circuit breaker alone.

[005] Air Circuit Breaker is a kind of circuit breaker that is customarily used in low voltage power distribution systems to carry, make and break current in low-voltage applications. These air circuit breakers are generally categorized broadly into two categories viz. fixed type and withdrawable or draw-out type. The draw-out type air circuit breakers usually employ a fixed compartment or a cradle that is connected to the main supply. This compartment is a separable component and needs to be inserted into the cradle compartment during normal operating conditions without which the electrical path is not complete; and also it needs to be removed from cradle during maintenance or as and when the need arises.

[006] As electric current passes through the air circuit breaker, heat is generated. The heat generated and temperature at different points in air circuit breaker depends on various factors like actual current flowing, type of conductors (Copper or Aluminium), orientation of conductors (vertical, horizontal or flat), cross section of conductors used, ventilation of panel, quality of termination, ambient temperature etc. Excessive heat generation and temperature rise in the air circuit breaker can cause permanent damage to conductor connections as well as the air circuit breaker itself. Such condition can result in faults which will lead to isolation of all the loads connected to the air circuit breaker and complete breakdown of the system. This shutdown can lead to production loss in plants. Therefore, it is very important to monitor the temperature near the conductors. In case of any abnormality, the complete system can breakdown leading to loss of property and production.

[007] The drawbacks associated with the existing technology are that temperature monitoring can be performed for internal parts of the air circuit breaker or external terminal connection of air circuit breaker. Since the internal part is not accessible to an end user to verify the temperature in running condition of the air circuit breakers, the end user is forced to access only the rear external connection of air circuit breaker for monitoring. Notably, there is a temperature gradient between rear external terminal connection temperature and temperature on internal part of air circuit breaker. Therefore, if only the temperature on the internal part is measured, it results in mismatch in temperature readings sensed by thermistors and actual temperature measured by end user. This mismatch in temperature values results in confusion and inefficient monitoring of air circuit breaker, even when their operating conditions are healthy.

[008] Accordingly, there is a need to perform real-time temperature sensing and monitoring of switchgears that would allow continuous monitoring of the temperature on external terminal connection and verify the same with the temperature displayed on an electronic trip unit display for accuracy. Moreover, if temperature monitoring is to performed at the internal portion of higher current carrying capacity air circuit breakers that have two conductors in parallel type of construction, two temperature modules will be required, one for each internal part thereby making the system bulky and costly.

[009] The above-described need for to perform real-time temperature sensing and monitoring of the external terminal connection of the switchgears and verifying the same with the temperature displayed on an electronic trip unit display 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

[0010] 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.

[0011] An object of the present invention is to perform real-time temperature sensing and monitoring of switchgears.

[0012] Another object of the present invention is to provide an assembly for sensing and monitoring temperature of circuit breakers and a method thereof.

[0013] Yet another object of the present invention is to measure the temperature on the external terminal connection and verify it with the continuous displayed temperature value on an electronic trip unit display.

[0014] Yet another object of the present invention is to ensure that only one temperature module is required per phase for higher current carrying capacity air circuit breakers that have two conductors in parallel type of construction.

[0015] According to a first aspect of the present invention, there is provided an assembly for sensing and monitoring temperature of a circuit breaker. The circuit breaker comprising a moving compartment housed within a fixed compartment, and an electronic trip unit, said fix compartment comprising: an external terminal connection comprising a plurality of thermistors for sensing temperature mounted therein, a secondary isolation contact cross piece comprising a fixing plate; and a plurality of secondary isolating contacts. The assembly is characterized by: a temperature module mounted on the fixing plate and comprising a plurality of input terminals and a plurality of output terminals; said input terminals of the temperature module are operably coupled to the thermistors to receive the temperature sensed therein; wherein said temperature module is adapted to process the temperature received from the thermistors and generate a signal; said output terminals of the temperature module are operably coupled to the secondary isolating contacts to send the signal generated by the temperature module; an electronic trip unit mounted on the moving compartment and operably coupled to the secondary isolating contacts to receive the signal generated by the temperature module; wherein the electronic trip unit is adapted to process the signal received therein and generate temperature value; said electronic trip unit comprises: a display unit to display the temperature value generated by the electronic trip unit, and an indicator; wherein the electronic trip unit compares the signal with an pre-set ALARM temperature limit and a TRIPPING temperature limit set for protection of the circuit breakers; said electronic trip unit is adaptively configured to: power the indicator as ALARM when the temperature value sensed by the thermistors reaches the pre-set ALARM temperature limit; trip the circuit breaker when the temperature value sensed by the thermistors goes beyond the TRIPPING temperature limit to isolate said circuit breaker.

