Powering an impedance injection unit during startup operations

An impedance injection unit for injecting reactive power into a phase of a power transmission line, the impedance injection unit comprising:

• a controller configured to control injection of the reactive power into the phase of the power transmission line;
• and
• a power supply configured to withstand a surge current, an in-rush current, or an over-voltage arising from a disturbance on the phase of the power transmission line, or mode switching of the impedance injection unit, the power supply comprising:
• a charge harvester configured to harvest charges from the phase of the power transmission line;
• and
• circuitry configured to clamp a voltage of the harvested charges to a specific value to withstand the in-rush current or the over-voltage to generate a supply voltage to the controller;
• wherein:
• the impedance injection unit is configured to start from a powered down state;
• the controller is configured to execute a boot up routine when the controller receives the supply voltage from the power supply;
• and
• when the controller completes the boot-up routine, the controller is configured to disable the circuitry that clamps the voltage of the harvested charges.