QUESTION #4: A 3 phase 50 MVA, 11 kV alternator having 15% reactance is connected through a 50 MVA, 11 kV/33 kV Delta-Star connected transformer of 5% reactance to a 33 kV transmission line having negligible resistance and a reactance of 4 2. At the receiving end of the line there is a 50 MVA, 33 kV/11 kV delta-star connected transformer of 5% reactance stepping down the voltage to 11 kV. Both the transformers have their neutral solidly earthed. Draw the one line diagram and the positive, negative and zero sequence networks of this system and determine the fault currents for the following types of faults at the receiving station LV Bus Bars. a) All the three phases are short circuited. b) A single line grounded. c) A short circuit between two lines. For generator assume negative sequence reactance of 70% that of positive sequence.
Load flow analysis
Load flow analysis is a study or numerical calculation of the power flow of power in steady-state conditions in any electrical system. It is used to determine the flow of power (real and reactive), voltage, or current in a system under any load conditions.
Nodal Matrix
The nodal matrix or simply known as admittance matrix, generally in engineering term it is called Y Matrix or Y bus, since it involve matrices so it is also referred as a n into n order matrix that represents a power system with n number of buses. It shows the buses' nodal admittance in a power system. The Y matrix is rather sparse in actual systems with thousands of buses. In the power system the transmission cables connect each bus to only a few other buses. Also the important data that one needs for have a power flow study is the Y Matrix.
Types of Buses
A bus is a type of system of communication that transfers data between the components inside a computer or between two or more computers. With multiple hardware connections, the earlier buses were parallel electrical wires but the term "bus" is now used for any type of physical arrangement which provides the same type of logical functions similar to the parallel electrical bus. Both parallel and bit connections are used by modern buses. They can be wired either electrical parallel or daisy chain topology or are connected by hubs which are switched same as in the case of Universal Serial Bus or USB.
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