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.

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.

Siemens Limited, launched manufacturing of High Voltage Instrument transformers in , in the existing HV products factory at Aurangabad in India. The state-of-the-art facility is producing CVTs with Oil insulation and CT/PTs with SF insulation and is the only factory in India manufacturing SF CT/PTs with Composite insulators with technology support by Trench Germany. The factory also supplies GIS components (Instrument Transformers and Bushings) and Grading Caps to Siemens India. With a total area of Sq. Meters, Siemens Instrument Transformers is the market leader for CVTs in the domestic market. For SF CT/VTs, the facility has its own set up of Composite insulators. There are some key utilities/ industries from Power Generation in India, who have completely switched their CT/PT requirements to SF technology. Siemens India is also working continuously together with Global R&D on new generation and digitalized products to serve the customers with advancements further.

Trench Germany, the former MWB Messwandler-Bau &#; founded in &#; is located in the world-heritage city Bamberg. Based on the long-time experience with the production of high voltage equipment with epoxy-resin and oil-paper insulation, the company pioneered the design and production of gas insulated instrument transformers and developed in the first GIS SF insulated voltage transformer for encapsulated switchgear (GIS). In Trench Germany completed its kV portfolio in supplying the first kV combined current and voltage instrument transformer for outdoor installation (AIS). Today it is the competence center for gas insulated equipment in the Trench Group and offers plant and office space totaling . m². With the introduction of SF free instrument transformers with Clean Air insulation, Trench Germany once again demonstrates its technological leadership for gas insulated equipment.

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.