DNV GL checks and measures the grid parameters occurring during normal operations and during abnormal conditions. 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, and 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 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 the its reaction to a grid fault.
- Electromagnetic compatibility: HSE regulations require a short-term manned measurement to be conducted to determine electromagnetic levels inside the device.
- Grid monitoring: A small grid surveillance device installed in the substation, to monitor the correct behaviour in the event of grid failure is regularly checked by 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 devices, can be conducted either in the field or on a test bench.