Table of Contents
What happens to voltage during LG fault?
Voltage swells can occur due to: Single line to ground fault, Load rejection, Addition of large capacitive kvar to the system etc. Single line to ground fault can result in voltage swell on unfaulted phases while load rejection and excess kVar results in three phase voltage swell.
What happens when LG fault occurs?
Line to ground fault (L-G) is most common fault and 65-70 percent of faults are of this type. It causes the conductor to make contact with earth or ground. These are also called unbalanced faults since their occurrence causes unbalance in the system.
What is the voltage between two lines?
The conductors between a voltage source and a load are called lines, and the voltage between any two lines is called line voltage. The voltage measured between any line and neutral is called phase voltage. For example, for a 208/120 volt service, the line voltage is 208 Volts, and the phase voltage is 120 Volts.
What happens to voltage during earth fault?
In the event of an earth fault in one of the two systems of a three-winding transformer, an increase in the star- point voltage occurs in the disturbed system. This voltage is transferred to the undisturbed systems due to capacitive coupling, to affected earth faulty system and to earth.
What happens in a line to line fault?
A line to line fault or unsymmetrical fault occurs when two conductors are short circuited. The LL fault is placed between lines b and c so that the fault be symmetrical with respect to the reference phase a which is un-faulted.
What is fault voltage?
An electrical fault is the deviation of voltages and currents from nominal values or states. Under normal operating conditions, power system equipment or lines carry normal voltages and currents which results in safer operation of the system.
Why does voltage drop during a fault?
Why the Voltage and Reactance of a system under fault condition is low and fault current may rise to the highest dangerous value? When short circuit occurs, there will be no resistance or reactance and current will be too much high. In this case, when power is constant and current increases, voltage will be decreased.
What is line line fault?
line-to-line fault – a short circuit between lines, caused by ionization of air, or when lines come into physical contact, for example due to a broken insulator. In transmission line faults, roughly 5\% – 10\% are asymmetric line-to-line faults.
What happens when an LG fault occurs in a system?
When LG, LL, LLG, LLL or LLLG fault occur in a system then current increases and voltage decreases.Increase in current occur due to the fact that system impedance decreases during fault condition where as decrease in voltage happens due to demagnetizing nature of armature reaction.
What is the difference between L-G fault current and 3ø fault current?
The L-G fault current will exceed the 3Ø fault current whenever you are near the terminal of a D-Y transformer. The Delta winding effectively blocks the zero sequence impedance contributed by the source. Thus Z0 source is zero and the only Z0 contribution to the impedance is the transformer impedance.
What are the types of electrical faults in three phase power system?
Electrical faults in three-phase power system mainly classified into two types, namely open and short circuit faults. Further, these faults can be symmetrical or unsymmetrical faults.
What happens when a line to ground fault occurs on neutral?
Line to ground fault in grounded neutral systems behave little differently. A line to ground fault on a grounded neutral system can result in one of the following on unfaulted phases a) Voltage Sag b) No change in voltage c) Voltage Swell.