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Recommendation ITU-T K.21 specifies resistibility requirements and test procedures for telecommunication equipment that is attached to or installed within a customer's premises.
Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction from adjacent alternating current (a.c.) power lines or railway systems, earth potential rise due to power faults, direct contact between telecommunication lines and power lines, and electrostatic discharges (ESDs). The sources for overvoltages in internal lines are mainly inductive coupling caused by lightning currents being conducted in nearby lightning strikes or lightning currents being conducted by nearby conductors.
Changes compared with Recommendation ITU-T K.21 (2018) include:
• added special resistibility requirements
• added DC insulation resistance test;
• added Test 7.10
• changes to some test labels.
Amendment 1 refers to Annex A, which applies to special environments, in particular primary protection that has a poor earth connection that does not meet the requirements of Recommendation ITU-T K.66. This condition is simulated by increasing the STP earth resistance (R1) from zero to 100. Readers have overlooked this change, possibly because the test circuit diagram is in Recommendation ITU-T K.44. To alert readers of this, a text note has been inserted in the Comments column. |
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ITU-T Supplement
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Title
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Status
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Summary
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Table of contents
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Download
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K Suppl. 3 (10/2015)
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ITU-T K.20, K.21, K.45, K.82 – Additional criteria to protect telecommunication cabling during a power cross event
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In force
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here
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here
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here
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K Suppl. 8 (11/2017)
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Resistibility analysis of 5G systems
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In force
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here
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here
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here
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K Suppl. 9 (05/2019)
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5G technology and human exposure to radiofrequency electromagnetic fields
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In force
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here
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here
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here
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K Suppl. 10 (11/2017)
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Analysis of electromagnetic compatibility aspects and definition of requirements for 5G mobile systems
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In force
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here
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here
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here
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K Suppl. 13 (12/2021)
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Radiofrequency electromagnetic field (RF-EMF) exposure levels from mobile and portable devices during different conditions of use
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In force
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here
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here
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here
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K Suppl. 14 (09/2019)
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The impact of RF-EMF exposure limits stricter than the ICNIRP or IEEE guidelines on 4G and 5G mobile network deployment
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In force
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here
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here
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here
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K Suppl. 15 (09/2018)
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ITU-T K.20, K.21 and K.44 – Internal DC powering interface surge testing factors
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In force
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here
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here
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here
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K Suppl. 16 (10/2022)
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Electromagnetic field compliance assessments for 5G wireless networks
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In force
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here
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here
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here
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K Suppl. 19 (09/2019)
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Electromagnetic field (EMF) strength inside underground railway trains
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In force
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here
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here
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here
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K Suppl. 21 (05/2021)
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ITU-T K.21 – Rationale for setting resistibility requirements of telecommunication equipment installed in customer premises against lightning
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In force
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here
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here
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here
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K Suppl. 29 (07/2022)
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Electromagnetic field strength inside and outside of electric vehicles using wireless power transfer technology
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In force
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here
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here
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here
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| Title |
Approved on |
Download |
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Guide on the use of the overvoltage resistibility for Recommendations ITU-T K.20, K.21 and K.45
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2023-11-22
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here
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Guide on the use of the overvoltage resistibility for Recommendations ITU-T K.20, K.21 and K.45
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2012-04-19
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here
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| Title |
Approved on |
Download |
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Mitigation measures for telecommunication installations – Chapter 10
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2006
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here
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Mitigation measures for telecommunication installations
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2004
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here
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Earthing and bonding
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2003
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here
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Guide to the use of ITU-T Publications produced by Study Group 5 aimed at achieving Electromagnetic Compatibility and Safety
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2002
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here
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Earthing of telecommunication installations
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1976
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here
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