Megger’s new DAC-30 test and diagnostic system for medium voltage cables is the first test set of its kind with the power source and partial discharge (PD) coupler integrated into a single unit. Because of this unique form of construction, no live parts, other than the cable under test, are accessible during testing, which guarantees the highest possible level of operator safety.
The DAC-30 is a fully isolated DAC (damped AC voltage) partial discharge test set with a peak voltage of 30 kV. It is ideally suited for performing quality control checks on newly installed cables in line with the IEEE 400.4 standard, and also for condition monitoring on older cables as an aid to preventing unplanned outages.
A versatile test and diagnostic system for MV cables up to 16 km in length, including the 10, 11 and 20 kV cables commonly found in the UK and Ireland, the DAC-30 identifies, evaluates and locates partial discharge activity in cable insulation and accessories. This activity is a reliable guide to incipient faults and is, therefore, widely regarded as one of the best “early warning” indicators of insulation deterioration, allowing remedial action to be taken before weaknesses progress to complete failure.
An important benefit of the DAC-30 is that the frequency of the test voltage is close to normal power frequency. This means that partial discharge activity can be accurately evaluated and will closely reflect the behaviour of the cable in normal operation. In addition, the decaying amplitude of the test voltage makes it is easy to determine the partial discharge inception voltage (PDIV), which is the voltage at which PD activity starts, and the partial discharge extinction voltage (PDEV), which is the voltage at which PD activity stops after the test.
For ease of transportation, the DAC-30 can be split into two modules, each weighing less than 35 kg. These modules contain all of the high-voltage components and are controlled by notebook computer running specially developed software. Designed for convenience and ease of use, this software features fully automatic calibration as well as dynamic real-time PD analysis and display of results. Detailed reports can be generated with a single mouse click.
