Long-Range Response to Transmission Line Disturbances in DC Electricity Grids

TL;DR

This paper analyzes how adding transmission lines affects power flow and load distribution in DC electricity grids, revealing long-range responses, the occurrence of Braess' paradox, and the influence of disorder on system load.

Contribution

It introduces a nonlinear model for DC grid response to line additions, highlighting long-range effects and the increased likelihood of Braess' paradox compared to linear models.

Findings

Power flow changes decay slowly with distance from added lines.

Adding lines can increase maximum load, demonstrating Braess' paradox.

Load increases with disorder in the distribution of consumers and producers.

Abstract

We consider a DC electricity grid composed of transmission lines connecting power generators and consumers at its nodes. The DC grid is described by nonlinear equations derived from Kirchhoff's law. For an initial distribution of consumed and generated power, and given transmission line conductances, we determine the geographical distribution of voltages at the nodes. Adjusting the generated power for the Joule heating losses, we then calculate the electrical power flow through the transmission lines. Next, we study the response of the grid to an additional transmission line between two sites of the grid and calculate the resulting change in the power flow distribution. This change is found to decay slowly in space, with a power of the distance from the additional line. We find the geographical distribution of the power transmission, when a link is added. With a finite probability the maximal load in the grid becomes larger when a transmission line is added, a phenomenon that is known as Braess' paradox. We find that this phenomenon is more pronounced in a DC grid described by the nonlinear equations derived from Kirchhoff's law than in a linearised flow model studied previously in Ref. \cite{witthaut2013}. We observe furthermore that the increase in the load of the transmission lines due to an added line is of the same order of magnitude as Joule heating. Interestingly, for a fixed system size the load of the lines increases with the degree of disorder in the geographical distribution of consumers and producers.