EP0795183B1 - Method and device for preventing explosions and fires in electrical transformers - Google Patents

Method and device for preventing explosions and fires in electrical transformers Download PDF

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Publication number
EP0795183B1
EP0795183B1 EP96932665A EP96932665A EP0795183B1 EP 0795183 B1 EP0795183 B1 EP 0795183B1 EP 96932665 A EP96932665 A EP 96932665A EP 96932665 A EP96932665 A EP 96932665A EP 0795183 B1 EP0795183 B1 EP 0795183B1
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Prior art keywords
coolant
transformer
enclosure
valve
pressure
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German (de)
French (fr)
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EP0795183A1 (en
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Philippe Magnier
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/10—Liquid cooling
    • H01F27/12—Oil cooling
    • H01F27/14—Expansion chambers; Oil conservators; Gas cushions; Arrangements for purifying, drying, or filling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/40—Structural association with built-in electric component, e.g. fuse
    • H01F27/402—Association of measuring or protective means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/40—Structural association with built-in electric component, e.g. fuse
    • H01F27/402—Association of measuring or protective means
    • H01F2027/406—Temperature sensor or protection

Definitions

  • the present invention relates to the field of prevention against explosion and fire of electrical transformers cooled by a combustible fluid.
  • Electric transformers suffer losses both in the windings only in the iron part, which require dissipation of the heat produced. So the high power transformers are generally oil-cooled. The oils used are dielectric and are liable to catch fire beyond temperature of the order of 140 °. The transformers being elements very expensive, their protection requires special attention.
  • Explosions can be caused by overloads, overvoltages, progressive deterioration of the insulation, a level insufficient oil, the appearance of water or mold or a breakdown an insulating component.
  • WO-A-94 28 566 relates to a device for monitoring a partial discharge in equipment high voltage electrical such as a transformer.
  • the device includes a transducer capable convert ultrasonic pressure waves following an insulation fault. We then evacuate the resulting electrical energy to the earth.
  • document EP-A-238,475 describes a fire extinguisher device of an electric oil transformer by injection of nitrogen under pressure at the bottom of the tank to stir the oil and cool the hottest parts of the oil.
  • Document DE-A-2 624 882 describes a device for overpressure protection in the transformer tank containing a coolant.
  • This device includes a safety valve in the form of a cover fitted an electrical contact.
  • the object of the present invention is therefore to provide a process which protects both against overpressure inside the transformer, due to deflagration when the insulation breaks internal electrical and against fire resulting from such ruptures insulation.
  • the invention also relates to a device for explosion and fire prevention which allows detection instant of the break in the electrical insulation.
  • the fire protection process of an electrical transformer comprising a tank filled with combustible coolant in which cools hot parts of the coolant by injection of an inert gas under pressure into the bottom of the tank in order to stir the coolant and expel the oxygen located nearby, includes, before the cooling step, a transformer explosion and fire prevention step by detection of a break in the electrical insulation of the transformer by a safety valve fitted with an electrical contact and forming a sensor means instant pressure and decompression of the transformer tank by draining partial cooling fluid by means of a valve.
  • the fire protection device of an electric transformer includes a tank filled with combustible coolant, and a safety valve fitted with an electrical contact and forming a sensor means pressure in said tank said valve being part of means of prevention against the explosion and the fire which also include a valve (15) instant decompression of the transformer tank by partial emptying of the coolant contained in the tank.
  • An insulation fault first generates a significant electric arc which causes an action of the electrical protection which triggers the supply cell of the transformer (circuit breaker).
  • the electric arc also causes a consequent diffusion of energy which generates an increase of enough internal transformer pressure to tear the tank.
  • the device is equipped with a means for detecting the triggering of the transformer supply cell and control box which receives the signals emitted by the sensor means of the transformer and which is capable of transmitting control signals.
  • the device includes means for cooling the parts hot fluid, by injecting inert gas into the bottom of the tank, controlled by a control signal from the control unit.
  • inert gas into the bottom of the tank
  • a control signal from the control unit controls a heating capable of igniting it.
  • Injection of an inert gas into the bottom of the tank causes a cooling fluid circulation which homogenizes the temperature and makes it possible to expel the oxygen present at proximity to the fluid.
  • the transformer 1 comprises a tank 2 resting on the ground 3 by means of feet 4 and is supplied with electrical energy by wires 5 surrounded by insulators 6.
  • the tank 2 is filled with cooling fluid 7, by example, dielectric oil.
  • cooling fluid 7 by example, dielectric oil.
