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2. Three-phase fault calculations Three-phase faults are unique in that they are balanced, that is, symmetrical in the three phases, and can be calculated from the single-phase impedance diagram and the operating conditions existing prior to the fault. A fault condition is a sudden abnormal alteration to the normal circuit arrangement.
Use the following procedure to calculate the level of fault current at the secondary of a second, downstream transformer in a system when the level of fault current at the transformer primary is known.
How to Figure Volt Loss. Multiply distance (length in feet of one wire) by the current (expressed in amps) by the figure shown in table for the kind of current and the size of wire to be used, by one over the number of conductors per phase.
a one-line diagram of the power system involved, showing the type and rating of the protection devices and their associated current transformers. the impedances in ohms, per cent or per unit, of all power transformers, rotating machine and feeder circuits.
4.2 THREE-PHASE FAULT CALCULATIONS Three-phase faults are unique in that they are balanced, that is, symmetrical in the three phases, and can be calculated from the single-phase impedance diagram and the operating conditions existing prior to the fault. A fault condition is a sudden abnormal alteration to the normal circuit arrangement.
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.
current in one phase of a three phase bolted fault. The SC MVA can be calculated from the short-circuit current using the following equation: SC MVA = 1.732 I SC V LL, where I SC is expressed in kA and V LL - in kV Power factor (PF) is sometimes specified instead of X/R. This must be the short circuit power factor. Power factor
