Modern cable fault testing systems generally adopt the “comprehensive testing method”, using the combination of multiple technologies to achieve precise detection of different types of cable faults. A complete testing system mainly consists of a main control unit, a high-voltage signal generation unit, a path detection and precise positioning unit, and ancillary equipment. The system selection also needs to be comprehensively considered based on various factors.
I. System Composition
(1) Main Control Unit (Distance Measurement Host)
The main control unit is the core analysis unit of the system. Its main function is to preliminarily determine the nature of the fault, including high resistance, low resistance, open circuit, and flashover, and to make a rough measurement of the fault distance.
The main technologies applied in this unit include two types. One is the low-voltage pulse method, which can be used to test the full length of the cable, identify the position of intermediate joints, and is also applicable to the measurement of low resistance and open circuit faults. The other is the pulse current method / voltage method, including flashover method and direct flash method, which are mainly used for the measurement of high resistance and flashover faults.
From the composition structure, the main control unit is composed of a laptop computer or an embedded industrial control computer, a signal acquisition card, and an analysis software.
(2) High-Voltage Signal Generation Unit (Path / Fault Location Power Supply)
The core function of the high-voltage signal generation unit is to provide sufficient high voltage for high-resistance faults, causing the faults to breakdown and generating detectable discharge signals.
Its components include a high-voltage generator (DC withstand test instrument), a high-voltage pulse capacitor (energy storage capacitor), and a ball gap. Among them, the high-voltage generator can generate DC high voltage and is used for “direct flash method” and “flashover method”; the high-voltage pulse capacitor in “flashover method” is responsible for storing energy and discharging instantly to form periodic discharge pulses; the ball gap is used to control the discharge timing of the capacitor.
(3) Path Detection and Precise Positioning Unit
Based on the rough measurement of the fault distance, the path detection and precise positioning unit can follow the cable laying path to more accurately determine the location of the fault point below the ground, with a positioning accuracy usually controlled within 1 meter.
The equipment of this unit includes a path signal generator, a path detection receiver (A-frame / probe), and a sound-magnetic synchronous positioning instrument. The function of the path signal generator is to send specific frequency audio or radio frequency signals to the cable; the path detection receiver uses the received ground magnetic signal to achieve relatively precise positioning of the cable laying path and depth; the sound-magnetic synchronous positioning instrument is the key equipment for precise positioning, consisting of a high-sensitivity acoustic sensor (probe) and a magnetic sensor. The core working principle is to capture the time difference between sound waves and electromagnetic waves, and find the position with louder sound and synchronous electromagnetic signals on the ground, which is directly below the fault point.
(4) Ancillary Equipment
Ancillary equipment is an important supplement to the cable fault testing system, mainly including cable identification instruments, insulation resistance testers (megohmmeters), multimeters, as well as connection lines, grounding wires, safety protection equipment, etc. The cable identification instrument can accurately identify the target cable among multiple cables to ensure the safety of the testing process; the insulation resistance tester is used to preliminarily determine the fault type and distinguish high-resistance and low-resistance faults; the multimeter can achieve continuity measurement and low-resistance measurement; connection lines, grounding wires are essential connection components in the testing process, while insulating boots, insulating gloves, warning fences, etc. are safety protection equipment used to protect the safety of the test personnel.
II. System Selection Key Points.
The selection of the cable fault testing system needs to comprehensively consider factors such as cable type, voltage level, laying environment, and budget to ensure that the system can meet the actual testing requirements.
(1) Core Consideration Factors Cable Voltage Level: The voltage level determines the output voltage range of the high-voltage unit required by the testing system. Different voltage levels correspond to different output voltage requirements for cables.
Cable Type and Length: Cable types include low-voltage cables, medium-voltage cables (10-35kV), and high-voltage cables (110kV and above). Cable length affects the effective application range of the testing method. When selecting, it is necessary to consider the actual cable type and length.
Common Fault Types: Different testing systems have different handling capabilities for various faults. High-resistance faults are a difficulty in cable fault detection, so when selecting, it is necessary to focus on whether the system has the “impulse flash method” and strong point detection capabilities to deal with common fault types.
Installation Environment: The installation environment of cables includes urban areas, fields, tunnels, and cable trays, etc. Complex installation environments place higher requirements on the anti-interference ability of the system and the sensitivity of the point detection instrument. It is necessary to select a testing system that is compatible with the installation environment.
Integration and Portability: Split-type equipment has more powerful functions but is larger in size and weight, and has poor portability; integrated equipment has good portability but may have certain limitations in power and functionality. When choosing, it is necessary to consider the skill level of the team.
Team Skill Level: Equipment with a friendly operation interface and high intelligence level has relatively lower requirements for the experience of the operator, which can reduce training costs and improve testing efficiency. When selecting, it is necessary to consider the skill level of the team.
(II) Configuration Suggestions
Basic Configuration: Suitable for operation and maintenance units, mainly dealing with common low-voltage / medium-voltage cable faults. The configuration includes integrated distance measurement host (including low-voltage pulse and impulse flash method), sound-magnetic synchronous point detection instrument, path detector, cable identification instrument, and megohmmeter.
Professional Configuration: Suitable for construction units, professional testing companies, which can deal with various complex faults. The configuration includes high-performance split-type distance measurement host, large-capacity high-voltage generator and pulse capacitor, multi-mode and highly anti-interference sound-magnetic point detection instrument, and complete path identification equipment.
Special Configuration for High / Ultra-High Voltage Cables: For 110kV and above high-voltage and ultra-high-voltage cables, usually a higher voltage level oscillation wave testing system or an online monitoring system based on the traveling wave principle is required. Such systems have high technical complexity and relatively expensive equipment.
(III) Brand and Service Considerations
When selecting a cable fault testing system, in addition to focusing on the performance and configuration of the equipment, it is also necessary to pay attention to the market reputation of the brand, technical training services, and after-sales service network. Choosing a brand with a good market reputation can ensure the quality and reliability of the equipment; complete technical training services can help operators quickly master the use of the equipment, improving testing efficiency; a sound after-sales service network can provide timely maintenance and technical support when the equipment fails, ensuring the smooth progress of the testing work.
Post time: Jan-08-2026