Fault protection for a medium voltage transformer branch

In a power circuit composed of a main current path and a plurality of parallel branch paths connected in series with the main current path and each containing a winding of a medium voltage transformer, a fault protection system comprising:

• first and second current interrupter means for switching the current flowing through the paths and for protecting the paths against fault currents, each said interrupter means being bidirectionally switchable between a closed, current conducting, state and an open, current blocking, state, said first interrupter means being connected in one branch path for interrupting fault currents in a first amplitude range and said second interrupter means being connected in the main current path for interrupting fault currents in a second amplitude range, which second amplitude range is higher than the first range and includes short circuit currents;
• and current monitoring and switching control means connected for monitoring the current in the one branch path and connected to said first interrupter means for maintaining said first interrupter means in the closed state when the current in the one branch is below the first amplitude range, for placing said first interrupter means in the open state in response to the presence of a fault current in the first amplitude range, and for maintaining said first interrupter means in the closed state in response to the presence of a fault current in the second amplitude range.