In France, the action of disconnection for distributed generations (DG) of a few MW connected to the medium voltage (MV) network, is instantaneous in case of voltage sags as those due to faults. These existing disconnection protection settings can cause a large number of unwanted disconnections. Unexpected disconnections caused by disturbances could have local but also global impacts on the network operation, particularly for weak grids. The instantaneous action of protective relays is only necessary for DG with high short circuit current as rotating machines. The behavior of photovoltaic (PV) systems connected to the network via inverter and their ability to withstand disturbances (ex: voltage sags) is totally different compared to those of rotating machines. Therefore, the first investigation of this work is to study how actual requirements are suitable with PV power plants. Behaviors of PV systems connected to MV network during faults are then studied considering the real network protections. Then, unnecessary trip cases of PV plants are identified through simulations. Finally solutions to avoid these unwanted disconnections are proposed. A verification of the system operation with proposed solution is also carried out.