SI26151A

SI26151A - Arrangement of protection in the electrical circuit

Info

Publication number: SI26151A
Application number: SI202100016A
Authority: SI
Inventors: Mitja KOPRIVŠEK; Brane Lebar
Original assignee: Eti Elektroelement, D.O.O.
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2022-08-31
Also published as: EP4285452A1; WO2022164393A1

Abstract

Enosmeren (DC) ali pa izmeničen (AC) električni tokokrog je potrebno učinkovito zavarovati tako pred tokovno preobremenitvijo kot tudi pred prenapetostjo, npr. ob udaru strele, pri tem pa je treba zagotoviti tudi zadostno selektivnost tovrstne zaščite, kar pomeni, da bo v primeru prekinitve električnega tokokroga (1) možno nedvoumno ugotoviti, ali je do prekinitve prišlo zaradi pretalitve varovalke (4) v primarnem vodniku (11, 12) električnega tokokroga (1) ali pa zaradi prekinitve stikala (6) vprenapetostnem zaščitnem sklopu (5). Po izumu je predvideno, da premostitveni električni vodnik (13) prenapetostnega zaščitnega sklopa (5), s katerim sta premoščena omenjena primarna električna vodnika (11, 12) med napetostnim virom (2) in bremenom (3), poleg varistorja (50) s pripadajočim termičnim tipalom (50') vključuje tudi tritočkovno stikalo (6) s prekinjevalnim elementom (60), ki je pri vnaprej določenih pogojih s pomočjo prožilnega sredstva (7) odvihtljiv iz svojega prvega izhodiščnega položaja, vkaterem je omenjen premostitven električni vodnik (13) prenapetostnega zaščitnega sklopa (5) sklenjen, v svoj drug končni položaj, v katerem je omenjen premostitven električni vodnik (13) prenapetostnega zaščitnega sklopa (5) prekinjen, pri tem pa je električni tokokrog skozi vzporedno vejo (13') in varovalko (55) vzpostavljiv šele po prekinitvi stikala (6) v premostitvenem električnem vodniku (13), namreč potem, ko se v svoj drug končni položaj zavihten prekinjevalni element (60) stikala (6) premakne vstik z omenjeno vzporedno vejo (13').A direct current (DC) or alternating current (AC) electrical circuit must be effectively protected against both current overload and overvoltage, e.g. in the event of a lightning strike, and sufficient selectivity of this type of protection must also be ensured, which means that in the event of an interruption of the electric circuit (1) it will be possible to determine unequivocally whether the interruption occurred due to the melting of the fuse (4) in the primary conductor (11, 12) of the electric circuit (1) or due to the interruption of the switch (6) to the overvoltage protection assembly (5). According to the invention, it is envisaged that the bridging electrical conductor (13) of the overvoltage protection assembly (5), which bridges the mentioned primary electrical conductors (11, 12) between the voltage source (2) and the load (3), in addition to the varistor (50) with the associated thermal sensors (50') also includes a three-point switch (6) with an interrupting element (60) which, under predetermined conditions, can be swung out of its first starting position, in which the bridging electrical conductor (13) is mentioned, with the help of a trigger (7) of the overvoltage protection assembly (5) is closed, to its other end position, in which the mentioned bridging electrical conductor (13) of the overvoltage protection assembly (5) is interrupted, while the electric circuit through the parallel branch (13') and the fuse (55) can be established only after the switch (6) in the bridging electrical conductor (13) is interrupted, namely after the interrupting element (60) of the switch (6), which is rotated to its other end position, moves into contact with the aforementioned regular branch (13').

Description

Ureditev zaščite v električnem tokokroguArrangement of protection in the electrical circuit

Izum se nanaša na ureditev zaščite v električnem tokokrogu, namreč v električnem tokokrogu, ki obsega vsaj vir enosmerne ali izmenične električne napetosti in vsaj en električni porabnik, obenem pa tudi ustrezno zaščito za zagotavljanje prekinitve električnega tokokroga ob pojavi prekomernega toka ali napetostnega udara, ki vključuje vsaj en varistor. Po mednarodni patentni klasifikaciji so tovrstni izumi s področja elektrotehnike, namreč osnovnih električnih komponent za prenapetostno zaščito enosmernih električnih tokokrogov, namreč za samodejno prekinitev kot odziv na neželene spremembe v tokokrogu glede na običajne delovne razmere, razvrščeni v razred H 01 H3/087.The invention relates to the arrangement of protection in an electrical circuit, namely in an electrical circuit that includes at least a source of direct or alternating electrical voltage and at least one electrical consumer, and at the same time, adequate protection to ensure interruption of the electrical circuit in the event of an excessive current or a voltage shock, which includes at least one varistor. According to the international patent classification, such inventions from the field of electrical engineering, namely basic electrical components for overvoltage protection of DC electrical circuits, namely for automatic interruption in response to unwanted changes in the circuit in relation to normal working conditions, are classified in class H 01 H3/087.

Pri tem je izum osnovan na problemu, kako bodisi enosmeren ali pa izmeničen električni tokokrog učinkovito zavarovati tako pred tokovno preobremenitvijo kot tudi pred prenapetostjo, npr. ob udaru strele, ter se pri tem po eni strani ob zagotavljanju ustrezne odzivnosti zlasti v primeru izpostavljenosti tokokroga enosmerni električni napetosti izogniti generiranju električnega obloka in s tem povezanim negativnim učinkom, po drugi strani pa zagotoviti tudi zadostno selektivnost tovrstne zaščite, kar pomeni, da bo v primeru prekinitve električnega toka možno nedvoumno ugotoviti, ali je do prekinitve prišlo zaradi tokovne ali napetostne preobremenitve.In this case, the invention is based on the problem of how to effectively protect either a direct current or an alternating electrical circuit against both current overload and overvoltage, e.g. in the event of a lightning strike, while on the one hand ensuring adequate responsiveness, especially in the case of exposure of the circuit to DC voltage, avoiding the generation of an electric arc and related negative effects, and on the other hand also ensuring sufficient selectivity of this type of protection, which means that in the event of an interruption of the electric current, it is possible to determine unequivocally whether the interruption occurred due to current or voltage overload.

