Question

What is the classification of overhead transmission line?

Answer 1

Overhead transmission lines can be classified based on several criteria, including their voltage level, construction type, and the number of conductors. Here’s a detailed breakdown:

### 1. **Based on Voltage Level**
- **Low Voltage (LV)**: Up to 1 kV. Used for local distribution.
- **Medium Voltage (MV)**: 1 kV to 33 kV. Commonly used for distribution networks.
- **High Voltage (HV)**: 33 kV to 230 kV. Used for regional transmission.
- **Extra High Voltage (EHV)**: 230 kV to 765 kV. For long-distance transmission.
- **Ultra High Voltage (UHV)**: Above 765 kV. Designed for very long distances and bulk power transmission.

### 2. **Based on Construction Type**
- **Single Circuit**: Contains one set of conductors, typically used for lower voltage applications.
- **Double Circuit**: Contains two sets of conductors on the same tower, enhancing capacity and reliability.
- **Multi-Circuit**: More than two sets of conductors, used for high-capacity routes.

### 3. **Based on the Number of Conductors**
- **Single Conductor Line**: Uses a single conductor.
- **Bundled Conductor Line**: Uses multiple conductors bundled together, which reduces losses and improves stability.

### 4. **Based on Insulation Type**
- **Insulated Lines**: These lines have insulated conductors and are typically used in urban areas or near airports.
- **Bare Lines**: Uninsulated conductors used for most overhead transmission lines.

### 5. **Based on Construction Material**
- **Steel Towers**: Provide higher strength and are often used for high voltage lines.
- **Wooden Poles**: Used for lower voltage lines, often in rural areas.
- **Concrete Poles**: Durable and used for medium voltage lines.

### 6. **Based on Configuration**
- **Delta Configuration**: Conductors are arranged in a triangular shape, often used for HV lines.
- **Vertical Configuration**: Conductors are arranged in a vertical line, common in urban areas.

### 7. **Based on the Type of Current**
- **AC Transmission Lines**: Alternating Current, which is common for most overhead lines.
- **DC Transmission Lines**: Direct Current, often used for long-distance and underwater cables.

### Conclusion
Understanding the classification of overhead transmission lines is essential for designing, constructing, and maintaining efficient electrical systems. Each category serves specific purposes and helps in determining the most suitable solution for power transmission needs.

Answer 2

Overhead transmission lines can be classified in various ways based on different criteria. Here are the primary classifications:

### 1. **Based on Voltage Levels**
- **Low Voltage Lines**: Typically, these are lines carrying up to 1 kV. They are often used for distribution within residential or commercial areas.
- **Medium Voltage Lines**: These lines operate between 1 kV and 69 kV. They are commonly used for regional distribution.
- **High Voltage Lines**: Operating between 69 kV and 345 kV, these lines are used for long-distance transmission from generation sources to substations.
- **Extra High Voltage (EHV) Lines**: These lines operate between 345 kV and 765 kV. They are used for very long-distance transmission and interconnecting major power grids.

### 2. **Based on Construction**
- **Bare Conductor Lines**: These lines use bare wires without insulation. They are commonly used in medium to high-voltage applications. The conductors are made of materials like aluminum, copper, or a combination of these.
- **Insulated Lines**: These lines have insulating materials covering the conductors. They are used in urban areas where there is a need to prevent electrical hazards and reduce maintenance. They can be single-phase or multi-phase lines with various types of insulation such as PVC, rubber, or composite materials.

### 3. **Based on Conductor Configuration**
- **Single Circuit Lines**: These lines have a single set of conductors on a single tower. They are generally used for lower voltages.
- **Double Circuit Lines**: These lines have two sets of conductors on the same tower, allowing them to transmit power in both directions. This configuration is used to increase transmission capacity and reliability.
- **Triple Circuit Lines**: Less common, these lines have three sets of conductors and are used where very high capacity is needed.

### 4. **Based on Tower Types**
- **Suspension Towers**: Used primarily for medium to high voltage lines, where the conductors are suspended by insulators. They are the most common type of tower for overhead lines.
- **Tension Towers**: Used where the line changes direction or where it needs to be supported in a straight line. These towers are designed to handle the mechanical stress caused by the tension in the conductors.
- **Angle Towers**: Designed to handle the angle in the line’s direction, typically where the line changes direction by a significant degree.

### 5. **Based on Terrain and Environment**
- **Urban Lines**: Installed in cities or heavily populated areas, often requiring special designs to minimize aesthetic impact and ensure safety.
- **Rural Lines**: Installed in less populated areas with considerations for longer spans and lower cost construction.
- **Oversea Lines**: These lines cross bodies of water and require specialized towers and construction methods to deal with environmental conditions.

### 6. **Based on the Type of Conductor Material**
- **Aluminum Conductors**: Light and resistant to corrosion, commonly used in both medium and high voltage lines.
- **Copper Conductors**: Higher conductivity but more expensive and heavier, used in specific applications.
- **Steel Reinforced Aluminum Conductors (ACSR)**: A combination of aluminum and steel wires, used to provide strength and conductivity.

### Summary
The classification of overhead transmission lines helps in understanding their design, application, and operational characteristics. Each classification addresses different aspects of electrical transmission, including voltage levels, construction types, and environmental considerations. These classifications ensure that the transmission system is efficient, reliable, and suitable for its intended use.