Description:
FIELD OF THE INVENTION:

[0001] This invention relates to Solid State Circuit Breaker (SSCB). More particularly the present invention is related to SSCB that is achieving minimal voltage overshoot without using Metal Oxide Varistor (MOV).

BACKGROUND OF THE INVENTION & PRIOR ART:

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Although conventional electro-mechanical circuit breakers have a proven record as effective and reliable devices for circuit protection, emerging power distribution technologies and architectures, such as dc microgrids, require improved interruption performance characteristics (e.g., faster switching speed). The need for faster switching operation, in combination with the latest developments of advanced power semiconductor technologies, has stimulated an increase in the research and development in the area of Solid State Circuit Breakers (SSCB).

[0004] The existing electro-mechanical protection solutions have limited capability to protect DC systems due to the very high current magnitude, high rate of rise (di/dt) of fault current, non-availability of current zero and inherently slow response time of mechanical systems. As response time of SSCB is several times shorter than that of conventional breaker, SSCB is preferred for DC transmission (from low voltage to high voltage). Hence, development of SSCB with minimal voltage overshoot is important.

[0005] Solid State Circuit Breakers are power semiconductor-based protection apparatuses, with no moving parts for fault current interruption, renowned for their excellent operational and system level benefits. First and foremost, the response time of semiconductor devices is several orders of magnitude shorter than that of the electro-mechanical devices typical of conventional circuit breakers. Secondly, unlike electromechanical circuit breakers, which rely on contact separation for current interruption, semiconductor devices can interrupt the flow of electrical charges without arcing. Furthermore, because of the absence of moving parts, power semiconductor devices can execute a much higher number of operations. This translates into a greatly increased lifetime for circuit breakers. Lastly, because semiconductor devices have no moving parts, they operate without making any noise.

[0006] There are different types of voltage clamping solutions for SSCB to suppress the voltage rise or transient voltages across the switch during turn off process when fault occurs. The clamping solution can be either linear or non-linear according to the type of voltage clamping component used. A simple linear solution, C type, is by using a snubber capacitor across the power semiconductor. The charging of snubber capacitor slows down the voltage rise rate as well as the peak voltage across the power device. In this process the capacitor absorbs some of the energy stored in system inductance. However, the C type snubber may oscillate with system inductance during the turnoff event as well as it can cause high discharge current through power semiconductor when the device is turned on. To solve these issues a resistor can be added in series with the capacitor to form RC snubber. The resistor would damp the oscillations and limit the turn-on discharge current into power semiconductor. However, during turnoff, the voltage drop across this resistor is also reflected on power semiconductor.

[0007] This additional drop can increase the peak turn-off voltage requirement of the power semiconductor. These demerits make RC snubber solution quite challenging for solidstate circuit breaker applications. An improved version of RC snubber is a resistorcapacitor-diode (RCD) snubber, where, a diode is added in parallel to the resistor. This combination eliminates the additional drop of voltage across the resistor as well as significantly reduces the voltage oscillations during the turn-off. Another type of clamping solution is by using Metal Oxide Varistor (MOV). The MOVs are made from different materials such as zinc oxide (ZnO) or combination of other oxides. The fundamental operating principle of the MOV is the change of resistance as a function of applied voltage. The change in resistance is negatively proportional to voltage i.e. when zero voltage is applied it has very high resistance and when the applied voltage reaches clamping voltage it has the lowest resistance. In spite of these voltage clamping solutions, still there is a significant voltage with overshoot across the switch and selection of the rating of the switch should be accordingly. The patents, which already have been filed in this field are as follows:

[0008] In the patent US 20030183838A1, a high current, high speed Solid-state DC circuit breaker is built based on the ETO thyristor technology. The ETO-based DC circuit breaker Shortens the turn-off time from milliseconds to microseconds, providing fast protection for critical loads. The ETO thyristor has an anode, a cathode and first, Second and third gate electrodes. The anode is connectable to a Source of DC current, and the cathode is connectable to a load. A Solid-State trip circuit is connected to the first, Second and third gate electrodes for controlling interruption of DC current to the load by turning off said ETO thyristor.

