What is Prefault voltage?
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What is Prefault voltage?
The prefault voltage is equal to the open-circuit voltage that will drive the fault current through the Thévenin equivalent impedance when the short circuit occurs at the fault location. The prefault voltage is the Thévenin equivalent voltage that drives the fault current.
What is the significance of short circuit MVA?
The short circuit MVA is a method to determine the fault currents for points within a power system. This allows for proper sizing of breakers and protection devices for these points.
How do you calculate short circuit fault current?
The formula is I = V/R. When there is a short circuit the resistance becomes very small, and that means the current becomes very large. If the resistance was zero, then the calculated fault current would go to infinity.
Why are the pre-fault current usually neglected in fault computation?
The effects of pre-fault system loading have been neglected. Usually this is justified because fault currents are much larger than load currents. However, in some situations it may become necessary to consider the effect of load current.
How do short circuits occur in a power system?
A short circuit will occur where there is a low resistance connection between two conductors that are providing a circuit with power. This leads to the generation of an excess of voltage streaming and causes an excessive current to flow through, which will go via a ‘short’ (unexpected) route and cause a short circuit.
Why short circuit analysis is done?
“Short Circuit analysis is required to ensure that existing and new equipment ratings are adequate to withstand the available short circuit current at each point in the electrical power systems.” Short circuit study is used to determine the available fault current or short circuit current at each point in the system.