الفهرس 
CHAPTER 1 INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Cascaded tripping events may represent a challenge for protective elements in Electrical networks. The cascaded tripping is a sequence of events that start with an initial disturbance, or set of disturbances, triggering a sequence of one or more dependent component outages. Some cascaded tripping cases are mitigated after tripping few transmission lines. In other worse cases, the cascaded tripping may not be mitigated and causes the blackout. This condition was experienced in Egypt in a substation of an iron plant in the industrial Sadat city in November 2010. A single line to ground fault took place on a current transformer in the region between the current transformer and the live-tank circuit breaker of a transmission line. The main protection did not recognize this fault case. Then, the backup protection in the grid responded dividing the power grid into three islands. This unnecessary response should be avoided by realizing a dedicated protection scheme to be able to pinpoint this faulted case and minimize the disconnected area as possible. In order to investigate this problem, a detailed simulation of a real power network from the Sadat city with its detailed parameters and accompanied protective elements were constructed with EMTP/ATP package simulation program. Then, a thorough investigation study was carried out to emphasize the core of the cascaded tripping problem in order to clarify its causes and possible solutions. Three different solutions were proposed. First, a distance relay was utilized as a backup to the differential protection on the short transmission line. Then, a proposed acceleration scheme of the distance protection discussed. The second solution proposed a direct transfer trip signal scheme to clear the fault in case of tripping of one terminal of the transmission line. The third one discussed the activation of the inversetime function of the utilized overcurrent protection to avoid these situations.