Conductor screen •Ensures smooth and void free interface with insulation
Insulation •Prevents the flow of electricity from the energized conductors to the ground or an adjacent conductor •Withstands the electrical stresses produced by the alternating voltage •Withstands superimposed transient voltage stress on the conductor
Construction of XLPE cables
Insulation screen •Ensures that the electrical field is confined within the polymeric insulation •Strippable type and bonded type.
Copper Screen •Keeps the insulation screen at Earth potential. •Carries the charging current. •Serves as a path for earth fault currents.
Filler •Fills gaps between cores •Rounds up the cable
Construction of XLPE cables
Binder Tape •Binds the cores & filler together and separates the cores from the next layer
Bedding •Serves as a cushion for the armour •Extruded bedding protects ingress of water
Construction of XLPE cables
Armour •Protects against mechanical stresses •Serves as a path for earth fault currents.
Eliminating air voids in cables •Triple extrusion •Super clean XLPE •Dust proof extrusion area •Smooth interface between conductor screen and XLPE insulation
Equipotential lines without control Equipotential lines with control
Stress control layer at the screen termination
STRESS GRADING BY GEOMETRICAL PROFILE
STRESS GRADING IN ‘M-SEAL PUSH-ON’
QS-1000 Field Plot
E1 : E2 : E3 : E4 :
1.45 kV / mm 1.66 kV / mm 2.07 kV / mm 2.32 kV / mm
Max. Electrical Stress in Connector Area Max. Electrical Stress in the Insulation Max. Electrical Stress at Semi-con Edge Max. Electrical Stress in the Original Cable
Basic Concepts
IMPORTANT While preparing the cable: • Take care to avoid any damage on insulation •The end of semi-conducting screen is the most stressed area of a joint or termination. Take care to avoid any damage or nick on the insulation in this area. •While removing strippable type semi-conducting screen, take care not to lift up the edge of the screen termination. •After removing the semi-conducting layer,polish the insulation surface with Al. oxide cloth and cleaned with cleaning fluid.
CONDUCTOR CONNECTION
Conductor connections
Methods of conductor connections: •Soldering •Compression •Mechanical Connector
Conductor Connection Crimping •Correct connectors •Good crimping tool •Correct dies •Required no. of crimps •Always smoothen any sharp edges by filing. •Use corrosion inhibiting paste for Aluminium conductors
Important Connector is the heart of a joint. Wrong selection of connector and/or crimping tool/die can lead to overheating of ferrule and premature failure of joint/termination.
