Serial defects are identical, or similar, defects which occur on an agreed percentage of WTGs at that wind farm.
If enough failures occur, the OEM must carry out a root cause analysis to determine if the reason for the failure is common across all the broken components.
If it is, the OEM must replace or repair that component on all the other WTGs on site, even if they have not yet failed.
Any revenue lost due to a defect, or the time taken to repair it, is not compensated by the OEM.