IEEE C37.122.7-2021 IEEE Guide for Field Testng of Gas-Insulated Substatons Rated Above 52 kV.
4. Field testing in accordance with IEEE Std C37.122™ 4.1 Introduction In most cases, field tests performed on newly installed gas-insulated substation (GIS) are not repeats of the factory tests, but rather tests required to confirm that both the GIS has been assembled properly at site, and that there is no damage caused by shipping or installation. This guide will describe the tests required on the newly installed GIS systems, why these feld tests are performed, and why certain tests are repeated in the feld when they were already completed in the factory. Following the discussion of the individual tests, certain best practices will be described that will assist the testing effort in dealing with unique situations or typical questions commonly encountered during feld testing of GIS. Please refer to the feld-testing clause, in IEEE Std C37.122.1™ for additional information. 11 4.2 Mechanical tests: Leakage 4.2.1 Introduction This test is performed to demonstrate that there are no gas leaks at the field assembled joints of the GIS. Leaks may occur during field assembly as a result of the following: — Sealing surface damage — Improper placement, damage or omission of seals — Improper application of lubricants and sealants — Improper alignment and tightening of the mating surfaces — Contamination
Typically, leakage through the walls of gas compartments, or at other joints that were assembled at the factory, is not a concern because they were already tested at the factory—the exception being if damage occurred during transportation and assembly, or if feld repairs were made. Factory leak testing is covered in 8.4 of IEEE Std C37.122™-2021. If factory joints were disassembled for any reason during feld assembly, these joints should be tested again. Prior to flling the GIS gas compartments with insulating gas, some manufacturers require a vacuum rise test be performed to verify moisture levels within the gas compartment. If a vacuum rise test is required by the manufacturer, its results may identify a substantial leak prior to flling the gas compartment with insulating gas.IEEE C37.122.7  pdf download.