A numerical approach to the evaluation of uncertainty in nonconventional measurements on power systems

The application of the rules endorsed by the ISO Guide to the expression of uncertainty in measurement (GUM) can turn into a difficult task when quantities that characterize the operation of modern power systems are measured by means of DSP-based instruments. A numerical approach to easily tackle this task is proposed in this paper, as an alternative to the uncertainty evaluation based on the analytical solution of the uncertainty propagation law, as prescribed by the GUM. The validity of the numerical approach, which is based on a Monte-Carlo procedure, is first proved in the case of the spectral analysis of a periodic signal, which is the first step for many non-conventional measurements. Then the evaluation of the accuracy of a method for the measurement of the harmonic losses in a power transformer supplying nonsinusoidal load currents is dealt with as an application example.