1. Inspection, inspection and acceptance of zinc oxide arresters
1. Inspection and inspection of zinc oxide arrester
(1) There are no loose strands, broken strands, over-tightening or over-loosening of the down conductor of the arrester. (There is no discoloration or bending deformation in the arrester lead).
(2) The arrester joints are not loose, heated or discolored, and the voltage equalizing ring is not skewed.
(3) There is no abnormal sound when the arrester operates.
(4) The arrester base is well fixed and the fixing screws are not corroded.
(5) The porcelain sleeve of the arrester has no cracks, traces of discharge, no damage, and a clean appearance (for synthetic arresters, check that the synthetic insulation sleeve has no cracks or damage).
(6) There is no bird's nest in the discharge nozzle of the arrester.
(7) The arrester action counter is intact, there is no moisture inside, and the reading is correct.
(8) The small bushing on the arrester leakage current meter is clean and the screws are tightened. The leakage current reading is within the normal range and there is no moisture inside.
(9) The ground connection of the arrester base is good, and there is no breakage or corrosion in the ground lead (wire) row.
2. Acceptance of zinc oxide arresters
(1) There is no damage, broken strands, or loose strands in the lead wire, and there is no slack that is too tight or too loose. The connectors are firmly connected and the contact surfaces of the connectors should be coated with electrical grease.
(2) The arrester must not be inverted or tilted, the porcelain sheath shed should be facing downwards, and the inclination of the center line of the arrester relative to the vertical line must not be greater than 1.5% of the total height of the arrester. The pressure equalizing ring is horizontal and not skewed, and is installed firmly and in the correct direction.
(3) The arrester is installed firmly (check that the bottom bolts are tightened) and is well sealed. The porcelain part of the arrester should be intact, without cracks or damage, and the insulator should be clean.
(4) For arresters with 2 (or more) components connected in series, check whether the arrester is installed correctly according to the position specified on the signboard.
(5) Check that the explosion-proof disc of the pressure relief nozzle of the arrester is complete and that the nozzle is oriented correctly (in compliance with the requirements that once the arrester is exhausted during operation, it shall not cause flashover between phases or to the ground, and shall not spray onto other electrical equipment).
(6) Check that the four grooved gaskets of the arrester base close to the basic steel frame are in the correct direction (the water grooves are facing downwards). The grooves must not be blocked by dust, and the grooved gaskets must not be installed above the insulating base.
(7) The action counter is well sealed and there is no moisture ingress. It should be installed correctly, the counter indication is at zero, and the insulation pad and grounding are good.
(8) The online leakage current monitoring meter of the arrester is well sealed and there is no moisture ingress. The installation should be good and the reading should indicate zero.
(9) The paint is complete and the color is correct.
Zinc oxide arrester
2. Operation precautions
1. The online leakage current meter reading of the arrester should be recorded once a week. The action counter reading should be recorded promptly after each lightning strike and arrester repair and test. The action counter reading should also be recorded after the system overvoltage protection is activated.
2. When the counter operates, the cause should be identified; if the online leakage current meter reading changes by 5% compared with the original value, the cause should be analyzed and monitoring should be strengthened.
3. It is strictly forbidden to approach lightning protection equipment (lightning arresters and lightning rods) during thunderstorms to prevent step voltage from causing harm to people.
4. The connection and corrosion of the lightning rod should be checked once a year, and the grounding resistance of the grounding grid should be measured once a year.
3. Analysis of abnormal conditions of lightning arresters and accident handling
1. In case of the following situations, the arrester should be deactivated as soon as possible for processing
(1) When the upper and lower leads of the arrester are loose or broken. Because when the system is over-voltage, loose or broken leads will render the arrester ineffective. Therefore, the leads should be carefully inspected before the thunder season every year. Once the lead is found to be loose or broken during operation, it should be dealt with immediately.
(2) After lightning discharge of the arrester, if the connecting leads are seriously burned or blown, inspection and treatment should be arranged immediately.
(3) The arrester is poorly grounded and the resistance is too high. The arrester should be disabled and dealt with as soon as possible.
(4) There is discharge sound inside the arrester. A lightning arrester that normally operates at power frequency voltage exhibits a high resistance value and only a small leakage current flows through it, so there should not be any sound. If there is abnormal sound inside the arrester, it can be considered that the arrester and the valve gap are damaged and lose the function of preventing overvoltage, and may cause a single-phase ground fault. If this phenomenon is found in the arrester during operation, it should be reported to dispatch and the abnormal arrester should be promptly deactivated and replaced.
(5) After a lightning strike or arrester operation, if the arrester insulator is damaged or explodes, the faulty arrester should be removed from the system immediately and replaced.
(6) If the arrester fails and there is no grounding phenomenon, you should immediately apply to dispatch for a power outage and replacement.
2. The online leakage current meter reflects the current passing through the outer insulation of the porcelain sleeve and the arrester valve plate and the current passing through the arrester valve plate.
(1) The online leakage current meter reading of the arrester increases abnormally
When the online leakage current meter reading of the arrester increases abnormally during operation, climate, environmental and historical data should be analyzed comprehensively. If the weather is humid, the porcelain sleeve is dirty, etc., the leakage ammeter reading will increase. After the weather becomes clear, the leakage ammeter reading will return to the normal value. For outdoor arresters, if the leakage ammeter readings of all arresters are found to generally increase, it may be caused by the relatively dirty environment of the substation and the weather is humid. For indoor arresters, if the leakage ammeter readings of all arresters are found to be generally increased, it may be caused by condensation on the outer porcelain sleeve of the arrester.
If it is found that the online leakage current meter reading of the arrester during operation is greater than the normal value, the monitoring should be strengthened (observation with a telescope can be used). If there is a gradual increase trend, the internal moisture of the arrester is more likely; the valve plate may also be aging. If the leakage current meter reading exceeds 10% of the original value when put into operation, it should be reported as an urgent defect.
Moisture inside the arrester is mainly caused by poor sealing. Sources of moisture include:
① During the production process of the arrester, the humidity of the installation environment exceeded the standard;
②The valve plate and internal parts are not completely dried, and some moisture is retained;
③ During assembly, the sealing ring is leaked or misaligned. Or there is debris between the sealing ring and the sealing cover of the porcelain sleeve.
④After running for a period of time, the sealing parts are damaged and moisture enters.
Environmental humidity and heat are the main reasons for causing and accelerating the aging of arresters. For high-voltage zinc oxide arresters, they are greatly affected by environmental conditions. Under the dual effects of moisture and high temperature, the potential distribution of the arrester is extremely uneven. Near the upper flange, the temperature is very high and the current is also large, indicating that the charge rate here is high and may reach the tolerance limit of the valve plate, thereby accelerating the aging of the local valve plate and causing changes in the volt-ampere characteristic curve of the entire arrester.
(2) The online leakage current meter reading of the arrester is reduced or even zero
This situation mainly occurs during rain or within a few days after rain. It is mainly because the four insulating pipes with slotted gaskets at the base of the arrester are blocked or the insulation is poor, causing the leakage current to flow directly into the ground through the bracket without passing through the leakage ammeter. Generally, after the weather clears, the leakage current meter reading will return to the normal value. If the leakage current meter reading does not return, the meter may be crushed or damaged and should be reported to the competent authority for replacement.
