LOL, that's a good one. Call your utility company and have them come out and check it. I think you've had some wool pulled over your eyes by a cable company tech that should know better, judging from his comments.
A copper cable transports electrical signals. An optical cable transports light signals.
If the voltage is supplying any current through the cable, i.e. if there is any 'load' at the end, then the voltage will drop through the cable.
It will decrease the voltage drop.
Cable Television
Voltage Grade of cables specifies the safe voltages which the insulation of the cable can withstand.
An LT cable is a low tension (or low voltage) cable.
which term means to issue signals along a network medium such as a cable
Crosstalk
The voltage drop in a wire has nothing to do with the insulation. Voltage drop has to do with the cross sectional area of the wire.
To access the internet via broadband cable, you will need a cable modem. Bandwidth is used for transmitting the signals of the internet to and from your home, and the cable modem is in place to allow the signals to be sent and received.
cross sectional area of cable * voltage drop
The voltage is always determined by the device. (in this case a slow cooker).However, having established what voltage to supply to the device, the cable must be suitable for the voltage used. Everything in the chain of power transmission, must be rated for the correct voltage. Cables, plugs, fuses etc.