Voltage Grading of cable

Voltage Grading of cable Points : Voltage Grading of cable Generally wiring cables are manufactured in two voltages grading such as low and medium. The two grads are termed as 250/440V and 660/1100 voltage grade. For wiring purpose the cables are designed for maximum1100 V capacity. If there are two cables which have same conductor size insulation size is different. The insulation of medium voltage cable is thicker and the low voltage cable has thin insulation site. The minimum thickness of the insulation is determined by the supply voltage. If the supply voltage is 25OV the cores of the cable are insulated from each other and from the lead sheath. The 250/440 voltage grading shows that the each phase and neutral is 240V and between phases there is a voltage of 440 volts. This cable (250/440V) voltage wade could be used in 440V system but the neutral point of the system must be earthed.