Current Tolerance Capability Calculation Model of Transmission Lines and its Application in Overload Protection

Abstract

Traditional overload protection depends on pre-set values and cannot reflect the current tolerance capability of the line. If the current of a line exceeds the setting value of its overload protection, then it will be subsequently tripped off and cause power flow transferring, which may trigger the cascade tripping of power grid. So it is of significant importance for the overload protection to accurately evaluate the real-time safety status of transmission line and coordinate with power system control to eliminate the overload. In this article, starting from the mechanism analysis of conductor heat transfer, a thermal network model is established by focusing on radial and circumferential heat transfer paths. The temperature rise response of the network node is obtained through nonlinear iteration. The calculation model, which is verified by a test platform, is better than standard models. Then, the current tolerance capability calculation model of the whole line is constructed on the basis of the thermal network and applied to improve the overload protection. The proposed multi-parameter overload protection can effectively prevent unnecessary tripping to avoid the expansion of accidents. Finally, the validity of the proposed protection is verified by the New England 10-machine 39-bus test system.

Keywords:

• current tolerance capability
• cascade tripping
• overload protection
• transmission line
• thermal network

Additional information

Funding

This work was funded in part by the National Key R&D Program of China (2016YFB0900600) and the National Natural Science Foundation of China (51707018).

Notes on contributors

Jian Hu

Jian Hu received the B.S. degree in Electrical Engineering from South China University of Technology, Guangzhou, China, in 2013. He is currently pursuing the Ph.D. degree in electrical engineering. His research interests include electro-thermal coupling analysis of power equipment and its application in power system control and protection.

Xiaofu Xiong

Xiaofu Xiong received the B.S., M.S., and Ph.D. degrees in Electrical Engineering from Chongqing University, Chongqing, China, in 1982, 1986, and 2005, respectively. Currently, he is the Vice Director of State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, and a full Professor at Chongqing University. His research interests include smart grid, power system control and protection.

Jian Wang

Jian Wang received the B.E. and Ph.D. degrees in Electrical Engineering from Chongqing University of China in 2010 and 2016 respectively. He is currently a lecturer and postdoctoral fellow at school of electrical engineering, Chongqing University. His research interests include risk early warning of meteorological disaster for power grid, power system control and protection.