In modern high-voltage and extra-high-voltage (EHV) transmission systems, the use of bundled conductors is common. Bundled conductors help reduce corona losses, radio interference, and surge impedance, thereby improving the power transfer capability of the transmission line.
One important conductor arrangement used in EHV transmission is the Quad Bersimis conductor configuration. This configuration is particularly useful in very high voltage transmission lines because it helps increase the Surge Impedance Loading (SIL) and improve the overall performance of the transmission system.
Table of Contents
Bundled Conductors in Transmission Lines
In EHV transmission lines, instead of using a single conductor per phase, two or more conductors are used in parallel, known as bundled conductors.
Common bundle configurations include:
- Twin conductor bundle – 2 conductors per phase
- Triple conductor bundle – 3 conductors per phase
- Quad conductor bundle – 4 conductors per phase
The Quad Bersimis configuration is a four-conductor bundle per phase, arranged in a specific geometric pattern.
What is Quad Bersimis Configuration?
The Quad Bersimis configuration consists of four sub-conductors per phase, arranged in a square formation and connected by spacers to maintain fixed spacing.
Characteristics:
- Four conductors per phase
- Arranged in square geometry
- Maintained using spacer dampers
- Used in EHV transmission lines (400 kV and above)
The spacing between the sub-conductors is designed to optimize electrical and mechanical performance.
Purpose of Using Quad Bersimis Conductors
The main objectives of using this configuration are:
1. Reduction of Corona Loss
Bundled conductors increase the effective conductor diameter, which reduces electric field intensity at the conductor surface and thereby reduces corona discharge.
2. Reduction of Surge Impedance
Bundled conductors increase the capacitance and slightly reduce the inductance of the line. This results in lower surge impedance.
3. Increase in Power Transfer Capability
Since the Surge Impedance Loading (SIL) depends on surge impedance, reducing the surge impedance increases the natural power transfer capability of the transmission line.
Surge Impedance of Transmission Line
The surge impedance (characteristic impedance) of a transmission line is given by
[
Z_s = \sqrt{\frac{L}{C}}
]
where:
- (L) = inductance per unit length of the transmission line
- (C) = capacitance per unit length of the transmission line
Bundled conductors decrease (L) and increase (C), resulting in lower surge impedance.
Surge Impedance Loading (SIL)
The Surge Impedance Loading (SIL) represents the natural loading level of a transmission line, where the reactive power generated by capacitance equals the reactive power absorbed by inductance.
The SIL of a transmission line is given by
[
SIL = \frac{V^2}{Z_s}
]
where:
- (V) = line-to-line voltage of the transmission line
- (Z_s) = surge impedance of the line
Effect of Quad Bersimis Configuration on SIL
The Quad Bersimis arrangement affects SIL in the following ways:
1. Reduction in Surge Impedance
The bundle of four conductors increases the equivalent radius of the phase conductor, which reduces the surge impedance.
2. Increase in Capacitance
Because the conductors are spread out, the capacitance between the conductor and ground increases.
3. Higher SIL
Since
[
SIL \propto \frac{1}{Z_s}
]
a reduction in surge impedance results in higher Surge Impedance Loading.
Thus, Quad Bersimis lines can carry more power naturally without reactive compensation.
Line Voltage and Quad Bersimis Configuration
Quad conductor bundles are generally used for extra-high-voltage transmission lines, such as:
| Transmission Voltage | Conductor Configuration |
|---|---|
| 220 kV | Twin bundle |
| 400 kV | Quad bundle |
| 765 kV | Quad or Hex bundle |
At 400 kV transmission voltage, Quad Bersimis conductors are commonly used to:
- Reduce corona loss
- Increase SIL
- Improve voltage regulation
- Increase transmission capacity
Advantages of Quad Bersimis Configuration
- Higher power transmission capability
- Reduced surge impedance
- Lower corona loss
- Reduced radio interference
- Improved voltage regulation
- Higher SIL
Applications
Quad Bersimis conductor configurations are used in:
- Extra-high-voltage transmission lines
- Long-distance power transmission systems
- 400 kV and 765 kV transmission networks
- Interconnected national grids
Conclusion
The Quad Bersimis conductor configuration is an important design used in EHV transmission lines to enhance the performance of power transmission systems. By using four bundled conductors per phase, the configuration reduces surge impedance and increases capacitance, leading to a higher Surge Impedance Loading (SIL).
As a result, transmission lines using Quad Bersimis conductors can transmit larger amounts of power efficiently while reducing corona losses and improving voltage stability, making them suitable for high-voltage long-distance power transmission.