Metrological Performances of Current Transformers Under Amplitude Modulated Currents

All the measurement tasks, f.i. metering, protection and diagnostics, in electricity distribution and trasmission grids need instrument transformers (ITs) to scale voltage and current down to levels compatible with measuring instruments. Inductive voltage and current transformers (VTs and CTs) are still the most used ITs; however, their behaviour in presence of disturbances is not fully assessed. This paper analyses the behavior of CTs in presence of amplitude modulations, which is one of the disturbance under which the performance of Phasor Measurement Units (PMUs) has to be assessed. A measurement setup, able to test current transformers in accordance to the IEEE Std. C37.118.1 about the PMU performance testing, has been realized. Experimental tests on a commercial CT, changing the modulation frequency, are presented.The work reported here has received support from the EMPIR programme co-financed by the Participating States and from the European Union'