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The last decade has seen an immense growth in renewable energy sources such as solar photovoltaic (PV) plants due to environmental concerns. Due to this rapid growth, solar PV plants are starting to have a larger influence on power system stability and thus their dynamic behavior cannot be ignored in stability studies. The lack of well-established models and parameter sets is the primary reason solar PV plants are not modeled with dynamic characteristics. This paper presents a method to define a standard parameter set for representing large-scale and aggregated solar PV plants in stability studies from the perspective of the transmission system operator (TSO). The method takes into account primarily the conditions provided in the grid connection requirements, for illustrative purposes, the connection requirements of the Netherlands are used. Additionally, a relationship defined as short-circuit current (SCC) PV ratio is proposed to estimate the effect of solar PV plants on transient stability. To illustrate the workings of the proposed ratio, the transmission network of the TenneT TSO B.V. in the Netherlands is used. The analysis demonstrated that high values of SCC PV ratio are an indicator that solar PV plants affect the transient stability while low values of SCC PV ratio showed that solar PV plants have minimal effect on the transient stability. Additionally, methods to improve the transient stability are provided which include limiting the operation regions of critical generators, increasing short-circuit ratio by adding a synchronous condenser or static compensator (STATCOM) and decreasing the reactance between the critical synchronous generator and faulted bus.

This paper investigates the transient stability issues that may occur when long underground cables are added to EHV transmission systems. Dynamic behaviour of generators and terminal voltages with respect to various disturbances like cable disconnection/connection and fault currents are studied. Simulations are performed for the 2020 model of the Dutch transmission grid. The effects of partial undergrounding in two case studies with the total transmission length of 280 km are investigated. This work proposes criteria for accurate sizing of cable shunt compensation for dynamic simulation purposes based on grid voltages, generator reactive powers and power exchange with neighbouring grids. Moreover, a comparison between the dynamic behaviour of system variables for three different shunt compensation arrangements including line-end compensation, line-end middle compensation, and cable-end compensation is performed. Finally, a specific switching sequence for line disconnection/connection to improve voltage profiles and generator behaviours is introduced. The simulations are performed in PSS®E environment.

Energization overvoltages are among the severest overvoltages stressing insulations of EHV power system components. Since these overvoltages have a statistical nature, the insulation level should be determined with the use of a statistical approach by which the distribution of overvoltages is calculated. Literature has properly studied the distribution of energization overvoltages in purely overhead line (OHL) or cable systems, but such a study is not available for hybrid systems consisting of both OHLs and cables. It is expected that the overvoltage distributions change substantially when both OHLs and cables are used in a transmission line. This paper tackles this issue by analyzing the overvoltage distributions due to the energization of a 380 kV hybrid OHL-cable circuit, in which the cable length is variable. The study includes various sensitivity analyses to find out the impact of system parameters and topology on overvoltages. By the statistical analysis, it has been discovered that energization overvoltages of a hybrid OHL–cable circuit are higher than those of a fully-cable circuit and very likely lower than those of a fully-OHL circuit with the same transmission lengths.

Zero-missing is a phenomenon in shunt compensated cable systems in which the current through the line breaker does not cross the zero point for several cycles. This paper deals with a thorough investigation on countermeasures of the zero-missing phenomenon in transmission systems and determines the requirements, benefits, and risks of applying each method. The effectiveness of countermeasures is studied on a simulated cable project with different cable lengths in an actual grid model of the Dutch 380 kV transmission system. Results are analyzed based on three criteria related to the IEC standards and the Dutch grid code. In addition, the switching sequence of circuit-breakers is specified to maximize the effectiveness of the countermeasures. A statistical switching analysis is performed for the insulation coordination study since the application of some countermeasures increases the probability of high transient switching overvoltages. Moreover, the closing variation threshold of circuit-breakers is calculated as a function of the circuit impedance and the shunt compensation degree.

Integration of long EHV XLPE underground cables in traditionally OHL-based transmission systems can result in abnormal transients caused by large cable shunt capacitance. Transients associated with switching of long cables may result in severe temporary or transient overvoltages. This paper investigates energization transients related to the installation of long 380 kV cables in transmission systems. Voltages and currents at multiple locations were analyzed in the time-domain after energization of different cable lengths in a 80 km mixed OHL-cable connection in the future Dutch 380 kV grid. Moreover, zero-missing phenomenon, as one of the likely events during energization transients of shunt compensated cables, and its countermeasures are discussed. The study comprises time-domain simulations in PSCAD/EMTDC environment, where an accurate distributed frequency-dependent parameter model of the complete Dutch 380 kV grid is developed.