[0009] In the patent US-9543751-B2, a solid-state circuit breaker for a DC power system which may operate unidirectional and bidirectional and does not require an external power supply to provide current interruption protection during an event of a short circuit fault has been invented.

[0010] In the patent US3792289A, a solid state circuit breaker has been invented for controlling alternating electric current by placing an impedance element in series between the source and the load and sensing the voltage developing across the element with a trigger circuit where the output of the trigger circuit is coupled to a solid state latching device and also coupled in series with the current source whereby AC current in excess of a pre-selected amount causes the trigger to actuate the latch to interrupt the current flow from the source.

[0011] In the patent US10811867, a hybrid air-gap/solid-state device protection device (PD) for use in an electrical power distribution system includes an air-gap disconnect unit connected in series with a solid-state device, a sense and drive circuit, and a microcontroller has been invented. Upon the sense and drive circuit detecting an impending fault or exceedingly high and unacceptable overvoltage condition in the PD's load circuit, the sense and drive circuit generates a gating signal that quickly switches the solid-state device OFF. Meanwhile, the microcontroller generates a disconnect pulse for the air-gap disconnect unit, which responds by forming an air gap in the load circuit. Together, the switched-OFF solid-state device and air gap protect the load and associated load circuit from being damaged. They also serve to electrically and physically isolate the source of the fault or overload condition from the remainder of the electrical power distribution system.

[0012] A novel solid state circuit breaker is thus required for achieving minimal voltage overshoot without using Metal Oxide Varistor (MOV). Hence, the present invention has been proposed.

OBJECTS OF THE INVENTION:

[0013] An object of the present invention is to develop SSCB, a replacement to conventional electro-mechanical circuit breaker.

[0014] Another object of the present invention is to design and develop a SSCB without using MOV.

[0015] Another object of the invention is to design a SSCB which is achieving minimal voltage overshoot across the switch.

[0016] Yet another object of the invention is to reduce the overall cost of the SSCB and the voltage rating of the switch of SSCB.

[0017] Yet Another object of the present invention is to dissipate the energy stored due to fault in the circuit as quickly as possible.

[0018] Another object of the invention is to design the SSCB for any voltage rating.

[0019] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:

[0020] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0021] According to the present invention, there is provided a Solid State Circuit Breaker (SSCB) which can achieve minimal voltage overshoot without using Metal Oxide Varistor (MOV). The SSCB having two switches (S1, S2) in series to reduce the voltage overshoot across the switches comprising of two diodes, two capacitors, two voltage equalizing resistors, two damping resistors, one current transformer (CT) and one energy dissipating resistor (RED). When all the switches are turned on during the fault, the fault current flows through the switches S1 and S2. When the switch S1 is turned off, the fault current flows through diode D1 and switch S2. When both the switches S1 and S2 are turned off, the fault current flows through the diode D2 and energy dissipating resistor RED.

[0022] In an aspect, according to the present invention, the energy dissipating resistor (RED) is meant for dissipating energy of fault current after all the switches are turned off during fault. This value must be less for less voltage overshoot but high for fast energy dissipation and hence an optimal value must be chosen as per specification of turn off time and voltage overshoot across the switch.
.
[0023] In an aspect, the voltage equalizing resistors is used for equalizing the voltages across the switches in the steady state. The voltage equalizing resistor value must be high for low power loss during the time period between “all switches are tuned off” and “fault is cleared”. At the same time, its value must be low for equalizing voltages across the switches with less voltage overshoot. Hence, the optimal value of voltage equalizing resistors must be chosen as per design requirement.

