VLF Testing

Very low frequency (VLF) testing allows to detection of insulation damages in the shortest possible testing time without affecting the quality of the insulation material. This technique allows you test medium voltage cables.
VLF testing can be used in two ways: One way is to apply VLF to measure insulation losses at different VLF frequencies that typically range in 0.01 to 0.1 Hz. The IEEE Std. 400.2 in such case establishes the criteria for assessment. Accessories for partial discharge testing are also available from several VLF test set manufacturers. Another way is to apply VLF to XLPE cables as proof testing to detect faults in the cable system insulation. In this process, the tested cable must withstand a VLF AC voltage without flashovers for a specified testing- time.

VLF cable testing uses different wave shapes. The wave shapes are typically sine and square, and the voltages expressed for the wave shapes differs as RMS (Root Mean Square) is not always applicable. The reference is taken via the peak voltage in such cases.

VLF Testing is a short and economical testing criterion for network operators. In the past, instead of VLF Testing, DC Voltages were used for the purpose of cable testing, and which sometimes was resultant in damaging the cable insulation. The DC test procedure that was previously successfully used for decades for paper-insulated mass impregnated cables proved unsuccessful for the testing the plastic cables and led to serious faults.

The countless failures of plastic insulated cables with DC testing confirmed the need of the new way of testing plastic cables. With this, VLF Testing replaced DC testing in practice. VLF tests are very practical and beneficial utility to the network operators.

Amperis offers great range of VLF test equipments. The AXV Series is the latest product by Amperis in high voltage test equipments. The product is known worldwide as the most reliable high voltage test equipment available.

The VLF testing equipments by Amperis offer many great features like fully automatic test procedures. The devices are short-circuit proof. There is a Timer function to ensure automatic switch-off device. The device is easily transportable and portable. Devices are accompanied with menu-guides in different languages. An emergency-off switch is also added to device for better protection. Know the more product specifications here.

Using VLF Test Equipments: To use the VLF test equipments, you need to prepare the equipment for the cable testing. For this purpose, you need to prepare the cables first. To prepare the cables, disconnect the object under test on all contacts, secure it being switched on again and check that it is de-energized. Isolate the adjacent live parts and ensure that on the application of high voltage, there can be no breakdown to the adjacent parts of the cabling. If you are performing the test on multi-wire objects, all other wires except for the ones being tested, must be connected to the station ground. Clean the terminals if necessary.

An important advantage of the VLF testing devices by Amperis is their portability, especially when they are used on the site. The compact design makes the device easily carried anywhere within the site. The equipment is designed in an ultra-protective way that testing in bad weather is not a problem at all; the equipment is completely protected against splash water. Automatic test procedures are facilitated as the user-defined test sequences can be defined. The equipment has a graphics display with a menu for all control functions, this ensures a hassle free way of operation. The ease and simplicity of operation make it the best device.