I have a frayed 60w MagSafe with outer insulation / coaxial part is broken where some wires are cut (some are not). There's no problem with inner insulation part and the MagSafe working just fine when plugged to my MBP (I seal up the broken part with electrical tape).

My question is, is it safe to use MagSafe with broken outer insulation (some wires are cutted out)? Will it damage my MBP especially the logicboard in long term? What the purpose of the outer insulation part?

Update : I have already sealed the cable when I created the post, so I will use image I found on the net to illustrate the situation.

This is my magsafe look like after sealed by electrical tape