EP0750321A1 - Device protecting liquid media, especially electric insulating media, from fire involvement - Google Patents

Abstract

The arrangement makes a fluid esp. an insulating fluid for transformers etc, non-flammable. After switching off the transformer, a surrounding temperature monitor causes the simultaneous or nearly simultaneous opening of the valves which cause an exchange of fluid and gas. A valve can be selectively closed and, if desired opened again, pneumatically, hydraulically or electrically, to reduce erroneous triggering, by a voluntary act. The valve may be remote controlled and acts to empty the fluid. In an alternative embodiment, the valves are operated such that there is an exchange of fluid and gas. In the case of a transformer or other voltage device, it is switched off before the fluid is evacuated.

Description

Device for the safe discharge of the liquid from a transformer or other container by using the force of gravity, the mobility and the difference in density of liquids and gases and their largely immiscibility, as well as the actuation of valves by temperature sensors or manually, for damage-preventing or damage-reducing exploitation or the above. physical laws.

• 1. auf der Nutzung des o.g. Austauschs von Flüssigkeit und Gas, dergestalt daß ein branduneinbeziehbar (in der Schemazeichnung Bereich B) und unterhalb des zu schützenden brandeinbeziehbaren flüssigkeitsgefüllten Gegenstands (Bereich A) angeordnetes Gasvolumen, gewöhnlich Stickstoff, in einem Umgebungsbrand durch die aus dem Brandort in den Gasbehälter fortgeleitete Flüssigkeit ersetzt wird (das Flüssigkeitsvolumen nimmt, wie in Fig. 1 und Fig. 2 schematisch dargestellt, den Platz des sie ersetzenden Gasvolumens ein und umgekehrt; das in den Transformator oder ein analoges Gefäß gelangende Gas erwärmt sich, und es entsteht im Gesamtsystem ein Überdruck, der durch Ablassen von Inertgas beseitigt wird) und
• 2. dem Wirksamwerden dieses Austauschprinzips durch automatische Öffnung entsprechend angeordneter Ventile im Brandfall, gegebenenfalls unter Beibehaltung der Möglichkeit der Betätigung dieser Ventile, oder ihre Funktion außer Kraft setzender Ventile, von Hand.

All liquid-cooled transformers are affected by the invention, as are also other containers which are equally at risk of environmental fire and contain liquids whose fire involvement is to be prevented. The device is based

• 1. on the use of the above-mentioned exchange of liquid and gas, in such a way that it is incompatible with fire (in the schematic drawing area B) and gas volume, area nitrogen, arranged below the fire-encasable liquid-filled object to be protected (usually nitrogen), in an environmental fire caused by the fire from the location liquid that is passed into the gas container is replaced (the liquid volume, as schematically shown in FIGS. 1 and 2, takes the place of the gas volume that replaces it and vice versa; the gas entering the transformer or an analogue vessel heats up and arises overpressure in the overall system, which is eliminated by releasing inert gas) and
• 2. The effectiveness of this exchange principle by automatic opening of appropriately arranged valves in the event of a fire, if necessary while maintaining the possibility of actuating these valves or their function of overriding valves by hand.

State of the art, regulations of national and international regulations and their inadequacy

In the previous regulations, most of which are currently being revised or have already undergone changes, transformers and other static electrical machines in the medium, high and extra-high voltage ranges were mainly seen as potential causes of fire when assessing the risk they represented. (IEC 76-2 and national standards derived from it.) High-voltage fuses, surge arresters, switches actuated in various ways, as well as various structural measures such as fire protection walls and similar precautions are aimed primarily at reducing the risk of the cause of the fire. (Even some newer standards, such as the French NF C 17-300 or the Belgian BNB 18-200, see the fire risk only in the transformer as a potential cause of the fire.) A significant contribution to risk reduction it was hoped that so-called ascarels would be used. In NF C 17-300, when using a PCB-free askarel, the fire protection measures required for liquids classified as K-Class according to IEC 1100 are dispensed with. Since Askarele by definition do not have a measurable focal point, ie no focal point up to the boiling point, they cannot feed a flame that may exist for a short time in the event of bursting and cannot continue the fire.

