What is BS EN 50336 about?
BS EN 50336 is applicable to insulated bushings, excluding those plug-in bushings specified by EN 50180 series, for use in air-insulated, shroud insulated, and fully insulated cable boxes for liquid-filled transformers and reactors for rated voltages up to 36 kV, and rated currents up to 4 000 A at frequencies from 15 Hz to 60 Hz.
Who is BS EN 50336 for?
BS EN 50336 on bushings for transformers is relevant to:
- Manufacturers and suppliers of bushing insulators
- Manufacturers and suppliers of air insulated cable box
- Electrical engineers
- Mechanical engineers
- Cable manufacturers
Why should you use BS EN 50336?
Bushing is a hollow electrical insulator that allows an electrical conductor to pass safely through a conducting barrier such as the case of a transformer or circuit breaker without making electrical contact with it.
BS EN 50336 covers guidance on the requirements of bushings and their installation where the transformer side of the bushing fully immersed in insulating liquid and the other end is either:
- Fully immersed in an insulating liquid
- Shrouded insulation in air
- In air but not exposed to external atmospheric conditions
BS EN 50336 also covers the standard values of rated voltages for ceramic insulators and resin-insulated bushings, along with bushing conductor and nut specifications for currents based on diameter, material, screw thread and pitch and thickness.
Routine tests such as liquid leakage sample test, air leakage routine test, power frequency withstand voltage test, routine partial discharge test and their reference standards have been covered in BS EN 50336.
Complying with best industry practices with guidance from BS EN 50336 will help you maintain optimally efficient performance of transformers and reactor cable boxes. As a result, you will be able to avoid any damage to wire insulation by providing a smooth surface and minimizing friction.
What’s changed since the last update?
BS EN 50336:2021 supersedes BS EN 50336:2002, which is withdrawn. The following significant technical changes are:
- Minimum IP rating removed from air-filled cable boxes
- Clarification that transformer side bushing connection is to be fully immersed in insulating liquid
- Time frame for temperature cycle testing added
- Test criteria clarified for applications over 1.1kV
- Material corrected on the 400 and 630A rated items from brass to copper
