Background. The study is relevant due to the increase in the number of non-linear electrical receivers, such as computers, televisions, LED lamps and other devices, in household electrical networks in rural areas. The increase in the number of such devices leads to distortion of the consumed current and voltage waveforms, causing deviations from the ideal sinusoidal shape. The widespread use of power transformers with “star-star- with neutral” winding configurations, which have high zero-sequence impedance increase the negative impact of harmonic current components. The primary objective of the research is to study an electromagnetic device aimed at compensating third harmonic currents in the neutral conductor of power transformers in rural electrical systems.
Materials and methods. The electromagnetic compensator of the third harmonic current for the neutral of a power transformer under study is implemented in the form of a circuit that includes six current transformers installed in the network phases, a three-phase half-wave rectifier, a filter choke and an additional current transformer in the neutral. The technical solution using six transformers and a rectifier allows for compensation of currents that are multiples of the third harmonic, which is especially effective in networks with a “star-star with neutral” winding configuration and high sensitivity to zero-sequence harmonics.
Results. To evaluate the efficiency of the device, measurements have been conducted on low-voltage buses of thirteen 10/0,4 kV transformer substations supplying the household sector in the Volgograd region. A power quality analyzer has been employed to record current, voltage, power, and harmonic composition parameters at a one-minute resolution over a 24-hour cycle. The findings have confirmed that the third current harmonic is the dominant factor in parasitic power losses within residential grid power transformers, contributing an average of 67,2 % of the total losses caused by higher-order harmonics. Field tests in four-wire networks of rural 10/0,4 kV substations have demonstrated the high efficiency of the electromagnetic compensator. After installation, the neutral third harmonic amplitude has decreased by 64,4 %, resulting in a 9,95 % reduction in total electricity losses.
Conclusions. Thus, targeted suppression of the third harmonic not only enhances network stability but also ensures significant resource savings, particularly under conditions of growing non-linear loads.