Tovrsten električni tokokrog običajno obsega vsaj vir enosmerne električne napetosti in vsaj en električni porabnik, ki sta med seboj električno povezana preko električnih vodnikov. Z omenjenim virom in porabnikom je v enem izmed omenjenih vodnikov zaporedno vezana električna varovalka s talilnim elementom, ki je prirejena za prekinitev električnega tokokroga v primeru nadtoka. Razen tega je v omenjenem tokokrogu z omenjenim virom, porabnikom in omenjeno varovalko vzporedno vezan prenapetostni zaščitni sklop, ki ga tvorita vsaj med seboj zaporedno vezana nadaljnja varovalka s talilnim elementom in varistor. V ta namen primeren prenapetostni zaščitni sklop je opisan v WO 2012/026888 Al oz. EP 2 609 600 BI.This type of electrical circuit usually comprises at least a source of DC electrical voltage and at least one electrical consumer, which are electrically connected to each other via electrical conductors. An electric fuse with a melting element is connected in series with the mentioned source and the consumer in one of the mentioned conductors, which is designed to interrupt the electric circuit in the event of an overcurrent. Apart from that, in the said circuit with the said source, the consumer and the said fuse, there is an overvoltage protection assembly connected in parallel, which is formed by at least a further fuse with a fusing element and a varistor connected in series with each other. A suitable overvoltage protection assembly for this purpose is described in WO 2012/026888 Al or EP 2 609 600 BI.

Tovrsten prenapetostni zaščitni sklop, strokovnjakom znan kot varistorska varovalka, predstavlja kombinacijo klasične varovalke s talilnim vložkom in varistorja, ki sta vsak zase cevasto zasnovana in vstavljena drug v drugem. Omenjena varovalka s talilnim vložkom sestoji iz električno neprevodnega cevastega okrova, ki je na konceh zaprt z električno prevodnima pokrovoma, ki sta s tem v funkciji kontaktov za prevajanje električnega toka skozi varovalko. Varistor sestoji iz cevastega okrova, ki sestoji iz materiala, katerega električna prevodnost je odvisna od električne napetosti in se poveča, če napetost preseže vnaprej določeno vrednost. Na notranji in zunanji površini omenjenega okrova varistorja sta na voljo med seboj ločeni prevleki iz električno prevodnega materiala, ki predstavljata elektrodi varistorja. Talilni element varovalke je po eni strani električno povezan z enim izmed električno prevodnih pokrovov varovalke in po drugi strani prispajkan na eno izmed elektrod varistorja, preostala elektroda varistorja pa je električno povezana s preostalim pokrovom varovalke, tako da je skozi varistor in varovalko vzpostavljen električni tokokrog, v katerem sta varovalka in varistor zaporedno vezana. V primeru napetostne preobremenitve se zaradi povečane napetosti poveča prevodnost varistorja, preko katerega se v takem primeru električni naboj odvede v zemljo. V primeru nadtoka se tudi v primeru poškodovanega ali že vsaj deloma okvarjenega varistorja prevodnost varistorja poveča v vsakem primeru, četudi ne pride do napetostne preobremenitve. Glede na jakost toka je možno računati z različnimi situacijami. V primeru, če skozi varistor steče šibek tok velikostnega reda nekaj mA do približno 1 A, se okrov varistorja začne pregrevati, spajka med varistorjem in talilnim elementom se stali, s tem pa se prekine stik med elektrodo varistorja in talilnim elementom varovalke. V primeru, če skozi varistor steče tok srednje jakosti velikostnega reda približno 1A do nekaj 10A, se na oslabelem mestu talilnega elementa zaradi prisotnosti spajke pojavi tkzv. M-efekt, ki izkorišča toploto, dovedeno z oslabljenega mesta talilnega elementa in od pregretega varistorja, temu ustrezno pa se potem proces izklopa izvrši znatno hitreje kot bi se sicer brez pregretega varistorja. V tretji situaciji, kadar skozi varistor začne teči tok velikostnega reda od nekaj 100 A do nekaj 1000 A, sam varistor ne predstavlja velike upornosti, zato pa talilni element deluje v čistem kratkem stiku, tako daje čas taljenja celotnega preseka talilnega elementa v kratkostičnem delu dokaj kratek in znaša nekaj ms. Prekinitev talilnega elementa, še zlasti, ker je ta obdan s sipkim materialom, zlasti kremenčevim peskom, v izmeničnih tokokrogih lahko predstavlja dovolj zanesljiv način prekinitve tokokroga. Zlasti v visokonapetostnih enosmernih električnih tokokrogih pa je tendenca pojavljanja in gorenja obloka med prekinjenima deloma izjemno visoka, pri čemer pa se med gorenjem obloka sproščajo tudi plini, kar lahko privede do poškodb okrova varovalke ali celo do eksplozije. Še celo po tistem pa lahko oblok še naprej gori, in sicer v takem primeru celo v navzven popolnoma nezaščitenem okolju.This type of overvoltage protection assembly, known to experts as a varistor fuse, represents a combination of a classic fuse with a fusible link and a varistor, each of which is tubular in design and inserted into the other. The mentioned fuse with a fusible link consists of an electrically non-conductive tubular casing, which is closed at the ends with electrically conductive covers, which are thus in the function of contacts for conducting electric current through the fuse. A varistor consists of a tubular casing consisting of a material whose electrical conductivity depends on the electrical voltage and increases if the voltage exceeds a predetermined value. On the inner and outer surfaces of the aforementioned varistor casing, there are separate coatings made of electrically conductive material, which represent the electrodes of the varistor. The fusible element of the fuse is on the one hand electrically connected to one of the electrically conductive covers of the fuse and on the other hand soldered to one of the electrodes of the varistor, and the remaining electrode of the varistor is electrically connected to the remaining cover of the fuse, so that an electric circuit is established through the varistor and the fuse, in which the fuse and varistor are connected in series. In the event of a voltage overload, due to the increased voltage, the conductivity of the varistor increases, through which, in such a case, the electrical charge is led to the ground. In the event of an overcurrent, even in the case of a damaged or at least partially defective varistor, the conductivity of the varistor increases in any case, even if there is no voltage overload. Depending on the strength of the current, it is possible to calculate with different situations. If a weak current of the order of a few mA to about 1 A flows through the varistor, the varistor casing begins to overheat, the solder between the varistor and the fuse element melts, and thus the contact between the varistor electrode and the fuse fuse element is broken. If a medium-strength current of the order of about 1A to a few 10A flows through the varistor, a so-called tkzv occurs at the weakened point of the melting element due to the presence of solder. M-effect, which utilizes the heat supplied from the weakened point of the melting element and from the overheated varistor, and accordingly the shutdown process is carried out much faster than it would otherwise be without the overheated varistor. In the third situation, when a current of the order of magnitude from a few 100 A to a few 1000 A begins to flow through the varistor, the varistor itself does not represent a large resistance, and therefore the fusing element works in a pure short circuit, thus giving the melting time of the entire cross section of the fusing element in the short circuit part quite short and amounts to a few ms. Interruption of the melting element, especially because it is surrounded by loose material, especially quartz sand, in alternating circuits can represent a sufficiently reliable way of interrupting the circuit. Especially in high-voltage DC electrical circuits, the tendency of arcing and burning between interrupted parts is extremely high, and gases are also released during the arcing, which can lead to damage to the fuse cover or even to an explosion. Even after that, the arc can continue to burn, in such a case even in a totally unprotected environment.

