Preventive testing of electrical equipment regulations for most high-voltage equipment requirements test cycle are cycle 1 - 3 years if necessary. Requirements for the test cycle of the lightning arrester: every year before the rainy season. Transformer requires annual oil sample test. "Cycle 1 - 3 years" is well understood. "When necessary" I understand that you think there may be a problem when you can test the maintenance interval and maintenance out of service time to determine the repair cycle: generally in the operation of 1 year and every 3 years after the overhaul interval. Overhaul should be carried out when abnormalities are found during operation or after being subjected to short-circuit current. Whenever the circuit breaker opens and closes incorrectly, it should be checked once. The switchgear shall be inspected once when an accident occurs during operation or operation. For each inspection, repair, observation, measurement, etc., a record should be made by date. This not only provides valuable historical information, but also reflects whether or not the inspection steps developed need to be adjusted. Observe and repair all parts of the switchgear and circuit breakers. Special attention should be paid to the accumulation of dust, loose parts, and discoloration of insulation in the switchgear. Preparatory work before overhaul Defects and abnormal (accident) conditions found in operation, the number of times and conditions of bearing short circuits; checking the overhaul records and determining the key items of switch overhaul Checking the summary report of the last overhaul and the technical files; checking the test records and understanding the operation conditions; conducting tests before overhaul and determining the organization and division of labor of additional overhaul items personnel; construction projects and schedules; the construction plan of special projects; ensuring the Construction safety, quality of technical measures and on-site fire prevention measures; the main construction tools, equipment list, the main materials list; draw the necessary construction drawings. When checking the appearance of the vacuum circuit breaker under the running state, it is necessary to prevent accidentally entering the high-voltage hazardous area, and when it is necessary to touch the vacuum circuit breaker directly by hand to carry out overhaul, the vacuum circuit breaker must be in the state of "off", and at the same time, it is necessary to disconnect the main circuit of the vacuum circuit breaker and the control circuit, and pull the switch of the main circuit outside the cabinet before starting the overhaul. Start maintenance.