I have problem with Thyristors that are burning, when stormy weather appears ( Power failure )

Fuses before Convertors 6RA70 are as recommended, gS. Sometimes fuses burning, but also and thyristors. Fuses are easy and fast for changing, but for thyristors I need some time, delays.

Thermal magnetic circuit breaker on the power supply of the line is 500A.

My question is how to protect it, which effective protection to connect on the power supply voltage ?