V stanju tehnike je sicer znano, da je tudi v enosmernem električnem tokokrogu, obsegajočem vir električne energije in vsaj en električni porabnik, za prekinitev v primeru kratkega stika ali nadtoka pa tudi klasično električno varovalko s talilnim elementom, in sicer primarno varovalko, ki je v omenjenem tokokrogu vezana zaporedno z omenjenim bremenom, prenapetostno zaščito tovrstnega tokokroga možno zagotoviti v vgradnjo prenapetostnega zaščitnega sklopa, ki pa je v tokokrogu vezan vzporedno z bremenom in omenjeno primarno varovalko.In the state of the art, it is otherwise known that even in a one-way electrical circuit, comprising a source of electrical energy and at least one electrical consumer, there is also a classic electrical fuse with a melting element, namely a primary fuse, which is in to the mentioned circuit connected in series with the mentioned load, overvoltage protection of this type of circuit can be ensured by installing an overvoltage protection assembly, which is connected in the circuit in parallel with the load and the mentioned primary fuse.

Naprava za prekinitev električnega tokokroga, ki je opisana v EP 2 208 208 BI, obsega varistor, s katerega se tok v primeru preobremenitve oz. pregrevanja letega preusmeri na vzporedno vezano varovalko. S tem naj bi bilo preprečeno, da bi npr. zaradi pojava obloka prišlo do poškodbe oz. okvare same naprave. Vendar pa v takem primeru električni tok v vsakem primeru teče skozi varistor. Prav tako v omenjenem dokumentu problematika glede zagotavljanja selektivnosti niti ni omenjena, kje šele upoštevana.The device for breaking the electric circuit, which is described in EP 2 208 208 BI, comprises a varistor, from which the current in the event of overload or redirects the overheating of the flight to the parallel-connected fuse. This should prevent, for example, due to the occurrence of an arc, damage or malfunctions of the device itself. However, in such a case, the electric current flows through the varistor in any case. Also, in the aforementioned document, the issue of ensuring selectivity is not even mentioned, let alone taken into account.

Nadaljnja naprava za prekinitev električnega tokokroga, ki je opisana v EP 2 537 163 BI, poleg vrste komponent PTC, GDT, L je zaradi samega prekinjanja opremljena z rotirajočim diskom, kar znatno poveča kompleksnost izvedbe in otežuje realizacijo.The further device for interrupting the electric circuit, which is described in EP 2 537 163 BI, in addition to the series of PTC, GDT, L components, is equipped with a rotating disc due to the interruption itself, which significantly increases the complexity of the implementation and complicates the realization.

Še nadalje je v US 2019/0252142 opisan večfazni energetski sistem, pri katerem je v vsaki fazi na voljo prenapetostni odvodnik, ki sestoji iz zaporedno vezanih varistorja, prekinjevalnega sklopa in varovalke. Tudi rešitev iz omenjenega dokumenta problemu selektivnosti ne posveča nikakršne pozornosti.Furthermore, US 2019/0252142 describes a multiphase power system in which a surge arrester is provided in each phase, consisting of a varistor connected in series, a circuit breaker and a fuse. Even the solution from the mentioned document does not pay any attention to the problem of selectivity.

Najbolj relevantna doslej znana ureditev tovrstnega tokokroga je shematično ponazorjena na Sl. 1. Prenapetostni zaščitni sklop sestoji iz med seboj zaporedno vezanih varistorja in sekundarne varovalke s talilnim elementom. Varistor ščiti breme pred prenapetostjo, sekundarna varovalka pa je namenjena za kratkostično zaščito varistorja v primeru njegove odpovedi, npr. zaradi tkzv. termičnega pobega. Tovrstna zasnova električnega tokokroga je povezana s problemom selektivnosti med primarno in sekundarno varovalko. Vsakokrat primerne tehnične značilnosti primarne varovalke so določene v odvisnosti od preseka električnega vodnika do porabnika, medtem ko so vsakokratne tehnične značilnosti sekundarne varovalke določene v odvisnosti od varistorja in velikosti prenapetostnih impulzov, kar je v stroki znano pod izrazom »surge rating«. Zahteve, ki jih narekujeta izbiri primarne in sekundarne varovalke, so v medsebojni kontradikciji oz. se medsebojno izključujejo. Pri primarni varovalki zahteve v smislu odpornost proti prenapetostnim impulzom narekujejo izbiro čim večjega preseka talilnega elementa, medtem ko je učinkovitost izklopa boljša pri čim manjšem prečnem preseku talilnega elementa Zaradi zahteve po čim večjem preseku talilnega elementa je potem hitrost delovanja primarne varovalke oz. njena odzivnost na motnje v tokokrogu omejena s presekom talilnega elementa. Kot je bilo omenjeno, je termična zaščita varistorja izvedena preko prožnega kontaktnega elementa, ki je prispajkan na elektrodo na okrovu varistorja. Ker tok teče skozi vzmetni kontakt, je hitrost delovanja navzdol omejena z velikostjo toka, kar pomembno vpliva na hitrost delovanja. Velikost toka pogojuje velikost vzmetnega kontakta in s tem termično vztrajnost in hitrost odklopa. Ko se spajka segreje na določeno temperaturo in se stali, se kontakta razkleneta. V primeru visoke napetosti v enosmernem električnem tokokrogu se zaradi razmeroma majhne hitrosti odmikanja kontakta in prav tako razmeroma majhne medsebojne oddaljenosti med kontaktoma po razmikanju pojavi velik problem v zvezi z možnostjo pojava električnega obloka. Povrhu vsega so varistorji z vidika temperature razmeroma občutljive komponente, pri katerih kritična oz. naj višja še dopustna temperatura za regularno delovanje lahko znaša približno 100°C.The most relevant so far known arrangement of this type of circuit is schematically illustrated in Fig. 1. The surge protection assembly consists of a series-connected varistor and a secondary fuse with a fusing element. The varistor protects the load from overvoltage, and the secondary fuse is intended for short-circuit protection of the varistor in the event of its failure, e.g. because of the so-called thermal runaway. This type of electrical circuit design is related to the problem of selectivity between the primary and secondary fuse. The appropriate technical characteristics of the primary fuse each time are determined depending on the cross-section of the electrical conductor to the consumer, while the technical characteristics of the secondary fuse each time are determined depending on the varistor and the size of the overvoltage pulses, which is known in the profession under the term "surge rating". The requirements dictated by the choice of primary and secondary fuses are in mutual contradiction or are mutually exclusive. In the case of the primary fuse, the requirements in terms of resistance to overvoltage impulses dictate the choice of the largest possible cross-section of the fusing element, while the tripping efficiency is better with the smallest possible cross-section of the fusing element. Due to the requirement for the largest possible cross-section of the fusing element, the operating speed of the primary fuse its responsiveness to disturbances in the circuit is limited by the cross-section of the fuse element. As mentioned, the thermal protection of the varistor is performed via a flexible contact element that is soldered to the electrode on the varistor casing. As the current flows through the spring contact, the speed of downward operation is limited by the magnitude of the current, which significantly affects the speed of operation. The size of the current determines the size of the spring contact and thus the thermal inertia and speed of disconnection. When the solder heats up to a certain temperature and melts, the contacts open. In the case of high voltage in a direct current circuit, due to the relatively low speed of the contact movement and also the relatively small mutual distance between the two contacts after separation, a big problem arises regarding the possibility of an electric arc. On top of everything, varistors are relatively sensitive components from the point of view of temperature, in which the critical or. let the even higher permissible temperature for regular operation be approximately 100°C.

