Why fault currents are low when it is closer to the transmission bus?

Answer 1

Typically fault currents are high at buses. I'm assuming you're referring to fault current from a particular source is low at a specific bus. Fault current will drop off as more resistance is added between the source and the fault (ohms law). This is why fault currents are typically high at a bus - you often have many lines coming into a bus from multiple sources, so the apparent impedance from these sources is less (less resistance).

Answer 2

Induction until the current has completely stopped and Capacitance until the lines are fully charged. It is difficult to stop a high current flow, because even when you stop the current it has a high inertia (not exactly an electrical term, but similar) because the current does not want to stop "flowing" just because you open a switch. It will try to find other paths and theoretically the voltage at the open end will reach infinity trying to find an outlet. I hope this makes sense. I have been studying it for quite a few years, but this is an engineer's layman answer.