Day: October 28, 2025

The reason why partial discharge (PD) testing of ring-main units (RMUs) must be carried out inside a shielded room (Faraday cage) is that PD signals are extremely weak (pico-coulomb level, pC), while the on-site electromagnetic environment is complex and the background interference is much higher than the real signal. Without shielding, the test data will…

Gas-tightness tests on SF₆ ring-main units are mandatory because leakage erodes dielectric strength, risks explosion and releases the world’s most potent greenhouse gas. A 0.5 % annual limit safeguards grids, complies with F-Gas/Kyoto rules and preserves carbon credits worth ~1 900 $ per avoided kilogram. Factory helium mass-spectrometry (10⁻¹¹ Pa·m³/s) guarantees zero defects; field pressure-decay…

Power-frequency withstand-voltage testing is a vital checkpoint in ring-main-unit production. By applying 50 Hz over-voltage—typically 42 kV for 10 kV gear—for one minute, it verifies that insulation between live parts and earth, and across open contacts, can survive service surges without breakdown or flashover. The test reveals hidden defects such as cracks, moisture, or poor…

Assembling ring-main units inside a dust-tight cleanroom is the only way to keep their gas insulation reliable for 30 years. Even sub-millimetre particles settle on seals or epoxy spacers, create conductive paths, trigger partial discharges and finally cause leakage or explosion. By holding ≥0.5 µm particles below 350 000 m⁻³, humidity under 60 % RH…