Cable joints, also known as cable splices, are used to connect two or more sections of electrical cables together. They provide a reliable and insulated connection that allows the continuous flow of electrical current. Cable joints are commonly used in high-tension (HT) or high-voltage power systems to extend or repair cables, connect cables of different types, or accommodate changes in cable routing.
Reasons for Cable Joint Needs:
Cable Extension: Cable joints are used when it is necessary to extend the length of existing cables to reach new locations or connect different sections of a power distribution network.
Cable Repair: In the event of cable damage or faults, cable joints are employed to splice the damaged sections and restore electrical continuity.
Cable Type Transition: When there is a need to connect cables of different types, such as transitioning from a paper-insulated cable to a polymeric-insulated cable, cable joints are used to create a secure and reliable connection.
Cable Route Changes: Cable joints allow for changes in cable routing, such as redirecting cables around obstacles or accommodating new construction or infrastructure layouts.
Different Types of Cable Joints:
Cold Shrink Cable Joints: Cold shrink joints utilize pre-expanded rubber or silicone tubes that shrink when the support tube is removed, providing a tight seal around the cables. They require no heat source for installation.
Heat Shrink Cable Joints: Heat shrink joints involve the use of heat shrinkable tubes that, when heated, shrink tightly around the cables, creating a secure and insulated connection.
Resin-Filled Cable Joints: Resin-filled joints involve the encapsulation of the cable joint with a special insulating resin. The resin provides electrical insulation, moisture resistance, and mechanical protection.
Push-On Cable Joints: Push-on joints use prefabricated connectors that are simply pushed onto the cable ends, forming a connection without the need for heat or special tools.
Transition Cable Joints: Transition joints are used to connect cables of different types, sizes, or voltages. They ensure a reliable and safe transition from one cable type to another
Tests Required for Cable Joints:
Before and after making cable joints, various tests are conducted to ensure the quality and reliability of the joint. Some common tests include:
Insulation Resistance Test: This test measures the resistance between the conductors and the insulation to verify the integrity of the insulation.
High-Voltage Withstand Test: A high voltage is applied to the joint to check its ability to withstand the specified voltage without breakdown or flashover.
Continuity Test: This test ensures the continuity of electrical conductivity through the joint.
Partial Discharge Test: This test detects any partial discharge activity in the joint, which could indicate insulation defects or weak points.
Insulation Power Factor Test: This test assesses the quality of the insulation by measuring the power factor of the joint.
Scenario Example alomg with Remedy
Scenario-1:
After making a heat shrink joint, the insulation resistance test shows low insulation resistance.
Remedy: Check for proper stripping and cleaning of the cable ends, ensure correct installation of heat shrink sleeves, and retest after addressing any potential issues.
Scenario-2 :
A resin cast joint fails the high-voltage withstand test.
Remedy: Check for proper resin mixing, curing time, and joint encapsulation. Repair or replace the joint as necessary and repeat the test.
Scenario-3 :
Partial discharge activity is detected in a cable joint during the partial discharge test.
Remedy: Investigate the joint for insulation defects, voids, or improper sealing. Repair or replace the joint to eliminate the partial discharge and ensure proper insulation.
These are general scenarios, and specific situations may require different remedies and tests based on the joint type, cable specifications, and applicable standards and regulations. It is essential to consult the manufacturer's guidelines and seek assistance from qualified professionals for accurate joint installation and testing procedures..
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