PECULIARITIES OF THE IMPACT OF ELECTRICAL EQUIPMENT GROUNDING ON FIRE PROTECTION SYSTEM

Abstract

Статья посвящена исследованию влияния заземляющих устройств сети электроснабжения на пожарную опасность технических средств системы противопожарной защиты. Рассмотрены особенности проявления характерных пожароопасных режимов при замыкании фазы сети на открытые проводящие части. Показано, что вероятность возникновения пожароопасных режимов, связанных с системой противопожарной защиты, зависит от исправного состояния электрической защиты и от типа заземления в здании. Отмечено, что при утечке на землю ток не будет пожароопасным вследствие ограничения его сопротивлением заземляющего устройства и грунта. The paper presents the results of the study of the effect of grounding-related fire emergency modes on the fire hazard of the fire protection system. The influence of grounding devices on the fire hazard of electrical equipment of the fire protection system is shown. The performance of individual components of fire protection (for example, fire alarm systems) during operation is under constant control, and the condition of protection devices installed in the network and grounding devices is checked only periodically. Their faulty condition can be established by checking, the frequency of which is regulated by the Rules for the technical operation of consumer electrical installations. A failed protection device during the period between performance tests will not be able to turn off the electrical part of the fire protection system, in the elements of which a fire hazardous mode will occur, with the corresponding consequences. And besides, this system will not be able to perform a functional task. The features of emergency modes manifestation are noted. The most characteristic modes that occur during an emergency phase short circuit to open conductive parts of the electrical equipment of fire protection systems are considered. There are established features that characterize the fire hazard of electrical equipment when using TN and TT grounding as the most common in buildings. The change in the grounding device resistance during operation has a little effect on the magnitude of the earth fault current. The current is largely limited by the ground resistance and does not create a fire hazard from this emergency mode depending on the type of grounding, electrical equipment may present a fire hazard if the phase is short-circuited to grounded elements (including the PE conductor) and the protection devices fail to operate. At the same time, the absence of a differential current protective shutdown device in the power supply circuit will allow, in the event of a leakage to grounded elements during a fire, to continue working for a period of time until the overcurrent protection device trips.