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Magnitude of the asymmetry (transient component) depends on the phase of the generator voltage at the time of the fault. In this class, we will use the steady-state current component, , as our primary fault current metric. The reactance of the generator was assumed constant in the previous example.
18 Νοε 2019 · Solidly Grounded Systems. Ground fault currents in solidly grounded systems can approach phase fault levels. Ground fault protection for these systems is usually provided by residual protection, either calculated by relay or by external CT residual connection to IN input.
Cross polarization: (protective relaying) The polarization of a relay for directionality using some proportion of the voltage from a healthy (unfaulted) phase(s). One example of this is quadrature polarization. In this case, the polarizing voltage is in quadrature to the faulted phase voltage.
This white paper will go inside the motor and provide a more detailed look into what happens when one phase of the power supply is lost and how Sprecher + Schuh overload relays handle the phase failure. Most of the motors that we encounter are delta-connected squirrel cage induction motors.
Figure 1. Calculating Phase Margin From a Frequency Response Plot. As can be seen in the plot of Figure 1, an AC response, (Magnitude on top and Phase underneath), is given.
Typically, only 5% of the initial faults in a power system, are three phase faults with or without earth. Of the unbalanced faults, 80 % are line-earth and 15% are double line faults with or without earth and which can often deteriorate to 3 phase fault. Broken conductor faults account for the rest.
an unbalanced 3- phase circuit has to be solved. Since the direct solution of such a circuit is very difficult, the solution can be more easily obtained by using symmetrical components since this yields three (fictitious) single phase networks, only one of which contains a driving emf.
