A protection and control design begins with development of a preliminary single-line diagram, indicating the bus arrangement and major equipment such as power transformers, circuit breakers, voltage regulators, disconnect switches, capacitors, instrument transformers, etc. General information regarding metering, SCADA, relay interconnections, and communications may be included. The final protection and control scheme for the substation is presented on a relay and instrumentation single-line diagram that is based on the customer’s protection and control philosophy, as well as the recommendations of IEEE Standards Collection C37.

S&C then applies the customer’s available design and CAD standards to create ac and dc elementary diagrams — detailing operation of the protection and control equipment — in accordance with the final relay and instrumentation single-line diagram. These elementary diagrams are subsequently used to create panel layout, connection, and apparatus drawings. The connection drawings are used to create the bill of materials and bill of wire for the project. When included as part of the scope of work, S&C’s expertise in the evaluation of control and protective device settings are used to achieve proper settings for system protection and coordination.