الفهرس 
Thesis outlines
REVIEW OF LITRATURESOnly 14 pages are availabe for public view
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Abstract
Islanding is a situation that occurs when a part of the system containing both load and DG is disconnected from the main utility, but the independent DGs will continue to energize this part of the network that is isolated from the main utility. The islanding case could be dangerous to grid workers who may not realize that the load is still powered even though there is no power from the grid. So, When the main grid is disconnected and during the islanding operation, the DG can supply electrical power to the loads, but this must to be happened according to the IEEE Standard. IEEE1547 group has produced a standard which serves as a guide for the islanding operation in an electric power system.
Although DG systems have a vital role in the distribution systems, a critical demanding concern is the issue of islanding detection and prevention. Failure to trip islanded DG can lead to a number of problems for DGs systems and the connected loads. So the disconnection will be performed by a special protection schema called islanding detection relays. The operation of these relays can be implemented using different techniques. The international standards must be considered during the operation of islanding detection relays.
Islanding detection techniques are classified into three main groups ;( 1) Passive methods, (2) Active methods, and (3) communication-based method. Passive methods depend on measuring and monitoring the main parameters of the system and make a decision based on these measurements according to the preset thresholds. The advantage of the passive techniques are; simple, easy to be implemented and does not have an impact on the normal operation of the DG system. The disadvantage of the passive techniques is, that theses technique are having large non detective zone (NDZ). Passive techniques have many different methods based on the measurement parameter. There are many passive techniques such as under/over frequency, under/over voltage, rate of change of frequency (ROCOF), rate of change of voltage, rate of change of power signal, the phase-shift method, the vector surge technique, and the harmonic impedance estimation technique.
Active methods are those methods that inject disturbances locally into the system, and then monitor the response to detect an islanding condition. The advantage of these techniques is having smaller NDZ, but it has a major drawback on the system quality. There are many active techniques such as impedance measurement, voltage phase jump, Sandia voltage Shift (SVS) , phase shift, Slip Mode frequency(SMF) ,Frequency Bias or Active frequency Shift (AFD),Sandia frequency shift (SFS), and frequency jump(FJ).
Communication-based methods (Remote technique) based on communication between grid and DGs. The remote technique include supervisory control and data acquisition (SCADA) method, Methods that use the power line as a carrier for communication and methods that monitor the device used to connect/disconnect from the grid.
This thesis develops the investigation of different islanding detection techniques, passive and active, to incorporate the advantage of both techniques, and reduce their drawbacks. The analysis is based on multiple system parameters measurements to identify and classify any possible islanding operation at a specific target location (location at which the islanding detection relay is to be installed). The technique is based on under / over voltage method, under/over frequency, ROCOF, rate of change of phase angle difference (ROCPAD) and rate of change of voltage as passive technique and real power shift (RPS) as an active technique. The thesis investigates the validity of each technique under different loading conditions at different positions in the network, and under different types of faults. The thesis is also studying the response of the proposed technique in different position in the network.