In a DC circuit, a capacitor looks like an open circuit because after it fills up it just sits still. In an AC circuit, a capacitor looks like a resistor, it t

In a DC circuit, a capacitor looks like an open circuit because after it fills up it just sits still. In an AC circuit, a capacitor looks like a resistor, it takes work to fill and empty it every cycle. Transmission lines over the earth behave not just like wires, but also like capacitors. Higher voltage reduces resistive losses, but in AC they’re penalized by these “fill and empty a capacitor” ones, that DC doesn’t.