IEEE C37.38-1989 pdf free.IEEE Standard for Gas Insulated, Metal-Enclosed Disconnecting, Interrupter, and Grounding Switches. 1.1 Scope IEEE C37.38 applies to switches rated 72.5 kV and above intended for use in metal-enclosed, gas-insulated substations, including disconnecting, interrupter, and grounding switches. These switches are characterized by grounded. leak-tight metal enclosures that are tilled with a gas (most commonly sulfur hexa-tluoride, SF6) at...