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Question 2/5

Question 2/5 – Protective components and assemblies
(Continuation of Question 13/5)


Protection against overvoltages and overcurrents of telecommunication installation and equipment is achieved with adequate resistibility level of both equipment and lines insulation and proper installation of suitable protective devices. Changes have occurred in the resistibility requirements and protective devices technology.

These changes require studies to ensure that the recommendations on protective devices fit the needs of the operators and the user of telecommunication networks.

The following Recommendations and Handbooks, in force at the time of approval of this Question, fall under its responsibility:

  • K.11, K.12, K.28, K.36, K.55, K.65, K.69, K.77 and K.82.
  • Directives, Volume VIII


The objective of this question is to establish Recommendations for specifications, test methods and principles of application for protective components and assemblies intended to mitigate effects of lightning, power induction, ESD, fast transients and power contacts that may cause permanent damage. These protective components and assemblies are related to both telecommunication and power supply circuits of telecommunication equipment.

Study items to be considered include, but are not limited to:

  • Protective component changes to comprehend safety requirements, such as a thermal disconnect switch incorporated into a metal-oxide varistor;
  • Coordination of overcurrent protection components with the system current capability;
  • Protector parameters needed for broadband protection;
  • Coordination of overvoltage and overcurrent protection;
  • Considerations intended to facilitate the selection of most effective protection method (e.g. source and intensity of overvoltages and overcurrents);
  • Use of insulation barriers as a means of blocking longitudinal/common-mode voltage surges;
  • Transients generated by the operation of switching-type overvoltage protectors;
  • Reduction of equipment resistibility due to the use of “green” power saving techniques.


Tasks include, but are not limited to:

  • New Recommendations on the application of new protection elements and/or assemblies;
  • New Recommendations on the basis of the following criteria:
    • Basic requirements, based on K.11 and K.36;
    • Product requirements, based on K.12, K.28, K.30, K.55, K.65. K.77 and K.82.
  • New Recommendation on lightning isolation transformers with high impulse voltage ratings;
  • New recommendation on thyristor components used for overvoltage protection;
  • New Guides/Handbooks on the application of components and assemblies for protection of telecommunications installations/equipment;
  • Maintenance of the existing recommendations under the responsibility of the Question;
    • Withdraw K.36 when new Guides/Handbooks on the application of components and assemblies available.
  • Possible revision of Volume VIII of the Directives with material from new Guides/Handbooks on the application of components and assemblies.

An up-to-date status of work under this Question is contained in the SG 5 work programme (use URL as shown in the table below).




  • K-series


  • 4, 5, 10 and 12/5

Study Groups:

  • none

Standardization bodies:

  • IEC SC 37A, IEC SC 37B, IEC TC 64, IEC TC 81, IEC 108, IEC SC 77B, IEEE PES SPDC