Abstract: Scientifically correct power definitions and sound compensation strategies for three-conductor systems are known since many years, commercial products are available. Nowdays, many low-power power electronic devices together cause undesirable operating conditions in four-conductor systems, making an extension of the scope of definitions and compensation sreategies mandatory. Depending on the theoretical basis used, the extension from three-conductor definitions to four-conductor definitions is not always straightforward. Based on the straightforward approach given by Fryze, Buchholz and Depenbrock, known as the FBD method, this study gives guidance on how to avoid traps and common mistakes. Aims of compensation, mathematics for easy treatment and resulting consequences as well as solutions based on active and passive compensators are discussed.