Components of EHV d.c. system

Introduction

The EHV d.c. (Extra High Voltage direct current) system plays a crucial role in EHV A.C. (Alternating Current) and D.C. Transmission. It is responsible for converting alternating current to direct current and vice versa, enabling efficient long-distance power transmission. This topic focuses on the fundamentals of EHV d.c. system components and their importance in power transmission.

Converter Circuits

Converter circuits are an essential part of the EHV d.c. system. They are responsible for converting power between A.C. and D.C. forms. There are two types of converter circuits used in the EHV d.c. system: rectifier valves and inverter valves.

Rectifier valves convert A.C. power to D.C. power, while inverter valves convert D.C. power back to A.C. power. These converter circuits operate under precise control to ensure efficient power conversion and transmission.

Reactive power requirements in converter circuits must be carefully managed to maintain system stability and power quality.

Harmonics Generation and Misoperation

Harmonics are unwanted frequencies that can distort the waveform of the power system. In the EHV d.c. system, harmonics can be generated due to the non-linear characteristics of the converter circuits.

Harmonics can have adverse effects on the EHV d.c. system, including increased losses, reduced power quality, and interference with other equipment. They can also cause misoperation of the converter circuits, leading to system instability and potential equipment damage.

To suppress harmonics, various remedial measures can be implemented, such as the use of filters for harmonic mitigation and ground return techniques.

Commutation Failure

Commutation failure refers to the inability of the converter circuits to switch from one state to another properly. It can occur due to various factors, including improper circuit design, component failure, or external disturbances.

Commutation failure can have severe consequences in the EHV d.c. system, including voltage and current instability, increased losses, and potential equipment damage. Detection and protection methods are employed to identify and mitigate commutation failure to ensure the reliable operation of the system.

Multiterminal D.C. Lines

Multiterminal D.C. lines are a configuration of the EHV d.c. system that involves multiple terminals connected to a common D.C. line. This configuration offers advantages such as increased system flexibility, improved power flow control, and reduced transmission losses.

However, multiterminal D.C. lines also present challenges, including increased complexity in control and protection, and the need for advanced communication and coordination between terminals.

Real-world applications of multiterminal D.C. lines can be found in projects such as offshore wind farms and interconnecting power grids.

Conclusion

Understanding the components of the EHV d.c. system is crucial for ensuring the reliable and efficient operation of EHV A.C. and D.C. Transmission. Converter faults, harmonics misoperation, commutation failure, and multiterminal D.C. lines are key aspects that need to be addressed to maintain system stability and power quality.

By implementing appropriate control, protection, and mitigation measures, the EHV d.c. system can continue to play a vital role in long-distance power transmission.

Summary

The EHV d.c. system is an essential component of EHV A.C. and D.C. Transmission. It involves converter circuits, such as rectifier and inverter valves, which convert power between A.C. and D.C. forms. Harmonics generation and misoperation can have adverse effects on the system, but remedial measures like filters and ground return techniques can help suppress them. Commutation failure can lead to system instability, but detection and protection methods can mitigate its consequences. Multiterminal D.C. lines offer advantages like increased flexibility and improved power flow control, but they also present challenges in control and protection.

Analogy

Imagine the EHV d.c. system as a highway for power transmission. The converter circuits act as on-ramps and off-ramps, converting power between A.C. and D.C. forms. Harmonics are like traffic congestion on the highway, causing disruptions and delays. Remedial measures, such as filters and ground return techniques, are like traffic management strategies to alleviate congestion. Commutation failure is like a road closure, causing detours and disruptions. Detection and protection methods are like traffic cameras and road signs to identify and mitigate the issue. Multiterminal D.C. lines are like interconnected highways, offering more routes and options for power transmission, but requiring advanced coordination and communication between terminals.