This Technical Specification is applicable to high voltage (HV) bushings, intended for use in traction transformers of rail vehicles, cooled by insulating liquid with rated voltages up to 25 kV single phase and rated currents up to 630 A at frequencies from 16,7 Hz to 60 Hz. HV bushings within the scope of this Technical Specification are bushings for separable connectors that connect the power supply coming from a contact wire or from a contact rail to the primary winding of the traction transformer. The Technical Specification only deals with HV bushings that are mounted to the transformer. CLC/TS 50537-1 gives consideration to both technical and normative requirements of the railway environment and restricts the variety provided by industry-wide standards for bushings, such as EN 50180 and EN 60137. It determines requirements and tests enabling the interchangeability especially regarding electrical and mechanical interfaces. Furthermore, service conditions are described. The cable plug as the counterpart of the HV bushing’s plug-in end is not covered by this Technical Specification.