Product locator Product range overview Compliance with RoHS Directive 2002/95/EC What transients are and why you need protection Risk assessment Protection benefits When and where to protect How to get effective protection Location categories and exposure levels explained Installation advice What every Furse protector gives you Direct sales Worldwide distribution Request literature Enquiry form         Exposure levels The probable worst case transient overvoltage expected at each location category depends upon the probable number of lightning strikes, the vulnerability of the system and its consequential loss rating. Together, these factors determine whether electronic equipment is in a high, medium or low transient exposure level. This can be calculated from the risk assessment procedure in Appendix C of BS 6651:1999 (this is explained in Section 3 of the Furse Electronic Systems Protection Handbook). If the transient exposure level for the system is not known it is prudent to assume a high exposure level. Figures 3, 4, 5 and 6 below show probable worst case transients for location categories and exposure levels. Figure 3 - Mains power supply (Category C) System exposure level Peak voltage Peak current High Medium Low 20kV 10kV 6kV 10kA 5kA 3kA Figure 4 - Mains power supply (Category B) System exposure level Peak voltage Peak current High Medium Low 6kV 4kV 2kV 3kA 2kA 1kA Derived from original work in IEEE C62.41-1991 and reproduced from BS 6651:1999 Derived from original work in IEEE C62.41-1991 and UL 1449 and reproduced from BS 6651:1999 Figure 5 - Mains power supply (Category A) System exposure level Peak voltage Peak current High Medium Low 6kV 4kV 2kV 500A 333A 167A Figure 6 - Data lines (Category C) System exposure level Peak voltage Peak current High Medium Low 5kV 3kV 1.5kV 125A 75A 37.5A Derived from original work in UL 1449 and reproduced from BS 6651:1999 Derived from original work in CCITT IX K17 and reproduced from BS 6651:1999   1 | 2 | 3 | 4