ANALYSIS OF MEASUREMENT ERROR IN DIRECT AND TRANSFORMER-OPERATED MEASUREMENT SYSTEMS FOR ELECTRIC ENERGY AND MAXIMUM POWER MEASUREMENT

Analysis of error in measuring electric energy and maximum power within direct and half-indirect measurement system at the voltage of 0.4kV is presented in the paper. The analysis involved all the elements of the measurement system, i.e. calibration and testing of the transformer-operated and direct digital energy meters and measuring current transformers. This equipment was also used for measurements in the transformer substation aiming at error analysis at measurements made under the real conditions. The results obtained show significant negative measurement error introduced by the energy meters under overload conditions. Energy meters have lower values of both the consumed electric energy and maximum power in this operating mode, which can be interpreted as a loss.