Challenge
In the past, Stedin has experienced power failures in its distribution grid. In addition to displeased customers, those events entailed expensive compensation payments for Stedin. Reliable energy distribution has always been Stedin’s core task, and so their main objective is to significantly reduce the SAIDI (system average interruption duration index) in their medium-voltage grids. Today there are several self-healing distribution grids in operation worldwide, but they are usually built for overhead distribution feeders, primarily by applying automatic reclosers. The Dutch MV distribution grid, however, consists of underground cables, which cannot be quickly repaired in the event of faults, nor can they be fixed with automatic reclosers. Therefore a solution had to be developed that would work for the Dutch network system.
The self-healing algorithm is elegant, simple, and robust and works for almost all grid structures. The applied RTUs and the developed software are very stable.Dr. E. J. Coster, Expert Asset Manager Stedin
Solution
In collaboration with Stedin, Siemens developed a self-healing network solution. Substation automation was upgraded by implementing new distribution grid automation functions. The solution, which is based on a “regional controller” on the level of the substation, ensures automatic fault localization, isolation and restoration. The regional controller serves as an interface to the control center, which collects data from the distribution grid and hosts the regional, centralized applications of Stedin’s self-healing grid. Part of the solution consists of an intelligent local substation. Upgrade kits were installed to modernize older ring main units (RMUs), or where that was not possible, older RMUs were replaced with new RMUs.Benefits
With the innovative self-healing grid solution installed, Stedin will significantly reduce its SAIDI and re-supply most of its customers with power in less than a minute in the event of a power outage. This will result in both satisfied customers as well as considerable cost savings by minimizing the heavy contractual penalties that must be paid in case of power outages.