Shunt Capacitor Inrush Current Calculator
Substation power factor correction & reactive power: Calculate back-to-back capacitor bank switching peak inrush current (I_peak), inrush frequency, and damping reactors.
Substation & Capacitor Bank Ratings
Inrush Dynamics & Reactor Requirements
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
Why is "back-to-back" capacitor bank switching so much more severe than isolated switching?
When an isolated capacitor bank is energized, the inrush current is throttled by the large inductance of the upstream substation transformer. However, during back-to-back switching, an already energized adjacent capacitor bank dumps its stored charge into the closing bank through only a few meters of low-impedance busbar, resulting in massive inrush currents (15–40 kA) at frequencies of several kilohertz.
How does an air-core series reactor mitigate capacitor inrush current?
An air-core inrush damping reactor adds explicit inductance (typically 50 to 300 µH) directly into the inter-bank loop. Because peak inrush scales inversely with the square root of inductance (I_peak ∝ 1/√L) and frequency drops as 1/√L, even a modest reactor reduces inrush stress by 70% to 80%.
What are the IEEE C37.06 circuit breaker switching limits?
For high-voltage SF₆ circuit breakers in capacitor switching duty, IEEE C37.06 specifies maximum peak inrush current (typically 20 kA peak for general purpose breakers) and a maximum product of peak current and inrush frequency (I_peak · f_inrush ≤ 80 × 10⁶ A/s) to prevent contact welding and pre-strike restrikes.