Electrical Installation Zones & Conductor Standards
Altitude-Based Electrical Installation Zones
Zone A: Below 500 Meters Altitude
Zone A is located within 500 meters of altitude above sea level. No overhead ice load is taken into account.
Zone B: 500 to 1000 Meters Altitude
Zone B is situated at an altitude of between 500 and 1000 meters. Bare conductors are considered subject to the overhead of a sleeve of ice worth 180 * d grams per meter, where d is the conductor diameter in mm. On the wire in the overhead beam, 60 * d grams per meter will be considered, where d is the diameter of the beam in mm cable. For calculation purposes, the cable diameter of the beam is considered to be 2.5 times the diameter of the phase conductor.
Zone C: Above 1000 Meters Altitude
Zone C is situated at an altitude above 1000 meters. Bare conductors are considered subject to the overhead of a sleeve of ice worth 360 * d grams per meter, where d is the conductor diameter in mm. On the wire in the overhead beam, 120 * d grams per meter will be considered, where d is the diameter of the beam in mm cable. For calculation purposes, the cable diameter of the beam is considered to be 2.5 times the diameter of the phase conductor.
Conductor Standards
Maximum Permissible Traction
Maximum allowable traction for drivers must not exceed their breaking load divided by 2.5, considering the worst-case scenario of the following:
Zone A
- Under the action of its own weight and wind load at a temperature of 15°C.
- Under the action of its own weight and wind load divided by 3, at a temperature of 0°C.
Zones B and C
- Under the action of its own weight and wind load, at a temperature of 15°C.
- Under the action of its own weight and the load of ice for the area, at a temperature of 0°C.
Maximum Arrow
The maximum arrow adopted as a maximum for the conductor is the greater value of the comparison between the two scenarios for the climate zone that is considered. A third hypothesis of temperature (valid for all three zones) should also be considered, which would consider drivers under the action of their own weight and the maximum temperature expected, taking into account the weather conditions and network service. This temperature should not be below 50°C.
Support Structures
When the openings are less than 15 meters, the permanent loads have little influence, which generally can be neglected in the calculation thereof.
Implementation of Facilities
Installing Insulated Conductors
Drivers equipped with insulation wrap, with a rated voltage less than 0.6/1 kV, are treated as bare conductors for the purposes of installation (Section 3.2). The insulated conductors have a rated voltage of 0.6/1 kV.
Cables Mounted on Walls
Cables can be mounted directly on walls using clamps attached to them that are resistant to weathering. The drivers should be adequately protected in those places where they may suffer mechanical damage of any kind. Generally, they shall comply with a ground clearance of 2.5 meters. In the vicinity of openings in walls, the following minimum distances should be observed:
- Windows: 0.30 meters to the upper edge of the opening and 0.50 meters to the bottom edge and side edges of the opening.
- Balconies: 0.30 meters to the upper edge of the opening and 1.00 meter to the side edges of the balcony.
Tension Cables
Cables with a neutral guarantor may be tensioned between special pieces placed on props, facades, or walls with adequate mechanical stress, without considering these effects as resistant insulation. For the rest of the cables, tensioned cables are used with galvanized steel fasteners, whose breaking strength is at least 800 daN, and those fixed by clamps or other suitable devices.