For the same working voltage, the potential stress on the insulation is less than in case of DC system than that AC system. Therefore , a DC line requires less insulation.

In other words A DC System has a less potential stress over AC system for same Voltage level and power rating, this is why AC needs more insulation than DC system?Why AC needs more insulation than DC for the Same Working Voltage Level?

Let’s explain in detail..

When we talk about DC, let say 220 Volt DC, it means the maximum value (peak value) of the voltage is 220V, but when we talk about 220 Volt AC (As in our home distribution system = single phase AC Supply = 220 V AC or 110V AC in the US), then it is basically 220 RMS (Root Mean Square = ?2) value, i.e. it is the RMS value of 220V AC.

The peak value of AC voltage is equal to ?2xVRMS = 1.414 x VRMS (where ?2 = 1.414)

In other words. The peak value of AC voltage = VRMS / 0.707

For the same working voltage, the potential stress on the insulation is less than in case of DC system than that AC system. Therefore , a DC line requires less insulation.

In other words A DC System has a less potential stress over AC system for same Voltage level and power rating, this is why AC needs more insulation than DC system