Ensuring the safety of large flywheels providing high amounts of inertia in synchronous condenser applications

Inertia has become a global issue for transmission system operators and regulators. To secure power system stability with a high amount of inverter based renewables is a task getting more and more difficult. Especially frequency stability after a big fault or power outage is requiring additional measures. In UK and Ireland the transmission system operators are looking for additional inertia, which often result in solutions based on synchronous condensers with additional inertia provided by a flywheel. This could be several thousand MWs of inertia. Unfortunately, today there is NO existing standard defining the safety aspects for this enormous amount of energy stored in these flywheels. There is a clear need to address security questions for big flywheels, as international standards, national or international regulations are missing.

Despite the facts that ISO 12100:2010 "Safety of machinery - General principles for design - Risk assessment and risk reduction" is providing important principles for the design and risk management and Sandia National Laboratories, operating on behalf of the U.S. Department of Energy, published an important report "Recommended Practices for the Safe Design and Operation of Flywheels" (SAND2015-10759)  provide recommendations for flywheel design practices, there is still little awareness of the possible risks related to flywheel installations. During the last year bigger and bigger flywheels were asked for as well as offered, including enormous amounts of rotating energy, with little discussion or requirements about safety measures needed for these installations.  Therefore wrote ABB a specific white paper "Ensuring the safety of large flywheels" covering this issue. This white paper shall help TSO´s, DSO´s, consultants and EPC contractors to handle synchronous condenser projects with flywheels. Security requirements needs to be addressed already in the initial stage for a project, so that specifications, RfQ documents as well as tendering guidelines are including and defining the safety aspects and safety requirements. These requirements shall then be implemented in the supply project so that flywheel installations are NOT creating a potential risk for the asset owner or third parties. The white paper shall help users to understand the risks with flywheels and to design measures to protect third parties from possible catastrophic damages of flywheels. As parts of a damaged flywheel may fly several hundreds of meters, if no precaution is taken.