Dad while that's usu the case it isn't necessarily so. Sometimes power is also provided through the center conductor
Up the centre conductor and down the braid (or vice versa if you prefer; either way you need a circuit). You sometimes get a low DC voltage, 12 to 20 volts, carried up coaxial cable e.g. for a masthead amplifier, or with a satellite dish, the Low Noise Block downconverter. This will originate from a powered-up satellite or other receiver.
my DIRECTV boxes have burnt out twice in the past two months and burnt out the ports on my tv.
once i plunged in the coaxial cable it sparked again even though the tv or box did not have power.
It is possible for the outer braid of coax to carry AC because of "ground loop" conditions - this may mean there are problems with equipment or wiring inside or outside the house. Sparking and burned out ports does not sound like the regular operation of any TV equipment.