CUSTOMER NEEDS
China Southern Grid (CSG) is the second biggest grid in China operating both high voltage AC and DC transmission lines. The main loads are located at its east part of the grids however the major generators are located at the west. Both 500kV AC corridors and 500kV / 800kV HVDC corridors are used to transmit the needed electric power from west to east. Wuzhou 500kV substation is an important node in the middle of these corridors to receive power flow from both AC and DC transmission lines coming from the west.

- Black Lines AC Transm1ssion lines
- Blue Lines DC Transm1ssion lines
- Green Circle Wuzhou 500kV Substation
The power needs from the east had been increasing every year, which makes the existing corridors' transmission capability facing more and more pressure. CSG had to do its best to enhance their power transmission limits.
According to a system study a SVC rated 210Mvar at Wuzhou substation will improve the situation. The Guangxi - Guangdong corridor's transmission limit will increase by 100MW while Yunnan - Guangdong corridor by 30MW and Guizhou - Guangdong corridor also 30MW. So theoretically an extra 160MW power flow will be obtained with SVC in operation. Meanwhile the dynamic voltage stability can also be improved by this SVC when there is any line faults occurred nearby.
RXPE Solution
A SVC of 210Mvar was designed and delivered by RXPE for CSG Wuzhou 500kV substation in the year 2008. The SVC includes one TCR branch and two harmonic filter branches as well as two MSC branches, output capacity from -120Mvar inductive to +210Mvar capacitive. The MV busbar was designed as 35kV that is connected to 500kV busbar by a dedicated step down transformer.

The thyristor valves were designed as horizontal layout with water/air cooling method. Three circulating pumps had been applied in the cooling system to further improve its overall reliability and availability. Control & protection system were also designed as fully redundant.
 
Customer Benefits
Wuzhou SVC had successfully achieved its design targets. It enabled the CSG dispatching center to increase the transmission power flow of these corridors from west to east. Meanwhile it has also increased the voltage stability of the adjacent network. On June 5th 2009, the substation 500kV bus voltage dropped rapidly due to a line fault. The SVC acted to support the line voltage and helped the grid successfully ride through the incident, which also verified its dynamic performance.