On November 4, the 500 kV Green Ji line from the Green Valley converter station to the 500 kV Ji Neng substation of Jiangsu Rudong Offshore Wind Power Flexible DC Transmission Project resumed power transmission. So far, the company’s first batch of new power system series relay protection devices jointly developed by State Grid Corporation of China East China Branch, NARI Group Co., Ltd., State Grid Jiangsu Electric Power Co., Ltd. and other units have been put into demonstration application.

In recent years, the proportion of Jiangsu’s new energy power generation installed capacity has continued to grow. As of the end of October, Jiangsu’s new energy power generation installed capacity reached 56.66 million kilowatts, accounting for 33% of the province’s total installed power generation capacity. The widespread integration of new energy into the grid has increased the likelihood of faults with characteristics such as rising harmonic content in the “double-high” power system, resulting in the inability of traditional relay protection devices to accurately identify grid faults and isolate them.

The new power system series relay protection devices put into use this time are composed of transformer protection devices and line protection devices. They can adapt to the “double high” characteristics of the new power system and use adaptive distance protection and fast time domain distance based on transient information. Principles of protection and longitudinal protection based on model identification are not affected by factors such as voltage phase mutations, harmonics, frequency deviations and other factors after power electronic equipment faults. Among them, the line protection device can solve the problem of traditional distance protection malfunctioning or refusing to operate when the power grid fails in new energy grid-connected and flexible DC transmission scenarios, and realize rapid and sensitive identification of power grid faults; the transformer protection device can improve the internal faults of the transformer. The speed and accuracy of identifying minor faults between turns can improve the protection performance of existing transformers.

According to reports, under the guidance of the National Electric Power Dispatch Control Center of State Grid Co., Ltd., more than 10 units including the East China Branch of State Grid, Nari Group, and State Grid Jiangsu Electric Power established a research team to conduct research on the power grid under large-scale integration of new energy sources. Conducted research on fault mechanisms, fault characteristics, relay protection algorithms, etc., and proposed a new relay protection algorithm that does not rely on power supply characteristics.