  • the transformer 1 is provided with an auxiliary tank 8 in communication with the tank 2 by a pipe 9.
  • Line 9 is provided with an automatic valve 10 which closes line 9 as soon as it detects rapid movement of the fluid 7.
  • an automatic valve 10 which closes line 9 as soon as it detects rapid movement of the fluid 7.
  • the tank 2 is provided with a pressure sensor 11 capable of detect without delay the pressure variation due to the deflagration caused by the breaking of the electrical insulation of the transformer 1.
  • the pressure sensor 11 consists of a safety valve fitted with an electrical contact and thus capable of transmit information relating to pressure variation detected.
  • the tank 2 is also provided with temperature sensors 12 located in several points of the tank 2, in order to know the fluid temperature 7. However, these temperature sensors 12 have an estimated delay of 20 or 30 seconds from the pressure detector 11, due to the slower propagation of the heat than pressure.
  • the tank 2 comprises a sensor 13 for the presence of steam coolant also called buchholz mounted in a high point of tank 2, generally on line 9. Deflagration due to a break in electrical isolation quickly causes the release of vapor from the fluid 7 in the tank 2. A sensor for steam 13 is therefore effective in detecting a break in the insulation electric.
  • the transformer 1 is supplied via a supply cell, not shown, which comprises means for power cut such as circuit breakers and which is provided with trigger sensors 21.
  • the tank 2 is provided with draining means comprising a pipe 14 to which it is connected at the desired height of the level emptying. Line 14 is closed by a strong valve 15 diameter for example 100 to 150 mm.
  • the tank 2 includes a means of cooling of the fluid 7 by injection of an inert gas 16 such as nitrogen at the bottom of the tank 2.
  • the inert gas 16 is stored in a pressure tank 17 provided with a valve 18, a pressure reducer 19 and a pipe 20 bringing the gas 16 to the tank 2.
  • the pressure sensor 11, the temperature sensors 12, the steam sensor 13, trigger sensors 21, valve 15 of the pipe 14 and the valve 18 of the pipe 20 are connected to a housing of command 22 intended to control the operation of the device.
  • the control box 22 is provided with processing means receiving signals from different sensors and capable send control signals to valves 15 and 18.
  • the device is actuated by a high pressure signal in origin of the pressure sensor 11 coincident with a signal of trigger from the trigger sensors 21 of the transformer 1 supply cell to prevent explosion and the fire.
  • the device can also be activated by a signal high temperature from one of the temperature sensors 12 coinciding with a steam signal from the steam sensor 13 to start the extinction of a fire. So, two sensors are required to provide consistent information in order to avoid nuisance trips.
  • the device Under normal conditions, the device is triggered by the high pressure information, in accordance with the information of triggering of the supply cell, which controls instantly step 23 of opening the drain valve 15 which allows instant decompression of tank 2 of transformer 1 most of the components of which will therefore remain intact, except elements located in an area very close to the electric arc caused by the insulation fault.
  • the opening of the valve 15 allows avoid overflowing of inflamed fluid 2 when injecting inert gas 16 in the tank 2 which is liable to be damaged.
  • the opening of the valve 15 causes a decompression in the pipe 9 which leads to the closing of the automatic valve 10.
  • the make-up tank 8 is thus isolated and the fluid 7 which it contains does not fuel the fire.
  • the rapid opening of valve 15 decreases also the risk of explosion and increases the likelihood that the tank 2 of transformer 1 remains intact.
  • step 24 of injecting inert gas 16 at the bottom of the tank 2 is systematically triggered after a given time delay, for example 20 seconds, to brew the fluid 7 in order to homogenize its temperature and also for smother any flames on the surface of the fluid 7 while driving oxygen.
  • the fluid 7 generally oil, cannot ignite only at a temperature above the flash point, i.e. about 140 °.
  • the surface of the fluid 7 reaches this value while the average temperature is at most 80 °.
  • the mixing of the fluid 7 therefore allows a drop in the temperature of the hottest parts.
  • the tank 17 inert gas 16 is provided to be able to inject inert gas 16 for a period of the order of 45 minutes much greater than the expected time to extinguish the fire.
  • the transformer 1 can be equipped with one or more on-load changers 25 serving as interfaces between said transformer 1 and the electrical network to which it is connected to ensure a constant voltage despite variations in the current supplied to the network.
  • the on-load changer 25 is connected by a pipe 26 to line 14 intended for emptying. Indeed, the tap changer under load 25 is also cooled by a coolant flammable. Due to its reduced volume, the explosion of a tap changer is extremely violent and can accompanied by spraying of coolant jets inflamed.
  • Line 26 is provided with a calibrated diaphragm 27 able to tear in the event of a short circuit and therefore overpressure at inside the on-load tap-changer 25. This avoids the explosion of the tank of said on-load tap-changer 25.
  • This one also includes a pressure sensor 28 connected, on the one hand, to the transformer 1 supply cell to trigger it and, on the other hand, to the control unit 22 to trigger the operation of the prevention device during a short circuit in the on-load changer 25.

