SF6 gas treatment for 220 kV GIS station for Ban Chat Hydroelectricity

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Project: SF6 gas treatment for GIS 220 kV station for Ban Chat Hydropower (location in Ban Chat, Than Uyen, Lai Chau communes) (GIS: Gas insulated Substation/Swithgear)

Time: April 2022

1. Purpose: Performing SF6 gas services to help investors and contractors upgrade current transformers (TI), to improve station productivity and maximize plant efficiency

ABB Asia Co Ltd: prepare the following equipment: Compressor, Sf6 gas recovery machine, gas recovery machine, vacuum machine, specialized Sf6 gas filling machine, empty SF6 gas bottle, pure N2 nitrogen gas tank pure

2. Process/step of implementation:

Develop a construction plan, labor safety, approved by the investor and electricity owner
Check the safety of the construction area, hang warning signs
Check that the main contractor, the investor has cut off the power, closed the ground
Check if the connection ports of the GIS station are compatible
Implement 380V 3-phase power supply connector for mobile cabinets, to connect to construction machines
Take the step of draining all the SF6 in the pipes of the GIS station to be removed and lowered
Vacuum clean to ensure that the device is out of gas to ensure safe dismantling, no residual gas is released into the environment
Contractors and firms carry out dismantling of GIS pipes and equipment, repair, maintenance, and re-installation
ABB Asia, perform 1st to 2mb vacuum suction, vacuum pressure soak for 6 hours, to check if there is pressure drop
Perform N2 to 3 bar filling, soak, 2h
Drain N2 from the device, then continue to vacuum down to 1mbar, and pressurize for 3 hours
Check and monitor vacuum pressure
Fill with SF6 Gas up to 6 bar, as required by the manufacturer
Sign the acceptance test record with the contractor and investor

Summary: All processes are carried out within 7 working days, labor safety requirements, labor protection, experts and technicians perform on the basis of the approved plan, and adjust at the site at the request of the manufacturer and the investor. The N2, Sf6 gas cylinders are all tested, the pressure equipment such as the compressor’s pressure vessel must be tested. Experts and technical workers must be trained and issued with electrical safety cards and level 3 occupational safety cards.

Here are some pictures from the project