The present invention relates to a method for supervision of an electrical measurement in a wind power plant, with a plurality of wind turbine generators, the method comprises, a) measuring a measurement of an electrical parameter in the wind power plant, b) determining a difference between the measurement and a reference value, c) in case the difference is greater than a threshold value, incrementing an event counter, d) in case the event counter is incremented, raising a first warning flag. The invention also relates to a power plant controller arranged to supervise a wind power plant according to the method; the wind power plant comprises a plurality of wind turbine generators.