Resumão sobre LINHAS DE TRANSMISSÃO

Summary

This video provides an in-depth overview of power transmission lines, focusing on the key components like transmission towers, their mechanical resistance, and various types such as self-supporting and guyed towers. It explains the role of conductors, insulators, and phase transposition for maintaining voltage balance. The video also covers challenges like atmospheric discharges, vibration-induced fatigue, and ice buildup. Additionally, it discusses the effects of geometry on transmission capacity, methods to increase transmission power, and the use of capacitors to improve efficiency. It is a comprehensive guide for understanding the technical and operational aspects of power transmission lines.

Takeaways

• 😀 Transmission lines are designed to transport electrical energy over long distances.
• 😀 Transmission towers can be self-supporting (concrete-based) or guyed (supported by steel cables).
• 😀 Different tower types include suspension towers, angle towers, terminal towers, and transposition towers, each serving specific functions.
• 😀 Phase transposition is crucial for balancing inductance and capacitance across transmission lines to maintain voltage stability.
• 😀 Electrical isolation between the conductors and the ground is achieved using insulator chains made from porcelain, glass, or polymer materials.
• 😀 Lightning protection is provided by overhead lightning cables (called 'cable guards') that safely discharge lightning to the ground.
• 😀 The mechanical resistance of transmission towers must account for strong winds, which is governed by standards like NBR 5422.
• 😀 Wind-induced vibrations can cause fatigue and even break transmission cables, which is mitigated using vibration dampers.
• 😀 Overload of transmission lines can cause sagging, violating safety clearance, and posing risks to people and animals.
• 😀 Geometric factors like conductor diameter and spacing affect the transmission capacity, with larger diameters and tighter spacings improving power delivery.
• 😀 Transmission lines can behave as capacitors or inductors depending on the load, with the power factor and voltage regulation being crucial for efficient operation.

Q & A

What is the main objective of a power transmission line?

The main objective of a power transmission line is to transmit electrical energy from one location to another.

What are the two types of transmission towers discussed in the script?

The two types of transmission towers are self-supporting towers and guyed towers.

What is the difference between a self-supporting tower and a guyed tower?

A self-supporting tower has a concrete base built on the ground, while a guyed tower is supported by steel cables called guy wires.

What is the purpose of phase transposition in power transmission?

Phase transposition is used to balance the inductance and capacitance in each phase of the transmission line, ensuring that the voltages in each phase remain equal at the terminal.

How often is phase transposition carried out in a transmission line?

Phase transposition is typically carried out every 100 kilometers along the transmission line.

What is the function of an isolator in a transmission line?

An isolator in a transmission line is used to electrically isolate the conductors from the tower, preventing electrical current from flowing into the tower.

What is the advantage of polymer insulators over porcelain and glass insulators?

Polymer insulators have several advantages, including being resistant to cracking, not accumulating dirt, and being hydrophobic, meaning they repel water and reduce the risk of contamination.

What measures are taken to protect transmission lines from lightning?

Transmission lines are equipped with lightning protection cables, also known as ground wires, which redirect lightning strikes safely to the ground through grounding systems.

What is the problem of 'vibration' in transmission lines, and how is it mitigated?

Vibrations in transmission lines, caused by strong winds, can lead to fatigue and even break the cables. These vibrations are mitigated by using dampers such as counterweights and helical types.

What is the 'Ferranti effect' and how is it addressed in power transmission?

The Ferranti effect is the increase in voltage along a transmission line due to its capacitance. It is counteracted by using shunt reactors, which help to reduce voltage spikes.