Basic Requirements of DC Circuit Breaker in DC Transmission

With the development of high power electronic devices, DC transmission based on voltage source converter can be controlled independently because of its reactive power and active power. Advantages such as no filtering and reactive power compensation equipment, power supply to passive load, and no change of voltage polarity when the power flow reverses have become the main direction of DC transmission in the future. However, because there is no transformer and other equipment in the DC transmission line, the short-circuit current rises quickly and the amplitude is high when the short-circuit fault occurs.

At the same time, there are a large number of power electronic components in the DC transmission line. If a fault occurs and the fault cannot be quickly isolated, the circuit breaker will bear huge overcurrent pressure, and even damage the components, and the entire transmission network will be paralyzed. Compared with AC transmission, the current of DC transmission has no zero crossing. And conventional mechanical switches are not effective. Quickly isolate short circuit faults. Therefore, the DC circuit breaker is needed to solve the DC fault. In this article, ATO automation will introduce something about this.

At present, the DC transmission mainly relies on the AC circuit breaker on the AC side to remove the short circuit fault. First of all, this method cannot remove the fault circuit in a very short time, and the fault current rises rapidly, which brings great pressure to the DC transmission line and converter station, and damages the components. Secondly, this method will make the entire DC transmission network out of operation, resulting in a large area of power outage and other accidents. In order to ensure the reliability of transmission lines, ensure the reliable operation of DC transmission and reduce the pressure on transmission lines, it is very important to research the DC circuit breaker with excellent performance.

There is no DC circuit breaker product with strong breaking ability, fast breaking speed and meeting the requirements of DC transmission, which greatly restricts the development of DC transmission, especially multi-terminal DC transmission. Therefore, all countries in the world increase the research of DC circuit breaker, and strive to develop a good performance of DC circuit breaker. In recent years, with the development of DC transmission technology, the following requirements are put forward for DC circuit breakers:

• The DC circuit breaker must be able to quickly clear faults.
• It can quickly consume the energy stored in the DC line.
• When the DC current is cut off, it can withstand high overvoltage and overcurrent.
• With high breaking ability, can cut off high voltage or current class.
• With repeated breaking ability.
• Low cost, long service life, low maintenance cost, high reliability.