@sundberg84 - Actually before finding the standard You would need to identify which area. Exmaple. In Europe there would be a directive (2014/35/EU is the new LVD directive, there are also for EMC, RED, ATEX etc.) When You have identified which directives You would need to comply with you can see which standards they have as harmonized (to fulfill the directive). If You are certifying for North America/Canada You use cULus (Listed) or cURus (recognized) and other countries have others like EAC for Russia, Belarus etc. and so on
But it can be a tough job finding the correct standard and even harder to find the end product standard (if your product is used inside another application). Example. A controller (certified according to 60730-1) which is used in 60335-1, 2-89 application (normally it is our customers who uses the end application standard). Here You would also need to check if the end application standard(s) have more severe requirments than 60730-1, if so You would need to adopt these into the certification of your product, else he/she might fail his certification. I am working with controllers. For industrial it is 61800-5-1 and for household it is 60730-1 or 60335-1 directly. It is important to check normative in the end product standard and see if the standard You are using is mentioned. Example. 60335-1 mentioned 60730-1 but not 61800-5-1. So the industrial standard cannot be used if You know that the end application would be 60335-1 and 2-?.
Fulfilling a standard is not only clearance and creepage but we will only look at that here
My examples are from 61800-5-1 (i cannot insert tables, that was why I would like mails, but I will just refere to the tables)
Clearance. As previous told this standard has 3 ways to determine the clearance. By Impulse Voltage (table 7) or by Temporary Overvoltage (Table 9) or Wokring Voltage including recurring peak (table 9).
For the determine by impulse You would beed to know the OVC (Over Votlage Cat). Fix installed is normally OVC III and plugable is OVCII. System voltage is (phase to PE voltage). So if You have a 3 phase 500V in a TN grid the system voltage would be 500/squareroot(3) = 288V. In table 7 the voltages are 150, 300, 600. So here the 300V (remember that interpolation is not permitted) at OVC III should be used (we only make for fixed installation). That would give an impulse of 4KV. So the basic insulation (phase to PE) shall withstand 4KV (and that is all components that are bridging the basic insualtion. Now the Functional insulation can be determined. By using MOV You can supress the Impulse and hereby choose 2.5KV or 1.5KV or even less. Depeding on what the MOV is rated. Remember that there is NO MOV to basic insualtion. If You have it can be there for two reasons. 1. EMC purpose or 2. spacing reduction. If You use it for spacing reduction it has to be monitored so if it is broken the user is informed. For reinforced (live parts to PELV or SELV) You would need one level higher whih is 6KV.
In table 9 these impulse values can be transfered into a distance in mm. T.O.W which is also determined from table 9 is 1200V plus the voltage so in this case it would be (between the phase) squareroot(2)*500 = 707V. This can also be calculated into a distance in mm (here interpolation is permitted). If this value is less than the value from impulse, the impulse voltage is used. For the WV including recurring peak You would need to measure it on an actual board in the worst case condition You allow (since You do not have the option to simulate/calculate). Value measured can be calculated in to a distance in mm (table 9). All values are compared and the worst case is giving the clearance.
Creepage. Table 10 is used. Table 10 has values for PWB and also other insulators. The PWB column (PD1 and PD2) can be used on PWBs. Requirement is that CTI > 175. If You have components that are designed by You (e.g. DC coils, RFI choke, SMPS transformers, BUS bars etc. these would have to comply with other insulators. This menas that CTI value of all parts within the component has to be evaulated. Example. According to table 10 @ 500V for PWB at PD2 you would need 2.5mm. If we design a RFI choke (between phases, R, S and T) there should be 2.5mm bwtween the phases. Other insulators have 3 groups, I = CTI >600, II = 400<CTI<600 and IIIa/b = CTI less than 250. So if distance on the choke shall be 2.5mm the piolymeric used around the core shall have a CTI of 600, if we choose a polymeric with a lower CTI the creepage would be either 3.6mm or 5mm (taken at 500V in table 10). I cannot tell You why, personally I think it is crazy that CTI on PWB of 175 = 2.5mm and CTI of polymeric on choke of 175 = 5 is not the same. Table 10 is for functional and basic insulation. So if You would need to find the value to either PELV or SELV (reinforced You would need to multiply the distance You find by 2.
Remember that the standard also state that a creepage cannot be less than a clearance.
Thomas
