Alarm method of linear composite thermal detector

Abstract

The invention relates to an alarm method of a linear composite thermal detector. The linear composite thermal detector is mainly formed by connecting a conversion box, a detection cable and terminal resistors R1 and R2, and is characterized in that the structure of the detection cable is as follows: one detection conductor is coated with a meltable NTC characteristic plastic layer, the other detection conductor is coated with a meltable insulating layer, the two detection conductors with the coating layers are mutually wound together, and then the outer layer is sequentially coated with the third detection conductor and the outer sheath layer. The detection conductor coated with the meltable NTC characteristic plastic layer and the third detection conductor form a loop L1, the other detection conductor and the third detection conductor form a loop L2, and the two detection conductors which are wound together form a voltage difference loop L3. The conversion box always detects the working state between the detection conductors of each loop and the resistance change before and after the short circuit of the detection conductors, and judges and outputs correct fire alarm and fault signals.

Description

technical field [0001] The invention relates to linear temperature-sensing fire detection, and an alarm method for a linear composite temperature-sensing detector. [0002] technical background [0003] In the prior art, non-recoverable linear temperature-sensitive fire detectors are widely used with the following four working principles, and their structures are as follows: figure 1 shown; [0004] 1) A switch characteristic type linear temperature-sensitive fire detector, which is connected by a conversion box 17 to two elastic detection conductors 11 and 12 which are intertwined with each other, and a fusible insulation is provided between the two elastic detection conductors 11 and 12 The material barrier layers 13 and 14 are sequentially covered with an insulating layer 15 and an outer sheath layer 16, and are connected with a terminal resistor R. The working principle is: when a fire occurs, the fusible insulating material barrier layers 13 and 14 melt, and the two el...

AI Technical Summary

Problems solved by technology

Its disadvantage is that the conversion box 17 cannot distinguish whether the two elastic detection conductors 11, 12 are short-circuited due to mechanical external force damage, or short-circuited due to fire and heat, and it is easy to generate false fire alarms.

Its disadvantages are: in the event of a sudden extreme high temperature fire, the NTC characteristic material barrier layer 13, 14 is reduced in thermal resistance and melts and detects the conductor 11, 12, and a short circuit occurs at the same time, and the conversion box 17 judges the logic according to the preset short circuit fault , mistakenly believe that the short circuit is caused by mechanical damage, and wrongly output the short circuit fault alarm signal, which will seriously affect the judgment of the fire alarm and easily cause major accidents

[0006] Disadvantage 3 is: the correct working principle of the thermocouple is that the hot ends of two metal detection conductors of different materials are in contact with spot welding, so that the thermoelectric potential can be generated correctly, but the two different materials of the thermocouple type linear temperature-sensitive fire detector The metal detection conductors 1 and 2 are not in contact under normal circumstances. Only when the detection conductors 1 and 2 are subjected to heat, fire or mechanical damage can a short circuit occur, and the short-circuit point contact longitudinal distance is too long to be uncertain, so , a cold end and a hot end will be generated within the contact range, and the thermoelectric potential will be offset. The cold end of the conversion box 8 cannot detect the thermoelectric potential of the short circuit point, which cannot meet the fire alarm conditions of the conversion box 8, and it is wrongly judged as a short circuit. Fault, output fault alarm signal

The disadvantage 1 is that it cannot continuously monitor the change of the environmental temperature rise before the fire occurs, and the early fire warning function cannot be realized, which will cause delays in fire judgment and easily cause large losses; the disadvantage 2 is: due to the length Generally not more than 200 meters, the set alarm temperature is generally 85°C or 105°C, the application places are mainly cable trays, thermocouple type line type temperature-sensitive fire detectors, the temperature of the short-circuit point is between 88°C and 110°C, the short-circuit point The thermal potential of the cold end is less than 10mv. Since the linear temperature-sensitive fire detector is laid on the surface of the high-voltage cable, the electromagnetic field generated by the high-voltage cable will produce a transformer effect with the thermocouple-type linear temperature-sensitive fire detector. The voltage of more than 10mv can be generated on the device, so the conversion box 17 cannot correctly identify and judge whether the short-circuit point is heated to generate thermoelectric potential or voltage generated by interference. short circuit, the conversion box 17 misjudges and outputs the fire alarm signal according to the short circuit and the generated thermoelectric potential, and generates a false fire alarm; disadvantage 3 is: usually the correct working principle of a thermocouple is that the hot ends of two metal detection conductors of different materials are point The thermoelectric potential can be generated correctly only by welding and welding contact, but the metal detection conductors 11 and 12 of two different materials of the thermocouple type linear temperature-sensitive fire detector are not in contact under normal circumstances, and only when heated, fire occurs and mechanically Only when the conductors 11 and 12 are damaged can a short circuit be detected, and the short-circuit point contacting the longitudinal distance is too long to be uncertain. Therefore, a cold end and a hot end will be generated in the contact range, and the thermoelectric potential will be offset, and the conversion box 17 cold end Just can't detect the thermoelectric potential of short-circuit point, can't satisfy the fire alarm condition of switch box 17, judge as short-circuit fault by mistake, output fault alarm signal

Its shortcoming is: the conversion box 17 cannot distinguish whether the contact between the elastic detection conductor 12 and the semiconductor layer 14 is the contact caused by the mechanical external force damage, or the contact caused by the heat caused by the fire. Therefore, the conversion box 17 is confirmed as the contact caused by the fire. , and the wrong judgment outputs the fire alarm signal

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