For which of the following points is indoor substation superior to outdoor substation?

Indoor substations are generally superior to outdoor substations in terms of safety and fault location, while outdoor substations may be cheaper and require less maintenance. 

Safety: 

• Indoor substations provide better protection from environmental hazards (e.g., storms, dust, pollution).
• They reduce the risk of electrocution and accidental contact compared to outdoor substations, which are more exposed.
• They are usually enclosed, making them safer for personnel.

Cost:

• Outdoor substations are often cheaper to build and require less space, especially for lower voltage applications. 

Maintenance requirement:

• Indoor substations require higher maintenance because of the need for cooling, ventilation, and insulation protection.

Fault location:

• Fault location in indoor substations can be easier due to the enclosed environment and centralized equipment.