Operation and maintenance of arrester manufacturers

(1) Lightning arrester application:

The power transmission, transformation and distribution equipment of the power system will be affected by the following voltages during operation:

① Long-term working voltage;

②Temporary overvoltage due to ground fault, resonance and other reasons;

③ Lightning overvoltage;

④Operating overvoltage.

Lightning overvoltage and operating overvoltage may have relatively high values. It is not only economically unreasonable to withstand these two overvoltages simply by increasing the insulation level of the equipment, but it is also often technically impossible. The positive approach is to use electrical appliances that specifically limit over-voltage, limit the over-voltage to a reasonable level, and then select equipment with the corresponding insulation level accordingly. Lightning arrester is one of the most important electrical appliances that limit overvoltage. The protection characteristics of the arrester are the basis of the insulation coordination of the protected equipment. Improving the protection characteristics of the arrester can improve the safety and reliability of the operation of the protected equipment, and can also reduce the insulation level of the equipment, thereby reducing the cost. The higher the voltage level of the equipment, the more significant the economic benefits brought by reducing the insulation level.

The arrester is installed on the protected equipment, and the overvoltage is transmitted from the line to the arrester manufacturer. When the value reaches the arrester operating voltage, the arrester will act to limit the overvoltage to a certain level (called the protection level). After the overvoltage, the arrester immediately restores the cut-off state, and the power system returns to the normal state.

The arrester should meet the following basic requirements:

① It can withstand the continuous operating voltage of the system for a long time, and can withstand the transient overvoltage that may often occur in a short time;

②Under the action of overvoltage, its protection level meets the requirements of insulation level;

③Can withstand the energy generated by the discharge current under the action of overvoltage;

④The normal working condition can be quickly restored after overvoltage.

(2) The normal operating conditions of the arrester:

The normal operating conditions of the arrester are:

①Suitable for indoor and outdoor operation;

②The ambient temperature is +40℃～-40℃;

③Can withstand the radiation of sunlight;

④ The altitude does not exceed its design height;

⑤The frequency of the power supply is not less than 48Hz and not more than 62Hz;

⑥ The long-term power frequency voltage applied to the arrester does not exceed the allowable value of the arrester's continuous operating voltage;

⑦Earthquake intensity of 7 degrees and below;

(3) Lightning arrester classification:

The series of general-purpose arresters in my country and their scope of application are as follows:

General-purpose arrester series and its application range

Serial number                        name                                                        Series code                                          Scope of application

          1               Low pressure valve arrester                                                  FS                             Used in low-voltage networks to protect low-voltage windings of AC appliances, electric energy meters and distribution transformers

          2               Ordinary valve arrester for power distribution             Used for 3～10kV AC power distribution system, protection transformer and other electrical equipment

          3                Ordinary valve arrester for power station                            FZ                             Used for 3～110kV AC system, protection transformer and other electrical equipment

          4               Magnetic blow valve type arrester for power station           FCZ                           Used in 35kV and above AC systems, to protect electrical equipment such as transformers, especially suitable for occasions where the insulation level is low or the operating overvoltage needs to be limited

          5               Magnetic blow valve type arrester for protecting rotating electric machine                   FCD                      Used to protect alternators and motors

          6               Gap-free metal oxide arrester                                                YW                              Including the entire range of applications from serial number 1 to serial number 5

          7               Metal oxide surge arrester with series gap                             YC                               Used in 3～10kV AC systems to protect distribution transformers, cable heads and other electrical equipment. Compared with YW, each has its own characteristics.

          8               Oxide surge arrester with parallel gap                                    YB                               Used to protect rotating electrical machines and occasions requiring particularly good protection performance

          9               DC metal oxide arrester                                                           YL                                         Used to protect DC electrical equipment

2. Lightning arrester installation and operation maintenance

(1) Lightning arrester installation:

① Inspection before installation:

1) Whether the rated voltage of the arrester is the same as the line voltage;

2) Whether there are cracks in the porcelain plate of the chassis, whether there are cracks, breakages, flashover marks and glaze loss on the surface of the porcelain parts. If there is damage, the damaged surface should be less than 0.5cm2, and it can continue to be used when there are no more than three places;

3) Slightly shake the arrester in different directions, and there should be no loose sound inside;

4) Check whether the bonding and sealing of the porcelain sleeve and the flange connection are in good condition.

②Electrical test:

1) Insulation resistance, measure the insulation resistance with a 2500V megohmmeter, compare it with the test value of similar 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 standard: when the rated voltage is 3kV, 6kV, 10kV; newly installed and overhauled arresters are 9～11kV, 16～19kV, 27～30kV; in operation The lightning arrester is 8～12kV, 15～21kV, 23～33kV;

3) FZ type arresters generally do not need to do power frequency discharge test, but the arrester leakage current measurement should be done.