V električnem tokokrogu obravnavane vrste je v kontekstu zagotavljanja omenjene selektivnosti torej vsekakor zaželeno in pričakovano, da bi v primeru električne preobremenitve, četudi bi bil tok skozi sekundarno varovalko manjši od toka skozi primarno varovalko, sekundarna varovalka pregorela, primarna pa ne. Ob pojavu prenapetosti se električni naboj preko varistorja odvede v zemljo, v primeru poškodbe ali okvare varistorja pa naj bi prišlo do prekinitve zgolj sekundarne varovalke, medtem ko naj bi primarna varovalka ostala nepoškodovana.In the electrical circuit of the type in question, in the context of ensuring the aforementioned selectivity, it is therefore definitely desirable and expected that in the event of an electrical overload, even if the current through the secondary fuse were less than the current through the primary fuse, the secondary fuse would blow, but the primary would not. In the event of an overvoltage, the electric charge is led to the ground via the varistor, and in case of damage or failure of the varistor, only the secondary fuse should be interrupted, while the primary fuse should remain undamaged.

Izum se nanaša na ureditev zaščite v električnem tokokrogu, ki obsega vir enosmerne električne napetosti, ki je preko primarnih električnih vodnikov električno povezan z bremenom, pri čemer je v enem izmed omenjenih primarnih električnih vodnikov integrirana električna uporovna varovalka s talilnim elementom, pri tem pa sta primarna vodnika premeščena s premostitvenim sekundarnim vodnikom, ki vključuje prenapetostni zaščitni sklop z vsaj enim varistorjem in z njim v toplotno prevodnem stiku nahajajočim se termičnim odklopnim elementom, kot tudi z vsaj eno z omenjenim varistorjem električno povezano in sodelujočo nadaljnjo električno uporovno varovalko s talilnim elementom.The invention relates to the arrangement of protection in an electric circuit, which comprises a source of direct electric voltage, which is electrically connected to the load via primary electric conductors, whereby an electric resistance fuse with a fuse element is integrated in one of the mentioned primary electric conductors, and the primary conductor is replaced by a bridging secondary conductor, which includes an overvoltage protection assembly with at least one varistor and a thermal disconnection element located in thermally conductive contact with it, as well as with at least one electrically connected and cooperating further electric resistance fuse with a melting element with the said varistor.

Po izumu je predlagano, da omenjen sekundarni oz. premostitveni električni vodnik prenapetostnega zaščitnega sklopa, s katerim sta premoščena omenjena primarna električna vodnika med napetostnim virom in bremenom, poleg omenjenega varistorja s pripadajočim termičnim odklopnikom vključuje tudi tritočkovno stikalo s prekinjevalnim elementom, ki je pri vnaprej določenih pogojih s pomočjo prožilnega sredstva odvihtljiv iz svojega prvega izhodiščnega položaja, v katerem je omenjen premostitven električni vodnik prenapetostnega zaščitnega sklopa sklenjen, v svoj drug končni položaj, v katerem je omenjen premostitven električni vodnik prenapetostnega zaščitnega sklopa prekinjen, medtem ko je električna uporovna varovalka vgrajena v vzporedni veji premostitvenega električnega vodnika, ki poteka od enega izmed primarnih vodnikov električnega tokokroga in je razporejena na odmiku od vsakokrat preostalega primarnega vodnika, obenem pa tudi na primerni in vnaprej določeni oddaljenosti od omenjenega prekinjevalnega elementa stikala, pri čemer pa je omenjena oddaljenost tako izbrana, da je električni tokokrog skozi omenjeno vzporedno vejo in varovalko vzpostavljiv šele po prekinitvi stikala v premostitvenem električnem vodniku, namreč potem, ko se v svoj drug končni položaj zavihten prekinjevalni element stikala premakne v stik z omenjeno vzporedno vejo.According to the invention, it is proposed that the mentioned secondary or the bridging electrical conductor of the overvoltage protection assembly, with which the aforementioned primary electrical conductors are bridged between the voltage source and the load, in addition to the aforementioned varistor with the associated thermal circuit breaker, also includes a three-point switch with a breaking element, which can be released from its first position under predetermined conditions by means of a trigger starting position, in which said bridging electrical conductor of the surge protection assembly is closed, to its other final position, in which said bridging electrical conductor of the surge protection assembly is disconnected, while the electric resistance fuse is installed in the parallel branch of the bridging electrical conductor running from of one of the primary conductors of the electric circuit and is arranged at a distance from each remaining primary conductor, and at the same time at a suitable and predetermined distance from the mentioned interrupting element of the switch, whereby j e said distance is chosen in such a way that the electric circuit through said parallel branch and the fuse can only be established after the switch in the bridging electric conductor is broken, namely after the switching element of the switch, which is rotated to its other end position, moves into contact with said parallel branch.

