Lightning protection measures for secondary equipment of power system substation

First of all, this paper puts forward that it is of great importance that the substation strengthens the lightning protection settings of the secondary equipment, and briefly analyzes the hazards of lightning accidents on the substation equipment. Then, a more detailed argumentation was made on the aspects of the interference path of thunder and lightning to power system substations. Next, some opinions on lightning protection measures for the secondary equipment of substations were proposed, including lightning protection of the power system and lightning protection of the communication interface.

Overvoltage hazard CLC number: TM863 Document code: A Article ID: 1671-7597 (2014) 21-0123-01

With the rapid development of the power industry, the power system has also begun to improve, and its degree of automation is getting higher and higher. This has greatly improved the accuracy of components such as automation systems, network equipment, and communications equipment, but at the same time it has reduced its ability to withstand lightning currents and voltages. What is more noteworthy is that the secondary equipment's line or communication line, grounding line, etc. are often the natural way of forming a lightning strike, increasing the incidence of lightning strikes. In order to improve the safety and reliability of substation secondary equipment, effective lightning protection measures must be taken.

1. Hazard Analysis of Lightning Accident on Substation Equipment

Unlike other electronic devices, substation electronics have the special property of electronic pulses. This property determines that the substation electronic equipment has serious problems in the face of instant overvoltage attacks. When a lightning strikes an overvoltage, the ongoing data transmission or storage of the equipment may be interfered with by different degrees, even leading to serious consequences of data destruction and signal loss.

[1] In this extreme situation, it will cause misoperation of electronic equipment and cause temporary paralysis. Frequent occurrence of this type of phenomenon has extremely adverse effects on the service life of electronic equipment. In severe cases, components can be burned out, which ultimately damages people's normal production and living order.

2. Lightning interference to power system substations

In the thunder and lightning weather, there is a dangerous phenomenon that thunderclouds release high-voltage electricity, and the high voltage level often exceeds the insulation withstand voltage of the electronic equipment. This is because the current insulation withstand voltage has not yet reached and does not need to reach this level of voltage, because At the time of a lightning strike, the voltage is reduced after it has been conducted. After proving it with a large number of experiments, it was found that the lightning strikes can cause serious injuries, mainly due to lightning currents caused by lightning invasions. There are two types of hazard events that are closely related to this. One type is direct lightning strikes, that is, direct effects of lightning and buildings. The result is thermal effects and power; the other is indirect lightning strikes. The hazards are caused by the secondary effects of lightning, that is, lightning currents produce electromagnetic field effects. Because the substation belongs to a special environment, its working equipment is mainly composed of cables. If cables, thunderclouds, and land form a large electric field, the conductors in the electric field will be induced to generate charges that are opposite to those of thunderclouds.

[2] When the lightning disappears, the electric field disappears. However, the charge generated by the conductor still exists. This creates an electrostatic induction voltage.

3. Analysis of lightning protection measures for secondary equipment in substations

The secondary equipment of the substation includes continuous protection devices, automation equipment, communication equipment, electrical operation equipment, etc. High-intensity electromagnetic interference exists in the working environment. For the sake of safe operation of electronic equipment, it is not possible to carry out simple grounding alone, because doing so will make the lightning resistance and overvoltage resistance of the equipment very low. From practical experience, we can find that the secondary equipment damage in the substation is mainly concentrated on the communication interface, the power interface board of the microcomputer protection device, and the computer power interface. Therefore, it can be concluded that the induced lightning overvoltages such as the induced lightning of the transmission line and the induced lightning of the signal line together constitute the main incentive for the secondary device to cause a lightning strike.

