Power transformers are identified by their physical size, nameplate data, voltage class, cooling method and application context in the grid. The nameplate typically lists kVA or MVA rating, primary and secondary voltages, vector group, frequency, impedance percentage, cooling designation (ONAN, ONAF, OFAF, etc), serial number, insulation class, and standards compliance (IEC, IEEE, or ANSI). Visual inspection reveals bushings, radiators, OLTC compartments, conservator tanks and cooling fans. In substations, power transformers are usually installed on concrete pads with HV and MV connections routed through bushings to switchgear or transmission lines.