What Is the Three-Phase Symmetrical Fault Current & MVA Calculator?
A symmetrical three-phase fault occurs when all three phase conductors short together with zero arc impedance.
How Does the Three-Phase Symmetrical Fault Current & MVA Calculator Work?
Computes fault MVA = S_base / Z_th.
Calculates line fault current I_fault = S_fault / (√3 · V_LL).
Three-Phase Symmetrical Fault Current & MVA Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
S_fault = S_base / Z_th, I_fault = S_fault / (√3 · V_LL)
Symmetrical 3-phase fault MVA and RMS symmetrical breaking current equations.
How to Use the Three-Phase Symmetrical Fault Current & MVA Calculator
- Input nominal bus voltage in kV.
- Input positive sequence per-unit Thevenin impedance.
- Enter system base MVA.
Step-by-Step Example Calculation
11 kV Substation Bus Fault
Input Values:
nominalVoltage:11
theveninImpedance:0.05
systemBaseMva:100
Worked Steps: 11 kV substation bus with 0.05 p.u. impedance on 100 MVA base.
Understanding Your Result
Primary output indicates symmetrical fault current in kA.
Summary displays short-circuit power in MVA.
Factors That Affect the Result
- Transformer impedance and grid upstream stiffness.
When Should You Use This Calculator?
- Switchgear breaker selection and protective relay coordination.
Assumptions & Limitations
- Assumes pre-fault voltage is 1.0 p.u. and bolted zero-impedance fault.
Frequently Asked Questions
Calculation Accuracy & Reference Note
IEC 60909 symmetrical fault formulation.