Bayonet fuse

For the majority of padmount transformers, bayonet (Bay-O-Net) style fuses are the preferred protective device. Learn more about fusing transformers. For various transformer designs and uses, a variety of fuse link alternatives are available. Changing these connections within the same bayonet housing is made simple by bayonet-style fusing. When combined with a current-limiting backup fuse, a Bay-O-Net fuse is the best option for a two-fuse protection system. The Bay-O-Net fuse in this configuration clears secondary faults and overload currents, while the current-limiting fuse clears high-level faults. In order to ensure that the current-limiting fuse only activates in the event of an internal equipment failure, the two fuses are connected in series.

Table of Contents

• What is a Bay-o-net fuse?
• Core Features of Bay-o-net fuse
• Classification of Bay-o-net fuse
• What is the difference between dual sensing and dual element fuses
• Conclusion

What is a bayonet fuse?

A protection package for single- and three-phase transformers is provided by Eaton's Cooper Power series Bay-O-Net fuse. When replacing a blown Bay-O-Net link, the assembly prevents line workers from closing into a defect by combining the simplicity of hotstick operation with the security of deadfront construction. It is used in conjunction with an isolation link. Bayonet fuses are regarded as the industry standard for transformer fusing and are frequently used in padmount transformers. These fuses are an example of an expulsion fuse, which is frequently seen within transformers and on utility poles in electrical distribution systems.

Core Features of Bayonet Fuse

• An isolation link is necessary when using a Bay-O-Net fuse in series with a current-limiting fuse.
• Comparable in price to internal cartridge fuses, Bay-O-Net fuses offer the benefit of field replacement. Coordinating Bay-O-Net fuses with upstream devices is simple.
• When used in conjunction with a Bay-O-Net-type fuse or MagneX interrupter, an isolation link offers additional protection during refusal and switching operations.
• Because the MagneX Interrupter is an integral unit and doesn't require calibration or a cumbersome linkage, installation and use are quick and easy.
• An internal "weak link" expulsion fuse is the oil-immersed current-sensing weak link cartridge fuse.

Classification of Bayonet Fuse

Which fuse link is most effective depends on the transformer's size, voltage, and purpose. Five fuse links—current sensing, dual sensing, dual element, high-amp, and 38 kV—will be discussed in this article. 

1. Current-sensing bayonet fuse

With its Cooper Power series, Eaton shields distribution networks against malfunctioning equipment and distribution equipment from harmful currents. sensing of current Eaton's Cooper Power series Bay-O-Net fuse assemblies employ the Bay-O-Net fuse link. They are utilized on three-phase equipment rated up to 1500 kVA and on traditional, self-protected, single-phase distribution transformers and other equipment rated up to 500 kVA. When combined with a current-limiting backup fuse, a Bay-O-Net fuse is the best option for a two-fuse protection system. With this configuration, secondary flaws and The Bay-O-Net fuse clears overload currents, whereas the current-limiting fuse clears high-level faults. There is a connection between the two fuses. Synchronized in series, ensuring that the current-limiting fuse only activates in the event of an internal equipment failure.

Current sensing Bay-o-net fuse
Image used courtesy of asbeam

2. Dual-sensing Bay-o-net fuse

Eaton protects both distribution apparatus from damaging currents and distribution systems from failed apparatus with its Cooper Power series dual-sensing Bay-O-Net fuse link that is used in Eaton's Cooper Power series Bay-O-Net fuse assemblies. Dual sensing links sense not only secondary faults, excessive load currents, and transformer faults, but also transformer fluid temperature. They will limit long-term transformer heating caused by overloads and high-temperature environments.

Dual sensing Bay-o-net fuse
Image used courtesy of asbeam

3. Dual-element Bay-o-net fuse

Eaton's Cooper PowerTM series dual element Bay-O-Net fuse link, which is utilized in Eaton's Cooper Power series Bay-O-Net fuse assemblies, protects distribution systems from malfunctioning equipment and distribution equipment from harmful currents. Dual element linkages detect the temperature of the transformer fluid in addition to secondary faults, high load currents, and transformer defects. They will reduce the long-term heating of transformers brought on by overloads and hot conditions.

Dual element Bay-o-net fuse
Image used courtesy of asbeam

What is the difference between dual-sensing and dual-element fuses?

The dual-sensing fuse protects the primary circuit and overload by being sensitive to both current and oil temperature. The two are combined in Dual Element. The bayonet fuse must be connected in series with an isolation link or a current-limiting fuse to prevent closing on a fault.

High-Amp Fuses

One component of the high-amp fuse link is composed of silver and eutectic material. It has a melting point of 145°C throughout. It offers protection from overloading caused by high oil temperatures, just like the dual sensing and dual element connections. The other linkages are ineffective for larger kVA applications; thus, this link is for them. Additionally, the high-amp fuse connector looks different. A cartridge that fastens to the end of the bayonet assembly contains the fuse link. High-amp fuses, such as the dual-sensing and dual-element models, guard against secondary faults and overload. Up to 15.5 kV of electricity is protected by them.

High-Amp Fuse
Image used courtesy of Maddox

38 kV Fuses

Higher voltage applications between 24 kV and 38 kV are handled via the 38 kV link. The silver-plated cartridge and fuse link are one piece. For 25 kV and 35 kV delta or ungrounded wye primary applications (with bayonet-style fusing), this fuse link is the only choice. Additionally, the 38 kV link has a dual-sensing-type fuse that can detect secondary faults as well as high oil temperatures.

38 kV Fuse
Image used courtesy of Maddox

Conclusion

Bay-O-Net fuses are suitable for use on three-phase equipment as well as conventional and self-protected single-phase distribution transformers. It works best in a two-fuse protection system that includes a backup fuse that limits current. The Bay-O-Net fuse in this configuration clears secondary faults and overload currents, while the current-limiting fuse clears high-level faults. In order to ensure that the current-limiting fuse only activates in the event of an internal equipment failure, the two fuses are connected in series. An isolation link is necessary if the Bay-O-Net fuse is not going to be used in series with a current-limiting fuse. Comparable in price to internal cartridge fuses, Bay-O-Net fuses offer the benefit of field replacement. Coordinating Bay-O-Net fuses with upstream devices is simple. Bayonet expulsion fuses are practical, dependable, and easy to operate. They remain the preferred option for padmount transformers' primary overcurrent protection.