The company was founded in in Switzerland by Emil Haefely, an inventor who played a decisive role in the development of the electrotechnical industry at beginning of the th century. With the patent of the OIP Condenser type bushing in by Emil Haefely, the company became a pioneer in Oil type bushings. Trench France is part of the Trench & HSP Bushing group belonging to Siemens with locations in France (Trench France), Germany (HSP) and China (THVS). This close cooperation for innovation and design is supported by Siemens process and manufacturing know how. In , the Trench Group decided for Trench France to focus specifically on bushings by making extensive manufacturing investments and improving all customer relevant processes.

Trench Italy is located in the village of Cairo Montenotte, in the northwest of Italy near the town of Savona and approximately km from Genoa harbor. The Company was founded in under the name of Scarpa e Magnano. In came the merger with Magrini and the whole enterprise was acquired by Merlin Gerin in , before being integrated in the VATECH group in and finally in the Trench Group in . Since the production start of oil insulated instrument transformers as early as , Trench Italy has a high competence in the design and manufacturing of high voltage instrument transformers. The European production of oil insulated voltage and current transformers, capacitor voltage transformers, grading capacitors and special instrument transformers of the Trench Group is concentrated in Cairo Montenotte on a . m² total surface. Significant investments in production and testing facilties since as well as the outstanding technical expertise allowed Trench Italy to introduce state-of the art manufacturing processes that are leading to high quality products and a proven reliability.

Trench Brazil was established in Contagem, Minas Gerais State, Brazil in and moved to Jundiai, Sao Paulo State, Brazil in . Manufacturing of the first reactors and line traps began in July of . Trench Brasil was established by the Trench Group to better serve our customer needs in South America and to improve the position in the global market. The technology and manufacturing techniques used by the company in Brazil are all from Trench Limited Canada who transferred its reactor and line trap technology to Trench Brasil during the plant construction phase. Today Siemens Brazil manufactures Air Core Reactors from up to kV, KVA to MVA and Line Traps from kV to kV , to mH.

HSP Hochspannungsgeräte GmbH – known as HSP – has a long history in manufacturing bushings and high voltage equipment. Over years ago it was founded as a division of Meirowsky & Co., was then taken over by Dielektra AG and later by Felten & Guilleaume Energietechnik AG (F&G). Since HSP is an independent company. We develop and manufacture condenser graded high voltage bushings in RIP technology (resin impregnated paper) and RIS technology (resin impregnated synthetic) up to kV rated voltage for AC applications and HVDC transmissions. Our bushings are suitable for power transformers, switchgears, generators, HVDC and for test equipment – meeting all international standards. By consistently maintaining the highest quality standards, we have become a leader on the world market for high-voltage bushings in recent decades.

In Trench Austria was established by Alois Esslinger, an electrical engineer known beyond the borders of Austria. The former name of the company until was Spezielektra Esslinger KG. From the very beginning, one focus area of the company was the development and production of reactors for electrical power system. The use of glass fiber reinforced plastic as part of the insulation of reactors was revolutionary in the s . Trench Austria gained significant international reputation in the s when supplying high current and high voltage test reactors for leadin test laboratories like KEMA in Arnheim/The Netherlands. In Spezielektra was merged with Trench Electric Toronto/Canada. This was also the starting point for the foundation of the Trench Group. Today Trench Austria in Leonding near Linz produces reactor/coil products for medium and high voltage electrical systems, both in dry type as well as oil immersed technology and is one of the worldwide leading companies in this special area of the electrical industry.