vlf ac technology

VLF AC Technology

Delivering Seamless Cable Testing Efficiency

VLF technology applies high AC voltages to cables, motors, generators, and other highly capacitive loads using test equipment that is portable, easier to use, and more economical than conventional methods. These tests can now be conducted at 0.1 Hz. or lower with test voltages of 1 Uo – 3 Uo, or 1 – 3 x normal operating voltage, including:

  • AC withstand/proof testing
  • Insulation diagnostic testing including tan delta and partial discharge

A VLF hipot is an AC output tester with an output frequency of 0.1 Hz or lower rather than 50/60 Hz. Although the frequency is very low, it is an alternating current with polarity reversals every half cycle. At 0.1 Hz output, it takes 600 times less current and power to apply an AC voltage to a capacitive load.

VLF hipots perform voltage withstand tests and provide the voltage source for diagnostic cable testing. Customers frequently purchase tan delta and partial discharge measurement accessories along with VLF equipment to further extend their testing capabilities.

HVI provides the largest selection of VLF instruments (including CE marked models), the most powerful and highest voltage models, and two design configurations:

VLF Series

Original Power Supply Design with Simple Analog Controls

The VLF Series uses an oil-immersed, conventional power supply design protected under US Patent #6169406, providing economical and easy to use options for cable testing. HVI’s VLF Series hipots demonstrate high reliability and can be serviced worldwide as needed.

VLF E Series

Fully Programmable Digital Design with Wireless Remote Control

The VLF E Series uses a state-of-the-art, switching power supply design with wireless computer controls. Equipped with HVI’s E-Link software, the E Series stands among the most advanced cable testing systems available. Our customers praise its flexible data capture and reporting capabilities, full remote operation via XBee wireless technology, and seamless tan delta testing with HVI’s TD units.

Cable Diagnostic Tools

For non-destructive diagnostic testing to determine the quality of a cable’s insulation with minimal risk of failure, HVI recommends tan delta and partial discharge testing for valuable diagnostic data about cable insulation integrity. Both use a VLF source to perform elevated voltage, off-line testing. Tan delta testing measures insulation health, while PD identifies specific problem areas and assesses their severity.

TD E Series

Tan Delta/Tan δ Loss Angle Testing

The TD E Series measures the level of insulation degradation in a cable. Absolute measurements, trends over time, and comparative analysis to other cables provide reliable data on cable health in accordance with IEEE 400.2 and NEETRAC acceptance criteria.

PDIX Series

Partial Discharge and Tan Delta

PDIX is a combined partial discharge and tan delta cable diagnostic testing system. By combining HVI’s VLF products with PDIX products, users can perform VLF AC withstand, partial discharge detection, and tan delta measurement on medium and high voltage cables, rotating machinery, and other apparatus with one integrated package fully supported by HVI & PDIX.