I'm considering on creepage distances on my PCB. I have read UL840,there are two significant tables. 6.1 "Minimum acceptable creepage distances" and 6.2 "Minimum acceptable creepage distances on printed wiring boards". I have read post: Trace width and clearance calculations. I noticed that Dave Tweed recommends to use 6.2 table. But in table 6.1 there is a sentence: "Creepage distances for equipment subject to long-term stress". I'm considering what does it mean, and when i should use values from table 6.1?
The difference between 6.1 and 6.2 is based on the continuous voltage differential between the traces.
For example: If you expect a continuous 1000V between two traces, it should be spaced according to 6.1.
If you only need to be able to withstand a 1000V surge infrequently and/or for brief periods of time, then the spacing can be according to 6.2.