Thunderstorm weather, lightning strikes more. When lightning strikes the lightning arrester or lightning rod, the lightning current through the grounding device, through the earth, because of the existence of grounding resistance of the grounding device, it through the lightning current potential will rise very high, the nearby equipment or personnel may cause counterattack or step voltage, a threat to personal safety. Therefore, lightning arresters or lightning rods should not be near in thunderstorm weather.

The arrester is connected between the cable and the ground, usually in parallel with the device being protected. The lightning arrester can effectively protect communication equipment, once there is an abnormal voltage, the lightning arrester will take action, play a protective role. When communication cables or equipment are in the normal operating voltage operation, the arrester will not have a role in the ground as a circuit breaker. Once there is a high voltage, and endanger the insulation of the protected equipment, the arrester immediately action, the high voltage impulse current directed to the earth, to limit the voltage amplitude, protect the insulation of communication cables and equipment. When the overvoltage disappears, the arrester quickly returns to its original state, so that the communication line works normally.

Therefore, the main role of the arrester is to trim the amplitude of the intrusion flow wave through the parallel discharge gap or the role of nonlinear resistance, to reduce the over-voltage value of the protected equipment, to protect the communication lines, and equipment.

The arrester can be used not only to protect against high voltages generated by lightning but also to protect against high operating voltages.

The role of the lightning arrester is used to protect various electrical equipment in the power system from lightning over the type of voltage, operating overvoltage, power frequency transient overvoltage impact, and damage of an electrical appliance. The type of arrester mainly has a protection gap, valve type arrester, and zinc oxide arrester. The protection gap is mainly used to limit atmospheric overvoltage, generally used in distribution systems, lines, and substations into the line protection. Valve-type arrester and zinc oxide arrester for the protection of substation and power plant, in 500kV and the following system, is mainly used to limit the atmospheric overvoltage, in the ultra-high voltage system will also be used to limit the internal overvoltage or as the internal overvoltage backup protection.

In the normal operation of the voltage transformer, the probability of its internal failure is very small. The high-voltage fuse is often blown because of the resonance of the voltage transformer. When the operation mode of the system changes in some way, the iron core of the voltage transformer is saturated, the inductance and capacitive reactance to the ground are equal or approximately equal, and a relatively large current is generated, causing the fuse to blow. At this time, the voltage transformer must be shut down. Replace the fuse.

What we are now using is a quartz sand-filled porcelain tube fuse equipped with a rain cover.

The fuse is installed in the rain cover and fixed with four screws on both sides. When replacing, you must unscrew the screws on both sides, hold the pliers in one hand to fix the nut, and the other hand to tighten the screw. Due to high-altitude operations, there are few places to focus. Such an operation is time-consuming, laborious, and dangerous. The side cover and screws are made of ordinary wrought iron, which is easy to rust and deform due to long-term sun and rain. After the screw is unscrewed, the fixed iron ring is easy to jam due to uneven force, and it is difficult to remove it. Especially in special weather, the replacement has to be postponed, which reduces the reliability of metering and protection.

To overcome the above shortcomings, we can use the rotating shaft type instead of the screw fixed type,

The fixed shaft adopts screws (pins can also be used), the nut and fixed iron ring are eliminated, and the other end of the screw is directly screwed on the side cover. During operation, only unscrew the screw at one end to open the side cover. Even if the fuse cannot be removed due to the obstruction of the connecting wire, another screw can be unscrewed, so that at most two screws can be unscrewed, and it can be done easily with only one hand.

To overcome corrosion, the main body of the side cover is made of steel, the outside is plated with anti-rust material (nickel-chromium alloy, etc.), and the screws are made of stainless steel.

The improvement has increased the flexibility and reliability of the high-voltage fuse, reduced the cost, and it easier to operate, creating good conditions for ensuring the safe operation of the system.

The ±1100 kV line has 4 base towers with DC arresters installed, 3 bases are located in Gansu, and the other is located in Haiyuan County, Ningxia. The DC arresters installed on the towers are the only set of high-voltage line arresters in Ningxia Power Grid. Since a single lightning arrester weighs 3 tons and the tower is in a cornfield, the cost of using a crane to experiment is relatively high and there are significant safety hazards. For this reason, State Grid Ningxia Electric Power tried for the first time to carry out DC reference voltage and leakage current tests without removing the arrester at high altitudes.

