Short Circuit Fault Current

Short Circuit Analytic version 1.0 mobile app performs available short circuit fault current calculations in three-phase radial power system you are working with. The app takes into consideration all of the key electrical parameters of power distribution system including power supply, cables, transformers, generators and motors.

The source can be set as a transformer supply or a busbar with a specified short circuit level. If a transformer source is used, the short circuit level on the primary side can be set to infinity by setting the data field blank.

Add components one by one to build up a single line diagram. The components can be cables, transformers, ligting loads, electrical devices, motors and generators. After a component has been added, its data can be edited by tapping the component when displayed on the screen.

Tap on 'Run Analysis' button to calculate available 3-phase and phase-to-phase short circuit current values and fault X/R ratio at each busbar.

Additional information about SCA V1.0 mobile and the comprehensive method for short circuit analysis

Simple point-to-point short circuit fault current calculations are carried out using Ohm's law and equipment resistance values. To determine fault current at various locations within power system, the system characteristics such as available short circuit value at service entrance, line voltage, transformer KVA rating and percent impedance, conductor characteristics are utilized.

The calculations become more complicated when resistance values are replaced with an impedance values. For instance, transformer ratio of reactance to resistance (X/R) is used along with transformer percent impedance to determine X and R values on a per unit bases. Similarly, the impedance for conductors within the electrical system are also broken down into X and R components of the impedance.

The peak asymmetric fault current is also determined by X/R ratio. The total asymmetric current is a measure of the total DC component and the symmetrical component. The asymmetrical component decays with time and will cause the first cycle of a fault current to be larger in magnitude than the steady-state fault current. Also, the decay of the DC component depends on the X/R ratio of the circuit between the source and the fault.

Knowing the fault X/R ratio is essential when selecting electrical and protection equipment. For example, all low-voltage protective devices are tested at predetermined X/R ratios. If the calculated X/R ratio at any given point in the electrical distribution system exceeds the tested X/R ratio of the overcurrent protective device, alternate gear with adequate X/R rating should be considered or the device effective rating must be reduced.

Features and Capabilities:

1. Calculate 3-phase, phase-to-phase short circuit currents at each bus within your power distribution system
2. Determine maximum available short circuit current, the amount of maximum upstream short circuit current and the minimum available short circuit current contributed by one source only. Both the available short circuit current (ASCC) and the part of ASCC through protection device current values are required for comprehensive arc flash hazard analysis using NFPA 70E and IEEE 1584 methods
3. Compute contributions from generators and motors
4. Add North American wire gauge cables as well as international cables
5. Perform comprehensive short circuit analysis by taking into account both active and reactive parts of equipment impedance
6. Determine fault X/R ratio at each bus
7. Save, rename, duplicate single-line diagrams and equipment data
8. Export, import one-line diagrams and all the equipment data for easy sharing
9. Send calculation results and captured single-line diagrams by email