Pri prednostni izvedbi izuma je poleg doslej navedenega še nadalje predvideno, da omenjeno prožilno sredstvo, s pomočjo katerega se pri vnaprej določenih pogojih izvrši premik prekinjevalnega elementa stikala v smislu zavihtenja iz njegovega prvega izhodiščnega položaja, v katerem je premostitveni vodnik sklenjen, v njegov drug končni položaj, v katerem je premostitveni vodnik prekinjen, pri tem pa se prekinjevalni element stikala nahaja v električno prevodnem stiku z vodnikom uporovne varovalke, predstavlja pirotehnično stikalo z aktuatorjem, ki je sprožljiv na osnovi signala, prejetega s strani magnetnega Reed (NO) stikala, ki je v pripadajoči električno prevodni veji vgrajeno med omenjeno premostitveno vejo in aktuatorjem, oziroma s strani termičnega tipala, ki se nahaja v toplotno prevodnem stiku z varistorjem in je v pripadajoči električno prevodni veji vzporedno s prej omenjeno vejo magnetnega Reed (NO) stikala vgrajeno med omenjeno premostitveno vejo in aktuatorjem. Pri tem pa je omenjeno Reed (NO) stikalo v pogojih regularnega delovanja električnega tokokroga razklenjeno, ob pojavu motnje pa sprememba magnetnega polja privede do njegove sklenitve in temu ustreznega vpliva na aktuator v smislu proženja le-tega in posledično premika prekinjevalnega elementa stikala, in pri čemer je tudi omenjeno termično tipalo med regularnim delovanjem tokokroga razklenjeno, v primeru preseženja vnaprej določene temperature varistorja pa se sklene.In the preferred embodiment of the invention, in addition to what has been stated so far, it is further provided that the mentioned triggering means, with the help of which, under predetermined conditions, the movement of the interrupting element of the switch is carried out in the sense of swinging from its first starting position, in which the bridging conductor is closed, to its second final position the position in which the bridging conductor is interrupted and the interrupting element of the switch is in electrically conductive contact with the conductor of the resistance fuse represents a pyrotechnic switch with an actuator that is tripped based on a signal received by the magnetic Reed (NO) switch, which is installed in the associated electrically conductive branch between the mentioned bridging branch and the actuator, or by the thermal sensor, which is located in thermally conductive contact with the varistor and is installed in the associated electrically conductive branch in parallel with the previously mentioned branch of the magnetic Reed (NO) switch between the mentioned bridging branch and actuators. In this case, the mentioned Reed (NO) switch is open in the conditions of regular operation of the electric circuit, and in the event of a disturbance, a change in the magnetic field leads to its closing and a corresponding effect on the actuator in terms of triggering it and consequently moving the interrupting element of the switch, and whereby the mentioned thermal sensor is also open during regular operation of the circuit, but in case of exceeding the predetermined temperature of the varistor, it is closed.

Reed (NO) stikalo smiselno predstavlja stikalo s časovno zakasnitvijo vsaj 1 ms, vendar ne več kot 2 ms, medtem ko vir električne napetosti lahko predstavlja bodisi vir enosmerne (DC) električne napetosti ali pa vir izmenične (AC) električne napetosti.A reed (NO) switch reasonably represents a switch with a time delay of at least 1 ms, but not more than 2 ms, while the source of electrical voltage can represent either a source of direct current (DC) electrical voltage or a source of alternating (AC) electrical voltage.

Izum bo v nadaljevanju podrobneje obrazložen s primerom izvedbe, ki je shematično ponazorjen na priloženi skici, kjer kažeIn the following, the invention will be explained in more detail with an example of implementation, which is schematically illustrated in the attached sketch, where it shows

Sl. 1 shematično ponazoritev že obravnavane zaščite električnega tokokroga iz stanja tehnike;fig. 1 schematic illustration of the previously discussed electrical circuit protection from the state of the art;

Sl. 2 pa shematično ponazorjen primer enega izmed možnih primerov izvedbe izuma v stanju po prekinitvi tritočkovnega stikala, pri čemer je za prekinitev tokokroga v primeru preobremenitve uporabljeno pirotehnično stikalo.fig. 2 schematically illustrates an example of one of the possible examples of the implementation of the invention in the state after the interruption of the three-point switch, whereby a pyrotechnic switch is used to interrupt the circuit in the event of an overload.

Kot rečeno, se izum nanaša na ureditev prenapetostne zaščite v električnem tokokrogu 1. Tudi električni tokokrog po Sl. 2 obsega vir 2 enosmerne električne napetosti, ki je preko primarnih električnih vodnikov 11, 12 električno povezan z bremenom 3, pri tem pa je v enem izmed omenjenih primarnih električnih vodnikov 11,12 integrirana električna uporovna varovalka 4 s talilnim elementom. Podobno kot pri rešitvi iz stanja tehnike (Sl. 1) sta tudi v tem primeru primarna vodnika 11, 12 premoščena s sekundarnim vodnikom 13, ki vključuje prenapetostni zaščitni sklop 5 z varistorjem 50 s termičnim tipalom 50' kot tudi z vsaj eno z omenjenim varistorjem 50 električno povezano in sodelujočo nadaljnjo električno uporovno varovalko 55 s talilnim elementom.As said, the invention relates to the arrangement of overvoltage protection in the electrical circuit 1. Also the electrical circuit according to FIG. 2 comprises a source 2 of DC voltage, which is electrically connected to the load 3 via primary electrical conductors 11, 12, and an electric resistance fuse 4 with a fuse element is integrated in one of the mentioned primary electrical conductors 11, 12. Similar to the solution from the state of the art (Fig. 1), in this case also the primary conductors 11, 12 are bridged by the secondary conductor 13, which includes an overvoltage protection assembly 5 with a varistor 50 with a thermal sensor 50' as well as at least one with the aforementioned varistor 50 an electrically connected and cooperating further electrical resistance fuse 55 with a fusing element.

