Detection And Processing Of Weak Magnetic Signal In Path Locator

With the development of society,the disadvantages of overhead transmission cables have become increasingly prominent,and buried cables have been more widely used in the power industry.However,with the increasing number of buried cables,the lack of information on buried cables and the intricacy of cable locations have led to a disarray in the layout of buried power cables in China.Once the buried power cable breaks down,it is difficult to find the specific location of the cable fault point because it is not clear the trend of the cable route.This brings great trouble to the maintenance and repair of the cable in the later period,and also causes much more inconvenience to the construction.Therefore,the study of buried cable route detection has become a hot topic in recent years.Taking the detection of the buried cable route as the research background,this thesis studies the design of buried cable route detecting system and the acquisition and detection technology of weak magnetic signal.Firstly,the research background,research status,characteristics and applications of the route detection technology of buried cables are elaborated.Then,several methods on how to deal with the weak signal are listed,such as narrow-band filtering,synchronous accumulation method,correlation detection algorithm,the time domain average method and so on.Next,the in-depth analysis of the features of weak magnetic signal is done.For receiver,when detecting the buried cable,it will influenced by interference of 50Hz signal and thermal noise.When judging the indoor path,the receiver will be disturbed by thermal noise and random noise.Secondly,the integral structural system is designed according to the characteristics of magnetic signal around the buried cable.And using differential coils to improve the capacity of resisting disturbance is promoted,in which the differential coils are wound in Z method and the parameters are designed and optimized,including wire diameter,inductance value,quality factor,distributed capacitance and sensitivity.Based on the digital filter,narrow-band filter is chosed to process the weak magnetic signal.Since only the magnitude is taken into consideration for the receiver,ignoring the phase information of signal,the IIR filter is adopted.And the cascade IIR narrow-band filter can implement the zero and pole points of digital filter precisely and nearly immune to parameters.Thus,the cascade IIR narrow-band filter is taken to handle the received signal.With a large number of simulations and experiments conducted after determining suitable parameters,the result shows that the filtering performance is improved significantly and the noise interference is leached effectively.Finally,the transmitter and receiver programs are designed in a modular manner,which can easily upgrade and replace the function.The transmitter mainly achieves the function of man-machine interaction and signal generation function while the receiver implements the function of man-machine interaction,signal acquisition,signal processing and stethoscope function.Because of the complex interface,abundant functions and difficult development of software,the receiver transplant ?C/OS-II and ?C/GUI embedded operating system into ADSP-BF561 to develop applications.Then,the transmitter and receiver are experimentally in the environment with the power cable buried underground in three aspects,comprising differential coils,IIR filter and the total scheme.The result shows that the cable route detector and the detection method about weak magnetic field signal in this thesis can detect the position and depth of buried power cables quickly and accurately?...