INF.12 Cabling

When selecting cable types, the necessary transmission features MUST be checked. The relevant standards and regulations MUST be observed. The environmental conditions present during operation and installation MUST also be taken into account. With regard to environmental conditions, the following factors MUST be considered:

• temperatures
• cable paths
• tensile forces during installation
• type of installation
• distance between end points and possible sources of interference

Cables, cable routes, and cable trays MUST be dimensioned adequately from both a functional and a physical perspective. In this respect, future requirements MUST also be taken into account, such as sufficient space for possible technical expansions in cable channels and trays. When routing IT and power cabling together in a tray, crosstalk MUST also be prevented among the individual cables. Care MUST be taken to ensure that IT cabling and electrical cabling are routed with the amount of separation specified in the relevant standards. Cables MUST be routed to avoid identifiable sources of risk.

Installation work on cabling MUST be carried out competently and carefully. All the relevant standards MUST be observed during installation. A person with corresponding expertise MUST check that cabling is installed properly at all stages. Whether the right cables and connection components have been delivered MUST be checked at the time of delivery. Care MUST be taken to ensure that the installation does not cause any damage. In addition, the cable routes MUST be chosen in a way that prevents the installed cables from being damaged by normal use of the surrounding building.

The power supply at hand MUST be EMC (electromagnetic compatibility) compliant. To this end, the corresponding power distribution network MUST be designed as a TN-S system. When setting up and operating the power distribution network, the separation distances recommended in the relevant standards MUST be observed to the greatest extent possible. Precautions MUST be taken against external irradiation, power line emissions, and detection of transient currents.

As a general rule, the requirements that may affect the economic efficiency of a cabling installation and its ability to meet all current and future requirements SHOULD be analysed. This requirements analysis SHOULD initially project how the cabling will be used within the organisation in question in the short term. On this basis, estimates SHOULD be made as to how usage might evolve over the longer term. Furthermore, the security objectives of availability, integrity, and confidentiality MUST also be taken into consideration during requirements analysis for cabling.

There SHOULD be an approval process for cabling. Cabling SHOULD always be approved only after all the tasks at hand (possibly within the framework of a milestone) have been completed. The party responsible for its installation SHOULD have reported the tasks as completed and ready for approval. In addition, inspections by the client SHOULD not have revealed any unacceptable defects. The approval date SHOULD be selected so that there is enough time in advance to prepare for the approval inspections. The contractor involved MUST provide written evidence of compliance with all the applicable standards and regulations no later than the approval date. The actual scope of the services rendered MUST be verified during the approval process. A checklist SHOULD be drawn up for the approval report. The approval report MUST be signed in a legally binding manner by the participants and all the persons in charge. The report MUST be part of the internal documentation of cabling.

Every electrical network SHOULD be protected against overvoltage. For this purpose, a corresponding overvoltage protection concept MUST be created that complies with the applicable standards. Emergency power systems (EPS) and uninterruptible power supplies (UPS) MUST be included in the overvoltage protection concept.

If power cables are no longer required, they SHOULD be properly and completely removed. After cables have been removed, firestop seals MUST be professionally sealed.

Cables that are currently no longer needed but can be reasonably left in place as a reserve with the existing technology SHOULD be maintained in a serviceable condition. At minimum, such cables MUST be labelled accordingly at their end points.

In principle, an overview of cables that are no longer needed SHOULD be created. The documentation SHOULD show which cables have been removed or disabled.

Trays SHOULD be adequately dimensioned. Trays SHOULD have adequate ventilation.

An organisation SHOULD ensure that it has internal and external documentation for its cabling. The internal documentation MUST include all records on the installation and operation of the cabling. The internal documentation SHOULD be comprehensively produced and maintained in such a way that operations and further development are supported as effectively as possible. The external documentation (labelling of connections to support operations) of the cabling SHOULD be kept as neutral as possible.

Every change in the network SHOULD be documented. An interim or working version of the documentation SHOULD be adapted immediately (i.e. on the same day as a given change). The master documentation MUST be updated no later than four weeks after completion of the respective work. Whether a document management system can be used for the documentation SHOULD be checked. The documentation SHOULD be reviewed and updated regularly. All technical equipment documented within the scope of cabling MUST be checked with regard to documentation compliance after four years at the latest.

There SHOULD be documentation in every distributor that reflects the current marshalling and line assignments. The documentation in the distributor MUST enable safe switching.

The documentation in the distributor SHOULD be kept as neutral as possible. The documentation in the distributor SHOULD only list existing and used connections and accumulating reserve cables. If possible, no references to the way cables are used SHOULD be given. References SHOULD be limited to those that are expressly prescribed. All further information SHOULD be provided in review documentation.

All electrical installations and equipment SHOULD be inspected regularly according to DGUV Vorschrift 3 [DGUV Regulation 3] in line with the implementation instructions mentioned in section 5, "Tests". Any irregularities detected MUST be documented immediately. Any irregularities detected MUST also be reported immediately to the responsible organisational units. The responsible organisational units MUST remedy the detected irregularities promptly enough to ensure there is no threat to people. The availability of the electrical installations and equipment MUST be ensured to the extent they are required.

The use of electrical appliances and equipment intended for private use SHOULD be clearly regulated within an organisation. All electrical equipment MUST be tested and deemed safe by a qualified electrician before it is used. The use of power strips SHOULD be avoided whenever possible. If additional sockets are required, they SHOULD be professionally retrofitted by a qualified electrician.

Instead of a single-line power supply, a two-line A-B supply SHOULD be considered to supply important IT components and other consumers. The functionality of the power supply SHOULD be continuously monitored by suitable technical equipment.

Consideration SHOULD be given to securing cables and distributors against unauthorised access in all rooms of a building, especially in rooms frequented by the public and in areas that are difficult to see. In any case, the number and extent of places where power supply equipment and data network access points are accessible to unauthorised persons SHOULD be minimised.

Electrical connections and distributors SHOULD be placed or built into cabinet systems. The dimensioning of the cabinet systems SHOULD take into account the growth expected for the planned period of use.

Consideration SHOULD be given to creating redundant primary IT cabling that is routed through independent trays. Whether or not redundant connections to IT or telecommunication providers should be installed SHOULD also be examined. In case of high or very high availability requirements, consideration SHOULD be given to installing redundant secondary and tertiary cabling in the relevant buildings. Redundantly designed parts of the secondary cabling SHOULD be routed through different fire zones. If redundant cabling is used, its proper functioning SHOULD be checked at regular intervals.