Po izumu pa je predvideno, da električni vodnik 13 prenapetostnega zaščitnega sklopa 5, s katerim sta premoščena omenjena primarna električna vodnika 11, 12 med napetostnim virom 2 in bremenom 3, poleg omenjenega varistorja 50 s pripadajočim termičnim tipalom 50' vključuje tudi tritočkovno stikalo 6 s prekinjevalnim elementom 60, ki je pri vnaprej določenih pogojih s pomočjo prožilnega sredstva 7 odvihtljiv iz svojega prvega izhodiščnega položaja, v katerem je omenjen premostitven električni vodnik 13 prenapetostnega zaščitnega sklopa 5 sklenjen, v svoj drug končni položaj, v katerem je omenjen premostitven električni vodnik 13 prenapetostnega zaščitnega sklopa 5 prekinjen oz. razklenjen. Pri tem pa je omenjena električna uporovna varovalka 55 vgrajena v vzporedni veji 13' premostitvenega električnega vodnika 13, ki poteka od enega izmed primarnih vodnikov 11, 12 tokokroga 1, in je na odmiku od z vsakokrat preostalega primarnega vodnika 11, 12 voljo na primerni in vnaprej določeni oddaljenosti od prekinjevalnega elementa 60 stikala 6. Omenjena oddaljenost veje 13' od prekinjevalnega elementa 60 stikala 6 je tako izbrana, da je električni tokokrog skozi omenjeno vzporedno vejo 13' in varovalko 55 vzpostavljiv šele po prekinitvi stikala 6 v premostitvenem električnem vodniku 13, namreč potem, ko se v svoj drug končni položaj zavihten prekinjevalni element 60 stikala 6 premakne v stik z omenjeno vzporedno vejo 13', in je obenem tolikšna, da je po prekinitvi premostitvenega vodnika 13 še zlasti v primeru enosmernega električnega vira 2 preprečeno formiranje obloka.According to the invention, it is provided that the electric conductor 13 of the overvoltage protection assembly 5, which bridges the mentioned primary electric conductors 11, 12 between the voltage source 2 and the load 3, in addition to the mentioned varistor 50 with the associated thermal sensor 50', also includes a three-point switch 6 with interrupting element 60, which, under predetermined conditions, can be swung from its first starting position, in which said bridging electrical conductor 13 of the overvoltage protection assembly 5 is closed, to its second end position, in which said bridging electrical conductor 13 is of overvoltage protection circuit 5 interrupted or unlocked. In this case, the mentioned electric resistance fuse 55 is installed in the parallel branch 13' of the bridging electric conductor 13, which runs from one of the primary conductors 11, 12 of the circuit 1, and is at a distance from the remaining primary conductor 11, 12 in each case at a suitable and predetermined distance from the interrupting element 60 of the switch 6. The mentioned distance of the branch 13' from the interrupting element 60 of the switch 6 is chosen in such a way that the electric circuit through the mentioned parallel branch 13' and the fuse 55 can only be established after the interruption of the switch 6 in the bridging electric conductor 13, namely, after the interrupting element 60 of the switch 6, which is pivoted to its other final position, moves into contact with the mentioned parallel branch 13', and is at the same time such that after the bridging conductor 13 is interrupted, especially in the case of a one-way electric source 2, the formation of an arc is prevented.

Pri prednostni izvedbi izuma je zlasti zaradi zahtevane odzivnosti na električne preobremenitve predvideno, da omenjeno prožilno sredstvo 7, s pomočjo katerega se pri vnaprej določenih pogojih izvrši premik prekinjevalnega elementa 60 stikala 6 v smislu zavihtenja iz njegovega prvega izhodiščnega položaja, v katerem je premostitveni vodnik 13 sklenjen, v njegov drug končni položaj, v katerem je premostitveni vodnik 13 prekinjen, pri tem pa se prekinjevalni element 60 stikala 6 nahaja v stiku z vodnikom 13' uporovne varovalke 55, predstavlja pirotehnično stikalo z aktuatorjem 71. Ta aktuator 71 pa je sprožljiv na osnovi signala, prejetega s strani magnetnega Reed (NO) stikala 75, ki v pripadajoči električno prevodni veji 13 vgrajeno med premostitveno vejo 13 in aktuatorjem 71, oz. s strani termičnega tipala 50', ki se nahaja v toplotno prevodnem stiku z varistorjem 50 in je v pripadajoči električno prevodni veji 13' vzporedno s prej omenjeno vejo 13 magnetnega Reed (NO) stikala 75 vgrajeno med premostitveno vejo 13 in aktuatorjem 71. Pri tem je omenjeno Reed (NO) stikalo 75 v pogojih regularnega delovanja električnega tokokroga 1 razklenjeno, ob pojavu motnje v električnem tokokrogu 1 pa sprememba magnetnega polja privede do njegove sklenitve in temu ustreznega vpliva na aktuator 71 v smislu proženja le-tega. Prav tako je tudi omenjeno termično tipalo 50' med regularnim delovanjem tokokroga 1 razklenjeno, v primeru preseženja vnaprej določene temperature varistorja 50 pa se sklene in spusti tok proti aktuatorju 71 stikala 6.In the preferred embodiment of the invention, in particular due to the required responsiveness to electrical overloads, it is provided that the mentioned trigger means 7, with the help of which, under predetermined conditions, the interrupting element 60 of the switch 6 is moved in the sense of swinging from its first starting position, in which the bridging conductor 13 closed, in its other end position, in which the bridging conductor 13 is interrupted, and the interrupting element 60 of the switch 6 is in contact with the conductor 13' of the resistive fuse 55, represents a pyrotechnic switch with an actuator 71. This actuator 71 is triggered on based on the signal received by the magnetic Reed (NO) switch 75, which is installed in the corresponding electrically conductive branch 13 between the bridging branch 13 and the actuator 71, or from the side of the thermal sensor 50', which is located in thermally conductive contact with the varistor 50 and is installed in the corresponding electrically conductive branch 13' parallel to the previously mentioned branch 13 of the magnetic Reed (NO) switch 75 between the bridging branch 13 and the actuator 71. the mentioned Reed (NO) switch 75 is open under the conditions of regular operation of the electric circuit 1, and when a disturbance occurs in the electric circuit 1, a change in the magnetic field leads to its closing and correspondingly affects the actuator 71 in terms of activating it. Likewise, the mentioned thermal sensor 50' is open during the regular operation of the circuit 1, and in case of exceeding the predetermined temperature of the varistor 50, it is closed and the current flows towards the actuator 71 of the switch 6.

Pri tem pa omenjeni vir 2 električne napetosti lahko predstavlja bodisi vir enosmerne (DC) električne napetosti ali pa vir izmenične (AC) električne napetosti, omenjeno reed (NO) stikalo (75) pa prednostno predstavlja stikalo s časovno zakasnitvijo vsaj 1 ms in prednostno ne več kot 2 ms.In this case, said source 2 of electrical voltage can represent either a source of direct current (DC) electrical voltage or a source of alternating (AC) electrical voltage, and said reed (NO) switch (75) preferably represents a switch with a time delay of at least 1 ms and preferably not more than 2 ms.

