Optimal Transmission Line Switching under Geomagnetic Disturbances

TL;DR

This paper presents an optimization framework for transmission line switching to mitigate the adverse effects of geomagnetic disturbances on power systems, using convex relaxations and demonstrating effectiveness on test systems.

Contribution

It introduces a novel model incorporating GIC effects into power system optimization and applies convex relaxations for effective mitigation strategies.

Findings

Line switching effectively reduces GIC impacts.

Convex relaxation provides reliable lower bounds.

Optimal switching decisions are sensitive to GMD direction.

Abstract

In recent years, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We use this model to derive an optimization problem that protects power systems from GIC impacts through line switching, generator redispatch, and load shedding. We employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and the UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of optimal switching decisions with respect to GMD direction.