Cable Testing: VLF Withstand & VLF TD/PD Diagnostic Methods

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200 kV VLF on the job with HVI trailer package

0 – 200 kVac peak sinusoidal output, 0.1 Hz – 0.02 Hz up to 3.75 uF of load.

Analog controls easy to use, rugged, reliable, and serviceable. Two piece transportable design.


VLF Medium & High Voltage Cable Testing

The words “Cable Testing” cover many topics and a broad range of testing methods and equipment used, including everything from simple DC hipoting the insulation of a cable, Insulation Resistance (IR)  measurements, AC Withstand testing using 50/60 Hz. power frequency, or 0.1 Hz. Very Low Frequency (VLF) AC hipots, and several other lesser used methods. It also can cover the “Diagnostic” methods of cable insulation testing, like Tan Delta Assessment and Partial Discharge Detection. Besides insulation testing, other integrity tests are performed routinely, like Sheath testing, Concentric Neutral Resistance testing, and can also include cable fault locating methods and technologies.

Listed below are the subjects to five, one page pdf Application papers describing various cable testing and fault locating topics. Discussed are the test descriptions, test definitions, methodologies, and the HVI equipment for the job.

VLF Withstand/Proof Testing: A Go/No-Go Result

This section mostly describes the use of VLF AC hipots for performing a Withstand/Proof test on a cable. A VLF Withstand test is a go/no-go or pass/fail over voltage test. Can the cable hold the test voltage? That is the point of the VLF test, let bad defects or installation errors fail during the test and fix them before going into service. It is especially valuable as a test to verify the integrity of new installations before energizing. It is also ideal for Maintenance testing on aged cable, especially when used to perform diagnostic testing, such as Partial Discharge and Tan Delta measurements.

HVI produces two lines of VLF hipots used for this and other tests; its original, patented design VLF Series that uses conventional analog controls, electro-mechanical operation, and oil insulated high voltage sections. The VLF E Series is an all solid state, microprocessor controlled, fully programmable in operation and data logging and reporting, and operates with XBee wireless control to a PC using the E-Link Software package created by HVI.

Diagnostic Cable Testing Using Tan Delta & Partial Discharge Methods

Diagnostic testing is a term for methods that test the health of a cable’s insulation without risking its failure during the test. The intent is to learn something about the cable insulation to permit the user to make a qualitative analysis of its condition to make a judgement as to how long the cable may last. Some diagnostic tests indicate the overall deterioration of a cables insulation while others show specific locations of trouble. Which one used depends on several factors. There are two methods that are the most commonly used and offered by HVI: Tan Delta and Partial Discharge testing. Call HVI and let us help you with your testing applications.


Wind & Solar Farm Cable Testing

Typically 35 kV cables are used – playing into the strength of the several HVI VLF models produced for this application.

Alternative Energy production requires its own specific test equipment needs. All installations should be Acceptance tested to expose the inevitable faults that occur during installation. HVI has everything needed to meet all cable testing and cable fault locating needs.  This subject has its own Application paper, as it is a specific test, very commonly performed, and is ideal for the use of VLF Withstand and Diagnostic equipment.

Concentric Neutral Resistance Testing with the HVI Ω-Check®

How are your neutrals?

  • How many strands are broken?
  • Where is my return current going?
  • Where is my fault current going?
  • Will my fault protection system clear properly?
  • How well can we TD or PD test cables with no neutrals left?
  • Why bother injecting cables with no neutrals?

Healthy neutrals are vital to the stability, reliability, and safety of any distribution or transmission system. All of the above can be severely compromised if much of the concentric neutral is missing.

The Ω-Check® Concentric Neutral Resistance Tester from HVI. The only instrument available designed to easily, economically, and accurately perform this test with cables energized.

Cable Fault Locating with Thumpers/Surge Generators & TDR

Cable Faults Happen.  Many faults occur throughout the year. How quickly they are found depends on the quality and features of the equipment, the methodologies used, and the skills of the locator. These factors will determine how consequential your faults will be. Refer to the separate Cable Fault Locating Application page in this section of the Knowledge Center.