Description:TECHNICAL FIELD
[0001] The present disclosure relates generally to the technical field of electrical circuit breakers. In particular, it pertains to a residual current circuit breaker with current sensor design and signal processing technology to detect leakage current.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed disclosure, or that any publication specifically or implicitly referenced is prior art.
[0003] Conventionally, a ‘B’ type residual current circuit breaker (RCCB) device intends to provide protection from the shock as well as fire risks due to AC and DC leakage current. With the advent of roof top solar devices, caused both high frequency AC and pure DC components in the earth leakage. The new-age installations are prone to leakage currents that are any combination of supply frequency and pure DC components causing tripping in absence of a sustained residual current above a pre-determined level. This phenomenon is unnecessarily trouble the consumer to get it reset. Hence, it would be advisable to provide a solution to the problem.
[0004] Patent document US9136074B2 discloses a residual current circuit breaker having a core-balance current transformer for detecting AC and DC residual current, in a way such that the AC and DC measurement arrangements are designed to operate simultaneously and in parallel. The signal at the output of the differential amplifier is evaluated via two different paths, first path is a part of the alternating-current measuring arrangement and the second path is part of the direct-current measuring arrangement. This also enables the further processing of the signal by a microprocessor which can further trigger the actuator in case a residual current is detected.
[0005] Patent document EP1260821B1 relates to a to a sensitive differential protection device to AC & DC currents comprising a single toroid contact transformer, an excitation circuit, a processing circuit connected to the secondary winding, and a power supply circuit connected to the excitation circuit and the processing circuit. When a direct current or a DC component of a fault current must also be detected, the protection devices comprise processing circuitry for measuring a shift of the magnetization of the measuring toroid.
[0006] While the referred patent documents provide evaluating leakage current via two different paths or using single toroid, there is a possibility of providing a more efficient solution to the problem.
[0007] There is, therefore, a need to provide a simple and cost-effective solution which can eliminate the abovementioned problem of a conventional residual current circuit breaker, avoid frequent false tripping, and keep abreast of new technology for Type ‘B’ residual current circuit breaker (RCCBs)

OBJECTS OF THE INVENTION
[0008] A general object of the present disclosure is to provide a simple, efficient, and cost-effective solution to the problem of leakage current.
[0009] An object of the present disclosure is to provide a compact mechanism that relates to a novel method of providing earth leakage protection for both AC and DC type leakage current in a switching apparatus.
[0010] Another object of the present disclosure is to provide a residual current circuit breaker that keep abreast with new technology for Type ‘B’ RCCBs.
[0011] Another object of the present disclosure is to provide a current sensor design with specific core material that can detects AC as well as DC leakage current with a single circuit arrangement.
[0012] Another object of the present disclosure is to provide to detect the leakage current with all analog circuitry arrangement enables more reliable and robust design.
[0013] Yet another object of the present disclosure is to provide a unique approach for DC leakage current detection that does not require high order filtering.
SUMMARY
[0014] Aspect of the present disclosure relate generally to the technical field of electrical circuit breakers. In particular, it pertains to a residual current circuit breaker with current sensor design and signal processing technology to detect leakage current.
[0015] In an Aspect, the present disclosure provides a residual circuit breaking device may include a residual current transformer configured with a voltage independent circuit, a voltage dependent circuit, and a tertiary winding wound over the secondary winding of the residual current transformer to detect at least the AC leakage current, such that the voltage independent circuit provide protection from at least AC leakage current when supply is not available, the voltage dependent circuit ensures the protection from AC leakage and DC leakage if the supply is available and in both cases the supply circuit is cut off through a trip unit, and a signal processing unit electrically coupled to a power supply unit and operatively coupled to the voltage dependent unit, where the signal processing unit including a demodulator unit to bring out the leakage current from the incoming signal and generate the trip signal based on incoming leakage current and its frequency.
[0016] In an aspect, the residual current transformer is a current sensor including primary, secondary and tertiary windings, and the residual current transformer detects both AC and DC leakage current with single toroidal core which has secondary excitation winding to detect DC leakage current.
[0017] In an aspect, the residual current transformer with defined magnetic properties and designed number of turns in each winding is configured to sense the leakage currents.
[0018] In an aspect, both winding pattern and number of winding is designed in such a way that they should not affect the each other circuit performance which may be the case due to change in magnetization of the core.
[0019] In an aspect, the tertiary winding consists of higher number of winding turns to affect the saturation level of the core and change the response for voltage dependent circuit.
[0020] In an aspect, the signal processing unit discriminate between trip and no trip level to generate trip signal.
[0021] In an aspect, a demodulator unit carries out dual demodulation where a first demodulation is frequency demodulation which detects the change in frequency scale of the signal due to leakage, and a second demodulation is amplitude demodulation that converts the change in frequency to its relative amplitude to detect the change in terms of voltage.
[0022] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0023] 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.