Abstract

PCT No. PCT/FR96/01513 Sec. 371 Date May 19, 1997 Sec. 102(e) Date May 19, 1997 PCT Filed Sep. 27, 1996 PCT Pub. No. WO97/12379 PCT Pub. Date Apr. 3, 1997An electrical transformer which is filled with a combustible coolant may experience a break in the electrical insulation within the transformer. This break in the electrical insulation may lead to an explosion or fire. A pressure sensor and a vapor sensor are preferably coupled to the enclosure to monitor the pressure and vapor content of the enclosure. An increase in pressure of the enclosure may indicate that an insulation breakdown has occurred. When an increase in pressure is detected, the coolant is partially drained from the enclosure. After draining some of the coolant, an inert gas may be injected into the bottom of the enclosure to stir the remaining coolant.

Description

La présente invention concerne le domaine de la prévention contre l'explosion et l'incendie des transformateurs électriques refroidis par un fluide combustible.The present invention relates to the field of prevention against explosion and fire of electrical transformers cooled by a combustible fluid.

Les transformateurs électriques subissent des pertes tant dans les enroulements que dans la partie fer, qui nécessitent la dissipation de la chaleur produite. Ainsi, les transformateurs de grande puissance sont généralement refroidis à l'huile. Les huiles utilisées sont diélectriques et sont susceptibles de prendre feu au-delà d'une température de l'ordre de 140°. Les transformateurs étant des éléments très onéreux, leur protection nécessite une attention particulière.Electric transformers suffer losses both in the windings only in the iron part, which require dissipation of the heat produced. So the high power transformers are generally oil-cooled. The oils used are dielectric and are liable to catch fire beyond temperature of the order of 140 °. The transformers being elements very expensive, their protection requires special attention.

Les incendies de transformateurs de puissance isolés par l'huile diélectrique surviennent en général en raison de la rupture de l'isolation électrique interne qui provoque une déflagration souvent très violente. Il en résulte une importante déchirure de la cuve du transformateur et un incendie de l'huile qui propage le feu aux autres équipements du site qui sont également susceptibles de contenir de grandes quantités de produits combustibles.The fires of power transformers isolated by dielectric oil generally occur due to the breakdown of internal electrical insulation which often causes deflagration very violent. This results in a significant tear in the tank of the transformer and an oil fire that spreads fire to others site equipment which may also contain large quantities of combustible products.

Les explosions peuvent être provoquées par des surcharges, des surtensions, une détérioration progressive de l'isolation, un niveau d'huile insuffisant, l'apparition d'eau ou de moisissure ou une panne d'un composant isolant.Explosions can be caused by overloads, overvoltages, progressive deterioration of the insulation, a level insufficient oil, the appearance of water or mold or a breakdown an insulating component.

On connaít dans l'art antérieur, des soupapes de sûreté se déclenchant lors d'une surpression à l'intérieur de la cuve du transformateur. Toutefois ces soupapes ne sont pas adaptées aux conséquences d'un défaut d'isolement interne du transformateur.We know in the prior art, safety valves are triggering during an overpressure inside the tank of the transformer. However, these valves are not suitable for consequences of a transformer internal insulation fault.

Le document WO-A-94 28 566 concerne un appareil de surveillance d'une décharge partielle dans un équipement électrique à haute tension tel qu'un transformateur. L'appareil comprend un transducteur capable de convertir des ondes de pression ultra sonores consécutives à un défaut d'isolement. On évacue alors l'énergie électrique qui en résulte vers la terre. WO-A-94 28 566 relates to a device for monitoring a partial discharge in equipment high voltage electrical such as a transformer. The device includes a transducer capable convert ultrasonic pressure waves following an insulation fault. We then evacuate the resulting electrical energy to the earth.

On connaít également des systèmes de protection incendie pour transformateurs électriques qui sont actionnés par des détecteurs de température.We also know fire protection systems for electrical transformers which are activated by detectors of temperature.

D'autre part, le document EP-A-238 475 décrit un dispositif d'extinction d'incendie d'un transformateur électrique à huile par injection d'azote sous pression dans le bas de la cuve pour brasser l'huile et refroidir ainsi les parties les plus chaudes de l'huile.On the other hand, document EP-A-238,475 describes a fire extinguisher device of an electric oil transformer by injection of nitrogen under pressure at the bottom of the tank to stir the oil and cool the hottest parts of the oil.

Mais ces systèmes se mettent en ouvre avec une inertie importante, lorsque l'huile du transformateur est déjà en flamme. On se contente donc de limiter l'incendie à l'équipement concerné pour ne pas propager le feu aux installations voisines.But these systems are implemented with a significant inertia, when the transformer oil is already in flame. So we just limit the fire to the equipment concerned so as not to spread the fire to neighboring installations.

Le document DE-A-2 624 882 décrit un dispositif de protection contre la surpression dans la cuve d'un transformateur contenant un fluide de refroidissement. Ce dispositif comprend une soupape de sûreté sous la forme d'un couvercle équipé d'un contact électrique.Document DE-A-2 624 882 describes a device for overpressure protection in the transformer tank containing a coolant. This device includes a safety valve in the form of a cover fitted an electrical contact.

