Have you tried bitter apple spray? As long as you make sure the cords are unplugged when you spray them and then dry before you plug them back in, you can use the bitter apple spray on them to deter the kittens from chewing. I had to use this spray on many things when my dog was a puppy. Good luck!
I had a rabbit that did the same thing, and at the same time I had a daughter who was a chronic nailbiter. For her I bought this stuff called Thumz, its in the drugstore where the baby stuff is. It's really for thumbsuckers. it's like a nailpolish but it taste like hot pepper. It stopped the rabbit from chewing the wires and stopped the nailbiter from biting. It was only like 5 bucks, just paint the wires with it where she is chewing, I"m sure the cian (or however you spell it) pepper will not taste good to her.
When our dog was a pup she would chew on the corners of the coffee table.
I went to SuperPetz and got some Bitter Apple stuff.
She watched as I applied it and immediatly started to lick it off and sit and look at me for more.
I went to the fridge and got out the jar of jalepenos and put the juice on the corners.
One lick and she never did it again!