[0024] FIG. 1 illustrates an advanced circuitry for AC and DC leakage current detection using a toroidal core, in accordance with embodiments of the present disclosure.
[0025] FIG. 2 illustrates an exemplary block diagram for voltage dependent AC & DC leakage current detection system, in accordance with embodiments of the present disclosure.
[0026] FIG. 3 illustrates a detailed signal processing block diagram, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION
[0027] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail 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.
[0028] Embodiments explained herein relate generally to the technical field of electrical circuit breakers. In particular, it pertains to a residual current circuit breaker with current sensor design and signal processing technology to detect leakage current.
[0029] In an embodiment, disclosure is a residual circuit breaking device may include a residual current transformer configured with and a signal processing unit, a voltage independent circuit, a voltage dependent circuit, and a tertiary winding wound over the secondary winding to detect at least the AC leakage current, such that the voltage independent circuit provide protection from at least AC leakage current when supply is not available, the voltage dependent circuit ensures the protection from AC leakage and DC leakage if the supply is available and in both cases the supply circuit is cut off through a trip unit. The signal processing unit includes a demodulator unit to bring out the leakage current from the incoming signal and generate the trip signal based on incoming leakage current and its frequency.
[0030] Referring to FIG. 1, where an advanced circuitry for AC and DC leakage current detection using a toroidal core 114 is shown. The disclosed device 100 ensures the high frequency AC current and smooth as well as pulsating DC leakage current detection.
[0031] In an embodiment, a residual current transformer 102 configured with a voltage independent circuit 104, a voltage dependent circuit 106, a tertiary winding 108 wound over the secondary winding 110, and a trip unit 112 is shown. The residual current transformer 102 is to detect at least the AC leakage current. The voltage independent circuit 104 provide protection from at least AC leakage current when supply is not available, the voltage dependent circuit 106 ensures the protection from AC leakage and DC leakage if the supply is available and in both cases the supply circuit is cut off through a trip unit 112.
[0032] In an embodiment, the advancement of technology and versatility of load requires highly sensitive leakage current sensors of wide range in current level few milli Amp to Amp. In case of a power generating unit like a solar panel where DC drives or UPS systems, conventional AC currents sensors cannot be used due to smooth DC residual currents. Also, in case of a frequency inverter, for example, used for motor speed control, supplied between phase and neutral, a composite residual current including the power frequency, the motor frequency and the chopper clock frequency of the frequency inverter may occur in addition to alternating or pulsating DC residual currents.
[0033] In an embodiment, a single toroidal core 114 is used that has a secondary winding 110 to detect DC leakage current. Secondary excitation signal is designed in such a way that it pushes the core 114 in near saturation by which DC residual current can be detected and a tertiary winding 108 is used on the core 114 which detects AC leakage current independent of its own or Auxiliary supply availability.
[0034] In an embodiment, the tertiary winding 108 is wound over the secondary winding 110 where the number of turns in the tertiary winding 108 is so calculated to get the output at very low leakage current up to 30mA. As the higher number of tertiary winding 108 turns can affect the saturation level of the core 114 and change the response for voltage dependent circuit 106, hence, the design of both voltage dependent circuit 106 and voltage independent circuit 104 winding is done accordingly.
[0035] In an embodiment, the residual current transformer 102 material with high magnetic permeability makes it possible to detect the DC leakage current. DC leakage current as low as 30mA can change the magnetic material properties which further reflects the change in output of the residual current transformer 102. The leakage current detected from the incoming signal and generated trip signal based on incoming leakage current and its frequency activate trip unit 112 to cut off supply of an electrical consumer in the circuit that stops fire that may likely to occur as well as shock to an individual, in case of working with the circuit due to leakage current.
[0036] In an embodiment, a high frequency signal 116 suitable to operate the residual current transformer 102 in non- linear zone is injected from the one terminal of secondary winding 110. The other terminal connected to suitable burden so that core 114 can be operated in desirable mode. In case of leakage signal, it is fed to a signal processing unit to further process the signal and to generate trip or no-trip signal for trip unit 112 to trip the incoming supply or not.
[0037] FIG. 2 illustrates the functional block diagram 200 for AC and DC leakage current detection for the device 100 where trip signal is generated in case a leakage current is present an to trip supply of the circuit. The block diagram 200 shows a residual current transformer 102 working also as a current sensor with defined magnetic properties and designed number of turns to sense the leakage current. A high frequency carrier signal 116 is generated by its own supply or auxiliary supply which is connected to the secondary winding 110 of the residual current transformer 102. Carrier signal 116 is designed in such a way that it keeps the core 114 at or near the nonlinear zone which changes in the presence of leakage current with low as well as high frequency. Further the voltage dependent circuit 106 detects the AC & DC leakage current with available supply signal and voltage independent circuit 104 detects at least the AC leakage signal in the situations when supply is not available.