Zahvaljujoč opisanim značilnostim je odzivanje tovrstne ureditve zaščite tokokroga na različne motnje neprimerno boljše kot pri rešitvah iz stanja tehnike.Thanks to the described characteristics, the response of this type of circuit protection arrangement to various disturbances is inappropriately better than that of solutions from the prior art.

Ob pojavu prenapetosti v tokokrogu 1 je tokovna pot sklenjena preko premostitvenega vodnika 13, namreč preko prekinjevalnega elementa 60 sklenjenega stikala 6 in varistorja 50. Presek kontaktov v območju omenjenega stikala 6 je bistveno, namreč za najmanj desetkrat, večji od preseka talilnega elementa uporovne varovalke 55, zato ni nevarnosti, da bi prišlo do nenamerne prekinitve omenjene tokovne poti. Trajanje tokovnega impulza v primeru udara strele običajno znaša do 1 ms, zato se za omenjeno Reed (NO) stikalo 75 smiselno stikala 6 je bistveno, namreč za najmanj desetkrat, večji od preseka talilnega elementa uporovne varovalke 55, zato ni nevarnosti, da bi prišlo do nenamerne prekinitve omenjene tokovne poti. Trajanje tokovnega impulza v primeru udara strele običajno znaša do 1 ms, zato se za omenjeno Reed (NO) stikalo 75 smiselno izbere stikalo s časovno zakasnitvijo vsaj 1 ms, največ pa do 2 ms, s čimer se prepreči delovanje nadtokovne zaščite v primeru pojava kratkotrajne prenapetosti.When an overvoltage occurs in circuit 1, the current path is closed via the bridging conductor 13, namely via the interrupting element 60 of the closed switch 6 and the varistor 50. The cross-section of the contacts in the area of the mentioned switch 6 is significantly, namely at least ten times, larger than the cross-section of the fuse element of the resistance fuse 55 , so there is no risk of accidental interruption of the mentioned current path. The duration of the current pulse in the event of a lightning strike is usually up to 1 ms, therefore for the mentioned Reed (NO) switch 75, the switch 6 is essential, namely at least ten times larger than the cross-section of the fuse element of the resistance fuse 55, so there is no risk of to the accidental interruption of said current path. The duration of the current pulse in the event of a lightning strike is usually up to 1 ms, therefore, for the mentioned Reed (NO) switch 75, a switch with a time delay of at least 1 ms, and a maximum of 2 ms, is selected, which prevents the operation of the overcurrent protection in the event of a short-term overvoltage.

Ob pojavu kratkega stika na varistorju 50 se okoli vodnika 13 pojavi razmeroma močno magnetno polje, ki povzroči sklenitev Reed stikala 75, zato skozi Reed stikalo 75 steče tok proti prožilnemu sredstvu 7, ki potem premakne prekinjevalni element 60 stikala 6 iz njegovega prvega izhodiščnega položaja, v katerem je vodnik 13 skozi varistor 50 sklenjen, v njegov drug končni položaj v stiku z vzporedno vejo 13' z integrirano varovalko 55, po tistem pa vodnik 13 skozi varistor 50 ostane prekinjen. Varovalka 55 potem zaradi preobremenitve in pretalitve v njej razpoložljivega talilnega elementa prekine tokokrog skozi omenjeno vzporedno vejo 13'. Kratkostični tok v tem primeru ne teče skozi tokovni senzor, zato je hitrost delovanja velika, pa tudi samo Reed stikalo 75 ima majhno vztrajnost. Zato za razliko od rešitve s klasično talilno varovalko po stanju tehnike po Sl. 1 v tem primeru nazivna vrednost toka prenapetostnega impulza ne pogojuje velikosti tokovnega senzorja.When a short circuit occurs on the varistor 50, a relatively strong magnetic field appears around the conductor 13, which causes the reed switch 75 to close, therefore a current flows through the reed switch 75 towards the triggering means 7, which then moves the interrupting element 60 of the switch 6 from its first starting position, in which the conductor 13 through the varistor 50 is closed, to its other end position in contact with the parallel branch 13' with the integrated fuse 55, after which the conductor 13 through the varistor 50 remains disconnected. The fuse 55 then breaks the circuit through the mentioned parallel branch 13' due to overloading and melting of the fuse element available in it. In this case, the short-circuit current does not flow through the current sensor, so the operating speed is high, and also the Reed switch 75 itself has a low inertia. Therefore, unlike the solution with a classic fusible link according to the state of the art according to Fig. 1, in this case, the nominal value of the current of the overvoltage pulse does not condition the size of the current sensor.

Če pride do segrevanja varistorja 50, termično tipalo 50', ki je v toplotno prevodnem stiku z varistorjem 50, vzpostavi tokokrog proti aktuatorju 71 prožilnega sredstva 7, ki potem premakne prekinjevalni element 60 stikala 6 iz njegovega prvega izhodiščnega položaja, v katerem je vodnik 13 skozi varistor 50 sklenjen, v njegov drug končni položaj v stiku z vzporedno vejo 13' z integrirano varovalko 55, po tistem pa vodnik 13 skozi varistor 50 ostane prekinjen. Tudi v tem primeru varovalka 55 zaradi preobremenitve in pretalitve v njejIf heating of the varistor 50 occurs, the thermal sensor 50', which is in thermally conductive contact with the varistor 50, establishes a circuit towards the actuator 71 of the triggering means 7, which then moves the interrupting element 60 of the switch 6 from its first initial position, in which the conductor 13 closed through the varistor 50, to its other end position in contact with the parallel branch 13' with the integrated fuse 55, after which the conductor 13 through the varistor 50 remains disconnected. Also in this case fuse 55 due to overloading and melting in it

