Impact of smart grid and green power generation on distribution systems

A significant amount of green power is being installed at the distribution level through the installation of green power generation facilities in the United States and Canada. This paper discusses green power generating sources (of 10 MW or less), which are connected to the utility system at the distribution level, and their impact on distribution system. The paper outlines the various types of wind generators (Type I through IV) and their modeling and fault current contributions to system supply faults. Distribution circuits are designed to supply radial loads. Therefore, the introduction of green generation could mean: redistribution of fault and load currents on the feeder circuit, overvoltage and ferroresonance, plus a possible loss of protection system coordination-all of which can result in customer outages. The paper discusses these issues which are generally not well understood by many distribution protection engineers and can adversely affect distribution system reliability.