Must the tolerance associated with a Gas Discharge Tube (GDT) specification for insulation breakdown be considered per sub-clause 184.108.40.206 in IEC 62368-1:2014?
More specifically you asked: As per Clause 220.127.116.11 of 62368-1, 2nd Ed, GDT shall meet the electric strength test of 18.104.22.168 for basic insulation. When identifying a specific GDT which has Hi-Pot properties, do we have also to consider its tolerance, so that its value plus its negative tolerance is greater than the value of basic insulation?
In response, 22.214.171.124 of IEC 62368-1:2014 mainly applies to where an SPD (Surge Protective Device) is used between the mains and protective earth, and it covers a varistor and a GDT (Gas Discharge Tube) connected in series with two specific criteria.
For the varistor, it is required to comply with Annex G.8 for the consideration of safeguards against electric shock and fire. For the GDT, both the electric strength test per 126.96.36.199 and the external clearance and creepage distance requirement per 5.4.2 and 5.4.3 respectively for basic insulation are required.
In the case of the application of the electric strength test per 188.8.131.52 to the GDT, it relies fully on a type testing procedure on the GDT alone. Therefore, the informative tolerance listed in the GDT specification for the insulation breakdown is not required to be a formal part of the compliance check. Even if the relative ratings plus their negative tolerances result in the worst specification greater than the required test voltage for basic insulation for the application, the electric strength test per 184.108.40.206 as stated in 220.127.116.11 is the specific compliance criteria to be considered in IEC 62368-1.
As your question is not specified in the context of a detailed product configuration, you are encouraged to contact UL for a more in-depth consultation, either via your local account executive or via https://62368-ul-solutions.com/contact-ul.html.