With the new testing system from HIGHVOLT, operators can now test the transformers in wind turbines directly in the rear housing itself, saving time and avoiding unnecessary downtime.
When the rotor blades of a wind turbine are spinning away merrily, everything looks deceptively harmless. But up in the turbine’s rear housing (known as a nacelle), where the transformers are housed, huge forces are at play. The transformer is subject to constant vibrations and weather-related temperature fluctuations—not to mention the frequent variations in load when wind strength changes as well as the high stresses from frequency converters. All this puts pressure on the insulation, thus increasing the risk of costly downtime for the entire installation.
Replacing and repairing the transformer in the nacelle, which is very difficult to access, is time-con suming work. For this reason, the experts at HIGHVOLT looked for a solution that would allow operators or service providers to perform regular on-site insulation inspections themselves in order to anticipate damage in advance. The standard methods of achieving this are the induced voltage test and partial discharge diagnostics. The problem is that there is hardly any space to conduct these in the turbine’s nacelle.
HIGHVOLT has therefore developed a portable testing system that operators or service providers can use to inspect the condition of the transformer insulation directly from the nacelle itself. The system consists of a frequency converter with a step-up transformer connected in series, a partial discharge filter (PD filter), and the measurement instrumentation. All components are housed in four compact boxes and can be installed quickly.
The system provides sufficient power for the induced voltage test at all three phases. Thanks to the design, the technology achieves a very low partial discharge level of less than ten picocoulombs. The measurement process is completed in less than an hour, so system downtimes are kept to a minimum. If the system detects an impending sparkover, operators can immediately introduce countermeasures in order to avoid break-downs. The testing system is designed for transformers of up to 10 megavolt-amperes (MVA) and is therefore suitable for distribution transformers as well.
YOUR CONTACT 
Do you have any questions about the testing system from HIGHVOLT?
Stefan Bergmann is happy to assist:
bergmann.stefan@highvolt.de