Substation areas are fenced electrical areas, which can only be accessed by people under supervision. In conjunction with normal operation, the equipment in a substation area may emit a humming sound with the frequency of the grid current. When the switching situation in the grid is changed, there may also be clacking sounds, and electric arcs lasting a few seconds may be visible.
The operation and condition of substations is monitored by means of operation control and camera surveillance systems. There are also a number of annual inspections concerning technology, the environment and safety.
The substation equipment is maintained by service providers on the basis of a condition-based programme and technical specifications. The structure of the grid is such that electricity can be transmitted along several connections, and most of the maintenance work can be carried out without causing disadvantage to the customers.