Question 4/5 - Resistibility of communication equipment
(Continuation of Questions 4 and 13/5)
Motivation
New types of equipment (examples are routers, set-top units and cable modems) are appearing in the network. Also, different types of equipment are being interconnected at a customers' premises and the requirements for the internal interfaces and the effects of these interconnections need to be considered.
At least four major changes have occurred which affect the requirements of the existing resistibility recommendations.
a) The access network is rapidly changing from a traditional exchange (switching centre) which may be kilometres from the customer to the switching equipment being close to the customer. As an example, digital circuits (e.g. ISDN) are being used, high-speed data services (xDSL) are being introduced, voice can now be transmitted over the Internet and routers with packet-switching compete with conventional switching systems.
b) The environment where the equipment is housed is also changing. Traditionally switching equipment has been installed in a controlled environment with the protection installed in an MDF. With miniaturization and changing technologies bulky rack-mounted equipment has been replaced by small equipment, which may be installed on a wall, in a shelter or underground with the high current protection integral to the equipment.
c) Many countries have regulations regarding grade of service where the operator can be fined if an adequate grade of service is not provided. There is a need to reduce the level of overvoltage and overcurrent damage to equipment.
d) In the past some operators have specified more stringent requirements for their equipment due to environmental factors requiring specific equipment designs. With globalization, competition and bans on trade barriers it is necessary to have global requirements.
These changes require study to determine what steps are required to ensure that the recommendations fit the needs of the operators and the user of the telecommunication network.
The following Recommendations, in force at the time of approval of this Question, fall under its responsibility:
K.20, K.21, K.44, K.45.
Question
The objective of this question is to produce resistibility requirements for equipment installed in telecommunications centres, in outdoor enclosures in the access and trunk networks and at customer premises. The sources of overvoltages and overcurrents that may cause damage to the equipment include lightning, power induction and mains power contacts. The types of interfaces include symmetric pair, coaxial, dedicated power feeds and mains power ports.
Study items to be considered include, but are not limited to:
- Requirements for coaxial ports connected to external coaxial cables (network cables and cables connected to antennas mounted on the building) (K.20, K.21, K.44 and K.45)
- The use of Coupling and De-coupling Network (CDN) during surge tests (K.44)
- The effects of lightning surges with long wave shapes on switch mode power supply: Mains port test waveshape (K.20, K.21, K.44 and K.45);
- The effects of different waveshapes (rise time, length of waveform and current) on equipment damage at customer’s premises (K.21);
- Coordination test for fast rising waveshapes (K.20, K.21, K.44 and K.45);
- Acceptable period for equipment recovery after application of surges (K.20, K.21, K.44 and K.45);
- Resistibility and safety tests (Coordination between SG 5 and IEC TC 108)
- Coordination of IEC 60950 mains frequency and impulse safety test levels and SG 5 resistibility test levels.
- Coordination of the overvoltage safety test levels in IEC 60950 with the bond wire lengths known to exist at customer premises (K.20, K.21, K.44, K.45 and K.pcp, see Q 6/5).
- Classify cabling from equipment mounted on outside of building to equipment inside the building for K.20, K.21 and K.45
- Power contact test, specifically whether a single line to earth test should be performed (K.20, K.21, K.45 and K.44).
- Resistibility test level of ITE ports (e.g. USB, Ethernet, RS232, E1) compared with telecommunication ports (K.21).
Tasks
Tasks include, but are not limited to:
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Maintenance and enhancement of the existing recommendations K.20, K.21, K.44, K.45 for protection of communication equipment.
Relationships
- Recommandations: K.11, K.12, K.28, K.36, K.pcp (see Q 6/5)
- Questions: 1, 5, 6, 8, 9 10, 11, 12, 13, 14 and 15/5
- Standardization bodies: IEC TC 108, IEC TC 81, IEC TC 37, CENELEC TC 81X, ETSI ERM
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