12 Questions
What is a characteristic of an ungrounded system?
Low equipment damage
Why are ungrounded systems sometimes used in industrial plant systems?
To minimize interruptions of expensive production processes
What happens to the voltage triangle during a phase-to-ground fault on an ungrounded system?
It shifts to a new position
What is the relationship between the distributed capacitive reactance values and the series reactance values in an ungrounded system?
The capacitive reactance values are very large, while the series reactance values are very small
What is a disadvantage of ungrounded systems?
They are subject to high transient overvoltages
What happens to the positive sequence network in an ungrounded system?
X1C is shorted out by X1S and XT
What is the reason why Ia = 3I0 in the fault current calculation?
Because X0C is very high
What is the purpose of Ib and Ic currents in the system?
To provide a return path for Ia fault current
What is the equivalent of X0C in industrial applications?
The charging capacitance of the transformers, cables, motors, and so on
What happens to the unfaulted phase-to-ground voltages when a phase-to-ground fault occurs?
They increase, particularly by 3
What is the definition of the neutral point in a three-phase system?
The point with the same potential as the point of junction of a group of equal nonreactive resistances
Why is it impractical to use selective location of faults by protective relays in ungrounded systems?
Because the fault currents are practically the same and independent of the fault location
Learn about ungrounded power systems, which are used in industrial plants to minimize interruptions of expensive production processes. Understand how they work and their advantages, including low fault current levels and minimal equipment damage.
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