Schematic diagrams are to be checked for errors.
Special consideration must be given to schematic diagrams for differential relaying current circuits and for ground relay polarizing circuits since errors are most frequently found in these circuits. All detail wiring diagrams should be checked against the schematic wiring diagrams. Check control wiring against the detail wiring diagrams. Check the polarity of all current transformers, and check the ratio where practicable. Test and set all protective relays, and test all switchboard instruments.