Characteristics and case analysis of extra-high voltage electromagnetic loop networks

In view of the still existing extra-high voltage (EHV) and ultra-high voltage (UHV) electromagnetic loop networks, the different forms and structures of development of electromagnetic loop networks are summed up with the cases and examples in a provincial power grid. It is believed that the main risk of electromagnetic loop networks lies in the transfer and control of power flow. The degree of coupling is proposed as an index to measure the intensity and risk of electromagnetic loop networks. In terms of network structure optimization and strengthening, it is considered that the higher voltage power system should be strengthened prior to the strongly coupled weak electromagnetic loop, and the short circuit level control and structure simplifying are more important for the weakly coupled strong electromagnetic loop while multilevel electromagnetic loops should be decoupled as soon as possible. Then the typical split schemes of electromagnetic loop networks are analyzed. Since EHV and UHV electromagnetic loop networks will exist for a long period of time, practical power flow transfer control algorithms for single element trip and cascading trip of electromagnetic loop networks are elaborated. Especially, a kind of unconventional stability control measure of the fast tie-element removal strategy after serious fault is put forward to decouple electromagnetic loops and balance power flow for high-power and strong-coupling electromagnetic loop networks. The stability level and transmission ability of the electromagnetic loops are effectively enhanced. The research results have been applied in actual power grids with good effect. © 2017 Automation of Electric Power Systems Press.