Abstract: Disclosure is made of a rectifier-inverter system of a converter substation intended for the transmission of energy between a.c. networks having different frequencies, which system comprises one or more pairs of rectifier and inverter converters connected to a common d.c. circuit.According to the invention, the poles of at least one rectifier or inverted converter are connected to a protective grounding via resistor-capacitor elements.The absence of direct contact with the ground in the d.c. circuit rules out the possibility of a low-resistance closed circuit being formed as a result of a short-circuit earthing at any point of the d.c. circuit. This reduces the voltage across the insulation with respect to the ground at each pole of all the converters and diminishes the steady voltage component across the insulation with respect to the ground of transformer valve windings.

Abstract: A method for regulating the work current of half circuits of a bipolar d.c. transmission line comprising a plurality of interconnected electric valve bridges in the half circuits with the aid of current regulators acting upon control electrodes of the electric valves in combination with changing the number of bridges connected to the half circuits, whereby a preselected transmitted power magnitude is ensured by putting into operation an optimum number of bridges and by the optimum setting of the current regulators, the number of the operating bridges and the work current magnitude in each half circuit being determined by minimizing the sum of the transmission power loss components which depend upon the number of operating bridges, the work current magnitude, and the operating voltage in the half circuits.