Cable fault tester principle

The cable fault tester is an important tool for maintaining cables. It can quickly identify the fault point and eliminate the fault in time to ensure the normal operation of the cable line and the smooth flow of wired communication and transmission. Currently, most of the cable fault testers commonly used on the market are intelligent. Their working principles and components are introduced as follows:

1. Basic principles of cable fault tester

According to the fault detection principle, when the instrument is in the flashover trigger mode, the flashover echo formed by the instantaneous breakdown discharge at the fault point is a random single transient waveform. Therefore, the test instrument should have a storage function that can capture and display Single transient waveform. The ht-tc cable fault tester adopts digital storage technology and uses high-speed A/D converter sampling to convert the input transient analog signal into a digital signal in real time, store it in the high-speed memory, and send it to the computer after being processed by the CPU microprocessor. To the LCD display control circuit, it changes into time series dot matrix information, so the currently sampled waveform parameters are displayed on the LCD screen.

When the instrument is in the pulse trigger mode, the instrument sends out detection pulses at a certain period and adds them to the cable and input circuit under test, immediately starting the A/D work. Its sampling, storage, processing and display are the same as the aforementioned processes. There should be reflection echo on the LCD display.

2. Composition of cable fault tester

The cable fault tester is based on a microprocessor and controls the transmission, reception and digital processing of signals. The working principle block diagram of the instrument is shown in the figure.

The digital processing tasks completed by the microprocessor include: data collection, storage, digital filtering, cursor movement, distance calculation, graphics comparison, image proportion expansion, until sending to LCD display. You can also communicate with the PC through the communication port as needed.

The pulse generator automatically forms a logic pulse of a certain width based on the encoded signal sent by the microprocessor. This pulse is converted into a high-amplitude transmit pulse by the transmitter circuit and sent to the cable under test.

The high-speed A/D generator converts the signal returned from the cable under test to the high-speed A/D sampling circuit through the input circuit into a digital signal, and finally sends it to the microprocessor for processing.

The keyboard is the window for human-machine dialogue. The operator can input commands to the computer through the keyboard according to the test needs, and then the instrument completes a certain test function.

The intelligent cable fault intelligent tester is a comprehensive set of cable fault detection instruments. It can test cables for high-resistance flashover faults, high- and low-resistance grounding, short circuits, cable disconnections, poor contacts and other faults. If equipped with an acoustic measuring pointer, the precise location of the fault point can be accurately determined. It is especially suitable for testing power cables and communication cables of various types and voltage levels. This instrument adopts a variety of fault detection methods, applies the most advanced achievements and devices of the contemporary era, adopts computer technology and special electronic technology, and combines the long-term successful experience in developing cable testers to launch a new high-tech, intelligent, full-featured product.

The cable fault tester can test various faults of copper and aluminum core power cables and local telephone cables of various types and voltage levels below 35kv. The radio wave propagation speeds of four commonly used power cables, including oil-impregnated paper cables, cross-linked vinyl cables, non-drip cables and plastic cables, have been preset in the instrument. The radio wave propagation speeds of some special cables can be temporarily preset on site using the keyboard. , cable length and fault distance do not need manual conversion, the instrument automatically converts and displays the fault distance.

main feature

1. Complete functions, safe, fast and accurate testing. The instrument uses low-voltage pulse method and high-voltage flashover method for detection, which can test various faults of cables. It can directly test flashover and high-resistance faults of power cables without burning through. If equipped with a sound point meter, the location of the fault point can be accurately determined.

2. High testing accuracy. The instrument adopts high-speed data sampling technology and has a reading resolution of 1m. High degree of intelligence. The test results are automatically displayed on the large-screen LCD in small format and data, making fault judgment intuitive. It is also equipped with a menu display operation function, eliminating the need for special training for operators.

3. It has wave opening and parameter storage and recall functions. Using non-volatile components, waveforms and data will not be lost after shutdown.

4. It has dual trace display function. The test waveform of the faulty cable can be compared with the normal waveform, which is helpful for further judgment of the fault.

5. It has the function of waveform expansion ratio. Change the waveform scale to expand the waveform for accurate testing.

6. Control the measurement cursor to automatically search along the line and automatically stop at the inflection point of the fault waveform.

7. The position of the double cursors can be changed arbitrarily to directly display the direct or relative distance between the fault point and the test point.

8. With printing function. Print and archive test results.

Application scope and purpose

This cable fault detector can test various types of power cables (voltage level 1kv ~ 35kv) and local telephone cables, FM communication cables, coaxial cables and metal overhead lines for short circuit, grounding, high resistance leakage and high resistance flashover. faults, cable disconnection, poor contact and other faults. It can also test the length of the cable and the propagation speed of radio waves on the cable.