The reason of oil level rise includes: The increasing of oil temperature causes the increasing of oil volume. Due to the oil layer of the bubble adhering to the oil layer surface in the oil tank and gradually thickening,  the oil level indicator rise, but the actual oil amount does not increase. Water enters to the oil system .During starting of the unit , the oil temperature is low , the filter resistance is big, so the oil flow rate between the oil return chamber and oil absorption chamber is lowered, causing higher oil level of the oil return bin and even cause oil to spill, but the oil level of oil absorption chamber decreases. It shall be specially noticed that when the two auxiliary pumps are running at the same time, the phenomenon above mentioned is more serious. The exhaust fan is stopped, causing the higher positive pressure of oil tank.（js）