Two-stage valve arrangement for hydraulic control of a piston- cylinder arrangement of a high- or medium-voltage power switch

A two-stage valve arrangement for the hydraulic actuation of a piston in a cylinder of a high voltage or medium voltage power switch, the two-stage valve arrangement comprising:

• a main stage with a first main valve configured as a 2/2-way valve and a second main valve configured as a 2/2-way valve, a high pressure line configured to conduct a fluid under high pressure being connected directly to an inlet-side valve connector of the first main valve, and a low pressure line configured to conduct a fluid under low pressure being connected directly to an inlet-side valve connector of the second main valve, an outlet-side valve connector of the first main valve and an outlet-side valve connector of the second main valve being connected hydraulically to one another and to a space situated on one side of the piston, and
• a pilot control stage with at least one pilot control valve having two connectors on the inlet side, one of the two connectors being connected to the high pressure line and the other of the two connectors being connected to the low pressure line, a hydraulic pilot control outlet of the pilot control stage being connected both to a first control face of the first main valve, to act in an opening manner, and to a first control face of the second main valve, to act in a closing manner,
• wherein the pilot control stage is configured to establish a connection between the high pressure line and the hydraulic pilot control outlet in a first position of the at least one pilot control valve, such that the high pressure acts on the first control face of the first main valve and on the first control face of the second main valve to cause an opening of the first main valve and a closing of the second main valve, with the result that fluid under high pressure is fed to the space which is situated on the one side of the piston
• wherein the pilot control stage is configured to establish a connection between the low pressure line and the hydraulic pilot control outlet in a second position of the at least one pilot control valve, such that the low pressure acts on the first control face of the first main valve and on the first control face of the second main valve to cause a closing of the first main valve and an opening of the second main valve, with the result that fluid is discharged in a direction of the low pressure line from the space which is situated on the one side of the piston,
• wherein the first main valve further comprises a second control face configured to act in a closing manner, a third control face configured to act in a closing manner, and a fourth control face configured to act in an opening manner, the second control face of the first main valve being connected to the high pressure line, the third control face of the first main valve being connected to the low pressure line, and the fourth control face of the first main valve being connected to the outlet-side valve connector of the first main valve, and
• wherein a size ratio of the first and fourth control faces of the first main valve with respect to the second and third control faces of the first main valve is configured such that a resulting force which acts in an opening manner remains in force in an open state of the first main valve.