Direct Current Generation in Single-Phase Residential Systems DC Effects and Permissible Levels

This paper suggests the value of 50 mA direct current as an acceptable level of dc pollution in residential single-phase 120V/240V services. This conclusion is based on experimental measurements carried out on a typical single-phase distribution transformer and on an analytical model which considers the flux- magnetizing current characteristic of the transformer. The response to dc biasing of single-phase motors and transformers used in residential circuits was the key factor in establishing the permissible level of dc injection.