Medium-Voltage Engineering Analysis Tools & Design Calculators

Evaluate the Transient Recovery Voltage (TRV) duty imposed on circuit breakers interrupting faults limited by current-limiting reactors. This tool calculates oscillatory TRV and Rate of Rise of Recovery Voltage (RRRV) for terminal fault conditions in accordance with IEEE C37.011 and IEEE C37.04, and compares the calculated duty to applicable circuit breaker capability.

Download: Reactor-Limited Fault TRV Assessment Tool
VarStec Brief: Reactor-Limited Fault TRV and Breaker Duty Assessment

Evaluate the transient discharge duty imposed on a circuit breaker during a close-in fault adjacent to an energized capacitor bank or harmonic filter bank. This tool applies current industry guidance from IEEE Std C37.012-2022, IEEE Std C37.04-2018, IEEE PES TR16, and IEEE Std C37.09-2018 to assess breaker duty under capacitor discharge fault conditions.

Download: Capacitor Bank Outrush & Close-in Fault Analysis Tool
VarStec Brief: The Need for Outrush and Close-In Fault Analysis When Applying Capacitor Banks

Evaluate peak inrush current magnitudes and transient frequencies during capacitor bank energization, including isolated single-bank and back-to-back switching conditions in multi-stage capacitor banks. This tool assists in the selection of inrush current-limiting reactors and verifies switching device application by comparing calculated duty to applicable current, frequency, and peak-making limits in accordance with IEEE C37.012, IEEE C37.04, IEEE C37.66, and IEEE 1036.

Download: Capacitor Bank Switching Inrush Analysis Tool
VarStec Brief: Capacitor Bank Switching Transients: Single-Bank and Back-to-Back Switching

A comprehensive spreadsheet workbook for the design and evaluation of medium-voltage notch, high-pass, and C-high-pass harmonic filters. The workbook supports both forward design and reverse calculation, allowing users to develop or reconstruct key filter parameters when only selected component values are known. It helps determine reactive power output, tuning point, damping factor, component duties, resistor requirements, current and voltage distribution, and estimated losses, while also supporting design verification of capacitor, reactor, and resistor application. The workbook uses IEEE standards including IEEE 519-2022, IEEE 1531-2020, and IEEE 18-2025.

Download: Medium-Voltage Harmonic Filter Design Tool
VarStec Brief: Harmonic Filter Design Verification 

Evaluate medium-voltage equipment dielectric performance at high elevations using both physical altitude derating and insulation coordination methods. This workbook applies air-density correction factors to dielectric withstand ratings for equipment installed above 1000 meters in accordance with IEEE C37.20.2 and IEEE C37.20.3, and also evaluates surge arrester coordination, protective margins, and arrester lead-length effects using IEEE C62.22 and IEC 60071-2. The tool helps determine when higher insulation ratings are necessary and when proper insulation coordination can avoid unnecessary equipment uprating and cost.

Download: Medium-Voltage Altitude Derating and Insulation Coordination Tool
VarStec Brief: When at High Altitude, You Don’t Always Need to Derate

Compare medium-voltage motor-starting configurations and evaluate MotorVar-assisted solutions for reducing voltage sag without the complexity of VFD-based starting systems. This workbook supports the preliminary sizing and evaluation of MotorVar systems by comparing unassisted motor starting to MotorVar-assisted configurations, including RVSS-, captive-transformer-, and line-reactor-assisted arrangements. It helps assess motor terminal voltage, available starting torque, system inrush current, and voltage sag at both the motor bus and point of common coupling (PCC), supporting feasibility assessment and interconnect impact evaluation.

Download: MotorVar Capacitor Start Sizing Tool
VarStec Brief: Starting Large Motors with Capacitor Banks