Kontaktledning/Kabelbeskyttelse for høyspentkabler
1 SCOPE AND PURPOSE
These specifications apply to the production of cable protection for the high voltage cables associated with overhead contact lines to be mounted in tunnels. The cable protection can also be used in other places where special measures are needed to prevent damages. Many old tunnels in Norway are narrow and with ingress of water/ice. This ice have to be removed whit sharp tools, or by steam. Another characteristic of traditional tunnels is that vaults are not smooth, and the mounting of the cable position can vary quite a lot. These characteristics require that the cable protection system and its fastenings have to be flexible. The cable protection is intended to protect the cable mechanically and the personnel from high voltage shock when chopping ice with tools.
2 FUNCTIONAL REQUIREMENTS
The cable protection for high voltage cables has to be solid and protect the cable, or cables, inside against several hits by sharp tools. Absolutely protection against several hits is impossible, (e.g. by an axe can hardly be avoided) but the material and/or construction shall give a reasonable protection. The material should have good properties and be durable in its environment in normal operation and installation. The cables diameters can vary, but will typically be approximately 55 mm. The protection system should be able to cover one or more such cables.
a) Solid material: The material or system shall withstand hard physical impact by sharp tools.
- Exception: Absolute protection agents repeated hits by sharp tools is not expected.
b) Fastening system: The material or system should be delivered whit necessary equipment to be suspended in hooks or bolts, or a recommendation for such fastening.
- Implementation: The material or system should have a high tensile strength so that distance between fastenings can be long.
- Implementation: Extra load of ice can be expected, and the material or system should be able to carry this, both by its strength and by means of shorter distances between fastenings.
- In tunnels the cable with protection will be hanging via bolts in rock or casted arches.
- The fastening system will be exposed for magnetic fields; therefore heating of objects forming a circle around the cables can be expected.
- If the fastening system is made of a non-magnetic material it will probably be the best.
c) Short circuit forces: Additional measures shall be done to prevent damage by short circuit where attraction and repulsion forces could act.
- Implementation: Extra bands or bandage shall be possible to place on the cables or outside the cable protection to prevent damage.
- In the internal technical regulations the short circuit current for most of the Norwegian catenary network is Ip = 27,4 kA (for mechanical dimensioning) refered to 15 kV level.
d) Smooth and uniform surface: The material or system should have a smooth and uniform surface to reduce the possibility of hooking loose parts from passing trains.
e) Material properties: The material shall be resistant and retain its properties by the chemical and physical conditions that can be expected near the railway.
- Implementation: The material shall withstand moisture and dust.
- Implementation: The material shall withstand UV radiation.
- Implementation: The material should tolerate conducting electrical current or be made by insulating material.
- Implementation: The material shall tolerate low temperatures in accordance whit EN 50125-3, climatic class T2, i.e. temperatures down to 40 °C whiteout getting brittle or change mechanical properties substantially, or high temperatures caused by steam over 100 °C.
- Implementation: The cable protection should be equipped with drainage utilities if necessary.
f) Material properties in the case of a fire: The material shall be self-extinguishing and fire retardant.
- Implementation: Halogen free materials are preferred.
g) Colour: The material should have a colour that gives contrast to its surroundings.
- Implementation: Yellow or orange is preferred, but other colour should be delivered by request.
h) Easy installation: The material or system should be easy to assemble, be flexible and have joints that are easy to assemble.
- Implementation: The system or the material itself should be flexible so that direction changes are allowed.
- Implementation: The system or material should be flexible and have as small physical dimensions as possible, so that it can be used in most places without special adaptations.
- Implementation: Mounting should be possible without special tools.
i) Thermal properties: The material or system should have good thermal conductive properties to prevent reduction of the cable(s) current-carrying capacity.
j) Physical dimensions: The cable protection system should have small physical dimensions.
- Implementation: The cross section of the cable protection should be a minimum relative to the cable cross section.