Density table upgrade and renovation

What problem is being solved?

Sulfur hexafluoride gas has been widely used in power transmission and transformation equipment due to its excellent insulation and arc extinguishing properties. However, sulfur hexafluoride has the highest global warming potential among known gases and has a strong greenhouse effect. With the goal of "carbon peak and carbon neutrality" proposed, pure SF6 gas insulated switchgear will gradually be upgraded to mixed gas insulated and environmentally friendly gas insulated equipment, and SF6 density relays will also be upgraded accordingly.
Micro water content is an important indicator of gas insulated switchgear, and routine preventive tests are conducted on an annual basis, which cannot detect changes in micro water content inside the equipment in a timely manner. Conventional density relays do not have remote real-time pressure density reading function, and manual meter reading is time-consuming and laborious, making it difficult to grasp equipment information in a timely manner, which does not meet the construction requirements of smart substations and data substations.

Why provide this service?

State Grid Corporation of China is currently piloting the transformation of some substations above 110kV using mixed gas (SF6/N2) to replace pure SF6 gas, and has issued the "Q/GDW 11921.3-2018 Rated Voltage 72.5kV and Above SF6/N2 Mixed Gas Insulated Metal Enclosed Switchgear Part 3: Technical Specification for Density Relays". New requirements have been put forward for the density relay of equipment after gas replacement.
In order to monitor the changes in micro water content and gas density pressure of insulation gases in switchgear in real time, and to create a data-driven smart station, it is imperative to upgrade and install density micro water sensors on conventional gas density relays.

Related experience and operational procedures

Installation process of mixed gas density relay:
1. Apply for a work permit, confirm that the equipment has been powered off, and clarify the scope of work.
2. Switchgear gas recovery.
3. Replacement and installation of mixed gas density relay.
4. Leak detection of mixed gas density relay.
5. Vacuum the switchgear and recharge the mixed gas.
6. Mixed gas density relay test.