A wind turbine comprising - a number of rotor blades; - a hydraulic pitch drive system for aligning a rotor blade into the incoming wind; and - an arrangement to detect an oil leakage between a first section and a second section of a hydraulic cylinder (HC, HC1, HC2) of the hydraulic pitch drive system, - wherein a movable piston of a hydraulic cylinder (HC, HC1, HC2) of the hydraulic pitch drive system interacts via its position with a rotor blade, turning the rotor blade to specific pitch angles, and is arranged between the first section and the second section in a way that the piston changes its position between the sections (S1, S2) in dependency of a difference between a first force, which acts at the first section on a first cross sectional area of the movable piston, and a second force, which acts at the second section on a second cross sectional area of the movable piston, - wherein the first section comprises hydraulic oil with a predefined first pressure, while the first force is the product of the first pressure and the first area, - wherein the second section comprises hydraulic oil with a predefined second pressure, while the second force is the product of the second pressure and the second area, - wherein the first section is connected with a first valve (V1, which is remotely controlled by a control (CONT) of the arrangement, the control (CONT) being prepared and arranged to close the first valve when performing the leakage detection, - wherein a sensor is coupled with the movable piston in a way that any change in its position is detected, while the change of the position results from the difference of forces (F1, F2) resulting from the closed valve and from the alignment of the first pressure to the second pressure due to the leakage, - wherein the sensor is coupled with the control (CONT), which is prepared and arranged to detect the leakage of oil based on the change of the position, and - wherein the control (CONT) is prepared and arranged to turn the blade when performing the oil leakage detection to a chosen pitch angle between 0° and 15° as these blade angles are most relevant for wear and tear of the blade. - a number of rotor blades; - a hydraulic pitch drive system for aligning a rotor blade into the incoming wind; and - an arrangement to detect an oil leakage between a first section and a second section of a hydraulic cylinder (HC, HC1, HC2) of the hydraulic pitch drive system, - wherein a movable piston of a hydraulic cylinder (HC, HC1, HC2) of the hydraulic pitch drive system interacts via its position with a rotor blade, turning the rotor blade to specific pitch angles, and is arranged between the first section and the second section in a way that the piston changes its position between the sections (S1, S2) in dependency of a difference between a first force, which acts at the first section on a first cross sectional area of the movable piston, and a second force, which acts at the second section on a second cross sectional area of the movable piston, - wherein the first section comprises hydraulic oil with a predefined first pressure, while the first force is the product of the first pressure and the first area, - wherein the second section comprises hydraulic oil with a predefined second pressure, while the second force is the product of the second pressure and the second area, - wherein the first section is connected with a first valve (V1, which is remotely controlled by a control (CONT) of the arrangement, the control (CONT) being prepared and arranged to close the first valve when performing the leakage detection, - wherein a sensor is coupled with the movable piston in a way that any change in its position is detected, while the change of the position results from the difference of forces (F1, F2) resulting from the closed valve and from the alignment of the first pressure to the second pressure due to the leakage, - wherein the sensor is coupled with the control (CONT), which is prepared and arranged to detect the leakage of oil based on the change of the position, and - wherein the control (CONT) is prepared and arranged to turn the blade when performing the oil leakage detection to a chosen pitch angle between 0° and 15° as these blade angles are most relevant for wear and tear of the blade.