Zahvaljujoč opisanim značilnostim je v primeru motenj delovanja tokokroga 1 zagotovljena nedvoumna selektivnost med varovalko 4 in zaščito varistorja 50 proti nadtoku. Prav tako je zaradi majhne termične vztrajnosti termičnega tipala 50' in majhnosti Reed stikala 75 delovanje zaščitnega sklopa 5 v primerjavi z rešitvami iz stanja tehnike lahko mnogo hitrejše in je sklop 5 torej znatno bolj odziven na motnje v električnem tokokrogu 1. Razen tega je velikost oz. nazivna vrednost varovalke 55 v zaščitnem sklopu 5, ki je vsekakor bistveno nižja od velikosti oz. nazivne vrednosti varovalke 4 v enem izmed primarnih vodnikov 11, 12 tokokroga 1, praktično tudi neodvisna od vrednosti prenapetostnega impulza, pri čemer je tovrstna ureditev s pomočjo opisanega zaščitnega sklopa 5 univerzalna in uporabljiva pri širokem naboru rešitev. Ureditev zaščite tokokroga 1 po izumu se nadalje odlikuje po visoki odklopni zmogljivosti ne glede na zahteve po odpornosti na prenapetostne impulze. Za razliko od uporovne varovalke 4 v zaporedni vezavi z varistorjem 50 po stanju tehnike (Sl. 1) v primeru predlagane rešitve zaščitnega sklopa po izumu (Sl. 2) tudi presek kontaktov v območju prekinjevalnega elementa 60 stikala 6 ne vpliva na izklopno zmogljivost, razen tega pa je odzivni čas zaščite pred nadtokovnimi obremenitvami neodvisen od velikosti prenapetostnega impulza. Zato ureditev zaščite po izumu omogoča obvladovanje tudi zelo visokih vrednosti prenapetostnih impulzov brez nehotenega izklapljanja v primeru prenapetosti, kar omogoča dovolj masiven presek kontaktnega elementa 60 stikala 6, s tem pa je obenem zagotovljena tudi odpornost proti degradaciji v primeru dolgotrajne uporabe.Thanks to the described characteristics, in the event of a malfunction of circuit 1, unambiguous selectivity is ensured between fuse 4 and varistor protection 50 against overcurrent. Also, due to the low thermal inertia of the thermal sensor 50' and the small size of the Reed switch 75, the operation of the protective assembly 5 can be much faster compared to solutions from the state of the art, and the assembly 5 is therefore significantly more responsive to disturbances in the electrical circuit 1. In addition, the size or . nominal value of fuse 55 in protective assembly 5, which is definitely significantly lower than the size or nominal values of the fuse 4 in one of the primary conductors 11, 12 of the circuit 1, practically also independent of the value of the overvoltage pulse, whereby this type of arrangement with the help of the described protective assembly 5 is universal and applicable to a wide range of solutions. The circuit protection arrangement 1 according to the invention is further characterized by a high breaking capacity regardless of the requirements for resistance to overvoltage impulses. Unlike the resistive fuse 4 in series connection with the varistor 50 according to the state of the art (Fig. 1), in the case of the proposed solution of the protective assembly according to the invention (Fig. 2), the cross-section of the contacts in the area of the interrupting element 60 of the switch 6 does not affect the breaking capacity, except however, the response time of the protection against overcurrent loads is independent of the size of the overvoltage pulse. Therefore, the protection arrangement according to the invention enables handling even very high values of overvoltage pulses without involuntary switching off in the event of overvoltage, which enables a sufficiently massive cross-section of the contact element 60 of the switch 6, while at the same time resistance to degradation in case of long-term use is ensured.

Claims

PATENT CLAIMS

1. Protection arrangement in an electric circuit (1), comprising a source (2) of electric voltage, which is electrically connected to a load (3) via primary electric conductors (11, 12), whereby in one of the mentioned primary electric conductors (11 , 12) an integrated electric resistance fuse (4) with a fusing element, while the primary conductors (11, 12) are bridged with a secondary conductor (13) that includes an overvoltage protection assembly (5) with at least one varistor (50) and with thermal sensors (50') located in thermally conductive contact with them, as well as with at least one further electric resistance fuse (55) with a melting element electrically connected and cooperating with the mentioned varistor (50), characterized by the fact that the bridging electric conductor (13 ) of the overvoltage protection assembly (5), with which the mentioned primary electrical conductors (11, 12) are bridged between the voltage source (2) and the load (3), in addition to the mentioned varistor (50) with the associated thermal sensor (50') also includes a three-point switch (6) with an interrupting element (60) which, under predetermined conditions, can be swung out of its first starting position by means of a triggering means (7), in which the aforementioned bridging electrical conductor (13) of the overvoltage protection assembly (5) is closed, to its other end position, in which said bridging electrical conductor (13) of the overvoltage protection assembly (5) is interrupted, while the electrical resistance fuse (55) is installed in the parallel branch (13') of the bridging electrical conductor (13) passing from one of the primary conductors (11, 12) of the circuit (1) and is terminated at a distance from each remaining primary conductor (11, 12) and at a suitable and predetermined distance from the interrupting element (60) of the switch (6), while if the said distance is chosen in this way, the electric circuit through the said parallel branch (13') and the fuse (55) can only be established after the switch (6) in the bridging electric conductor (13) is broken, we that is, after the pivoted interrupting element (60) of the switch (6) has moved to its second final position in contact with said parallel branch (13').

2. Arrangement according to claim 1, characterized by the fact that said triggering means (7), with the help of which, under predetermined conditions, the interrupting element (60) of the switch (6) is moved in the sense of swinging from its first starting position, in which bridging conductor (13) closed, to its other end position, in which the bridging conductor (13) is broken, and the breaking element (60) of the switch (6) is in contact with the conductor (13') of the resistance fuse (55) , represents a pyrotechnic switch with an actuator (71) which is triggered on the basis of a signal received by the magnetic Reed (NO) switch (75), which is installed in the corresponding electrically conductive branch (13) between the bridging branch (13) and the actuator ( 71), or from the side of the thermal sensor (50'), which is located in thermally conductive contact with the varistor (50) and is in the corresponding electrically conductive branch (13') in parallel with the previously mentioned branch (13) of the magnetic Reed (NO) switch (75) embedded between said bridging branch (13) and the actuator (71), whereby the mentioned Reed (NO) switch (75) is open in the conditions of regular operation of the electric circuit (1), and in the event of a disturbance, a change in the magnetic field leads to its closing and the corresponding effect on the actuator ( 71) in the sense of triggering it and consequently moving the interrupting element (60) of the switch (6), and whereby the mentioned thermal sensor (50') is also unlocked during the regular operation of the circuit (1), in case of exceeding the predetermined temperature of the varistor ( 50) is concluded.

3. Arrangement according to claim 1 or 2, characterized in that the Reed (NO) switch (75) represents a switch with a time delay of at least 1 ms.

4. Arrangement according to claim 3, characterized in that the Reed (NO) switch (75) represents a switch with a time delay of up to 2 ms.

5. Arrangement according to any one of claims 1-4, characterized in that the source (2) of electric voltage represents a source of direct current (DC) electric voltage.

6. Arrangement according to any one of claims 1-4, characterized in that the source (2) of electrical voltage represents a source of alternating (AC) electrical voltage.