FIELD: chemistry.
SUBSTANCE: invention relates to fire safety and specifically to methods and apparatus for warning fires caused by faults in power grids or electrical installations in rooms, buildings, aircraft, ships, railway transport etc. Low-frequency components (<103 kHz) are suppressed in measured resultant current flowing in a protected circuit. Without storage, the value of the obtained signal is compared with a given value and a pulse with a fixed duration which is slightly less than half the period of the mains supply is generated every time said value is exceeded. The pulse is transmitted to a storage unit with a charging time constant of 0.1…0.3 s and a discharge time constant of about 0.4…0.6 s. The signal is transmitted from the output of the storage unit to the input of an additional comparator unit where it is compared with a given second level value. If said second level value is exceeded, a voltage jump occurs at the output of the comparator unit, which triggers a command generating unit which generates a pulse which is transmitted to an actuating device which disconnects the protected circuit from the mains and (or) outputs a warning signal.
EFFECT: high fire safety.
2 cl, 1 dwg
