Overhead Power Line Structures and Network Configurations
Overhead Power Line Structures
Benches are structural elements supporting conductors and other components of overhead power lines. They withstand compression and bending forces from the weight of the materials and wind action. While various materials are permissible, wood, concrete, and steel are commonly used. Transmission lines typically employ standard lattice masts, categorized by their standardized load capacity (kg) and height (m). Determining the appropriate height and load capacity requires considering factors like voltage, number of conductors, ground wire circuits, and tension.
Types of Support Structures
- Alignment Supports: Support the weight of conductors and ground wires, maintaining line alignment.
- Angle Supports: Withstand stresses from changes in line direction at angles formed by two alignments.
- Anchor Supports: Provide line stability, withstanding stresses from potential conductor or support breakage.
- In-Line Supports: Withstand longitudinal stresses from all conductors.
- Special Supports: Serve specific functions like high-voltage line crossings over other lines, waterways, or railroads.
Network Configurations
Different network configurations exist for power distribution:
- Radial Network: Characterized by a single feed point for transmitting radio energy. Advantages include simplicity and ease of protection. A drawback is the lack of service guarantee.
- Loop/Ring Network: Features two feed points within the loop. Advantages include operational safety and ease of maintenance. Disadvantages include greater complexity and more complicated protection schemes.
- Mesh Network: Combines rings and radial lines, forming interconnected loops. Advantages include operational reliability, flexibility, power capacity, and ease of maintenance. Disadvantages include increased complexity and rapid short-circuit power increases.
Insulators and Ties
Insulators support conductors while isolating them from the ground. Common materials include porcelain, glass, and synthetic materials. Insulators are classified into:
- Fixed Insulators: Attached to fixed hardware with a non-changeable position.
- Chain Insulators: Consist of multiple elements based on operating voltage, forming a mobile chain. Commonly used in medium and high-voltage applications.
- Special Insulators: Designed for specific environments like maritime fog or corrosive areas.
Ties secure conductors to the insulators. The tie’s insulation distance varies based on voltage:
- 110 kV: 8-9 discs
- 220 kV: 14-15 discs
- 380 kV: 20-22 discs
Different tie types exist:
- Suspension Tie: Used for alignment supports.
- Dual Suspension Tie: Used for road or other alignment protection.
- Single Tie: Used for angle supports in frequented areas.
- Double Tie: Provides double protection for highway or similar crossings.
Support Structures: Materials and Specifications
Wooden Supports
Wooden poles are used for overhead lines up to 36 kV. They should be straight and well-formed. Length is indicated by “PM” followed by the length and type (e.g., PM 10 III). Breaking load is applied 5 cm from the pole top.
Concrete Supports
Concrete poles are designated by four groups of letters/numbers followed by “UNESA” (e.g., HV 400 11 UNESA). “HV” indicates concrete vibrator, and “400/11” represents load and length.
Metal Profile Supports
Load hypotheses for metal supports consider factors like wind pressure, ice, traction imbalance, and wire breakage. Loads are categorized as vertical (V), longitudinal (L), and transverse (T).