HV Cable Termination Method and Precaution-PART-1

HV CABLE TERMINATION METHOD AND PRECAUTION. (PART-1)

INTRODUCTION:

Power cable is most important part of power transmission and distribution systems. * Terminations and joints are the essential part for the power cables. It makes connections between Cable or between Cable and electrical apparatus. * Cable terminations make physical and electrical connections between the cable and the equipment to flow electricity in the desired manner. * Cable terminations are weak parts for electrical system and most of the cable faults happen at this section, hence the quality of cable terminations directly affects the safe operation of the cable lines. The mistake will cause troubles, widespread power outages and cause great loss of finance, the people’s life and property. * There are three types of cable terminations. it can be heat-shrink type, cold-shrink type or pre-moulded push on type cable terminations.

TYPE OF CABLE TERMINATION:

There are various types of High / Medium Voltage cable termination for substation switchgears, transformer, poles, and cable boxes. * Termination Kit are classified by its application. * It can be pre-molded push-on, cold shrink or heat shrinkable type. * Selecting the appropriate termination method is essential for maintaining the mechanical integrity of the cable and it depends on the cable types, operating parameters, voltage applications and site conditions. * Each technology has specific advantages depending on the needs of the user.

Heat shrinkable terminations:

It names suggests that it required Heat and have shrinkable type tubing. * when we applied heat (with an electric or gas heat gun) to shrink tube. It expanded shrinkable tubes to the size of the substrate beneath and enabling quick and easy installation. * Material: * Heat shrinkable products are usually made from polyolefin type plastics which have been modified to give additional properties such as improved weathering and enhanced insulation levels. * Heat Shrink is resistant to most chemicals. It will become rigid once it has been recovered and making it a good option for mechanical protection. * Application: * Use on low and medium voltage cables, * Heat shrink termination kits can be used for XLPE cable in both indoor and outdoor applications, even for extreme hazardous atmospheric conditions. * The cable terminations provide non-tracking stress control connections for medium to high voltage cables with water, UV, erosion and corrosion resistant performance. * Advantage: * When stored correctly, there is unlimited shelf life for the product. * Drawback: * the Material rigidity prevents flexing with the cable during normal operation hence an effective environmental seal cannot be maintained without the mastic tapes.

Cold shrink terminations:

It names suggests that it does not require heat. * They can be used for medium-high cable installations which do not require naked flame or heat source to install especially in explosive atmospheres. * By removing the supporting cord during the installation process causes the tube to shrink so that it fits onto the desired place. * The cold shrinkable cable terminal offers excellent insulation and high resilience. * Material: * Cold Shrinkable products are made from elastomeric materials such as Silicon or EPDM rubbers, which are pre-stretched onto a tubular hold-out made from plastic tape in a tight spiral. * By unwinding the spiral tube, the material recovers to its original size. * Application * The cold shrinkable cable joints are especially suitable for installation in hazardous environment, such as coal mine, oil field etc, where fire is strictly prohibited. * Advantage: * The Cold Shrink eliminate any heat source required for installation. * The rubber material will follow the normal expansion and contraction of cables without need for additional adhesives or mastics. * Disadvantage: * Care is needed to store product and there is a finite shelf life.

Push On type termination:

Similar to Cold Shrink, these are made from elastomeric material and are not expanded before installation. * The product is applied by sliding onto cable cores with the use of silicone grease as a lubricant. * It has similar benefits to Cold Shrink, but with restricted application diameter range.

PARTS OF TERMINATION KIT

(A) Environment Sealing Shrinkable Tubes:

Breakout Boot * Anti-tracking Heat Shrink Sleeve Tubes * Stress Control Tubes * Lug Sealing Tubes * Rain Sheds

(B) Mastic Taps:

Stress Control Yellow Mastic * Red Sealing Mastic * Black Sealing Mastic * PVC Insulation Tape

(D) Cleaning Accessories

(E) Other:

(1) HEAT SHRINKABLE BREAKOUT BOOT