DNV GL checks and measures the grid parameters occurring during normal operations. The grid code in question may require a device to have a grid protection system installed (where the release values have to be checked) or a specifically defined behaviour during grid failure. This so-called fault ride-through behaviour, which ensures the device stays connected during a grid fault, also has to be checked and certified. In many grids, e.g. Germany or Spain, a certificate of compliance with the required fault ride-through levels guarantees the site owner or operator a higher tariff for the electricity generated.
DNV GL employs the following methods to obtain the required grid data:
- Power quality measurement
- Grid protection measurement: The grid protection system can be checked at the device itself or on a test bench, with a test procedure run to obtain reaction times and values, e.g. under-voltage or over-frequency.
- Fault ride-through: A voltage dip unit and a system to measure voltage and current at different points inside the voltage dip unit, grid and device are installed at the device to measure its reaction to a grid fault.
- Electromagnetic compatibility
- Grid monitoring: A small grid surveillance device installed in the substation DNV GL staff and details of high frequency data occurring during a grid failure reported to the client.
- Small devices: Electrical measurements similar to those for utility-scale turbines can be conducted either in the field or on a test bench.