Fuse cutout can be divided into high voltage fuse cutout and low voltage fuse cut out according to the service voltage.  It can be divided into dropout fuse for protecting transformers and general electrical equipment,  for protecting voltage transformers, for protecting power capacitors, for protecting semiconductor components, dropout fuse for protecting motors, and dropout fuse for protecting household appliances, etc. According to the structure can be divided into open type, semi-closed type, pipe type, and jet type fuse cutout

The rated current of the fuse link is not equal to the rated current of the whole fuse cutout. The rated current of the fuse link shall be selected according to the load current of the protected equipment. The rated current of the fuse cutout shall be greater than the rated current of the fuse link.

1. The test items of suspension insulators and post insulators shall include the following:
2. Measure the insulation resistance of the insulator;
3. AC withstand voltage test of insulators.
4. The insulation resistance value of the insulator shall meet the following requirements:
5. The insulation resistance value of suspension insulators used for voltage levels of 330KV and below should not be less than 300MΩ; for suspension insulators used for voltage levels of 500kV, it should not be less than 500MΩ;
6. The insulation resistance value of post insulators with voltage levels of 35kV and below shall not be lower than 500MΩ;
7. Use Dingsheng Power DC2403 2500V insulation resistance tester to measure the insulation resistance value of insulators, which can be spot-checked at 10% of the same batch of products;
8. Rod insulators are not subject to this test;
9. The insulation resistance of the semiconductor glaze insulator meets the requirements of the product technical conditions.
10. The AC withstand voltage test of the insulator shall meet the following requirements:
11. Pillar insulators with voltage levels of 35kV and below can be carried out together after the busbar is installed. The test voltage should meet the requirements of the “Power Frequency Withstand Voltage Test Voltage Standard for High Voltage Electrical Equipment Insulation”;
12. The AC withstand voltage test value of 35kV multi-element post insulators should meet the following requirements:

① For two glued components, each component is 50kV;

② For three glued components, each component is 34kV.

3. The AC withstand a voltage test voltage of suspension insulators are all 60kV.

Composite insulators were developed 45 years ago, largely due to these defects, and were introduced on an industrial scale in the 1980s. When suppliers adjust their products through successive generations of designs based on their initial service experience, there is a learning curve, but the technology is now mature. In fact, in most countries, it is considered equivalent and interchangeable with porcelain and glass. This is an impressive achievement, especially if one thinks that 25 years ago, power engineers knew little about the technology and did not trust composite insulators.

With the increase of operating time of 500 kV substation equipment, the pollution degree of pillar insulators becomes more and more serious. The creepage of the insulators is more and more obvious, and the discharge sound increases on rainy and foggy days. Regular cleaning or emergency cleaning of insulators is an extremely effective anti-pollution flashover measure. In response to the requirements of high equipment reliability, there are fewer opportunities for power outage maintenance. At the same time, with the advancement of state maintenance work, there are fewer opportunities for equipment power outages. The hidden danger of flashover threatens the safe operation of equipment more and more seriously. To solve this contradiction, effectively improve the insulation level of the pillar insulators, clean the surface of the equipment in time, and prevent equipment pollution and flashover accidents, live cleaning has become a necessary means.

The layout of live equipment in the 500 kV substation is compact. The distance between some equipment is small, and there are many types of structures. When carrying out live work on high voltage equipment, safe working regulations must be strictly followed, and a sufficient safety distance can be met to ensure the personal safety of live workers. And safe operation of live equipment. To make live cleaning equipment acceptable to the user department, and to realize the live cleaning operation of high-voltage and ultra-high voltage substation equipment conveniently, safely, and reliably, the following requirements must be met: (1) The live-cleaning equipment must be miniaturized and adopted. Potential and indirect live working methods to ensure that the range of activities of the operators during live work must meet the safety distance requirements; (2) The live cleaning equipment must meet the requirements of the insulation level to ensure the personal safety of live workers and the safe operation of live equipment; ( 3) The equipment must be light, flexible, and easy to assemble to minimize the labor intensity of the operators; (4) The live cleaning equipment must be able to meet the cleaning requirements of equipment with different heights installed in the substation; (5) The cleaning equipment must be easy to operate and easy to maintain Maintenance, few vulnerable parts, long trial life.