Based on the types of cable faults, various fault detection and testing methods have been developed domestically and internationally. However, the basic steps of these methods are generally the same. Generally speaking, the first step is to conduct fault diagnosis to preliminarily determine the type of fault; then, based on the diagnosis results, proceed with fault location to preliminarily determine the approximate location of the fault; finally, carry out precise location of the fault point. Specifically, the main methods for detecting power cable faults are as follows: This method was once an important method for detecting power cable faults. The advantage of these two detection methods is that they are relatively accurate for detecting low-resistance line faults, but they are not suitable for high-resistance circuits. Some technicians, when using these two methods for high-resistance fault detection, increase the current to burn through the insulation, thereby reducing the line resistance. The drawback of this approach is that it also adversely affects the intact parts of the power cable. Therefore, to solve high-resistance faults in cable lines, technicians proposed the high-voltage current flash testing method, which has been widely applied in practical detection by Zhongshi Holding. However, this method requires the assistance of technicians' experience, and reducing errors has always been a key point in the technological innovation of this method. The principle of the secondary pulse method is to use a low-voltage pulse and a high-voltage generator to emit an impact pulse in the faulty cable line and generate an arc at the fault location. At the moment the arc is generated, a low-voltage pulse is emitted inside the instrument. When this pulse reaches the cable fault, it causes a short circuit, and the reflected wave generated by the short circuit is memorized in the instrument. Then, a low-voltage measurement pulse is emitted, which passes through the fault point to the end of the cable and induces an open-circuit reflection. By comparing the waveforms of the two low-voltage pulses, the location of the fault point can be accurately determined. The cable fault detector automatically matches based on the above principle, then judges and calculates the distance to the fault point. The application of the secondary pulse method in the field of cable fault detection has made high-resistance fault judgment as simple as low-resistance fault judgment, so it has been widely applied. The basic principle of this fault detection method is that when the power grid operates normally, the zero-sequence DC value of each branch line is extremely small, generally not exceeding 0.5mA. If a single-phase grounding fault occurs during grid operation, the zero-sequence DC in that branch line will rapidly increase, generally reaching about 50mA. Therefore, the rapid increase of zero-sequence DC can serve as an important indicator for judging grounding faults in cable lines. Based on the above principle, we can monitor the zero-sequence DC magnitude at the outgoing lines of each branch of the cable line. Once a fault occurs in the grid, the faulty branch can be locked in sequence, and then the secondary pulse method mentioned in the previous section can be used to precisely locate the fault point and quickly eliminate the fault. Power cables are an important component of urban power grids, and their safe operation is of great significance to the normal functioning of the grid. Therefore, grid management and maintenance personnel must not only be able to quickly locate and eliminate faults but also actively take preventive measures for power cable faults. The specific measures include the following points: From the analysis in the first section, it is known that more than half of power cable faults are caused by mechanical external force damage. Therefore, it is essential to strengthen inspection efforts to minimize the probability of external damage to power cables. Specifically, power companies should formulate and improve the inspection system for underground pipelines; strengthen the training and assessment system for supervisors; and promptly rectify any violations found during inspections. Power companies should enhance the daily maintenance of power cables to ensure that cable lines are always in good working condition. In addition, many power cable faults are caused by human operational factors, so it is necessary to strengthen the training of operators, improve their sense of responsibility and professional technical level, avoid non-standard operations and misoperations in work, and improve the reliability of grid operation. Urban power cables are laid in underground conduits, and whether the channel selection is reasonable is an important factor affecting the safe operation of cables. Since the composition, acidity, alkalinity, and moisture content of the soil have a significant impact on power cables, it is necessary to analyze the soil environment of the channel before construction and try to avoid soil environments that have strong corrosive effects on power cables. In the past, power cables mainly used oil-based insulation. Its advantages are simple manufacturing process, low cost, and long lifespan, so it once occupied the main market share of cables. However, the disadvantages of this type of cable are also obvious: the insulating oil is prone to flow and poses a potential threat to the safe operation of cables. With the emergence of cross-linked polyethylene cables, oil-based insulation was quickly phased out. Therefore, we must pay attention to the research and application of new materials in the field of power cable manufacturing, and improve the safety factor of the power grid by providing superior performance power cables. Return to Sohu, view more
