The type of failure of the power cable mainly has parallel faults and tandem failures. The series fault refers to a plurality of or one wire in the cable, which is typically difficult to detect the tandem failure prior to in series to open a wire, and only the type of fault type of the short circuit power cable is mainly parallel. Faults and tandem failures. The serial failure refers to that there are multiple or one wire in the cable, which is typically difficult to detect the series failure before the wire is interrupted, and only the series failure is easily discovered when the short circuit is really short-circuited.
Parallel failure is due to the long-term overload operation of the cable, which causes an external insulation aging, thereby causing parallel failure. Differential cable faults with the length difference and the resistance value can be divided into high-resistance, low-resistance, open circuit failures. So what are the methods of cable failure detection? Bridge method: The bridge method is a traditional method of cable failure detection, which can achieve an ideal effect.
This method is convenient and fast, high detection accuracy, belongs to a common cable fault detection method. However, since the bridge voltage difference and the current meter are not high, it is only suitable for fault detection of cable resistance. Moreover, it is difficult to detect this method for equipment and cable discontinuation of resistance.
High-voltage bridge method: High voltage bridge method is a fault detection method commonly used in cable fault detection. Its detection principle is in the high voltage bridge, when the constant current power supply pierces the cable, a larger bridge current is guaranteed to a certain extent, thereby forming a certain potential difference on both sides of the overall bridge of the bridge. Thereby statistics on the fault point on the basis of coordinating the bridge. This method is suitable for high-voltage constant current power supplies, which can effectively expand the high-resistance detection range of the bridge. Relatively, the result is more convenient and accurate.
In addition, for the research theory of the bridge method, the cable centerline resistance and the characteristics of the whole line can promote the formation of the bridge detection system. Impact High Voltage Flashing Method: Impact High Voltage Flashing Law is a very broad method for use in some methods of cable failure detection. The detection principle of this method is to apply an impact high pressure at the beginning of the fault cable, so that the location of the fault occurred very quickly, and records data information of voltage mutation in a flash in the fault location.
The time distance is tested by the analysis of wired fault points and wired start data information, thereby derived the fault and uncertain countermeasures. Low voltage pulse reflection method: When detecting a low voltage pulse emission method, the low pressure pulse should be injected on the damaged line. When the pulse is transmitted along the cable, the reflective pulse is displayed in the detecting device during the transmission current process, and the reflection pulse is reflected by the data record of the device, thereby calculating the return time difference of the output pulse. Cable wave velocity, thereby obtaining the distance between the fault point and the test point.
This method is very simple, which enables the test results to be particularly significantly presented, and the detection is performed directly in the case where it is difficult to determine the fault data. But it also has a shortcoming, that is, it is not suitable for high-resistance failures and flashing failures. Secondary pulse method: For secondary pulse method, it is effectively applied to form an impact high pressure pulse of a comprehensive high pressure generator, and introduce it to the cable fault location to effectively pierce the fault part as a premise, extend the hit The absence of the fault site forms an uninterrupted time of the arc.
Obviously, it must be clear that at the same time, a trigger pulse can trigger the automatic trigger device of the secondary pulse and the operation of the cable detection instrument, on the basis of starting the secondary pulse automatic trigger device, transmitting two low pressure pulses, by forming The secondary pulse is used to perform effective transmission on the detection fault cable, thereby breaks through the cable. Using cable fault detector, the voltage waveform floating characteristics and the reflection wavelength of the formation of the arc are used, and the detection device screen is fully, systematically recorded, and distinguishes the various current fluctuations, one of which reflects the actual length of the cable, and the other is reflected Actual distance from short-circuit faults.
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