L'objet de la présente invention est donc de fournir un procédé qui protège à la fois contre la surpression à l'intérieur du transformateur, due à la déflagration lors de la rupture de l'isolation électrique interne et contre l'incendie qui résulte de telles ruptures d'isolation.The object of the present invention is therefore to provide a process which protects both against overpressure inside the transformer, due to deflagration when the insulation breaks internal electrical and against fire resulting from such ruptures insulation.

L'invention a également pour objet un dispositif de prévention contre l'explosion et l'incendie qui permet une détection instantanée de la rupture de l'isolation électrique.The invention also relates to a device for explosion and fire prevention which allows detection instant of the break in the electrical insulation.

Le procédé de protection contre l'incendie d'un transformateur électrique comprenant une cuve remplie de fluide de refroidissement combustible dans lequel on refroidit des parties chaudes du fluide de refroidissement par injection d'un gaz inerte sous pression dans le bas de la cuve afin de brasser le fluide de refroidissement et de chasser l'oxygène situé à proximité, comprend, avant l'étape de refroidissement, une étape de prévention contre l'explosion et l'incendie du transformateur par détection d'une rupture de l'isolement électrique du transformateur par une soupape de sûreté équipée d'un contact électrique et formant un moyen capteur de pression et décompression instantanée de la cuve du transformateur par vidange partielle du fluide de refroidissement au moyen d'une vanne.The fire protection process of an electrical transformer comprising a tank filled with combustible coolant in which cools hot parts of the coolant by injection of an inert gas under pressure into the bottom of the tank in order to stir the coolant and expel the oxygen located nearby, includes, before the cooling step, a transformer explosion and fire prevention step by detection of a break in the electrical insulation of the transformer by a safety valve fitted with an electrical contact and forming a sensor means instant pressure and decompression of the transformer tank by draining partial cooling fluid by means of a valve.

Le dispositif de protection contre l'incendie d'un transformateur électrique, selon l'invention comprend une cuve remplie de fluide de refroidissement combustible, et une soupape de sûreté équipée d'un contact électrique et formant un moyen capteur de la pression dans ladite cuve ladite soupape faisant partie de moyens de prévention contre l'explosion et l'incendie qui comprennent en outre une vanne (15) de décompression instantanée de la cuve du transformateur par vidange partielle du fluide de refroidissement contenu dans la cuve.The fire protection device of an electric transformer according to the invention includes a tank filled with combustible coolant, and a safety valve fitted with an electrical contact and forming a sensor means pressure in said tank said valve being part of means of prevention against the explosion and the fire which also include a valve (15) instant decompression of the transformer tank by partial emptying of the coolant contained in the tank.

Un défaut d'isolement engendre, dans un premier temps, un arc électrique important qui provoque une action des systèmes de protection électriques qui déclenchent la cellule d'alimentation du transformateur (disjoncteur). L'arc électrique provoque, également, une diffusion conséquente d'énergie qui engendre une augmentation de la pression interne du transformateur suffisante pour en déchirer la cuve.An insulation fault first generates a significant electric arc which causes an action of the electrical protection which triggers the supply cell of the transformer (circuit breaker). The electric arc also causes a consequent diffusion of energy which generates an increase of enough internal transformer pressure to tear the tank.

De préférence, le dispositif est muni d'un moyen de détection du déclenchement de la cellule d'alimentation du transformateur et d'un boítier de commande qui reçoit les signaux émis par les moyens capteurs du transformateur et qui est capable d'émettre des signaux de commande.Preferably, the device is equipped with a means for detecting the triggering of the transformer supply cell and control box which receives the signals emitted by the sensor means of the transformer and which is capable of transmitting control signals.

De préférence, le dispositif comprend un moyen de refroidissement des parties chaudes du fluide, par injection de gaz inerte dans le bas de la cuve, commandé par un signal de commande du boítier de commande. En effet, certaines parties du fluide de refroidissement subissent un échauffement capable de l'enflammer. L'injection d'un gaz inerte au fond de la cuve provoque un brassage du fluide de refroidissement qui homogénéise la température et permet de chasser l'oxygène présent à proximité du fluide.Preferably, the device includes means for cooling the parts hot fluid, by injecting inert gas into the bottom of the tank, controlled by a control signal from the control unit. In effect, certain parts of the coolant undergo a heating capable of igniting it. Injection of an inert gas into the bottom of the tank causes a cooling fluid circulation which homogenizes the temperature and makes it possible to expel the oxygen present at proximity to the fluid.

L'invention sera mieux comprise à l'étude de la description détaillée d'un mode de réalisation particulier pris à titre nullement limitatif et illustré par les dessins annexés, sur lesquels :

  • la figure 1 est une vue générale du dispositif de prévention selon l'invention; et
  • la figure 2 est une vue schématique représentant la logique de fonctionnement du dispositif selon l'invention.
    • The invention will be better understood on studying the detailed description of a particular embodiment taken without any limitation being implied and illustrated by the appended drawings, in which:
  • Figure 1 is a general view of the prevention device according to the invention; and
  • Figure 2 is a schematic view showing the operating logic of the device according to the invention.

