1) Lightning arrester installation:
①Inspection before installation:
1) Whether the rated voltage of the high-voltage arrester is the same as the line voltage;
2) Check whether there are cracks on the porcelain plate of the chassis, and whether there are cracks, damage, flash marks and glaze loss on the surface of the porcelain parts. If there is any damage, the damaged area should be less than 0.5cm2, and it can continue to be used if it is damaged in no more than three places;
3) Gently shake the arrester in different directions. There should be no loose sound inside;
4) Check whether the gluing and sealing of the connection between the porcelain sleeve and the flange are in good condition.
②Electrical test:
1) Insulation resistance, use a 2500V megohmmeter to measure the insulation resistance, and compare it with the test value of similar lightning arresters. There should be no significant change in the insulation resistance value;
2) Power frequency breakdown voltage test, FS type arrester power frequency discharge voltage standards: rated voltage is 3kV, 6kV, 10kV; newly installed and overhauled arresters are 9~11kV, 16~19kV, 27~30kV; operating arresters are 8~12kV, 15~21kV, 23~33kV;
3) FZ type arresters generally do not need to undergo power frequency discharge tests, but arrester leakage current measurements are required.
③Installation requirements:
1) Metal oxide arresters should be installed vertically, and the inclination should not be greater than 15°. The installation location should be as close as possible to the protection equipment. The electrical distance between the arrester and the 3-10kV equipment is generally no more than 15m. If the live part that is easy to inspect and patrol is less than 3m from the ground, a barrier should be installed;
2) The cross-sectional area of the joints between the arrester's leads, busbars, and conductors shall not be less than the specified value: the cross-sectional area of 3-10kV copper leads shall not be less than 16mm2, and the cross-section of aluminum leads shall not be less than 25mm2. For 35kV and above, the design requirements shall apply. It is also required that the upper and lower leads are firmly connected and must not be loose, and the oxide film and paint on each metal contact surface should be removed;
3) There should be enough space around the arrester. The distance between the live part and adjacent wires or metal structures should not be less than 0.35m, and the distance between the bottom plate and the ground should not be less than 2.5m, so as to prevent surrounding objects from interfering with the potential distribution of the arrester and reducing the gap discharge voltage;
4) The pull-wire insulator string of the high-voltage arrester must be firm, and its spring should be adjusted appropriately to ensure free expansion and contraction. The nut in the spring box must not be loose, and there should be a protective device; the tension of each tensioned insulator string in the same phase should be uniform;
5) The voltage equalizing ring should be installed horizontally and not skewed, and the three-phase center holes should be consistent; all loops (from busbars, lines to grounding leads) should not be circuitous and should be as short and straight as possible;
6) For arresters of 35kV and above, a discharge recorder should be installed on the ground loop, and the discharge recorder should be well sealed and installed in the same position as the arrester to facilitate observation;
7) Arresters composed of non-interchangeable multi-section basic components should be stacked in strict accordance with the factory serial numbers and order to avoid confusion of components of different arresters and reversal of the positions of components of the same arrester;
8) The arrester base should be well insulated from the ground, and the ground down conductor should be reliably connected to the metal shell of the protected equipment and connected to the main grounding device.
(2) Arrester operation:
The lightning arrester should be inspected and inspected at the same time as the power distribution device during operation. After lightning activity, special inspections should be added. The inspection items are as follows:
① Whether the porcelain sleeve is complete;
② Check whether the wires and grounding leads have burn marks or broken strands;
③ Whether the cement joints and paint are intact;
④ Check whether the upper cap lead of the 10kV arrester is tightly sealed and whether there is water intrusion;
⑤ Whether the surface of the porcelain sleeve is seriously contaminated;
⑥ Check whether the indication number of the action recorder changes, determine whether the arrester operates and make a record.
(3) Operation management of arrester:
① The time when the arrester is put into operation should be determined according to the local lightning activity. It is generally put into operation from early March to October every year;
② Before the arrester is put into operation every year, inspection and testing should be carried out. The test items are:
1) Use a 1000 to 2500V megohmmeter to measure the insulation resistance. Compared with the previous test value or the test value of the same model of arrester, the insulation resistance value should not change significantly;
2) Measure the power frequency discharge voltage. For the FS type arrester, when the rated voltage is 3kV, 6kV, and 10kV, the power frequency discharge voltage is 8~12kV, 15~21kV, and 23~33kV respectively;
3) FZ type arresters generally do not undergo power frequency discharge tests, but the leakage current of the arrester should be measured.
(4) Common faults during arrester operation:
①The arrester is damp inside. The phenomenon of moisture inside the arrester is that the insulation resistance is lower than 2500MΩ and the power frequency discharge voltage drops. damp inside
The reasons may be:
1) The fastening nut at the top is loose, causing water leakage or the washer of the bolt used to seal the top of the porcelain sleeve is not welded tightly. After the sealing washer ages and cracks, moisture and moisture seep into the inner cavity along the screw seams;
2) The small hole in the bottom sealing test is not welded firmly or blocked;
3) The porcelain sleeve is cracked, has blisters, and has cracks in the skirt gluing, etc. It is easy for moisture and moisture to enter;
4) After being used for a long time, the rubber gasket ages, becomes brittle and cracks, and loses its sealing effect;
5) The fan-shaped iron sheet used for pressing the bottom is not tightly plugged, causing the bottom plate to become loose, and the bottom sealing rubber gasket is not in the correct position, causing gaps to allow moisture to seep in;
6) The joint between the porcelain sleeve and the flange is uneven or the porcelain sleeve has cracks.
②The arrester explodes during operation:
It is common for explosions to occur during the operation of lightning arresters. The cause of the explosion may be caused by the system or the arrester itself:
1) Due to the occurrence of single-phase grounding in an ungrounded neutral point system, the non-faulty phase-to-ground voltage rises to the line voltage. Even if the voltage endured by the arrester is less than its power frequency discharge voltage, an explosion may occur under the action of a long-lasting overvoltage;
2) Due to ferromagnetic resonance overvoltage in the power system, the arrester is discharged, thereby burning out its internal components and causing an explosion;
3) When the line is struck by lightning, the arrester operates normally. Due to the poor arc-extinguishing performance of the spark gap itself, when the gap cannot withstand the recovery voltage and breaks down, the arc will re-ignite, and the power-frequency freewheeling will reappear, and the re-ignition valve will burn out the resistance, causing the arrester to explode; or due to the unqualified resistance of the arrester valve, although the residual voltage is reduced, the aftercurrent is increased, and the gap cannot extinguish the arc, causing an explosion;
4) An explosion may occur due to looseness or cracks at the joint between the lightning arrester sealing gasket and the cement, resulting in poor sealing.
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