Question 5/V - Protection policy aginst over-voltages
(Continuation of Question 5/V, 1985-1988; revised wording)
(See also Questions 1/V and 7/V)

The object of this Question is to produce new Recommendations on the
resistibility of equipment to over-voltage or over-currents. All types
of telecommunication equipment, except that covered by Question 21/V,
should be included.

All types of abnormal conditions should be covered - lightning, mains
induction, mains contacts, mains transients, rise of earth potential and
electrostatic discharges.

The questions are:

a) What are the statistics of voltage, current, source impedance,
waveform and duration of abnormal conditions encountered at exchange
terminations, subscriber's terminations and other significant points in
the line network? What methods of
measurement are used and what parameters should be measured?

b) What levels and durations of over-voltage or over-current should
equipment be designed to resist? Economic considerations should be taken
into account. Experiences of equipment failures due to surges would
assist study of this Question?

c) What testing procedures should be used to measure the resistibility
of equipment to abnormal conditions?

d) What problems arise of coordination of protective components,
including those built into equipment? Is operation of protective
components affected by the telecommunication equipment? How are these
problems dealt with?

Note 1 - The particular requirements of equipment resistibility at
subscriber installations where, for any reason, the earths of
telecommunications equipment cannot be simply bonded to the mains power
earth should be studied.
Note 2 - This Question covers the safety of telecommunications networks.
CCITT should cooperate with IEC and other standardization bodies on
matters of electrical safety in relation to telecommunications networks.
It may be necessary to establish supporting Recommendations on this
subject.