Showing papers on "Islanding published in 1988"

An industrial view of utility cogeneration protection requirements

Abstract: Most electric utilities have adopted a set of standardized requirements for protection at the interface with a cogenerating industrial system. Typical utility requirements are reviewed, the basis for their formulation is explained, and practical ways for the industrial cogenerator to satisfy them are suggested. The discussion covers engineering planning, fault detection, islanding, dead circuit pickup, and manual synchronization. >

Investigation of potential islanding of dispersed photovoltaic systems

Abstract: Photovoltaic sources feed power back to a utility through static power converters (SPCs) during normal operation. The SPCs are designed to shut down when the utility grid is abnormal; however, it has been shown that they continue to operate or ''run-on'' under certain abnormal conditions. This research was designed to establish the conditions of load vs generation under which run-on would occur. Computer simulations were made of a TESLACO self-commutated SPC and of a Gemini line-commutated SPC. The results of the simulations were verified by laboratory and field tests. Run-on was found to occur only when there was a very close match between PV generation (SPC output) and connected load. For the TESLACO, under matched-load conditions, run-on was limited to 4 seconds, due to destabilizing circuits and internal trip mechanisms. For the Gemini, external VAR support, necessary for matched-load conditions, allows the unit to run-on indefinitely. The addition of internal trip mechanisms based on sensing frequency and voltage, available from the Gemini manufacturer, reduced run-on to an extremely low probability event. The research did not reveal any dynamic interaction among multiple TESLACOs, multiple Geminis, or among TESLACOs and Geminis within an island that would cause the island to persist longermore » than it would for a single SPC. 29 refs., 117 figs.« less

Circuit allocation in subtransmission switching substations using best-first search strategy

Abstract: Based on the best-first search strategy, this paper develops a general computational model for the automatic determination of circuit allocation schemes in subtransmission substations. Starting from a discussion of the allocation requirements, fault indices based on the percentage of power rating loss of circuits are first derived. The best-first strategy is then defined by the group allocation and overall allocation index trees, which are formed from the relations of the fault indices. A search procedure implementing this strategy is developed to determine the best overall allocation arrangement, which is found by combining the best group allocation schemes. A general method for assigning interconnectors to the tasks of source and load circuits to assess the security level of the overall allocation schemes in the process of islanding constraint checking is reported. The model is implemented by a logic programming language, Prolog. The developed software system is applied to allocate six groups of circuits from seven substations to a 132 kV duplicate-busbar substation.

Test and study of utility interface and control problems for residential PV systems in Rokko Island 200 kW test facility

Abstract: A 200 kW test facility comprising one hundred 2 kWp PV systems and a simulated utility grid was constructed to establish an adequate utility interface and control technology for small-scale dispersed PV systems. Experimental results are described. Demonstration experiments were performed, and the results show that the harmonic distortion in the distribution line was little influenced, and the problem of harmonics has been almost solved. It is confirmed that appropriate measures must be established for prevention of voltage variation in the low-voltage distribution line and for prevention of islanding during power outages. Solutions to these problems were also investigated using this facility. >