The manufacturer has already tested the GIS at 100% voltage in a clean factory environment. Why must we repeat this dangerous test on-site after installation?
Because the factory test cannot account for the "Last Mile" risks associated with transportation and field assembly.
Transportation Trauma: Long-distance shipping over rough roads can loosen internal bolts or cause microscopic fractures in basin insulators that only manifest under high electric stress.
Installation Contamination: On-site assembly, even in a tent, is never as clean as a factory. A single human hair, a tiny sliver of metal from a tool, or dust particles can become "ticking time bombs" that trigger a catastrophic failure once energized.
The Verdict: Field testing is not a repeat; it is a verification that the shipping and assembly haven't introduced new, fatal flaws.