Claims:
1. A system for operating a trip coil, the system comprising:
a capacitor bank switching unit configured therewith a capacitor bank;
a trip coil unit that is configured to generate tripping command and provide trip coil output voltage selection; and
a microcontroller that is configured to control capacitor bank switching before tripping condition and provide effective tripping commands to the trip coil and wherein after tripping, the microcontroller is switched to the capacitor bank in previous position;
2. The system as claimed in claim 1, wherein said capacitor bank switching unit is configured to switch and/or arrange capacitors (series or parallel) of the capacitor bank before sending trip command to trip coil so that tripping will occurred more effectively.
3. The system as claimed in claim 1, wherein switching and/or arranging of capacitive bank improves overall voltage level as well as stored energy that increases the effectiveness of tripping mechanism.
4. The system as claimed in claim 1, wherein the system further comprises of a power current transformer and a sensing current transformer for signal conditioning and rectification of input current.
5. The system as claimed in claim 4, wherein output of sensing current transformer passes to signal conditioning unit for metering and monitoring of input current and output of power current transformer passes to power supply unit which is utilized for tripping as well as switching on/off of the microcontroller.
6. The system as claimed in claim 1, wherein the system further comprises of a capacitor bank voltage feedback unit that provides feedback of voltage at output tripping contacts to the microcontroller wherein after tripping, the microcontroller is switched to the capacitor bank in previous position.
7. The system as claimed in claim 1, wherein the system generates 24V DC/12V DC output even at very low VA burden of current transformer.
, Description:
TECHNICAL FIELD
[0001] The present disclosure relates generally to tripping systems for tripping of electrical circuits against fault current conditions. In particular, the present invention relates to a technique of operating a trip coil, especially in case when voltage of input source supply is not sufficient for operating the trip coil.

BACKGROUND
[0002] In medium voltage protection equipments (i.e., RMU panels), during current sensing, a low VA burden protection class current transformer is used. These current transformers are used to operate intelligent relays as well as tripping of circuit breakers. In general, rating of trip coil remains 12V/24V. Intelligent relays should be capable to self-power up at a very less current (approximately 200 mA) and must provide trip coil output of 24 V in case of tripping. However, VA burden of protection current transformers is very low, and hence, it is difficult to energize the relay as well as trip coil at low currents.
[0003] Existing tripping systems primarily use multi terminal current transformer topology for generating sufficient energy at 24V output. But this topology increases voltage drop across primary terminals of the current transformer. This voltage drop creates a hurdle for protection of the current transformer as VA burden is very low.
[0004] Thus there is a need of a trip coil system that generates 24V output with low VA burden and also provides solution of universal selectable trip coil output (24/12V).

OBJECTS OF THE INVENTION
[0005] A general object of the present disclosure is to provide a trip coil system that protects electrical systems from fault currents conditions such as short-circuit and overload conditions.
[0006] Another object of the present disclosure is to provide a trip coil system that operates at very low input current supply.
[0007] Another object of the present disclosure is to provide a trip coil system that provides a selectable output voltage for trip coil.
[0008] Another object of the present disclosure is to provide a trip coil system that generates 24V output at very low VA burden of a current transformer.
[0009] Another object of the present disclosure is to provide a trip coil system that provides intelligent switching of capacitor bank for selectable output voltage.
[0010] Another object of the present disclosure is to provide a trip coil system that generates trip commands such that tripping can occur more effectively.
[0011] Another object of the present disclosure is to provide a trip coil system that is cost effective.

SUMMARY
[0012] The present disclosure relates generally to tripping systems for tripping of electrical circuits against fault current conditions. In particular, the present invention relates to a technique of operating a trip coil, especially in case when voltage of input source supply is not sufficient for operating the trip coil. The present disclosure discloses a system for operating a trip coil wherein the system consists of a capacitor bank switching unit configured therewith a capacitor bank, a trip coil unit that is configured to generate tripping command and provide trip coil output voltage selection, and a microcontroller that is configured to control capacitor bank switching before tripping condition and provide effective tripping commands to the trip coil.
[0013] In an embodiment, the capacitor bank switching unit is configured to switch and/or arrange capacitors (series or parallel) of the capacitor bank before sending trip command to trip coil so that tripping will occurred more effectively. In an aspect, switching and/or arranging of capacitive bank improves overall voltage level as well as stored energy that increases the effectiveness of tripping mechanism.
[0014] In an aspect, the system further consists of a power current transformer and a sensing current transformer for signal conditioning and rectification of input current. Further, output of sensing current transformer passes to signal conditioning unit for metering and monitoring of input current and output of power current transformer passes to power supply unit which is utilized for tripping as well as switching on/off of the microcontroller.
[0015] In an aspect, the system further consists of a capacitor bank voltage feedback unit that provides feedback of voltage at output tripping contacts to the microcontroller.

BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0017] Fig. 1 illustrates an exemplary circuit diagram of a trip coil system in accordance with embodiments of the present disclosure.
[0018] Fig. 2 illustrates an exemplary flow diagram showing various operations of trip coil system in accordance with embodiments of the present disclosure.
[0019] Fig. 3 illustrates an exemplary representation of various systems/modules of trip coil system in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION
[0020] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims
[0021] Embodiments explained herein relate to tripping systems for tripping of electrical circuits against fault current conditions. In particular, the present invention relates to a technique of operating a trip coil, especially in case when current of input source supply is not sufficient for operating the trip coil. The present disclosure discloses a system for operating a trip coil wherein the system consists of a capacitor bank switching unit configured therewith a capacitor bank, a trip coil unit that is configured to generate tripping command and provide trip coil output voltage selection, and a microcontroller that is configured to control capacitor bank switching before tripping condition and provide effective tripping commands to the trip coil.
[0022] In an embodiment, the capacitor bank switching unit is configured to switch and/or arrange capacitors (series or parallel) of the capacitor bank before sending trip command to trip coil so that tripping will occurred more effectively. In an aspect, switching and/or arranging of capacitive bank improves overall voltage level as well as stored energy that increases the effectiveness of tripping mechanism.
[0023] In an aspect, the system further consists of a power current transformer and a sensing current transformer for signal conditioning and rectification of input current. Further, output of sensing current transformer passes to signal conditioning unit for metering and monitoring of input current and output of power current transformer passes to power supply unit which is utilized for tripping as well as switching on/off of the microcontroller.
[0024] In an aspect, the system further consists of a capacitor bank voltage feedback unit that provides feedback of voltage at output tripping contacts to the microcontroller.
[0025] Fig. 1 illustrates an exemplary circuit diagram of a trip coil system wherein an input of 12V DC current is applied at input terminal. A parameter (CNTL_input) is introduced as per pre-charge condition and tripping condition by a microcontroller for controlling capacitive bank switching before tripping.
[0026] In an aspect, when the value of parameter CNTL-input is associated with a value of 1, the tipping circuit is subjected to pre-charge condition. Further, during pre-charge condition, CNTL-1 gate input is associated with LOW input, CNTL-2 gate input is associated with HIGH input, and CNTL-3 gate input is associated with HIGH input. In this case, capacitor C1 and C2 are arranged in parallel and will charge upto 12V DC.
[0027] In an aspect, when the value of parameter CNTL-input is associated with a value of 0, the tipping circuit is subjected to tripping condition. Further, during tripping condition, CNTL_1 gate input is associated with HIGH input, CNTL-2 gate input is associated with LOW input, and CNTL-3 gate input is associated with LOW input. In this case, capacitor C1 and C2 are arranged in series and will discharge at 24V DC. Thus, in this case, tripping occurs when the current at the output terminal reaches 24V DC level.
[0028] In an embodiment, diode D1 and D2 are used for blocking reverse current and RC combination (R2C4, R1C3, R3C5) are used for providing intermediate delay between CNTL-1, CNTL-2, CNTL-3 gate inputs.
[0029] Fig. 2 illustrates an exemplary flow diagram showing various operations of trip coil system wherein when the tripping circuit is powered on, the tripping circuit is subjected to a pre-charge condition 202 during which parameters CNTL_1 gate input is associated with LOW input, CNTL-2 gate input is associated with HIGH input, and CNTL-3 gate input is associated with HIGH input. After execution of pre-charge condition 202, capacitor bank starts charging 204. Thereafter, once the capacitor bank is fully charged 206, microcontroller executes a trip signal 208 to check whether tripping conditions are met 210 that include the parameters CNTL_1 gate input to be associated with a HIGH input, CNTL-2 gate input to be associated with a LOW input, and CNTL-3 gate input to be associated with a LOW input. If the tripping conditions are met accordingly, the microcontroller sends trip command to trip coil 212 and thus, tripping of the switchgear/MCCB occurs.
[0030] In an aspect, whilst capacitor bank is not fully charged 206, tripping signal 208 is not generated by the microcontroller and pre-charge conditions 202 are again checked such that tripping only occurs when the capacitor bank is fully charged 206. Further, whilst tripping conditions 210 are not met, tripping signal 208 is withheld and charging of the capacitor bank 206 is verified along with pre-charge condition 202 parameters such that effective tripping of switchgear/MCCB can occur.
[0031] FIG. 3 illustrates an exemplary representation of various systems/modules of trip coil system wherein for tripping of circuit breaker in medium voltage line (i.e., 11kV to 33kV, 200A), it is required to use power current transformer 302 to convert higher current into 1A/5A output. Further, for signal conditioning and rectification purpose, both power and sensing current transformers 302 and 304 are required for each combination of phase current. In an aspect, output of sensing current transformer 304 passes to signal conditioning unit 308 for metering and monitoring of current and output of power current transformer 302 passes to power supply unit 306 which is utilized for tripping as well as microcontroller power on/off condition. In an aspect, a current transformer can be configured to sense electric field (EF) intensity.
[0032] In an aspect, during tripping condition, microcontroller 310 checks healthiness of voltage at output tripping contacts using the feedback provided from capacitive bank voltage feedback unit 312 and provides tripping command to trip coil. Further, before providing tripping command to trip coil, trip coil unit 316 selects proper capacitive bank and rearrange them (series or parallel) before sending trip command to trip coil so that tripping occurs more effectively.
[0033] In an aspect, capacitive bank switching unit 314 rearranges capacitor bank that further improves overall voltage level as well as stored energy that are more effective during tripping condition.
[0034] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0035] The present disclosure provides a trip coil system that protects electrical systems from fault currents conditions such as short-circuit and overload conditions.
[0036] The present disclosure provides a trip coil system that operates at very low input current supply.
[0037] The present disclosure provides a trip coil system that provides a selectable output voltage for trip coil.
[0038] The present disclosure provides a trip coil system that generates 24V output at very low VA burden of a current transformer.
[0039] The present disclosure provides a trip coil system that provides intelligent switching of capacitor bank for selectable output voltage.
[0040] The present disclosure provides a trip coil system that generates trip commands such that tripping can occur more effectively.
[0041] The present disclosure provides a trip coil system that is cost effective.