Current waveforms of the high voltage hybrid DC circuit breaker

The operation of a hybrid circuit breaker is divided into eight intervals, corresponding to four operational modes. These intervals and modes are as follows:

• Normal Mode (t0~t2):During this interval, power is transmitted seamlessly between the two sides of the circuit breaker.
• Breaking Mode (t2~t5):This mode is used to interrupt fault currents. The circuit breaker rapidly disconnects the faulty section to prevent further damage.
• Discharge Mode (t5~t6):In this interval, the voltage across the capacitor is reduced to its rated value. This ensures that the capacitor is safely discharged and ready for the next operation.
• Reverse Mode (t6~t7):This mode is used to change the polarity of the capacitor. The polarity reversal prepares the capacitor for subsequent operations and ensures proper functionality.

Key Components and Their Functions

• IS1: Residual DC current breaker. This component is responsible for breaking any residual DC current that may remain after the main current has been interrupted.
• IS2, S3: Fast mechanical switches. These switches are designed to rapidly open and close the circuit, ensuring quick response times during fault conditions.
• IC: Auxiliary branch capacitor current. This current flows through the auxiliary branch capacitor, which helps in energy storage and release during the operation of the circuit breaker.
• I MOV: Metal oxide varistor (MOV) current. The MOV is used to protect the circuit from overvoltage conditions by clamping the voltage to a safe level.
• IT3: Thyristor current for reversing the polarity of the capacitor. This current flows through the thyristor to reverse the polarity of the capacitor during the reverse mode.