Showing papers on "Islanding published in 1993"
TL;DR: In this paper, the requirements of an islanding, or "loss of grid", protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined.
Abstract: The requirements of an islanding, or 'loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system. >
277 citations
10 May 1993
TL;DR: In this article, the authors present results of islanding tests, with a preventive method of power capacitor insertion, which is effective to get rid of the islanding phenomenon in a short time.
Abstract: Islanding phenomenon can occur when a distribution line circuit, connected with a large number of PV generation systems, is opened. Islanding must be eliminated as rapidly as possible, because this phenomenon can cause many problems. This paper presents results of islanding tests, with a preventive method of power capacitor insertion. Insertion of capacitors during islanding is effective to get rid of the islanding phenomenon in a short time. This approach, involving the use of capacitors in the utility distribution circuit, promises to eliminate the need to provide an additional islanding detection function on the part of the PV power system. >
26 citations
17 May 1993
TL;DR: In this article, the authors discuss the types of power system disturbances, methods available for system protection and especially strategies for controlling the underfrequency islanding and island operation, and the earth-fault relay coordination during the island operation.
Abstract: A power system can be divided into islands in the case of serious system disturbances. The authors discuss the types of power system disturbances, methods available for system protection and especially strategies for controlling the underfrequency islanding and island operation. Dynamic simulation studies were made concerning three Finnish municipal energy utilities owning local power generation. The results are presented as general principles which aid any power producer in planning its islanding scheme. These include methods for selecting the island area and suitable load shedding and reactive power compensation practices for this area. In addition, the earth-fault relay coordination during the island operation is discussed.<
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7 citations
TL;DR: In this article, a protection scheme for an HVDC link that prevents damage due to islanding while still permitting the link to automatically restart on reclosure of the isolating breaker is described.
Abstract: When a high-voltage DC (HVDC) scheme is isolated from its receiving AC system, the inverter may continue to operate, generating its own AC bus voltages; this is defined as islanding. If islanding is allowed to continue unrestricted, main circuit components may in some conditions be damaged. It is therefore necessary to provide a suitable protection system. The author describes a protection scheme developed for an HVDC link that prevents damage due to islanding while still permitting the link to automatically restart on reclosure of the isolating breaker. Oscillograms showing the protection in operation on both the GEC ALSTHOM HVDC simulator and during tests carried out as part of the commissioning of the McNeill HVDC link are included. >
3 citations
01 Jan 1993
TL;DR: In this paper, the authors describe a network simulator system that has been developed in order to simulate special type of network conditions, e.g. islanding operation, for networks connected to thermal power stations, especially with regard to frequency control.
Abstract: This thesis describes a network simulator system that has been developed in order to simulate special type of network conditions, e.g. islanding operation, for networks connected to thermal power stations, especially with regard to frequency control. The simulator has been developed so that it can operate both connected to an actual power station in operation or to a power station simulator. It has been designed primarily with regard to the Stenungsund thermal power station, but is of a general design and will in the continuation of this project be adapted also for other types of power stations. The main principle of the simulator is that it can be applied to a power station in operation and perform simulations where special network conditions are simulated in spite of that the power station is still connected to its normal network. This simulator has been developed as a tool for further studies of special operating conditions for power stations, in particular islanding operation. Certain such studies have been carried out and are described in this thesis. The studies have shown that islanding operation is a complex situation where unexpected behavior of the power station can sometimes lead to very unwanted consequences and that it is therefore necessary to be able to test such situations in advance, as it is otherwise highly unlikely that the station will be able to remain in operation under such conditions. Tests as described above can show the need for new control systems or systems settings as well as new routines for operating the stations under such conditions and also for operator training so that the station operators know how to handle these situations. The simulator can be used as a tool for all these purposes.
1 citations
TL;DR: The unislanding of England as discussed by the authors, the defeat of the channel tunnel project of 1882, is considered a seminal event in the history of the English Channel Tunnel Project.
Abstract: (1993). “The un‐islanding of England”: The defeat of the channel tunnel project of 1882. Studies in Newspaper and Periodical History: Vol. 1, No. 1-2, pp. 163-175.
TL;DR: The overvoltages can occur when DSGs are separated from the utility source not at the primary side but at the secondary side of a delta-wye grounded transformer connected to the feeder and the ferroresonance circuit is established.
Abstract: Ferroresonant overvoltages can occur on an isolated feeder connected to Distribution System Generators (DSGs). This paper analyzed the overvoltages and the following results are obtained. (1) The overvoltages occur on a three-phase four-line wye-grounded system such as 400V class distribution lines but do not occur on a three-phase three-line ungrounded system such as 6.6kV distribution lines. (2) The overvoltages can occur when DSGs are separated from the utility source not at the primary side but at the secondary side of a delta-wye grounded transformer connected to the feeder. (3) The saturated reactances of transformer excitation circuit and the phase-to-neutral capacitances on the isolated feeder eatablish the ferroresonance circuit. (4) The ferroresonance generates the phase-to-neutral voltages of 2.6 pu. The voltages are suppressed to 1.8 pu with installation of surge-absorbers but continue. The DSGs have to be disconnected from the islanding system by overfrequency or overvoltage relays to drop the continuing over-voltages.