The general steps and methods of power cable fault diagnosis
in fact, several kinds of cable fault causes the result of joint action, can make the cable cable fault of any kind.
over the decades, people in exploration and production practice summarizes many cable fault test method. Such as the classic method of resistance bridge method, capacitance bridge method, high pressure electric bridge method, etc. Method can only be test of earthing resistance bridge or interphase short circuit of low insulation resistance of cable fault; Main test cable capacitance bridge method of linear break fault; High pressure method of bridge main tests (high impedance fault Leakage failure and flashover failure except) 。 Visible, the classic method in cable fault diagnosis technology has certain limitations, cannot meet the requirements of various types of cable fault test.
modern pulse reflection test technology including low voltage pulse method, dc high voltage flashover method and shock high voltage flashover method, they are suitable for all kinds of different types of cable fault testing. Many years of production practice has fully proved that the modern pulse reflecting the applicability and accuracy of testing technology, and has set up a mature and perfect. Power cable fault diagnosis, no matter choose what kind of test method, must according to certain procedures and steps. Are summarized as follows.
1。 Determine the fault nature
when to start on a particular fault cable fault test, the ongoing work of the first is to understand the relevant situations of the fault cable to determine the nature of the fault. Master this fault is ground and short circuit, wire, or their mixture; Is single phase and two phase or three phase fault; Is high resistance, low resistance and leakage resistance or flashover failure. Only determines the nature of the fault, can choose the appropriate test methods for specific cable fault diagnosis.
2。 Coarse distance
when determining the fault cable fault properties, can according to the nature of the fault, select the appropriate test method to detect fault point to the end of the test or distance, the work is called coarse distance. Coarse distance is important step in the process of cable fault test, the pros and cons of the job, decide the cable fault testing efficiency and accuracy of the whole process. As a result, often need to have very professional basic theoretical knowledge and rich practical experience of personnel to operate. People in the long-term production practice, discusses and summarizes various faults distance method of coarse, namely, classical method ( Such as bridge and its deformation, etc. ) And modern method ( Pulse reflection method) 。
3。 Detecting path or identify cable
fault cable after coarse Lx, it follows a fault distance the fault distance is by the test side ( The head end or begin) The distance to the point of failure. Theoretically, to test the client as the center of the circle, with Lx fault distance. For radius of a circle, all the points on the circumference of a circle is to satisfy the conditions of the point of failure to test the distance for Lx, clearly point of failure can be a point on the circumference of a circle, and it must be on the cable, it is can use another conditions. When the cable line with line drawing, all the lines will intersect with the circle R = Lx in one point, it is the desire to find the point of failure.
for cable directly buried underground, need to find out the actual cable line ( Can also be measured embedding depth) For detecting path. For bright cable in cable trench, tunnel etc, you need to choose from many cable fault cable, which identify the cable.
detection cable path or identify cable, usually to the fault cable ( If there is a fine line, general and on the whole line core) Plus one audio current signal, and then use the audio signal detecting coil, thus find the cable path or identify cable. For greater complex in interference environment, as the other. Cable clip-on ammeter is commonly used as an aid to identify from the end of the cable head end, or add a current signal, and make change regularity on and off, and then use clip-on table indicating value of the card on the cable to observe the current and break a rule, when people close to the end of the current value (indicating value of the current Because the line loss and reduced) And break a rule match, you can confirm the cable to cable fault.
4。 Precision measuring point
fine measurement point is cable fault testing, it is a important step. In coarse measure and determine the fault cable fault distance path or to identify the fault cable, why still need to fine measurement point? Because coarse measure of fault distance has certain error, fault distance measurement error. Therefore, before the precision measuring point can only judge the barrier point of the general location, in order to accurately determine the location of the fault point is located, must pass a fine point.
cable fault determination of fine point generally USES sound point method, fixed-point method and other special induction. More than 95% of the cable fault acoustic detection method can locate the fault point, gold property to ground fault induction method or special point.
these are the general steps of cable fault diagnosis, in the specific test work, according to the specific situation is different, some steps can be omitted. Cable line mark is clear, for example, don't need to test for cable path or identify cable; Ming fu the openness of the short cable fault ( Cable fault point has been exposed to appearance) ; Point of failure may place co. , LTD. ( Such as doubts among some head only) , also can be directly measuring point.