Cable Limiters: How Do They Affect Continuity Of Power?

Welcome to the August 2023 Issue #5 of the Dark Sparks Newsletter. This month we include the articles "Cable Limiters: How Do They Affect Continuity Of Power", The Product Owner Blog — Book Reviews “Decode And Conquer” by Lewis C. Lin, and Dogs Of Code - NEC Wire Types Part 2.

Over my three decades (since 1990) of experience in electrical engineering and design, I've seen the continuing development in electrical equipment, and cable limiters have been a part in ensuring the continuity of power.

The Cable Limiter - Not Your Ordinary Fuse

Cable limiters, also known as current limiters or fuse-links, are the brute force short circuit protection in the cabling systems. They serve as guardians of our power distribution systems, protecting them from short circuit overcurrents that could lead to catastrophic failures, as a result of faults and fires.

Cable limiters are different from fuses by their intended design of providing just short circuit response, and are not to provide overload protection. Cable limiters or Fuse Links are selected based on conductors sizing.

Cable limiters are manufactured in a variety of options, for conductor size, conductor materials, and various termination conditions. Two areas that typically define cable limiters are:

• 600V rated for commercial and industrial systems
• 300V rated for light commercial or residential systemsVariants of these are available and voltage ranges based on application requirements

The Inner Workings of Cable Limiters

A cable limiter is essentially a special conductive material that melts or opens when exposed to excessive current, as defined by the design requirement. This intentional breakage drops the circuit, preventing the flow of electricity and safeguarding the connected equipment.

A residential fuse that you would install in an older residential panel or sub-panel could be defined as a miniature cable limiter, which is why they are also referred to a fuse-links. However, cable limiters focus on short circuit currents and are not a true overcurrent protective device (OCPD).

If two devices are plugged into a receptacle, and draw too much current, the fuse blows, cutting off power to prevent damage. Cable limiters in industrial and commercial settings operate on the same principle, just on a larger scale.

There are often cable limiters at both ends of the cable section in the larger industrial installations.

Meeting Code: NEC Thoughts

National Electrical Code (NEC) Article 230.82 outlines the requirements for cable limiters.

It considers the use of cable limiters in various scenarios, such as protecting conductors against short circuit overcurrent's and ensuring their proper installation and sizing.

Real-World Applications

1. Industrial Plants: In factories and manufacturing facilities, where heavy machinery draws substantial current, cable limiters protect against short circuit equipment damage and potential downtime.
2. Data Centers: Ensuring uninterrupted power supply is critical in data centers. Cable limiters safeguard against short circuit current caused electrical faults that could disrupt operations and data integrity.
3. Renewable Energy: In renewable energy systems like solar and wind farms, cable limiters prevent short circuit overcurrent's from damaging inverters and transformers, maximizing energy generation.
4. Public Infrastructure: Cable limiters are used in electrical distribution systems for protecting street lighting, traffic signals, and public transportation, guaranteeing uninterrupted service for short circuits.

Again, a Cable Limiter's function is as a brute force short circuit overcurrent device and not a true Over Current Protective Device (OCPD).

Final Considerations

A Cable limiters ability to protect against overcurrent's is vital for preventing electrical fires, equipment damage, and downtime.

Cable limiters will remain a crucial component in safeguarding our power infrastructure. For further reading consult "cable limiters" on internet searches for more detail application information.

References

1. Eaton - Cable Limiters Overview
2. Mersen - Cable Limiters Brochure
3. Eng-Tips Forum - Cable Limiters Discussion
4. Additional Resources on Cable Limiters

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