Method to eliminate flux linkage DC component in load transformer for static transfer switch

Area of Science:

• Electrical Engineering
• Power Systems Engineering

Background:

• Sensitive industrial and commercial loads require reliable power quality, often using static transfer switches (STS).
• STS transfers can induce severe inrush currents (2-30 p.u.) in load transformers due to DC flux components.
• This inrush current risks disoperation of protective devices and transformer damage.

Purpose of the Study:

• To analyze flux linkage changes during STS transfer.
• To develop a method for calculating optimal transfer timing to eliminate inrush current.
• To validate the proposed transfer method through simulation and experiments.

Main Methods:

• Analysis of flux linkage variations in transformer windings during the transfer process.
• Calculation of the precise switching instant based on residual and prospective flux linkages.
• Implementation and testing of the developed transfer timing method using simulations and laboratory experiments.

Main Results:

• The study successfully analyzed the dynamic flux linkage behavior in transformers during STS operation.
• A novel method for determining the optimal phase transfer time was developed, effectively mitigating DC flux components.
• Simulations and experimental results confirmed the significant reduction in inrush current, validating the proposed technique.

Conclusions:

• The developed phase transfer method effectively eliminates the DC component, preventing severe inrush currents in transformers.
• This technique enhances the reliability and safety of power systems employing static transfer switches.
• The findings offer a practical solution for protecting transformers and ensuring stable power supply to sensitive loads.