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3.1.5 Operational Access
NGTS 2.1
Page 3 Issue 2
May 1995
Reasonable access shall be provided to the isolation facilities of each disconnector and earthing switch,
including the locking device, where fitted. Access shall comply with Clause 3.1.1 and shall be suitable for
use by an unaccompanied person.
Unless otherwise agreed with NGC the isolation facilities or locking devices shall be between 1 m and 1.8
m above the floor level or platform provided for access and shall not be further than 750 mm horizontally
from the edge of a platform.
Access above ground level shall be from mobile or fixed platforms (though the latter may be accessed by
ladder). Where movement of equipment within the substation would be restricted by the presence of ladders
it is acceptable that these should be removable. Removable ladders and mobile platforms shall be easily
handled and used on the finished substation surface by one person.
Ladders and permanent platforms shall, where applicable, comply with BS 5395: Part 3. Other Standards
may be acceptable by agreement with NGC.
3.1.6 Requirements for Maintenance
The substation layout shall make allowance for preventive or corrective maintenance within the outage
constraints specified in Clause 3.1.3 and using procedures compliant with Clause 3.1.1.
Access for maintenance shall be provided as follows:
(i) The substation layout and surfaces shall be adequate to allow the access and use of powered access
equipment, cranes and similar equipment required for any normal maintenance operation (circuit-breaker
interrupter change, disconnector contact change, insulator cleaning etc). Suitable sealed surface roads
shall be provided to substation main buildings and heavy items of plant (eg transformers), other surfaces
should be finished in accordance with NGTS 2.10.
(ii) Fixed platforms need not be provided for preventive or corrective maintenance requirements so long as
access can be gained by the use of pre-formed scaffolding, portable ladders or, in outdoor substations,
powered access equipment.
Arrangements of any fixed platforms provided shall be to the approval of NGC and shall meet the
requirements of BS 5395: Part 3. Other Standards may be acceptable by agreement with NGC.
Maintenance shall be taken to include the replacement of any component or sub-component within the
substation including GIS enclosures.
Suppliers shall, on request, provide a written procedure for carrying out any proposed maintenance
procedure in accordance with these requirements.
3.1.7 Interlocking
Substations shall be provided with a full interlocking scheme as specified in NGTS 3.1.1.
Requirements of electronic interlocking schemes provided as part of substation control systems are
specified in NGTS 3.7.11.
3.1.8 Cranes & Lifting Equipment
Fixed cranes should not be provided in indoor AIS substations except where specifically required for
maintenance or repair purposes. Fixed cranes shall be provided in indoor GIS substations except where
the supplier can demonstrate specifically that they are not required for dismantling or removing any part of
the substation for maintenance or repair purposes.