Mechanical Connectors
Connector Technology
Any electrical system however large or small, transmission or distribution, irrespective of voltage, is totally dependent upon the quality and reliability of conductor connectors.
If just one connection is inadequate, the performance of the system will be compromised.
So it is important to ensure that the connections and therefore the connectors, are not a “weak link” in the system.
Overhead systems are particularly vulnerable, due to their dependency on Aluminium conductors.
Technical Losses and the Reasons
Small Real Electric Contact Area
- Two metal components in contact (e.g. cable and connector) have a real electrical contact area that is much smaller than the nominal area.
- Just the “spot peaks” are in real electrical contact.
- In some connectors, the real contact area is just about 0.1% of the nominal area!.
Basic Chemistry
Contact Interface
High magnification SEM (Scanning Electron Microscope) image showing cracking (1/10 microns in width) on aluminum oxide film
Since Aluminum Oxide is electrically insulating, metal-to-metal electrical contact spots are only produced after the oxide layers at the location of mechanical contact are fractured.
In this example of a bolted connector on 2/0 conductor, the area of electrical contact is expected to be approximately 0.1% of the nominal contact area.
Examples of connector systems currently used for HV cables – Mechanical, Compression and Welding/Exothermic
There are two basic types of Mechanical Connector used in Joints
- Blocks of aluminium with bolts/screws to pull them together (e.g. “parallel groove” connectors” ) employed for LV applications
- A metal tube of aluminium alloy, brass or copper with bolts/screws to clamp onto the conductor.
Connectors
There are ranges of Mechanical Connectors designed specifically for LV use.
Most LV conductors for multi-core cables are sector shaped, so it is easier to use a connector designed to accept it.
These connectors greatly simplify the installation procedure.
Multiple shear points and bolt design ensure no harmful protrusion of sheared bolt from MV connector body
Typical Application for LV Mechanical Connectors
Resin straight, branch and service joints employ mechanical connector technology to provide simple, fast and effective solutions for many conductor connection problems and for cables of all types. This design uses individual connectors for each conductor.
These modern LV link boxes also employ Mechanical systems for all conductor connections
Above is a 2-Way Link Box and to the left is a 4-Way Link Box
Tyco HV Joint Kits use Mechanical Connectors
Installation of HV Connector
Employs torque controlled “shear head” bolts,
Mechanical connectors are used for joints and terminations up to 245kV and have been the sole connector offered for two decades.
Connectors and Connections – HV
Examples of current HV Mechanical Connectors:
(“Three Piece Joint”)
Advantage
- Correctly designed mechanical connectors provide excellent high temperature performance
- Applicable to all conductor types (copper and aluminium, solid and stranded)
- Tolerance for conductor dimensions
- Ability to be range taking
- Successfully used at low, medium and high voltage
- Proven long-term performance under all conditions