Customer Needs
CSG is the second biggest power grid in China, with major transmission lines rated at 500kV. In CSG most of the power generation plants are located at the west however main loads are located at the east. Long transmission corridors were built to transmit power from west to east every day.
The increasing needs for electric power had become a big challenge to CSG. Thus it becomes more and more important to enhance the power transmission capability at the existing AC and DC transmission lines.
A system study shows that Boshang 500kV substation in the area of Yunnan power grid is the transmission bottleneck in the big corridors that needs to be enhanced by series capacitors.

RXPE Solution

In Boshang SC project RXPE had delivered four sets of 500kV SCs in total. Two of them are installed at Dehong - Boshang double-circuit lines with capacity of 2*620Mvar and the other two of them are installed at Boshang - Mojiang double-circuit lines with capacity of 2*425Mvar, resulted as a compensation degree of 50% each.

Boshang SC protection scheme is designed as MOV plus spark gap and bypass circuit breaker. Assuming if an external line fault occurred, the fault current should be bypassed by the MOVs, neither the spark gaps nor circuit breakers are allowed to act; only if internal line faults occurred that the spark gaps and circuit breakers bypass is allowed. This means SC will be always online only except for internal lines faults, giving a high availability.

MOVs for Dehong - Boshang SC is designed as 58MJ/ph while Boshang - Mojiang is designed as 85MJ/ph. Polymer housing is adopted for all the MOV columns.

Capacitor banks, MOVs, spark gaps, damping circuits as well as the HV electronics are located on top of the insulated platform while the control and protection panels are located in the protection cubicle on the ground beside the platforms. Optic fibers are used for communications between C&P panels and the HV electronics. C&P system is designed as fully redundant to gain high reliability and availability.

Customer Benefits

Boshang Series Capacitors had been commissioned and put into operation in the year 2010. This project had significantly improved the “South Corridor” transmission capability of Yunnan Grid and had successfully solved the “transmission bottleneck” problem in this area. Besides, the successful operation of Boshang SCs also helped enhanced the system stability of the power grid.

Liaoning Rongxin Xingye Power Tech Co., Ltd

108 Keji Rd., Anshan 114051 China

Email:overseas@rxpe.com