Electrical power cable joints

The cable joints are used to connect low, medium or high voltage cables. The type of cable joint sizes, shapes and configurations vary according to the voltage, structure, insulation and the number of cores of the cable to be jointed. The joints provide electrical insulation as well as mechanical protection and strength. The electrical connection is made in various ways and can crimping, or use of mechanical connectors, soldering, etc.

Types of electrical power cable joints

There are about four commonly used types of joints; these differ in mechanical arrangement and where they are used. However, some manufacturers may provide custom designs to suit unique customer requirements.

• Straight through joints
• Branch which can be a T or Y joint
• Pot ends
• Indoor/Outdoor terminations

Electrical power cable terminations

The electrical cable termination is the physical and electrical connection of a cable end that connects to another cable, or to the terminal of the equipment. The cable terminations are often designed to enable the physical and electrical interconnecting of two cable ends, or a cable end and a terminal on the equipment.

The electrical connection requirements relate to the voltage drop, current carrying capacity, compatibility of the materials, etc. The physical requirements relate to the environmental protection as well mechanical security.

The methods used to terminate the cables vary according to the type of cable, type of connector and application. The common type of terminations are crimp connection, soldered connection, compression termination, and wire-wrapping connection, direct connection, loop or eye connection. Some of the factors that

determine the type are:

• Outdoor or indoor use
• Voltage
• Current
• Overhead, or underground
• Type of Connector on the equipment where the cable will be connected.

Testing And Commissioning

Installing cables is an expensive process and needs to be treated with the utmost care. During the time between cable installation and termination, cables are prone to damage from a range of factors including foot traffic and the movement of building materials. Therefore, to save time and money, it is important to test cables to ensure they’re working as they should be.

What to Check During Cable Testing

During cable testing it is important to perform commissioning tests, voltage tests and diagnostics. Early cable testing will significantly reduce the need for further testing. Things to check for include cable conformity, cable quality and cable functionality.

Types of Cable Testing

• IR Test (conductor).
• Conductor Resistance Test.
• Phase identification (conductor).
• Cross Bonding Test.
• Sequence Impedance Measurements.
• Serving Test.
• Sheath Resistance Test.
• SVL Test.
• High Voltage Test (conductor)

Types of Cable Faults

Cables are generally laid directly in the ground or in ducts in the underground distribution system. For this reason, there are little chances of faults in underground cables. However, if a fault does occur, it is difficult to locate and repair the fault because conductors are not visible.

Nevertheless, the following are the faults most likely to occur in underground cables:

• (i) Open-circuit fault.
• (ii) Short-circuit fault.
• (iii) Earth fault.