[0016] In a possible implementation of the assembly for sensing and monitoring temperature of a circuit breaker according to the first aspect, an external relay, bulb or hooter operably coupled to the indicator of the electronic trip unit.

[0017] In another possible implementation of the assembly for sensing and monitoring temperature of a circuit breaker according to the first aspect, the electronic trip unit comprises a flux shift device to trip the circuit breaker.

[0018] In yet another possible implementation of the assembly for sensing and monitoring temperature of a circuit breaker according to the first aspect, the ALARM and TRIPPING temperature limit for protection is set by a user.

[0019] According to a second aspect of the present invention, there is provided a method for sensing and monitoring temperature of a circuit breaker. The method comprising the steps of: sensing, by a thermistor, temperature of external terminal connection of the circuit breaker; receiving, by a temperature module, the temperature sensed by the thermistor on the external terminal connection; processing, by the temperature module, the temperature sensed on the external terminal connection to generate a signal; receiving, by an electronic trip unit, the signal generated by the temperature module; processing, by the electronic trip unit, the signal generated by the temperature module; and displaying, by the electronic trip unit, real-time continuous temperature value of the circuit breaker.

[0020] In a possible implementation of the method according to the second aspect, output terminal of the temperature module is operably coupled to secondary isolating contacts of the circuit breaker to send the signal generated by the temperature module.

[0021] In another possible implementation of the method according to the second aspect, the electronic trip unit is operably coupled to the secondary isolating contacts of the circuit breaker to receive the signal generated by the temperature module.

[0022] In yet another possible implementation of the method according to the second aspect, the electronic trip unit is adaptively configured to power an indicator as ALARM when the temperature value sensed by the thermistors reaches the pre-set ALARM temperature limit; trip the circuit breaker when the temperature value sensed by the thermistors goes beyond the TRIPPING temperature limit to isolate said circuit breaker.

[0023] 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

[0024] 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:

[0025] Figure 1 illustrates the temperature module mounting arrangement on an air circuit breaker according to a first embodiment of the present invention.

[0026] Figure 2 illustrates the air circuit breaker with it moving compartment completely inserted therein according to an implementation of the first embodiment of the present invention.

[0027] Figure 3 illustrates flow-chart of a method for real time sensing and monitoring of switchgears according to a second embodiment of the present invention.

[0028] 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

[0029] 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.

[0030] 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.

[0031] 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.

[0032] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The present invention lies in providing an assembly for sensing and monitoring temperature of circuit breakers and a method thereof for real time continuous temperature monitoring on external terminal connection. An end user measures the temperature on external conductor connection and verifies the same with the continuous displayed temperature value on an electronic trip unit display.

[0037] In the present invention, an arrangement that consists of thermistors for temperature sensing on external terminal connection, monitoring module, its wiring and integration with electronic trip unit is disclosed. The thermistors sense the temperature of the functional external connection i.e. fixed compartment terminal of air circuit breaker. The output of this thermistor is input to the temperature monitoring unit which is an electronic circuit. This input is processed in the electronic unit and this unit sends an output to secondary control wring that is connected to secondary isolating contacts of fixed compartment of air circuit breaker. The secondary isolating contact of fixed compartment is connected to secondary isolating contact of moving compartment which in turn is connected to electronic trip unit. The electronic trip unit based on the inputs from temperature module displays the temperature on the display. The temperature module is mounted with the help of fixing plate on the fixed compartment of air circuit breaker.