[0024] In an aspect, the damping resistors is provided in series with each capacitor of voltage divider circuit to damp the current oscillations during turn on time of the system. This resistance value must be high enough to damp the DC source current oscillations. At the same time, the value must be low in order to reduce the voltage overshoot across the switches. Hence, the optimal value of damping resistor must be chosen as per design requirement.

[0025] In an aspect, the current transformer (CT) is connected in series to switches along one of the equalizing resistors detects whether the fault is persisting or not. After the occurrence of fault and switches are open, switches shall be closed again only if the CT detects current flow less than the fault current flow and in the order of rated current.

[0026] Further, the SSCB can be designed for any voltage rating by connecting more switches in series. In general, the SSCB can have ‘n’ switches in series with ‘n’ diodes, ‘n’ capacitors and ‘n’ voltage equalizing resistors, ‘n’ damping resistors, one CT and one energy dissipating resistor, where ‘n’ is greater than or equal to 2.

[0027] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0028] 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.

[0029] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:

[0030] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

[0031] Figure 1 shows: A conventional SSCB with ‘n’ switches and MOVs in series.

[0032] Figure 2 illustrates the invented SSCB with two switches in series and without MOV.

[0033] Figure 3 illustrates the invented SSCB with three switches in series and without MOV.

[0034] Figure 4 illustrates the invented SSCB with ‘n’ switches in series and without MOV.

[0035] The figures depict embodiments of the present subject matter for the purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein. Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0036] A few aspects of the present disclosure are explained in detail below with reference to the various figures. Example implementations are described to illustrate the disclosed subject matter, not to limit its scope, which is defined by the claims. The detailed description is described with reference to the accompanying figures. Those of ordinary skill in the art will recognize a number of equivalent variations of the various features provided in the description that follows.

[0037] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0038] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0039] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0040] Various embodiments are further described herein with reference to the accompanying figures. It should be noted that the description and figures relate to exemplary embodiments and should not be construed as a limitation to the subject matter of the present disclosure. It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the subject matter of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the subject matter of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof. Yet further, for the sake of brevity, operation or working principles pertaining to the technical material that is known in the technical field of the present disclosure have not been described in detail so as not to unnecessarily obscure the present disclosure.

[0041] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.

[0042] The present subject matter discloses a Solid State Circuit Breaker (SSCB) (200) with two switches in series consists of two diodes, two capacitors, two voltage equalizing resistors, two damping resistors, one CT and one energy dissipating resistor.

[0043] FIG. 1 illustrates a conventional SSCB. The conventional SSCB has ‘n’ switches in series with ‘n’ resistors, ‘n’ capaciotors, ‘n’ diodes and ‘n’ MOVs. Each switch has resistor-capacitor-diode (RCD) snubber and MOV connected in parallel. Though the RCD snubber, where a diode is added in parallel to the resistor, supresses the voltage surge during the turn-off of swtich, MOV is still required to supress the voltage surge to the greater extent. Thus, the combination of RCD snubber and MOV for reducing the voltage surge during fault current interruption is quite common in conventional SSCB. In the present invention, the SSCB has been proposed without using MOV. The invented SSCB without MOV can still reduce the voltage surge during fault current interruption to the maximum extent.

[0044] FIG. 2 illustrates the invented SSCB (200) with two switches in series and without MOV. The SSCB with two switches (S1, S2) in series consists of two diodes (D1, D2), two capacitors (C1, C2), two voltage equalizing resistors (Re1, Re2), two damping resistors (Rd1, Rd2), one current transformer (CT) and one energy dissipating resistor (RED). When all the switches are turned on during the fault, the fault current flows through the switches S1 and S2. When the switch S1 is turned off, the fault current flows through diode D1 and switch S2. When both the switches S1 and S2 are turned off, the fault current flows through the diode D2 and energy dissipating resistor (RED). The invented SSCB does not use any MOV to reduce the voltage overshoot unlike conventional SSCBs. Though the invented SSCB cannot avoid voltage overshoot completely, the voltage overshoot is minimal. The rise of voltage across the switches in the present invention depends mainly on damping, energy dissipating and voltage equalizing resistors used. These resistors in SSCB have their unique role and hence the value of each resistor has to be chosen in such a manner that the transient voltage levels are less across the switches while interrupting fault current. Based on the level of current flow through the CT placed along one of the equalizing resistors, CT is useful in detecting whether the fault is removed.