[0038] In an embodiment, voltage independent circuit 104 is connected to the trip unit 112 when supply is not available and gets cut off otherwise. The disclosed device 100 ensures complete protection from leakage in case of supply failure. If the supply is available, voltage dependent circuit 106 ensures the protection from Both AC & DC leakage otherwise the protection from at least AC leakage current is ensured from voltage independent circuit 104.
[0039] In an embodiment, the high frequency signal 116 which functions as a carrier wave suitable to operate the residual current transformer 102 in non- linear zone is injected from the one terminal of secondary winding 110. The other terminal connected to suitable load so that core 114 can be operated in desirable mode. In case of leakage signal, leakage current gets mixed in a modulating unit 202 with the high frequency carrier signal 116 and generates a modulated output signal which is fed to the signal processing unit 204. Signal processing unit 204 further process the signal with reference to the incoming leakage current and its frequency to produce trip or no-trip signal for trip unit 112 to trip the incoming supply or not.
[0040] FIG. 3 illustrates a detailed signal processing unit 204 diagram that includes a high frequency noise elimination unit 304 where the mixed frequency signal 302 is further demodulated by the demodulating unit 206 to bring out the leakage signal. The demodulation is done in two stages, one being the frequency demodulation which detects the change in frequency scale of the signal 302 due to leakage, and other is amplitude demodulation which converts the change in frequency to its relative amplitude to detect the change in terms of voltage.
[0041] In an embodiment, the signal provided by the high frequency noise elimination unit 304 is applied as input to a unique sensitivity detector unit 306 which is a pulse splitter that increases the sensitivity of detection. As the filters configured in the high frequency noise elimination unit 304 attenuates the signal and reduce the signal to noise ratio, the sensitivity detector unit 306 enhances the signal to noise ratio and gives the better detection with increased buffer to discriminate between trip and no trip level.
[0042] Thus, the present disclosure provides a simple, efficient, and cost-effective solution as a compact mechanism that ensure earth leakage protection for both AC and DC type leakage current to solve the stated problem of leakage current. Hence, protection against probable electric shock to an individual working with the circuit or may ignite a fire through the circuit is provided.
[0043] 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
[0044] The present disclosure provides a simple, efficient, and cost-effective solution to the problem of leakage current.
[0045] The present disclosure provides a compact mechanism that relates to a novel method of providing earth leakage protection for both AC and DC type leakage current in a switching apparatus.
[0046] The present disclosure provides a residual current circuit breaker that keep abreast with new technology for Type ‘B’ RCCBs.
[0047] The present disclosure provides a current sensor design with specific core material that can detects AC as well as DC leakage current with a single circuit arrangement.
[0048] The present disclosure provides to detect the leakage current with all analog circuitry arrangement enables more reliable and robust design.
[0049] The present disclosure provides a unique approach for DC leakage current detection that does not require high order filtering.

, Claims:1. A residual circuit breaking device (100), the device (100) comprising:
a residual current transformer (102) configured with a voltage independent circuit (104), a voltage dependent circuit (106), and a tertiary winding (108) wound over the secondary winding (110) of the residual current transformer (102) to detect at least the AC leakage current;
wherein the voltage independent circuit (104) provide protection from at least AC leakage current when supply is not available, wherein the voltage dependent circuit (106) ensures the protection from AC leakage and DC leakage if the supply is available and in both cases the supply circuit is cut off through a trip unit (112); and
a signal processing unit (204) electrically coupled to input power supply and operatively coupled to the voltage dependent unit (106), wherein the signal processing unit (204) comprising a demodulating unit (206) to bring out the leakage current from the incoming signal and generate the trip signal to the trip unit (112) based on incoming leakage current and its frequency.
2. The device as claimed in claim in claim 1, wherein the residual current transformer (102) is a current sensor comprising the tertiary windings (108).
3. The device as claimed in claim in claim 2, wherein the residual current transformer (102) detects both AC and DC leakage current with single toroidal core (114) which has secondary excitation winding to detect DC leakage current.
4. The device as claimed in claim in claim 2, wherein the residual current transformer (102) with defined magnetic properties and designed number of turns in each winding is configured to sense the leakage currents.
5. The device as claimed in claim in claim 2, wherein both winding pattern and number of winding is designed in such a way that they should not affect the each other circuit performance which may be the case due to change in magnetization of the core (114).
6. The device as claimed in claim in claim 2, wherein the tertiary winding (108) consists higher number of winding turns to affect the saturation level of the core (114) and change the response for voltage dependent circuit (106).
7. The device as claimed in claim in claim 1, wherein the signal processing unit (204) discriminate between trip and no trip level to generate trip signal.
8. The device as claimed in claim in claim 1, wherein a demodulator unit (202) carries out dual demodulation.
9. The device as claimed in claim in claim 8, wherein a first demodulation is frequency demodulation which detects the change in frequency scale of the signal due to leakage.
10. The device as claimed in claim in claim 8, wherein a second demodulation is amplitude demodulation that converts the change in frequency to its relative amplitude to detect the change in terms of voltage.