Induced Surges in AC Lines and Telecommunication Lines - RME111 - RWS200 - AWS310-SITE - AWS430 - RWCC - AWS310 - FOC201

Grounding and Lightning Protection in Vaisala Outdoor Installations Technical Reference

Document code
M211786EN
Revision
B
Language
English (United States)
Product
RME111
RWS200
AWS310-SITE
AWS430
RWCC
AWS310
FOC201
Document type
User guide

The voltage of a direct lightning strike is virtually unlimited. In a lightning strike to medium voltage AC distribution lines (over 30 kV), the voltage is air-gap limited to around 100 kV at transformers.

Recommended protection capacities in 230 VAC line are (according to IEEE C62.41):

  • Category C: open distribution lines: 0 kV/10 ... 20 kA
  • Category B: building entry point: 6 kV/3 kA
  • Category A: distribution outlets: 6 kV/1 kA

An indirect strike within 100 m (330 ft) of cables or buildings can induce surges up to 5 kV and 1.25 kA in AC cables.

Telephone and instrumentation cables have higher series impedance, which typically limits the current to over 200 A.

  • Category C: (high) 10 kA (design value, acceptable for many small surges)
  • Category C: (low) 2.5 kA