    • Comme illustré sur les figures, le transformateur 1 comprend une cuve 2 reposant sur la sol 3 au moyen de pieds 4 et est alimenté en énergie électrique par des fils 5 entourés par des isolateurs 6.As illustrated in the figures, the transformer 1 comprises a tank 2 resting on the ground 3 by means of feet 4 and is supplied with electrical energy by wires 5 surrounded by insulators 6.

    La cuve 2 est remplie de fluide de refroidissement 7, par exemple, de l'huile diélectrique. Afin de garantir un niveau constant de fluide de refroidissement 7 dans la cuve 2, le transformateur 1 est muni d'un réservoir d'appoint 8 en communication avec la cuve 2 par une conduite 9.The tank 2 is filled with cooling fluid 7, by example, dielectric oil. In order to guarantee a constant level of coolant 7 in the tank 2, the transformer 1 is provided with an auxiliary tank 8 in communication with the tank 2 by a pipe 9.

    La conduite 9 est pourvue d'un clapet automatique 10 qui obture la conduite 9 dès qu'il détecte un mouvement rapide du fluide 7. Ainsi, lors d'une explosion de la cuve 2, la pression dans la conduite 9 chute brusquement ce qui provoque un début d'écoulement de fluide 7 qui est rapidement arrêté par l'obturation du clapet automatique 10. On évite ainsi que le fluide 7 contenu dans le réservoir d'appoint 8 vienne alimenter l'incendie du transformateur 1.Line 9 is provided with an automatic valve 10 which closes line 9 as soon as it detects rapid movement of the fluid 7. Thus, during an explosion of the tank 2, the pressure in the pipe 9 drops sharply which causes a start of flow fluid 7 which is quickly stopped by closing the valve automatic 10. This prevents the fluid 7 contained in the booster tank 8 comes to supply the transformer fire 1.

    La cuve 2 est munie d'un capteur de pression 11 capable de détecter sans retard la variation de pression due à la déflagration provoquée par la rupture de l'isolation électrique du transformateur 1. Le capteur de pression 11 est constitué par une soupape de sûreté équipée d'un contact électrique et ainsi capable de transmettre une information relative à la variation de pression détectée. La cuve 2 est également munie de capteurs de température 12 situés en plusieurs points de la cuve 2, afin de connaítre la température du fluide 7. Toutefois, ces capteurs de température 12 présentent un retard estimé à 20 ou 30 secondes par rapport au détecteur de pression 11, en raison de la propagation plus lente de la chaleur que de la pression.The tank 2 is provided with a pressure sensor 11 capable of detect without delay the pressure variation due to the deflagration caused by the breaking of the electrical insulation of the transformer 1. The pressure sensor 11 consists of a safety valve fitted with an electrical contact and thus capable of transmit information relating to pressure variation detected. The tank 2 is also provided with temperature sensors 12 located in several points of the tank 2, in order to know the fluid temperature 7. However, these temperature sensors 12 have an estimated delay of 20 or 30 seconds from the pressure detector 11, due to the slower propagation of the heat than pressure.

    La cuve 2 comprend un capteur 13 de la présence de vapeur du fluide de refroidissement également appelé buchholz monté en un point haut de la cuve 2, en général sur la conduite 9. La déflagration due à une rupture d'isolement électrique provoque rapidement le dégagement de vapeur du fluide 7 dans la cuve 2. Un capteur de vapeur 13 est donc performant pour détecter une rupture de l'isolation électrique.The tank 2 comprises a sensor 13 for the presence of steam coolant also called buchholz mounted in a high point of tank 2, generally on line 9. Deflagration due to a break in electrical isolation quickly causes the release of vapor from the fluid 7 in the tank 2. A sensor for steam 13 is therefore effective in detecting a break in the insulation electric.

    Le transformateur 1 est alimenté par l'intermédiaire d'une cellule d'alimentation, non représentée, qui comprend des moyens de coupure d'alimentation tels que des disjoncteurs et qui est munie de capteurs de déclenchement 21.The transformer 1 is supplied via a supply cell, not shown, which comprises means for power cut such as circuit breakers and which is provided with trigger sensors 21.

    La cuve 2 est munie de moyens de vidange comprenant une conduite 14 à laquelle elle est reliée à la hauteur souhaitée du niveau de vidange. La conduite 14 est fermée par une vanne 15 de fort diamètre par exemple 100 à 150 mm. La cuve 2 comprend un moyen de refroidissement du fluide 7 par injection d'un gaz inerte 16 tel que de l'azote dans le bas de la cuve 2. Le gaz inerte 16 est stocké dans un réservoir sous pression 17 muni d'une vanne 18, d'un détendeur 19 et d'un tuyau 20 amenant le gaz 16 jusqu'à la cuve 2.The tank 2 is provided with draining means comprising a pipe 14 to which it is connected at the desired height of the level emptying. Line 14 is closed by a strong valve 15 diameter for example 100 to 150 mm. The tank 2 includes a means of cooling of the fluid 7 by injection of an inert gas 16 such as nitrogen at the bottom of the tank 2. The inert gas 16 is stored in a pressure tank 17 provided with a valve 18, a pressure reducer 19 and a pipe 20 bringing the gas 16 to the tank 2.

