From the Revd Christopher Miles
Sir, - I was saddened to read of the severe lightning damage
to St Odulph's, Pillaton (
News, 1 February). Churchwardens and church councils have a
difficult task in balancing the finances of their churches, and
some feel that they cannot afford the cost of good lightning
protection.
Lightning protection is probably the oldest electrical
technology, having been invented by Benjamin Franklin more than 250
years ago. For most of that time, it has been recognised that a
single down conductor provides inadequate protection. A second down
conductor splits the current, halves the enormous voltage built up
during a lightning strike, and so reduces the risk of flashover
with consequent possible fire or structural damage.
A well-protected tower may provide fairly good protection, but
quite probably leave the chancel unprotected: lightning does not
always strike the highest point. The risk of a direct strike is
comparatively low, maybe once every 200 to 500 years, depending on
the size of the church and its location.
What is perhaps ten times as frequent is a strike in the
vicinity of the church or its service cables (power and telephone)
powerful enough to damage electrical and electronic equipment.
Well-installed surge protection can virtually eliminate such
damage. It is also important to consider the lightning-protection
implications of installing external electrical equipment such as
mobile-phone relays, broadband relays, PV panels, sensors, cameras,
lighting and their cables, to provide either sufficient separation
or, if not, to bond electrically to the nearest down conductor
where this can be done. Regular review and professional advice are
important.
CHRISTOPHER MILES
Lightning Protection Consultant for
Rochester and Canterbury dioceses
2 Spa Close, Hadlow
Tonbridge, Kent TN11 0JX
