A step-wise controlled SVC for a demanding application: design and operational experiences

摘要

This paper focuses on a unique type of Static Var Compensator (SVC) installed at Kirkland Lake 115 kV substation in Ontario, Canada in 2011. Special requirements as well as design particulars for this SVC are described in the paper. The SVC is intended to provide fast voltage support at the weak point of 115 kV Northeast transmission system during power system contingencies. Without the SVC, the post-fault power swing can cause severe undervoltages below 0.7 p.u at Kirkland Lake 115 kV bus. The uniqueness of this SVC is driven by the significant difference between the required maximum continuous reactive power (30 Mvar) and the required short-time reactive power (200 Mvar under 20 s). Additionally, some other stringent requirements, such as harmonic performance levels, low audible noise levels, high loss evaluation and high availability added to the list of challenges in this project. After initial feasibility studies, a step-wise solution was adopted. Selected scheme consisted of two Thyristor Switched Capacitors (TSC) and one Thyristor Switched Reactor (TSR). The novelty of the adopted solution is the possibility of dynamically changing the configuration of the branches by using five thyristor valves per branch. Thus making it possible to achieve two configurations for each branch, either wye- or delta-connection. The paper presents some salient design features, to illustrate how the design was brought to meet the functional specification requirements in the project. Operational experiences are also presented by demonstrating SVCs responses to small and large disturbances using actual site measurements.