    Le capteur de pression 11, les capteurs de température 12, le capteur de vapeur 13, les capteurs de déclenchement 21, la vanne 15 de la conduite 14 et la vanne 18 du tuyau 20 sont reliés à un boítier de commande 22 destiné à contrôler le fonctionnement du dispositif. Le boítier de commande 22 est muni de moyens de traitement d'information recevant les signaux des différents capteurs et capables d'émettre des signaux de commande à destination des vannes 15 et 18.The pressure sensor 11, the temperature sensors 12, the steam sensor 13, trigger sensors 21, valve 15 of the pipe 14 and the valve 18 of the pipe 20 are connected to a housing of command 22 intended to control the operation of the device. The control box 22 is provided with processing means receiving signals from different sensors and capable send control signals to valves 15 and 18.

    Le dispositif est actionné par un signal de pression élevée en provenance du capteur de pression 11 en coïncidence avec un signal de déclenchement en provenance des capteurs de déclenchement 21 de la cellule d'alimentation du transformateur 1 pour prévenir l'explosion et l'incendie. Le dispositif peut également être actionné par un signal de température élevée en provenance d'un des capteurs de température 12 en coïncidence avec un signal de présence de vapeur en provenance du capteur de vapeur 13 pour déclencher l'extinction d'un incendie. Ainsi, on exige que deux capteurs fournissent des informations concordantes afin d'éviter des déclenchements intempestifs.The device is actuated by a high pressure signal in origin of the pressure sensor 11 coincident with a signal of trigger from the trigger sensors 21 of the transformer 1 supply cell to prevent explosion and the fire. The device can also be activated by a signal high temperature from one of the temperature sensors 12 coinciding with a steam signal from the steam sensor 13 to start the extinction of a fire. So, two sensors are required to provide consistent information in order to avoid nuisance trips.

    En conditions normales, le dispositif est déclenché par l'information de pression élevée, en concordance avec l'information de déclenchement de la cellule d'alimentation, qui commande instantanément l'étape 23 d'ouverture de la vanne de vidange 15 qui permet la décompression instantanée de la cuve 2 du transformateur 1 dont la plupart des composants resteront donc intacts, à l'exception des éléments situés dans une zone très proche de l'arc électrique engendré par le défaut d'isolement. L'ouverture de la vanne 15 permet d'éviter des débordements de fluide 2 enflammé lorsque l'on injectera du gaz inerte 16 dans la cuve 2 qui est susceptible d'être détériorée. Enfin l'ouverture de la vanne 15 provoque une décompression dans la conduite 9 ce qui entraíne l'obturation du clapet automatique 10. Le réservoir d'appoint 8 est ainsi isolé et le fluide 7 qu'il contient n'alimente pas l'incendie. L'ouverture rapide de la vanne 15 diminue également les risques d'explosion et augmente la probabilité que la cuve 2 du transformateur 1 reste intacte.Under normal conditions, the device is triggered by the high pressure information, in accordance with the information of triggering of the supply cell, which controls instantly step 23 of opening the drain valve 15 which allows instant decompression of tank 2 of transformer 1 most of the components of which will therefore remain intact, except elements located in an area very close to the electric arc caused by the insulation fault. The opening of the valve 15 allows avoid overflowing of inflamed fluid 2 when injecting inert gas 16 in the tank 2 which is liable to be damaged. Finally the opening of the valve 15 causes a decompression in the pipe 9 which leads to the closing of the automatic valve 10. The make-up tank 8 is thus isolated and the fluid 7 which it contains does not fuel the fire. The rapid opening of valve 15 decreases also the risk of explosion and increases the likelihood that the tank 2 of transformer 1 remains intact.

