Cable fault locators are commonly used to test underground coaxial and twisted pair cabling, along with transmission lines and other industrial electrical cables. Cable fault locators also can be used for sheath testing and sheath fault location, determining the strength of the sheath of dielectric insulated cables. This is done to prevent water contamination and resulting cable faults.
what is cable fault testing?
A cable fault locator, or thumper, detects faults in electrical cabling by sending high-voltage electrical impulses into the cable system. When the surge of energy reaches the fault, a ‘thump’ ensues at the fault position, which can be measured with a ground microphone—thus the nickname of ‘electrical thumper’ or ‘cable thumper.’ By this process, the cable fault locating system will test the dielectric strength of the cable and determine at what points a voltage breakdown will occur.
An electrical thumper is complemented by a time domain reflectometer (TDR), a similar instrument that sends low-voltage pulses and focuses on providing a more detailed fault profile. The two come together in the Arc Reflection test method, which synthesizes the surge and pulse echo techniques. When testing a medium-voltage cable, a time domain reflectometer may miss faults that require breakdown voltage to be found. Thumpers provide high-voltage surges that cause voltage breakdowns and offer a reflection point for the pulse generated by the TDR.
how to find fault in underground cable
Cable fault testing is composed of several parts. The first testing method is with a time domain reflectometer (TDR) for incident signals on the electrical line. High-resistance applications require very low frequency (VLF) testing first. Both tests will determine whether the cable has a fault. To locate the fault, electrical testing personnel will then need a cable fault locator or thumper to send a surge wave through the cable, revealing the cable’s location by the arc reflection method, or ARM.
Discovering the precise coordinates of the fault and identifying its type is accomplished by acoustic breakdown detection, an audio frequency system, or pulsed DC power, in use with a step voltage receiver. Testing with a cable fault locator comes with a golden rule: find faults, don’t make new ones. Protecting the cable throughout testing is essential to cable fault location; personnel performing fault tests should be cognizant of insulation strength and accessory durability when thumping cables. The objective of the test is to generate surges at the lowest voltage possible while send the highest possible amount of energy to the fault in question.
Rent Cable Fault Locator and thumper Equipment
Modern cable fault locator and thumper systems offer users features like Megger’s “E-Tray” user interface that simplifies operation and allows for quick training. Such user experience systems provide users with each test step in a progressive fashion, allowing them to proceed without making adjustments for every step, and may help mitigate mistakes.
ATEC offers affordable cable fault locator rental rates for both electrical thumper rental equipment and systems that feature a full suite of fault-testing features. Advanced Test Equipment Corporation has cable fault locators from top manufacturers including Megger
, High Voltage
, and many more