This International Standard specifies the requirements and test methods for a stationary energy storage system to be introduced as a trackside installation and used in a power supply network of a DC electrified railway. This system can take electrical energy from the DC power supply network, store the energy, and supply the energy back to the DC power supply network when necessary. This standard does not apply to onboard energy storage systems. This system may be installed to achieve one or more of the following objectives: Absorption of regenerative energy; Effective use of regenerative energy (saving energy); Reduction of rolling stock maintenance (reduction of brake shoe wear, etc.); Avoidance of adverse effects of heat generated during braking (e.g. in tunnels, etc.); Power compensation; Compensation of line voltage; Reduction of peak power; Reduction in the requirement of the rectifier ratings. However, systems that are used exclusively for one or more of the following functions are outside the scope of this standard: Reverse transmission of regenerated power to the upstream power supply network (e.g. 106 inverting or reversible substations); Use of the regenerated energy for purposes other than the running of trains, such as for station facilities, etc.; Resistive consumption of regenerated power. Although, it is assumed that the system uses the following typical energy storage technologies, this standard may also apply to other existing or future technologies: Batteries (e.g. Lithium-ion, Nickel metal hydride, etc.); Capacitors (e.g. Electric Double Layer Capacitors, Lithium-ion Capacitors, etc.); Flywheels.