    Les risques d'incendie sont donc réduits, mais après la vidange partielle de la cuve 2, l'étape 24 d'injection du gaz inerte 16 dans le bas de la cuve 2 est systématiquement déclenchée après une durée donnée de temporisation, par exemple 20 secondes, pour brasser le fluide 7 afin d'homogénéiser sa température et également pour étouffer les flammes éventuelles à la surface du fluide 7 en chassant l'oxygène. En effet, le fluide 7, en général de l'huile, ne peut s'enflammer qu'à une température supérieure au point éclair, soit environ 140°. Or, dans le cas d'un incendie du transformateur 1 consécutif à un arc électrique, seule la surface du fluide 7 atteint cette valeur alors que la température moyenne est au maximum de 80°. Le brassage du fluide 7 permet donc une baisse de la température des parties les plus chaudes. Pour des raisons de sécurité, le réservoir 17 du gaz inerte 16 est prévu pour pouvoir injecter du gaz inerte 16 pendant une durée de l'ordre de 45 minutes largement supérieure à la durée prévue pour éteindre l'incendie.The risk of fire is therefore reduced, but after partial emptying of tank 2, step 24 of injecting inert gas 16 at the bottom of the tank 2 is systematically triggered after a given time delay, for example 20 seconds, to brew the fluid 7 in order to homogenize its temperature and also for smother any flames on the surface of the fluid 7 while driving oxygen. Indeed, the fluid 7, generally oil, cannot ignite only at a temperature above the flash point, i.e. about 140 °. However, in the case of a transformer fire 1 consecutive to an electric arc, only the surface of the fluid 7 reaches this value while the average temperature is at most 80 °. The mixing of the fluid 7 therefore allows a drop in the temperature of the hottest parts. For safety reasons, the tank 17 inert gas 16 is provided to be able to inject inert gas 16 for a period of the order of 45 minutes much greater than the expected time to extinguish the fire.

    Le transformateur 1 peut être équipé d'un ou plusieurs changeurs de prise en charge 25 servant d'interfaces entre ledit transformateur 1 et le réseau électrique auquel il est relié pour assurer une tension constante malgré des variations du courant fourni au réseau. Le changeur de prise en charge 25 est relié par une conduite 26 à la conduite 14 destinée à la vidange. En effet, le changeur de prise en charge 25 est également refroidi par un fluide de refroidissement inflammable. En raison de son volume réduit, l'explosion d'un changeur de prise en charge est extrêmement violente et peut s'accompagner de projection de jets de fluide de refroidissement enflammé. La conduite 26 est pourvue d'un diaphragme calibré 27 capable de se déchirer en cas de court-circuit et donc de surpression à l'intérieur du changeur de prise en charge 25. On évite ainsi l'explosion de la cuve dudit changeur de prise en charge 25. Celui-ci comprend également un capteur de pression 28 relié, d'une part, à la cellule d'alimentation du transformateur 1 pour déclencner celle-ci et, d'autre part, au boítier de commande 22 pour déclencher le fonctionnement du dispositif de prévention lors d'un court-circuit dans le changeur de prise en charge 25.The transformer 1 can be equipped with one or more on-load changers 25 serving as interfaces between said transformer 1 and the electrical network to which it is connected to ensure a constant voltage despite variations in the current supplied to the network. The on-load changer 25 is connected by a pipe 26 to line 14 intended for emptying. Indeed, the tap changer under load 25 is also cooled by a coolant flammable. Due to its reduced volume, the explosion of a tap changer is extremely violent and can accompanied by spraying of coolant jets inflamed. Line 26 is provided with a calibrated diaphragm 27 able to tear in the event of a short circuit and therefore overpressure at inside the on-load tap-changer 25. This avoids the explosion of the tank of said on-load tap-changer 25. This one also includes a pressure sensor 28 connected, on the one hand, to the transformer 1 supply cell to trigger it and, on the other hand, to the control unit 22 to trigger the operation of the prevention device during a short circuit in the on-load changer 25.

    Grâce à l'invention, on dispose ainsi d'un procédé et d'un dispositif de prévention contre l'explosion et l'incendie dans un transformateur qui nécessitent peu de modifications des éléments existants, qui détectent les ruptures d'isolation de façon extrêmement rapide et agissent quasi simultanément de façon à limiter les conséquences en résultant. Cela permet de sauver le transformateur ainsi que le changeur de prise en charge et de minimiser les dégâts liés au court-circuit.Thanks to the invention, there is thus a method and a explosion and fire prevention device in a transformer that require little modification of the elements that detect insulation breaks in an extremely fast and act almost simultaneously to limit consequences. This saves the transformer as well as the tap changer and minimize the related damage short circuit.

    Claims (13)

