Substation switchgear requires regular cleaning in accordance with its design, type of insulation, the degree of pollution of the atmosphere or ambient air etc. The frequency of cleaning depends upon the type of layout of the apparatus and insulators. However, cleaning must be done during each preventive maintenance. In the daily operation of the substation it is the duty of the attendant to inspect the equipment externally and remedy any abnormality that does not require disconnection of the apparatus. During this inspection, a watch is required to be kept for deposits of dust and dirt on the insulators heating of a contact, joint of some part, low oil level and oil leakage etc. A check should also be made that the locks and doors of the switch house are in good condition, no leaks have developed in the roof, the ventilating and heating systems are operating normally, the prescribed safety aids are in place and in good order, the earthing connection remain unbroken, the packing of the cables entering or leaving a cable trench or tunnel within the premises are intact, the ventilating louvers are not damaged, the access roads leading to the oil filled apparatus are unobstructed and will allow the approach of the fire engines in the event of an oil fire during an emergency.