From generating station the power is transmitted through three phase three wire EHV or HV transmission lines to distribution delta-star step down transformer via lightning arrester, CT, PT and CB to delta primary of distribution transforme. The voltage would step down from EHV or HV to lower HV on secondary, and transmitted to load areas from distribution substation by three phase four wire to pole mounted(star-star) transformers supplying different sub areas of load area, by single phase for domestic or three phase for industrial loads, for further step down from low HV(11 KV or lowerKV) to respective pole mounted transformers, single phase or three phase as needed, for having the needed domestic or industrial voltage and load (110, 220, or 440) main important is to have equal distribution of load current in all three phases all the time or to have minimum neutral current near to zero, to have maximum distribution efficiency with minimum loss.

Electric Power Distribution operate like any electric power system. The main characteristic is delivery electric energy to diferent users (loads). Nowadays, The Electric Power Distribution systems are confronted to the penetration renewable energies, and this is a reason to considerate like mix source and loads, and only not like a pure load's connections

the distribution substation is used to supply electrical energy to the various customers, whether industrial or tertiary, after having lowered the electrical voltage of HV/LV. the distribution station consists of: - high voltage incoming line - step-down transformer - circuit breakers - low voltage departure bays