Research On Detecting Of Fault Arc In Building Electrical Fire Pre-warning System

Fault arc is one of the important reasons that cause electrical fire. However, when power supply circuitry occurring arc the voltage and current peak values are always hereabout ideal values. Therefore, the being used protection equipments now are not able to detect arc. This paper researches power supply circuitry arc's characteristics through many experiments, and have designed fault arc on-line detecting system bases on arc characteristics. This system is an important component of electrical fire for-alarm system, that monitoring fault arc happened on the power supply circuitry promptly and effectively and playing the role of electrical fire alarm effectively. This system can monitor 6 branches signals and composes of upper computer and lower controller. The lower controller composes of detection slave controllers, receiving data host controller (host controller 1) and sending data host controller (host controller 2). The function of detection slave controller is to sample current, and with A/D transmission circuit and current sensor compose of current detecting circuit. Current sensor sends the sampling data to A/D chip and makes them to be digital signal. The digital signal is sent to detecting slave controller, and then the data is sent to host controller 1. The communication protocol between slave and host is RS-485 serial communication protocol. In host controller 1 the data is reset and sent to host controller 2 through parallel port. Host controller 2 sends the data to upper computer by serial port. The communication protocol is RS-232 serial communication protocol. The computer monitoring platform is "fault arc detection system" which developed by LabWindows/CVI. The system uses wavelet analysis as a tool for detecting the signal through the singularity, to determine whether the arc occurred. This system develops orthogonal quadratic spline wavelet as the mother wavelet and uses a'trous algorithm for dyadic wavelet transform. This paper determines the final modulus maxima through reducing the threshold value of details information gradually. In order to further allay supply line noise, after confirmed the modulus maxima points, this system determine whether the arc is burning and half cycle through the distance between maxima points. Once the arc is combusting over five half cycles, the system alarm. Through the experiment, this system can be used to have access to online real-time detecting fault arc effectively.