However, it was found that these liquids in the damage scenario in which the electrical object, e.g. a transformer or capacitor that represents a fire victim is very likely to form very dangerous connections. This has led to the ban on PCBs and similar ascarels in most countries.

However, since not only Askarele, but also all other common insulating materials including solid and gaseous insulating materials and, in addition, a great many other liquids pose a risk when incorporated into a fire that do not affect the contribution of the fire-retardant substance in terms of making additional fuel available limited, so the substance is always undesirable in the fire, it is desirable to make it fire-irrelevant in one way or another.

Constructive implementation of the theoretical specifications

Use and sensible combination of hydraulic and / or hydraulic-pneumatic laws, in particular the difference in mass between the insulating liquid and inert gas, sensibly nitrogen, and the mutual lack of mixing, shown using the example of a transformer at a fire-prone installation site.

In the event of an environmental fire in which there is a risk that the transformer or another liquid-filled object would be included in the fire and the liquid would escape and actively participate in the fire, a very high room temperature at the location of the fire can be assumed, which is far above the maximum permissible operating temperature (Oil temperature). This high temperature is usefully used to open a valve to evacuate the liquid when the power supply to the transformer is switched off. This is most useful after a warning triggered by an ambient temperature monitor and after a decision has been made by an authorized person to leave the second valve downstream of the first in the open position. This prevents accidental emptying. At the same time as the liquid emerges or with a slight delay, a further valve is opened which allows the inert gas to enter the emptying liquid container, here a transformer. Optionally, the downstream valve (which is open during normal operation) can be dispensed with and the liquid can be drained into the inert gas container, its contents, if there is a risk of fire to the transformer. The gas which is kept available, meaningfully nitrogen, can possibly be kept under negative pressure in order to avoid the creation of a strong excess pressure in the system of the transformer and gas container which communicates after liquid evacuation has occurred during the fire. In this case, the shut-off valve for the inert gas would be opened with a corresponding delay.

With the described arrangement and the described method, insulating liquids up to approximately 95% of the filling quantity, unlike solids or gases, can thus be made fire-unreliable by applying simple hydraulic-pneumatic laws.

By filling the emptying transformer or another vessel with inert gas it is ensured that there is never an explosive, in particular self-igniting mixture in the device / container in the surrounding fire. In addition, the liquid and possibly also solid materials are protected against oxygen attack.

Further advantages: To a large extent exclusion of contamination by the insulating liquid and the products of complete or incomplete combustion which it forms; Insulating liquid cannot take part in the fire in a thermally or toxicologically significant manner, fire protection measures of a conventional type are omitted (fire walls, etc.); the latter very often lead to an increase in the risk of bursting and fire, because the "protected" transformers are operated at higher temperatures, which is detrimental to their life expectancy and increases the risk of bursting.

The arrangement described is particularly useful for transformers that do not have a statistically quantifiable fire-causing potential, as is the case for transformers filled with K liquids.

Claims (2)

Arrangement and procedure for rendering a liquid, in particular insulating liquid, of transformers insoluble in fire, characterized in that an ambient temperature monitor after switching off the transformer causes the simultaneous or almost simultaneous opening of valves which bring about an exchange of liquid and gas - expediently nitrogen as an inert gas - optionally and, in order to avoid false triggers, a valve can be closed pneumatically, hydraulically or electrically and, if necessary, opened again, which is arranged downstream of the one causing the emptying of the liquid, remotely controlled. Arrangement and procedure for rendering a liquid, in particular insulating liquid, of transformers insoluble in fire, characterized in that, initiated by an act of will, the arrangement of valves described above is actuated in such a way that an exchange of liquid and gas takes place, in the case of a transformer or of another live device is switched off before liquid evacuation.

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