[0038] Figure 1 illustrates the temperature module mounting arrangement on an air circuit breaker. Thermistors (10) for sensing temperature are mounted on external terminal connection (1) of fix compartment (3) of air circuit breaker. The sensed temperature output from the thermistors (10) is given to input terminals (6) of the temperature module (2). The temperature module (2) is mounted on the fixing plate (5) which in turn in mounted on secondary isolation contact cross piece (11) of the fix compartment (3) of the air circuit breaker. The temperature input is processed by the temperature module (2) and provides suitable signal to output terminals (7) of the temperature module (2). The output terminals (7) of temperature module (2) are connected to secondary isolating contacts (4) of fix compartment of air circuit breaker. The signal from secondary isolating contacts (4) on fixed compartment (3) is transferred to an electronic trip unit (8) which is fixed on the moving compartment (9) of the air circuit breaker through secondary isolating contacts on moving compartment. This input to the electronic trip unit (8) is further processed and the temperature values are displayed on the screen of the electronic trip unit (8).

[0039] Figure 2 illustrates the complete air circuit breaker with its moving compartment (9) completely inserted in the fixed compartment (3) along with electronic trip unit (8).

[0040] According to a first embodiment of the present invention, an assembly for sensing and monitoring temperature of a circuit breaker is disclosed. The circuit breaker comprising a moving compartment (9) housed within a fixed compartment (3), and an electronic trip unit (8), said fix compartment (3) comprising: an external terminal connection (1) comprising a plurality of thermistors (10) for sensing temperature mounted therein, a secondary isolation contact cross piece (11) comprising a fixing plate (5); and a plurality of secondary isolating contacts (4). The assembly is characterized by: a temperature module (2) mounted on the fixing plate (5) and comprising a plurality of input terminals (6) and a plurality of output terminals (7); said input terminals (6) of the temperature module (2) are operably coupled to the thermistors (10) to receive the temperature sensed therein; wherein said temperature module (2) is adapted to process the temperature received from the thermistors and generate a signal; said output terminals (7) of the temperature module (2) are operably coupled to the secondary isolating contacts (4) to send the signal generated by the temperature module (2); an electronic trip unit (8) mounted on the moving compartment (9) and operably coupled to the secondary isolating contacts (4) to receive the signal generated by the temperature module (2); wherein the electronic trip unit (8) is adapted to process the signal received therein and generate temperature value; said electronic trip unit (8) comprises: a display unit to display the temperature value generated by the electronic trip unit (8), and an indicator (12); wherein the electronic trip unit (8) compares the signal with an pre-set ALARM temperature limit and a TRIPPING temperature limit set for protection of the circuit breakers; said electronic trip unit (8) is adaptively configured to: power the indicator (12) as ALARM when the temperature value sensed by the thermistors reaches the pre-set ALARM temperature limit; trip the circuit breaker when the temperature value sensed by the thermistors goes beyond the TRIPPING temperature limit to isolate said circuit breaker.

[0041] Figure 3 illustrates the working of the temperature module (2) during routine operation of the air circuit breaker. The thermistors (10) are mounted on the external terminal connection (1) of the fix compartment (3) of air circuit breaker. The temperature sensed by the thermistor is given to input terminal (6) of temperature module (2). The temperature module (2) processes this input from the thermistor and gives the processed signal to output terminal (7) of the temperature module (2). This output signal is given as input to the electronic trip unit (8) through secondary isolating contact (4). This input to the electronic trip unit (8) is further processed and the real time temperature values of each phase are displayed on the screen on electronic trip unit (8).

