Distributed generation and its impact on power grids and microgrids protection
The National Institute of Standards and Technology, NIST, is assigned by the US Department of Energy, DoE, to drive Smart Grid developments and harmonization efforts in the power industry. Distributed Generation has been identified as one of the important areas for the Smart Grid developments. Multiple generation sources, bi-directional power flow, power flow time co-ordination and management bring significant benefits and challenges for the existing and emerging power grids and microgrids. In particular, the effect of distributed generation on protection concepts and approaches needs to be understood, and accounted for. This paper describes distributed generation concepts, applications and scenarios. Benefits and challenges are discussed and analyzed on a number of real life examples. Special considerations are provided on ensuring security and dependability, as well as on protection parameterization and coordination.
Impact of green power generation on distribution systems
This paper discusses green power distributed generation (DG) sources (of 10 MW or less), which are connected to the utility system at the distribution level, and their impact on distribution system reliability. Distribution circuits are designed to supply radial loads. Therefore, the introduction of green generation can result in: 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 also discusses the specific reliability and protection issues in interconnecting green power generators to utility systems to mitigate the above cited reliability issues. These issues are not adequately discussed in IEEE standard 1547, which addresses interconnection of DG to utility systems.
Interconnect protection of dispersed generators
Much of the new generation capacity installed during the 21st century will be accomplished through the construction of IPP (independent power producer) facilities. These facilities can take the form of small dispersed generating units, or large capacity plants owned and even operated by non-utility personnel. This paper discusses the protection requirements to interconnect these generators to utility systems, as well as methods to reconnect these generators after interconnect protection tripping. The paper also discusses the limitations of present-day interconnection protection methods in addressing issues such as system generation support during major utility system disturbances.