[0045] When it comes to voltage overshoot, it is happened because of three elements: damping resistor, energy dissipating resistor and voltage equalizing resistor. Firstly, the voltage overshoot occurs when switch S1 is turned off during the fault because of the voltage drop across the damping resistor, which reflects across the switch. Secondly, the voltage overshoot across the switches occur when all the switches S1 and S2 are turned off because of the voltage drop across the energy dissipating resistor, which reflect across the switches. Thirdly, the voltage overshoot occurs across the switches because of voltage equalizing resistors and the voltage equalization takes time if the value of equalizing resistor is high.

[0046] The role of the damping resistor is to damp the current oscillations during turn on time of the system. The higher the value of damping resistor the lower will be the current oscillations. But the higher value of damping resistor leads to voltage overshoot across the switch when it is turned off. Hence, the optimal value of resistor is to be chosen such that both current oscillations and voltage overshoot shall be less.

[0047] The role of energy dissipating resistor is to dissipate the energy stored in the fault current quickly across it. The higher the value of energy dissipating resistor, the faster will be the fault current becoming zero. But the higher value of energy dissipating resistor leads to voltage overshoot across the switches when all the switches are turned off and the fault current still exists. Hence, the optimal value of resistor is to be chosen such that both energy dissipation will be fast and voltage overshoot will be less.

[0048] The role of voltage equalizing resistor is to equalize the voltages across the switches in the steady state. The lower the value of the voltage equalizing resistor, the faster will be the equalization of voltages across the switches. But the lower value of equalizing resistors leads to high power losses across the switch when all the switches are turned off and the fault still exists. Hence, the optimal value of resistor is to be chosen such that both power losses will be less and voltage equalization across the switches will be faster.

[0049] The role of Current Transformer (CT), used along with one of the equalizing resistors, is to detect whether the fault is persisting or not. After the occurrence of fault and switches are open, switches will be closed again only if the CT detects the current flow less than the fault current flow and in the order of rated current.

[0050] Moreover, the present SSCB can be designed for any voltage rating by considering more number of elements of the circuit. For example, as shown in Fig. 3, the invented SSCB can be designed with three switches in series. In this case, the number of diodes, capacitors, voltage equalizing resistors, damping resistors required shall be three and the number of energy dissipating resistors and current transformers required would be one.

[0051] Fig. 4 illustrates a general SSCB with ‘n’ switches in series. It require ‘n’ diodes, ‘n’ capacitors, ‘n’ voltage equalizing resistors, ‘n’ damping resistors, one energy dissipating resistor and one current transformer. Here ‘n’ is greater than or equal to 2. The invented SSCB circuit does not contain MOV for suppressing the voltage surges. But at the same time the invented SSCB reduces the over voltage shoot to the maximum extent.

ADVANTAGES OF THE PRESENT INVENTION:

[0052] Additionally, the novel Solid State Circuit Breaker (SSCB) is having the following advantages:

a) Achieved minimal voltage overshoot across the switch,
b) It reduces the voltage rating of the switch.
c) Cost of SSCB is optimized, as SSCB circuit does not contain MOV for suppressing the voltage surges.
d) Continuous reliable operation of SSCB as compared to that of existing SSCB as MOV failure can lead to unreliable operation.