[0042] According to a second embodiment of the present invention, a method for sensing and monitoring temperature of a circuit breaker is disclosed. The method comprising the steps of: sensing (S1), by a thermistor (10), temperature of external terminal connection (1) of the circuit breaker; receiving (S2), by a temperature module (2), the temperature sensed by the thermistor (10) on the external terminal connection (1); processing (S3), by the temperature module (2), the temperature sensed on the external terminal connection (1) to generate a signal; receiving (S4), by an electronic trip unit (8), the signal generated by the temperature module (2); processing (S5), by the electronic trip unit (8), the signal generated by the temperature module (2); and displaying (S6), by the electronic trip unit (8), real-time continuous temperature value of the circuit breaker.

[0043] A user can set temperature limit for alarm and protection in the electronic trip unit based on its load pattern and panel design. The temperature limit set in the electronic unit will be monitored continuously. Whenever the temperature sensed by the thermistors (10) reaches the value for which Alarm is set, electronic trip unit will raise an Alarm by continuously blinking of an indicator (12), this indicator (12) may be an Alarm LED. If any external relay, bulb or hooter is connected to Alarm contacts of the electronic trip unit, same will be provided with suitable indication when the temperature reaches the value for which as alarm is set. When the temperature reaches the Protection value which is more than the Alarm value, the electronic trip issues a command to the air circuit breaker to trip. This will isolate the air circuit breaker for the main system and protect the system against breakdown and permanent damage due to overheating.

[0044] Figure 3 illustrates the working of temperature module (2) during fault or tripping condition of air circuit breaker. The temperature sensed by the thermistors (10) mounted on the external terminal connection (1) of air circuit breaker is given as input to temperature module (2). The temperature module (2) processes this input temperature and gives output signal from output terminals (7) of temperature module (2) to electronic trip unit (8) through secondary isolating contacts (4). The electronic trip unit (8) compares this input signal with the pre-set ALARM temperature limit and TRIPPING temperature limit set for protection. When the temperature sensed reaches the pre-set ALARM temperature limit, the electronic trip unit gives a RED LED blink as indication of ALARM.

[0045] In case an external relay, bulb or hooter is connected to the Alarm contact of the electronic trip unit (8), it will be activated at the time of Alarm. If the temperature value sensed by the thermistors (10) further increases and goes beyond the TRIPPING temperature limit set for protection, the electronic trip unit (8) will give signal to flux shift device. The flux shift device will trip the air circuit breaker and thus isolate the complete system thereby protecting it from overheating and breakdown. The ALARM and TRIPPING temperature limit for protection can be set by the user based on individual requirements and load pattern.

[0046] The present invention discloses that real-time continuous temperature monitoring system of temperature module helps in continuous temperature display on electronic trip unit screen and protection against increasing temperature on external terminal connection of air circuit breaker. This temperature protection protects the air circuit breaker and system of conductors in the panel against overheating and system breakdown as system breakdowns can lead to loss of property and production.

[0047] Some of the non-limiting advantages of the present invention are mentioned hereinbelow:
1. It ensures real-time continuous monitoring of temperature at external terminal connection of switchgear;
2. The ALARM and TRIPPING of switchgear is based on the temperature protection limit set in the electronic trip unit by the user;
3. It allows the user to verify the actual temperature on the external terminal connection of switchgear and temperature displayed on the electronic trip unit of switchgear;
4. It ensures that just one temperature module is required per phase for higher current carrying capacity air circuit breakers that have two conductors in parallel type of construction;
5. It can be fitted to existing installed air circuit breakers on sites with minimal shutdown time; and
6. It provides protection to the switchgear against overheating and breakdown due to high temperature by continuous sensing and monitoring of temperature at external terminal connection of switchgear.

[0048] Although an assembly and method for real-time continuous monitoring of temperature at external terminal connection of switchgear 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 an assembly for sensing and monitoring temperature of circuit breakers and a method thereof.