TenneT TSO GmbH (hereinafter referred as TenneT) is the largest Transmission System Operator (TSO) in Germany (based on circuit length, installed capacity and size of operating zone as of 31 Decem-ber 2025). The company operates critical infrastructure that secures access to a reliable, sustainable and affordable electricity supply. TenneT is one of the largest investors in electricity grids on land and at sea in Germany. Located at the Northwest European energy crossroads, TenneT connects: North and South. Offshore and Onshore. Germany and Europe. With its approximately 5,000 employees the company builds, maintains and operates Germany´s largest transmission grid with a length over 14,000 km connect-ing more than a third of the European Union’s total offshore wind capacity. Its growth is driven by a rapidly evolving electricity demand that requires a flexible and growing grid architecture. The scope of this prequalification procedure covers the supply of Intelligent Electronic Devices (IEDs) used in the areas of protection and substation control technology within extra high-voltage and high-voltage substations. These devices constitute key components of the secondary technology and are essential for ensuring the safe, reliable and efficient operation of the transmission grid. The technical requirements are based on internationally recognized substation communication protocols commonly applied in the automation and operation of electrical power systems. The primary focus of the TQS is on IEC 61850, while other relevant protocols, such as IEC 60870 5 103 and IEC 60870 5 104, are also considered where applicable. This prequalification process aims to identify Economic Operators with proven expertise in the planning, production, implementation and integration of such devices in accordance with applicable technical and regulatory requirements. Candidates receive qualification status for each of their own production sites and each technical lot. The successful completion of the qualification process depends on various factors beyond TenneT’s control. TenneT can only commit to the processing time for the individual gates. The time required to complete the questionnaires and provide the necessary documentation is the sole responsibility of the participating Economic Operators.