Quoted by AMIR KHASHAIAR : ” This current will interfere with other systems particularly communication systems .” I agree with AMIR. Indeed we can use delta connection as a three harmonic current trap. Telephone circuits are particularly susceptible to the influence of ground return currents. In rural areas when power or telephone circuits use a ground return, the large inductive loop can have a large influence on the noise produced in telephone circuits. Particular care should be used to minimize nonlinear loads in this case. A voice band telephone channel is normally designed to pass frequencies between 300 and 3000 Hz. Although harmonics in this range of frequencies are very small compared with the fundamental, they still have an effect on the telephone reception. The effect that a