چكيده به لاتين
As demand for electricity increases, there is a need to increase transmission capacity over long distances. Implementing increased power generation in the existing power system is a challenge for alternative networks. To overcome this challenge, increasing the connections of load centers using HVDC transmission systems has been proposed as an efficient and economical solution. The most important advantage of HVDC systems is the ability to transmit power over long distances, which is why most HVDC systems are used for high power transmission over long distances and pass through unfavorable areas under adverse weather conditions. Therefore, there is a possibility of many faults on the HVDC transmission line. Therefore, protection of these lines is essential to ensure the security and reliability of the system. Also, since HVDC transmission systems play an important role in coordinating and connecting alternative and asynchronous networks and making full use of energy resources, great care must be taken to protect and clear faults to ensure the security and stability of the power system. The main protection for HVDC transmission lines usually includes travelling wave protection and voltage derivative protection, and backup protection includes under-voltage protection and current differential protection. These protection schemes have problems such as poor reliability and insufficient sensitivity. Therefore, this study presents new protection schemes to solve these problems. Due to the lack of exchange of information between the two sides of the transmission line in single-end protection schemes compared to two-end protection schemes and consequently less equipment and cost and more reliability, in this study, several single-end protection schemes are presented. For this purpose, the transient signal of HVDC transmission lines are studied in the event of a fault, and finally, using the performed analysis, two new protection schemes based on the boundary characteristics of the transmission line are presented to protect HVDC transmission lines. Based on the results of comprehensive simulations, the proposed protection schemes under different types of fault conditions can well distinguish internal faults from external faults and have reliability, sensitivity and high-performance speed and no need for complex calculations, so they can easily be used in real HVDC systems. Also, in order to better and more approve the proposed protection schemes, these schemes have been tested under field data, which in this case also have a good performance.
