Live power tester

Insulation power factor tests on bushings fitted to high-voltage switchgear, transformers and similar items of equipment can now be carried out rapidly, easily and safely without the need to take the equipment out of service. The tests, which give accurate information about the insulation quality, revealing such potential problems as cracks, surface contamination and incipient faults, are performed at the installation's full working voltage, and can typically be completed in under five minutes.

The basic Power Factor Live system comprises a set of three tap couplers which are installed in series on the bushing, and a sensing and interfacing system housed within an IP66 enclosure.

These components are intended for permanent installation with fitting, in most instances, taking less than 30 minutes. Up to 16 bushings can be connected to a single interface unit, keeping costs low, even in large and complex applications.

The interface system provides an output which is connected, via an analog-to-digital converter card, to a standard PC running AVO International's proprietary PF Live software under Microsoft Windows.

Using the data supplied by the Power Factor Live hardware, the software provides a rapid and positive evaluation of insulation integrity using a virtual Scherring bridge.

Both raw data and test results are stored in Microsoft Access 2000 format. This means that familiar software tools and standard statistical procedures can be used for subsequent analysis to provide trends graphically and in table format. The basic Power Factor Live system can readily be enhanced by adding the optional PF Live data acquisition module. Connected permanently or temporarily to the PF Live enclosure, this module continuously collects and evaluates data from the bushing taps, and can be programmed to produce an alarm output if a potentially serious problem is detected.

The data acquisition module includes outputs for modem and network connections, allowing remote access and alarm outputs for SCADA.