A Method to Evaluate the Safety Margin for the Setting Value of the Line Protection Device with Domestic Chips

Relay protection is the first defensive line of power system, and its reliability is vital to the power system. Therefore, high margin design is commonly used. On the other hand, the adoption of domestic chips in the relay protection may lead to the deterioration in the sampling process under special conditions, thus affecting its safety margin. However, the above characteristic are unknown. To deal with the above problems, this paper proposes an evaluation method to the safety margin of the protection device, and analyzes the influence of the localization of chips on the safety margin. Specifically, Firstly, based on the sensitivity coefficient, the safety margin evaluation indexes on setting value of line protection device with domestic chips are proposed. Secondly, the influence of CT transmission error and ADC sampling accuracy on the safety margin is introduced. Thirdly, combining the above two factors, the safety margin evaluation method to the setting value of protection device with domestic chips is proposed. Finally, the safety margin of the line longitudinal differential protection and the line zero sequence protection with domestic chips are analyzed, and the influence of the braking coefficient is quantitatively analyzed.