Why must contact shoe slippers not be used when wet?

Contact shoe slippers must not be used when wet primarily because they are not good insulators. In rail systems, the contact shoes are crucial for ensuring that there is a clear electrical connection between the train and the power supply through the overhead lines or rails. Wet conditions can compromise the insulating properties of the slippers, leading to potential electrical short circuits or interference.

When contact shoe slippers become wet, moisture creates a pathway for electricity that can bypass the slippers' intended insulating design. This can result in dangerous situations such as electrical shocks or system failures. Therefore, maintaining proper insulation is critical for safety and operational efficiency, making it essential to avoid using contact shoe slippers in wet conditions.

The other aspects, like losing friction or causing malfunction, while relevant in certain contexts, are secondary to the core issue of electrical insulation and safety when wet.