③Installation requirements:

1) The arrester 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 not more than 15m. If the live part that is easy to inspect and patrol is less than 3m from the ground, a fence should be set up;

2) The cross-sectional area of the joint of the lead wire of the arrester and the bus bar and the wire shall not be less than the specified value: the cross-sectional area of the copper lead of 3-10kV is not less than 16mm2, and the cross-sectional area of the aluminum lead is not less than 25mm2. 35kV and above are in accordance with the design requirements. And it is required that the upper and lower leads are connected firmly and not loose, and the oxide film and paint should be removed from the metal contact surface;

3) There should be enough space around the arrester, the distance between the live part and the adjacent phase wire or metal frame should not be less than 0.35m, and the bottom plate should not be less than 2.5m to the ground, so as to prevent the 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 properly adjusted to ensure free expansion and contraction. The nut in the spring box must not be loosened and there should be a protective device; the tension of the insulator string of the same phase should be uniform;

5) The equalizing ring should be installed horizontally without skewing, and the three-phase center holes should be consistent; all loops (from the bus bar, the line to the grounding lead) should not be circuitous, and should be as short and straight as possible;

6) For the lightning arrester of 35kV and above, the ground loop should be equipped with a discharge recorder, and the discharge recorder should be well sealed, and the installation position should be consistent with the arrester for easy observation;

7) For arresters composed of non-interchangeable multi-section basic components, they should be stacked in strict accordance with the factory number and order to avoid confusion between the components of different arresters and the position of the components of the same arrester to be reversed and disordered;

8) The base of the arrester should be well insulated to the ground, and the ground down conductor should be reliably connected to the metal shell of the protected equipment and connected to the general grounding device.

(2) Lightning arrester operation:

The lightning arrester should be inspected at the same time as the power distribution device during operation, and special inspections should be added after lightning activities. The inspection items are as follows:

①Whether the porcelain sleeve is complete;

②Whether there are burn marks and broken strands on the wires and ground leads;

③Whether the cement joints and painted paint are in good condition;

④Whether the sealing at the lead wire of the upper cap of the 10kV arrester is tight, and whether there is water ingress;

⑤ Whether the surface of the porcelain sleeve is seriously dirty;

⑥ Whether the indicator of the action recorder has changed, judge whether the arrester is operating and make a record.

(3) Operation management of arrester:

①The time when the arrester is put into operation should be determined according to the local lightning activity, and it is generally put into operation from early March to October each year;

② Before the arrester is put into operation every year, inspection and test should be carried out. The test items are:

1) Measure the insulation resistance with a 1000～2500V megohmmeter, and compare the measurement result with the previous test value or the same type of lightning 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, 23-33kV, respectively;

3) FZ type arresters generally do not do power frequency discharge test, but should be done to measure the leakage current of the arrester.

(4) Common faults in the operation of arresters:

① Moisture inside the arrester. The sign of damp inside the arrester is that the insulation resistance is lower than 2500MΩ, and the power frequency discharge voltage drops. The reasons for internal moisture may be:

1) The fastening nut on the top is loose, causing water leakage or the gasket of the sealing bolt on the top of the porcelain sleeve is not welded. After the sealing gasket is aging and cracked, moisture and moisture penetrate into the inner cavity along the screw seam;

2) The small hole in the bottom sealing test is not welded firmly or blocked;

3) If the porcelain sleeve is broken, there are blisters, and there are cracks in the glued part of the skirt, etc., it is easy to enter the moisture and water;

4) The rubber gasket is used for a long time, it becomes brittle and cracks after aging, and loses its sealing effect;

5) The fan-shaped iron sheet used for bottom pressing is not plugged tightly, which makes the bottom plate loose, and the position of the bottom sealing rubber gasket is not correct, causing a gap and infiltration of moisture;

6) The junction between the porcelain sleeve and the flange is uneven or the porcelain sleeve is cracked.

②The arrester explodes during operation:

Explosion accidents occur frequently during the operation of the arrester. The cause of the explosion may be caused by the system or the arrester itself:

1) Since single-phase grounding occurs in the neutral point ungrounded system, the non-faulty phase-to-ground voltage rises to the line voltage, even if the voltage that the arrester bears is less than its power frequency discharge voltage, and the effect of a longer duration of overvoltage Down, it may cause an explosion;

2) Due to the ferromagnetic resonance overvoltage in the power system, the arrester is discharged, which burns out its internal components and causes an explosion;

3) When the line is struck by lightning, the arrester operates normally. Due to the poor performance of the arc extinguishing of the spark gap itself, when the gap cannot withstand the recovery voltage and breaks down, the arc will reignite, the power frequency freewheeling will appear again, and the reignition valve will burn out the resistance, causing the arrester to explode; or because of the arrester valve. The sheet resistance is unqualified. Although the residual voltage is reduced, the freewheeling flow increases, and the gap cannot be extinguished, causing an explosion;

4) The joint between the arrester sealing gasket and the cement is loose or cracked, and the seal is not good enough to cause an explosion.

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