1) Lightning protection of the power system. Generally speaking, the secondary equipment of the substation adopts AC and DC power supply as the power supply equipment. There is a large-capacity filter capacitor in the rectifying device, which can play a role in preventing an instantaneous over-voltage attack. The transformer substation transformer low-voltage side to the substation power supply screen is shielded cable, so the performance of grounding equipment is relatively stable. In the design of the grounding device, the working and protective grounding share the same device with other electrical equipment, and they are all located in indirect minefields. This creates a situation in which a substation encounters a lightning strike. Under the action of a powerful electromagnetic pulse, the coupling of the line and the rise of the ground potential will cause the counterattack overvoltage to exist. It can be seen that it is necessary to provide strong overvoltage protection for the automatic power supply circuit of the equipment. The first is the protection of the power system. The core of the control is the suppression of lightning and the surges and overvoltages that appear on the power supply circuit. The following measures can be taken to protect the power system: First, multi-level drainage protection is used. This is a high

In the case of an electronic switch, the switch will automatically turn off when a lightning strike occurs. Use the ground wire of this device to pull the current down. When using, different levels of electronic switches should be used in combination to gradually reduce the lightning voltage to achieve the protection of secondary equipment.

[3] Secondly, realize equipotential bonding. This method is now widely known. Again, shielding means. The cables used in secondary equipment and secondary equipment are produced in shielded mode, which can effectively fight high-frequency electromagnetic interference.

2) Lightning protection of communication interface. Compared with the power supply system, the communication interface has a higher voltage sensitivity to lightning strikes, and the device's insulation resistance is also relatively low. Data lines, signal lines, and telemetry and control lines are all connected to these devices. Most of these lines are located in the LPZOB area, and some of them are located in the direct lightning zone, making the line more sensitive to voltage.

[4] When the electromagnetic field intensity is too large, data loss is most likely to occur. Therefore, overvoltage protection must be applied to the interfaces of important circuits. The structure of remote control and monitoring device for substation microcomputers is decentralized and is composed of different modules. Each module uses the electronic pulse effect for data collection. This collection mode responds very violently to high frequency electromagnetic interference. To solve this problem, shielding is the most effective way to combat high-frequency electromagnetic interference. The connection between the modules of each unit should be shielded. Since these interfaces and lines are generally arranged in an outdoor environment, the relative distance of the interface circuit is short, so that the voltage can be controlled within a certain intensity. However, once the secondary device and other automation devices sense excessive voltage, they will return the voltage to the communication interface, causing the communication interface to be damaged. Therefore, the necessary lightning protection equipment must be installed on the communication interface. The substations are now generally implemented

Dynamic and intelligent, so no one is on duty, its data collection is done by digital networks or light. The distance between the carrier transmission and the computer is longer. After the lightning strike, the line in the LPXOB area can quickly respond to the lightning strike.

[5] This shows that in order to ensure that the communication interface is free from the danger of lightning strikes, lightning arresters need to be installed at the interface between the computer terminal and the communication line.

4 Conclusion

This article analyzes the hidden dangers of substation secondary equipment in lightning accidents, and points out the importance of strengthening overvoltage protection of secondary equipment. The article discusses the hazards of lightning accidents to substation equipment and the way of lightning interference to power system substations, and makes serious judgments on the specific situation of lightning strikes. For lightning protection of secondary equipment in substations, corresponding solutions are proposed.

Substation secondary equipment lightning protection specific products:

Mainly related to the protection of power, signal equipment: for example

1 Substation main line AC screen or low-voltage distribution screen power supply level one lightning protection (380V line-in): Guoan GASPD-50B/4

2 After AC screen, AC bus output power level 2 lightning protection (380V incoming line): Guoan GASPD-80B/4

3 comprehensive self-screen AC power three-level lightning protection (220V AC incoming line): Guoan GASPD-40C/2

4 Install four-level lightning overvoltage protection at the power front: Guoan GA-D6

5 High Frequency Communication Power Screen 220V DC Protection: Guoan GA-220DC

6 Substation RS232 data lightning protection: GA-RS232/25

7 PCM Communication Device Fast Network Port Protection: Guoan GA100M-RJ45

8 RJ11 port protection for optical transceiver and telephone connection: Guoan GA-RJ11/TELE2

9 Lightning protection of substation video surveillance equipment: Guoan GABNC-220/3

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