Four-wire systems are the most common ones in everyday life. Electrical installations within the home, office, or industrial plant are mostly four-wire installations. Receivers connected to such a system are mainly single-phase loads, which from the power connection are an unbalanced three-phase load. Apart from, the load imbalance, the supply voltage also has some asymmetry. Voltage asymmetry, load imbalance, the design of reactance compensators are issues that were not simultaneously included in the power equation in fourwire systems. This article presents the mathematical fundamentals of the construction of reactance compensators operating in voltage asymmetry.

Electricity receivers in low-voltage networks are mainly single-phase loads, which, when grouped within a given consumer, create a three-phase load. Such a replacement three-phase load works in a four-wire system. Besides, under real conditions, the supply voltage has some amplitude and phase asymmetry. Voltage unbalances, load's imbalances are issues that not simultaneously included in the power equation in four-wire systems. This article eliminates the limitations of electrical engineering in this area by deriving the power equation for three-phase loads supplied with unbalanced voltage.

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Air-termination rods with height above 2,5 m must be fixed to objects by for example spacer bars to ensure proper separation distance. Commercially available spacer bars are suitable in laboratory conditions only. Real-life scenarios show weak points of this solution. Dirty or wet spacers do not fulfil proper isolation strength to ensure proper separation distance. This changes the km factor used to calculate the separation distance. The paper presents laboratory tests for clean spacers, wet spacers and a few real photos of damage caused by spacer bars.