Modeling a section of an electrical network with a series compensation device to study the parameters affecting the sensitivity of differential protection

One of the ways to enhance the transmission capacity of power transmission lines is to install series compensation devices (SCD). However, this technical solution has its advantages as well as disadvantages. These include current inversion during a short circuit (SC), voltage inversion during a SC, low-frequency oscillations (for example, after short-circuit clearing due to a change of the mode parameters due to subsynchronous resonance, etc.). All these phenomena impact on relay protection devices. Existing solutions to adapt the algorithms for relay protection operation of series-compensated power transmission lines are mainly aimed at improving the algorithms for distance protection operation. At the same time, the problem of differential protection operation of the line remains unresolved due to the insufficient sensitivity of this protection during a short circuit on the power transmission line in the high compensation mode. Due to the lack of information in public sources on deveoping models that allow quantitatively assessing the effect of the series compensation devices on the sensitivity of differential protection of power transmission lines with series compensation, it is advisable to develop a model of a section of an electric network with a series compensation device to study the parameters that affect the sensitivity of differential protection. Due to the applied nature of the study, the authors have focused on the Ukhta-Mikun 220 kV overhead power transmission line, where the installation of series compensation devices is planned. Due to the lack of published works describing the mathematical model of this transmission line, to solve the set tasks it is decided to develop a computer model in the PSCAD PC program to study the processes on the transmission line with the SCD and develop a relay protection complex. A computer model of the Ukhta-Mikun overhead power line with a voltage of 220 kV has been developed. The parameters influencing the sensitivity of differential protection of power transmission lines with series compensation in transient and steady-state short-circuit modes have been identified. It has been established that one of such parameters is the transition resistance at the point of short circuit. The specific character of the influence of a short circuit on the sensitivity of differential protection have been examined in detail. The developed model has been verified and its adequacy has been proven. The results of the study can be used to address problems of increasing the stability of differential protection on power transmission lines with series compensation devices, as well as to conduct additional research using the developed model.