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Three-phase thyristor switches are designed for pulsed formation of inrush currents of electrical equipment with their subsequent shunting in steady state operation. In transformer substations, they perform a bumpless turning on of a power transformer by connecting its primary winding first to two phases of the network at the moment of zero crossing by the phase voltage of the network third phase, and then to the network third phase at the moment of zero crossing by the line voltage of the other two network phases. In this case, the starting currents of the transformer almost immediately enter the steady state without the appearance of constant components in the magnetization currents and voltage drop. To expand the functionality of thyristor switches, it is proposed, in addition to bumpless turning on of a power transformer, to disconnect it without arcing between the contacts of electrical equipment, as well as to carry out continuous voltage regulation for consumers when voltage in the network changes. The proposed method and structure for its implementation on the basis of two three-phase thyristor reactor keys and a capacitor bank make it possible while changing the network voltage to stabilize the generated reactive power at the input of the substation without creating the current distortions in the power transformer and power transmission simultaneously with stabilizing the substation output voltage. Modeling and research of the start-regulating device as part of a transformer substation was carried out in the MatLab environment. The results of numerical experiments in stationary and dynamic modes of the substation operation showed the feasibility of using the developed technical solutions for the industrial power supply system.

Pakistan is facing a severe energy crisis of its time with significant generation deficit in recent years. The future plan shows hydro and thermal coal generation as major contributor and Wind power to replace Thermal-oil generation in long run. This paper proposes a Super grid model for the transfer of bulk power from generation station to the load centres, which can provide efficient transmission between generation and load centres and is also adaptive to deal with variations in power from renewable generations. A dynamic simulation analysis is performed on six-terminal MTDC (Multi-Terminal High Voltage Direct Current) system VSC (Voltage Source Converter) based MTDC meshed grid with different control operations. The results show that the proposed super grid model can provide efficient transmission between generation and load centres and it is also adaptive to deal with variation in power from renewable generation.