what do you think about the effect of the rain in electrical equipment earth fault? for example some times there is an earth fault in rectifier panel and it removes after hours spontaneously.

Water and electricity do not mix.

Electrical equipment exposed to the elements needs be appropriately designed and maintained - in particular regarding ingress protection.

Generally for outdoor equipment I'd specify IP65 as a minimum. If you have the budget and you don't want to revisit in a few years, go for a stainless steel enclosure, and have the electrical maintainers perform regular inspections to identify damage to equipment, perished seals, loose glands etc.

Water ingress into a panel is not healthy. Your equipment will malfunction and burn out if not well protected.Depending on the location of the panel and the nature of exposure of your
power electronics equipment to water,be it dripping,sprayed,splashed or submerged,it will provide a direct connection to earth and pose safety harzard to personnel.The best thing to do is to ensure the enclosure is water proof.The degree of proofing will depend on location. If it is exposed outside where the dusts abound and water hosed regularly,then it is appropriate to ensure it is dust and water proof. In that case, the Ingress protection level
as pointed out by Matthew will surfice but if it is not in a severe location,you may think of reducing the ingress protection level especially if it is indoor and not directly splashed.
But have a thorough check of the circuitry,at times such a fault may not be as a result of water ingress but a loose connection or circuit device that is showing signs of fatigue and requires replacement. On the last note,ensure your extractor fans and heaters are active.