BS EN 50122-1-2011 pdf download.Railway applications Fixed installations Electrical safety, earthing and the return circuit Part 1: Protective provisions against electric shock.
5.1 General
According to HD 603644-41 no protection against direct contact is required for circuits with nominal voltages up to and including AC 25 V or DC 60 V. This shall not apply, however, if the circuit concerned is connected to the traction return circuit.
In overhead contact line systems one of the following protective provisions shall be utilized for protection
against direct contact:
– protection by clearance;
— protection by obstacles.
All insulators Which are directly connected to a live part shall be regarded as a live part when considering clearance dimensions in this European Standard. [I)Exceptions are the parts of synthetic ropes which are further away from live parts than the creepage length (according to EN 50345) with a minimum of 1 m.
5.2 Protection by clearance
5.2.1 Standing surface
For standing surfaces accessible to persons, the clearance for touching in a straight line shown in Figure 3 and Figure 4 shall be provided against direct contact with live parts of an overhead contact line system as well as live parts on the outside of a vehicle (e.g. current collectors, roof conductors, resistors). This does not apply to conductor rail systems near the running rails (refer to 5.5).
The clearances given in Figure 3 and Figure 4 are minimum values which shall be maintained at all temperatures and in the full range of electrical and mechanical loads of the conductors. Due to national or regional existing practices, greater clearances or smaller mesh sizes may be prescribed by the relevant infrastructure manager.
This protection is not mandatory if. although contact with live parts is possible, other provisions have been taken to ensure Isolation from the supply.
NOTE 1 Touching m a straight line implies that live parts are accessible by a person froni a standing surface witheut use of cb9ed5
NOTE 2 Figure 3 and Figure 4 asssiies that the standing surface does not afford protechon against contact with live parts situated belov or to the sade thereof Depending on its construction the surface may in practice meet the requirement respecting provision of obstacles. In this case the lower clearances applicable to obstacles may be applied.
NOTE 3 These dearances have been determined on the basis of the arms reach as defined in I-ID 60364-4-41 to which a margin of safety was added. The margin of safety has been determined depending on the voltage of the contact lane system, on experience and on whether the standing surface is an a restncted area or in a public area.
5.2.2 Exceptions for working persons
The clearances to be observed for persons working near to energised contact line systems shall be defined in the operational specifications. If operational specifications do not exist, clearances shown in Figure 3 and Figure 4 or the clearances to obstacles according to 5.3 shaH be used.
Standing surfaces or platforms utilized solely for the execution of work at or in the vicinity of the contact line system are not included.
NOTE Examples are stabon plattomt roots. working platforms and workrng planks at signal bridges, working platforms at signals. mamtenance-iadders. work cages of hydraubc work Wig platforms. working platforms of lower cars.
5.2.3 Warning signs
Warning signs shall be used in areas where there is a serious risk of persons coming within the limits of live parts of a contact line system given in 5.2.1, Such warning signs shall be placed in a prominent position and be readily visible adjacent to the point of access. The sign shall be in accordance with ISO 3864 (see Annex B). If required an appropriate supplementary sign may be used.
5.2.4 MinImum height of overhead contact lines above roads
Where a road carrng normal vehicular traffic crosses or coincides with a railway, tramway or trolleybus electrified by means of an overhead contact line and no road traffic restrictions are specified, unless otherwise fixed by national regulation, a minimum vertical clearance as stated below shall be provided between the road surface and the lowest point of the overhead contact line and associated feeders.
The minimum vertical clearance between the road surface and the overhead contact line shall be:
for low voltages, 4,70 m;
— for high voltages. 5,50 m.
If the required minimum clearance cannot be provided and unless otherwise specified by national regulation, the maximum height of road vehicles permitted to pass under the overhead contact line shall be limited so as to guarantee the following minimum vertical clearances between the highest point of road vehicle (load included) and the live parts:
a) for low voltages:
1) 0.50 m, where only road traffic signs indicating the maximum permissible vehicle height are utilized,
2) 0,30 m, where additional fixed barriers (e.g. a rigid obstacle or a firmly fixed metallic wire made visible by means of a suspended warning sign) are erected on both sides of the crossing, physically limiting such vehicle height:
b) for high voltages:
1) 1.00 m, where only road traffic signs indicating the maximum permissible vehicle height are utilized.BS EN 50122-1-2011 pdf download.