WORKING OF THE INVENTION:

[0053] The present invention provides a SSCB with two switches in series. The SSCB consists of two diodes, two capacitors, two voltage equalizing resistors, two damping resistors, one energy dissipating resistor and one current transformer. When all the switches are turned on during the fault, the fault current flows through the switches S1 and S2. When the switch S1 is turned off, the fault current flows through diode D1 and switch S2. When both the switches S1 and S2 are turned off, the fault current flows through the diode D2 and energy dissipating resistor. The Current Transformer (CT) is used to detect whether the fault is persisting or not. After the occurrence of fault and switches are open, switches shall be closed again only if the CT detects current flow less than the fault current flow and in the order of rated current. The present SSCB provides continuous reliable operation as MOV is not used in present SSCB.

TEST RESULT

[0054] If the invented SSCB is designed for 3.6 kV and 11 kW rating with two IGBT switches in series, then values of circuit elements to be used are as given in below Table-1:

Table-1: Values of Circuit Elements for 3.6 kV SSCB
Parameter Value
IGBT switch 2.1 – 2.3 kV, 3 – 3.2 kA
Diode 3 – 3.2 kA
Capacitor 10 - 12 uF
Equalizing resistors 100 - 120 ohm
Damping resistors 0.02 – 0.06 ohm
Energy dissipating resistor 0.02 – 0.06 ohm

[0055] A number of example embodiments have been described above. Nevertheless, it should be understood that various modifications may be made to the system. For example, suitable results may be achieved if the described techniques are performed in a different manner and situation. Accordingly, other implementations are within the scope of the following claims.

[0056] The above be the only embodiment of the present utility system, but protection domain of the present system is not limited to the one as disclosed above. Any variation, modification and/or replacement of expecting without creative work is within all should being encompassed in protection domain of the present utility system. Therefore, protection domain of the present utility system should be as the criterion with the protection domain that claims were limited.

[0057] The above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0058] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0059] Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0060] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0061] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
, Claims:WE CLAIM:

1. A Solid State Circuit Breaker (SSCB) (200) having two switches (S1, S2) in series to reduce the voltage overshoot across the switches, the SSCB comprising of:
- two diodes (D1, D2);
- two capacitors (C1, C2);
- two voltage equalizing resistors (Re1, Re2);
- two damping resistors (Rd1, Rd2);
- one current transformer (CT); and
- one energy dissipating resistor (RED);
wherein,
in case both the switches are turned on during the fault, the fault current flows through the switches S1 and S2,
in case the switch S1 is turned off, the fault current flows through diode D1 and switch S2, and
in case both the switches S1 and S2 are turned off, the fault current flows through the diode D2 and energy dissipating resistor RED.

2. The SSCB (200) to reduce the voltage overshoot across the switches as claimed in claim 1, wherein the energy dissipating resistor (RED) is for dissipating energy of fault current after all the switches are turned off during fault.

3. The SSCB (200) to reduce the voltage overshoot across the switches as claimed in claim 1, wherein the voltage equalizing resistors (Re1, Re2) is for equalizing the voltages across the switches in the steady state.

4. The SSCB (200) to reduce the voltage overshoot across the switches as claimed in claim 1, wherein the damping resistors (Rd1, Rd2) is provided in series with each capacitor of voltage divider circuit to damp the current oscillations during turn on time of the system.

5. The SSCB (200) to reduce the voltage overshoot across the switches as claimed in claim 1, wherein the current transformer (CT) is connected in series to switches along one of the equalizing resistors (Re1, Re2) and detects whether the fault is persisting or not; and
when the fault is occur and switches are open, the switches closed again only if the CT detects the current flow less than the fault current flow and in the order of rated current.

6. The SSCB (200) to reduce the voltage overshoot across the switches as claimed in claims 1 to 5, can be designed for any voltage rating by connecting more switches in series,
wherein ‘n’ switches in series consists of ‘n’ diodes, ‘n’ capacitors and ‘n’ voltage equalizing resistors, ‘n’ damping resistors, one CT and one energy dissipating resistor, where ‘n’ is greater than or equal to 2.

Dated this 29th Day of March, 2024