Short Circuit Calculator — Calculate Fault Current & Protection

Short Circuit Calculator

Calculate short circuit current, fault levels, and protection requirements for electrical systems. Understand voltage, impedance, and transformer parameters.

Step 1: System Parameters

5%

Understanding Transformer Impedance

Transformer impedance (typically 3-10%) limits short circuit current. Lower impedance means higher fault current. Standard values are 5-6% for distribution transformers.

Step 2: Circuit Parameters

About Cable Impedance

Cable impedance increases with length and decreases with cross-sectional area. Copper cables have lower impedance than aluminum. Longer cables reduce short circuit current at the load end.

Short Circuit Results

Summary
Current Comparison
Impedance Analysis

Prospective Short Circuit Current

12.5 kA
Fault Level: 8.66 MVA
Transformer Contribution
11.8 kA
Cable Impedance
0.15 Ω
X/R Ratio
4.2
Protection Required
16 kA

Fault Current Comparison

Transformer Size Voltage Impedance Fault Current Fault Level

Impedance Breakdown Analysis

Short Circuit Formula

I_sc = V / (Z_transformer + Z_cable)

The short circuit current is calculated by dividing the system voltage by the total impedance (transformer impedance plus cable impedance). Impedance values are typically expressed as percentages or ohms.

Need Professional Electrical Advice?

Connect with our electrical engineering experts for detailed short circuit analysis, protection coordination studies, and electrical system design guidance.

Get Professional Advice