I was reading a high voltage pcb design guide and it talks about insulators insertions, routed slots, gradient rings, etc.. but it doesn't talk about creepage. As the creepage could be achieved by inserting a barrier or even be a hole on the PCB, here is my confussion.
Talking with my pcb manufacturer he also makes difference between creepage and routed slots close to the conductor pads.
He said that hole width must be calculated depending on the required voltage between pads to protect from arching. I know how to calculate distances for clearance and creepage. But if slots must be calculated I don't know how to do it. I didn' t find any information about routed slots like the pict. So, I hope someone here could tell me how to do it.