    1. Method of protection against fire of an electrical transformer (1) comprising an enclosure (2) filled with a combustible coolant (7), in which hot parts of the coolant (7) are cooled (24) by injecting an inert gas (16) under pressure into the bottom of the enclosure (2) in order to stir the coolant (7) and flush the oxygen located in proximity, characterized in that the cooling step is preceded by a step of prevention against explosion and fire of the transformer by detecting a break in the electrical insulation of the transformer (1) using a safety valve which is equipped with an electrical contact and forms a pressure-sensor means (11), and instantaneous decompression of the enclosure of the transformer by partial draining of the coolant (7) using a valve (15).
    2. Method according to Claim 1, characterized by a step of isolating a make-up tank (8) of coolant (7) using a check valve (10) in order to prevent the coolant (7) from spreading, the check valve (10) closing as soon as a rapid movement of the coolant (7) is detected.
    3. Method according to either of the preceding claims, characterized by a step of detecting the presence of coolant vapour (7) in the enclosure (2) of the transformer (1), using a vapour sensor (13) capable of causing partial draining of the coolant (7) and injection of inert gas (16).
    4. Method according to any one of the preceding claims, characterized by a step of detectirg the temperature of the coolant (7), using temperature sensors (12) capable of causing partial draining of the coolant (7) and injection of inert gas (16).
    5. Method according to any one of the preceding claims, characterized by a step of detecting the triggering of a supply cell of the transformer, using triggering sensors (21) capable of causing partial draining of the coolant (7) and injection of the inert gas (16).
    6. Method according to any one of Claims 3 to 5, characterized in that the step for partially draining (23) the fluid (7) is initiated only when two sensors simultaneously order initiation of the said step (23).
    7. Device for protection against fire of an electrical transformer (1) comprising an enclosure (2) filled with a combustible coolant (7), the device comprising a safety valve which is equipped with an electrical contact and forms a pressure-sensor means in the said enclosure (2), characterized in that the said valve forms part of the means of prevention against explosion and fire, which furthermore comprises a valve (15) for instantaneous decompression of the enclosure of the transformer by partial draining of the coolant (7) contained in the enclosure.
    8. Device according to Claim 7, characterized in that the means of prevention against explosion and fire additionally comprise a means (13) for sensing the vapour of the coolant (7) in the enclosure (2), means (12) for sensing the temperature of the coolant (7) in the enclosure (2), and a means (21) for sensing the triggering of a supply cell of the transformer (1).
    9. Device according to either one of Claims 7 and 8, characterized by a control unit (22) which receives the signals emitted by the sensor means of the transformer (1) and can emit control signals.
    10. Device according to Claim 9, characterized in that the decompression valve (15) has an opening which is initiated by a control signal from the control unit (22).
    11. Device according to either of Claims 9 and 10, characterized by a means for cooling the hot parts of the coolant (7) by injecting inert gas (16) into the bottom of the enclosure (2).
    12. Device according to Claim 11, characterized in that the means for injecting inert gas (16) comprises a pressurized gas tank (17), a pressure reliever (19) and a valve (18) whose opening is ordered by a control signal from the control unit (22).
    13. Device according to any one of Claims 7 to 12, characterized in that it comprises a means (28) for sensing the pressure in an on-load tap changer (25) of the transformer and a means, intended to stop it from exploding, for setting the said on-load tap changer at atmospheric pressure.
    EP96932665A 1995-09-28 1996-09-27 Method and device for preventing explosions and fires in electrical transformers Expired - Lifetime EP0795183B1 (en)

    Priority Applications (1)

    Application Number Priority Date Filing Date Title
    DE69608784T DE69608784T9 (en) 1995-09-28 1996-09-27 METHOD AND DEVICE FOR PREVENTING EXPLOSION AND FIRE FOR ELECTRIC TRANSFORMERS

    Applications Claiming Priority (3)

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    FR9511386A FR2739486B1 (en) 1995-09-28 1995-09-28 METHOD AND DEVICE FOR PROTECTION AGAINST EXPLOSION AND FIRE OF ELECTRICAL TRANSFORMERS
    FR9511386 1995-09-28
    PCT/FR1996/001513 WO1997012379A1 (en) 1995-09-28 1996-09-27 Method and device for preventing explosions and fires in electrical transformers

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    EP0795183A1 EP0795183A1 (en) 1997-09-17
    EP0795183B1 true EP0795183B1 (en) 2000-06-07

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    DE69608784D1 (en) 2000-07-13
    MX9703595A (en) 1997-08-30
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    KR970707563A (en) 1997-12-01
    HUP9800461A3 (en) 2000-03-28
    ES2148795T3 (en) 2000-10-16
    US5946171A (en) 1999-08-31
    UA45365C2 (en) 2002-04-15
    DE795183T1 (en) 1998-01-15
    RU2215352C2 (en) 2003-10-27
    CA2206793C (en) 2011-09-20
    HU221222B1 (en) 2002-08-28
    DE69608784T9 (en) 2012-03-29
    DK0795183T3 (en) 2000-10-02
    CA2206793A1 (en) 1997-04-03
    EP0795183A1 (en) 1997-09-17
    HK1003400A1 (en) 1998-10-30
    SK64597A3 (en) 1997-10-08
    DE69608784T2 (en) 2001-02-01
    GR3034274T3 (en) 2000-12-29
    CN1079573C (en) 2002-02-20
    ATE193784T1 (en) 2000-06-15
    JPH10510105A (en) 1998-09-29
    SK284150B6 (en) 2004-10-05
    KR100441193B1 (en) 2004-11-03
    CZ293859B6 (en) 2004-08-18
    FR2739486B1 (en) 1997-11-14
    CN1165581A (en) 1997-11-19
    CZ153297A3 (en) 1998-12-16
    RO116688B1 (en) 2001-04-30
    WO1997012379A1 (en) 1997-04-03
    FR2739486A1 (en) 1997-04-04
    PT795183E (en) 2000-11-30
    HUP9800461A2 (en) 1998-06-29

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