A substation is a part of an electrical generation, transmission and distribution system. The main principle of a substation is to transform high voltage to low voltage or execute various other important functions. Electric power may run through various substations at different voltage levels between the generating station and the consumer. In substations, the transformers may adjust the voltage rates between high and lower transmission voltages or when two separate transmission voltages are related.
Why we use stones instead of sand or soil in switchyards?
The reason behind using stones/gravel in electrical substations for resistance purposes. We need to increase resistance when a person is on the switchboard/sub-station area to prevent electric shocks during failure.
The resistance of stones is higher as compared to the resistance of sand and grass. The resistance of stones is up to 10,000 or maybe 9,000 ohmmeters. It makes it more feasible due to its cost and availability.
In Electrical substations (switchyards) stones are used rather than sand or grass for the following reasons :