Persian
English
20 Kilovolt (20kV) Distribution System – Overhead and Underground Lines:
20kV distribution networks play a vital role in transferring energy from distribution substations to local transformers (such as 20kV/400V). This system is implemented in two ways: overhead and underground, each having its own advantages and disadvantages.
Applications:
– Rural and low-density areas
– Suburban and roadside locations
– Places with budget constraints
Main Components:
| Component | Material/Type | Function |
| Poles | Wooden, Concrete, Steel | Support conductors and equipment |
| Conductors | AAC, AAAC, ACSR | Carry electrical current |
| Insulators | Porcelain, Polymer, Glass | Insulate and support conductors |
| Lightning Arresters | Rod or Wire | Protection against lightning strikes |
| Protective Devices | Fuses, Reclosers, Sectionalizers | Interrupt circuit during faults |
Advantages:
✅ Low installation and maintenance cost
✅ Faster installation compared to underground lines
✅ Easier repairs due to direct accessibility
Disadvantages:
❌ Vulnerable to wind, icing, and storms
❌ Requires safety clearance (distance from trees and structures)
❌ Negative impact on urban aesthetics
2. 20kV Underground Cables (UG)
Applications:
– Urban and densely populated areas
– Commercial and historical centers
– Locations with high safety requirements
Main Components:
| Element | Material/Type | Function |
| Cables | XLPE or PVC | High-insulation current transmission |
| Trench/Duct | Concrete, Polyethylene | Safe cable routing |
| Joints | Special connectors | Cable connection along the path |
| Underground Substations | Metal or concrete enclosures | Voltage transformation and branch distribution |
Advantages:
✅ Very high safety (no public contact)
✅ Excellent resistance to weather conditions
✅ No visual or urban space occupation
Disadvantages:
❌ High installation and repair costs
❌ Time-consuming fault detection and repairs
❌ Requires special equipment for installation
Overall Comparison:
Parameter | Overhead Lines | Underground Lines |
Execution Speed | 500-800 meters per day | 100-200 meters per day |
Installation Cost | Low | Higher |
Service Life | 25-30 years | 40-50 years |
Technical Losses | 3-5% | 1-2% |
Accessibility | Easy | Requires re-excavation |