33 00 00 Utilities
33 70 00 Electrical Utilities
33 71 00 Electrical Utility Transmission and Distribution 33 72 00 Utility Substations 33 73 00 Utility Transformers 33 74 00 Extra High Voltage (EHV) Switchgear and protection devices 33 75 00 High-Voltage Switchgear and Protection Devices 33 77 00 Medium-Voltage Utility Switchgear and Protection Devices 33 78 00 Substation Converter Stations 33 79 00 Site Grounding