Power supply lightning arrester(SPD) is also known as lightning arrester, surge protector, surge protector. In the information age, computer networks and communication equipment are becoming more and more precise, and the requirements for their working environment are also increasing. Lightning and the instantaneous overvoltage of large electrical equipment will more and more frequently invade indoor electrical and network equipment through lines such as power supplies, antennas, radio signal transmission equipment, etc., causing damage to equipment or components, casualties, and interference or loss of transmitted or stored data, Even causing electronic devices to malfunction or temporarily paralyze, system pauses, data transmission interruptions, and damage to local and even wide area networks. Its harm is shocking, and indirect losses are generally far greater than direct economic losses.
Power lightning arrester is a device that uses modern electronics and other technologies to prevent lightning strikes.
2. Development History
▪ Classified by purpose
▪ According to Elo rating system of lightning protection
5 Function characteristics
6 Selection points
▪ Power distribution system
▪ Important parameters
▪ Installation position
▪ Test report
7 Graded protection
▪ First level protection
▪ Second level protection
▪ Third level protection
▪ Fourth level and above
8 Installation method
▪ SPD General Installation Requirements
▪ Selection of SPD grounding wire diameter
Power lightning arrester is the most commonly used Surge protector, which is mainly used for surge protection of power system. In addition, there are network lightning protection devices, signal lightning protection devices, video lightning protection devices, three-in-one lightning protection devices, and so on.
The most primitive lightning arrester was a claw shaped gap, which appeared in the late 19th century and was used for overhead transmission lines to prevent lightning damage to equipment insulation and power outages, hence the name "lightning arrester". In the 1920s, aluminum lightning arresters, oxide film lightning arresters, and shot type lightning arresters emerged. In the 1930s, tubular lightning arresters emerged. In the 1950s, silicon carbide lightning arresters appeared. In the 1970s, metal oxide lightning arresters appeared again. Modern high-voltage lightning protection devices are not only used to limit overvoltage caused by lightning in power systems, but also to limit overvoltage caused by system operation. Since 1992, the industrial control standard 35mm guide rail plug-in SPD lightning protection module represented by Germany and France has been introduced to China on a large scale. Later, the integrated box type power supply lightning protection combination represented by the United States and Britain also entered China
The power lightning arrester includes power lightning protection module, power lightning protection box, power lightning protection socket, etc.
The difference between the power lightning protection module and the power lightning protection box lies in their different volume sizes. The latter is more powerful and has lightning counters, but the module is easier to install and cheaper than the lightning protection box.
Classified by purpose
(1) Switch type lightning arrester
Its working principle is that it presents high impedance when there is no instantaneous overvoltage, but once it responds to lightning instantaneous overvoltage, its impedance suddenly changes to a low value, allowing lightning current to pass through. The devices used for such devices include discharge gaps, gas discharge tubes, thyristors, etc.
(2) Voltage limiting lightning arrester
Its working principle is that it has high impedance when there is no instantaneous overvoltage, but its impedance will continuously decrease with the increase of surge current and voltage, and its current voltage characteristics are strongly nonlinear. The devices used for such devices are: zinc oxide, Varistor, suppression diode, Avalanche diode and other lightning protectors are mostly voltage limiting.
(3) Shunt or choke type lightning arrester
Shunt type: In parallel with the protected equipment, it presents low impedance for lightning pulses and high impedance for normal operating frequencies.
Choke type: connected in series with the protected equipment, exhibiting high impedance for lightning pulses and low impedance for normal operating frequencies.
The devices used for such devices include choke coils, high pass filters, low pass filters, 1/4 wavelength circuit breakers, etc. .
According to Elo rating system of lightning protection
Level 1 lightning arrester: Generally, the nominal value is above 30KA. There are switch type and voltage limiting type.
Secondary lightning arrester: generally nominal between 15-20KA. All are pressure limiting types.
Level 3 lightning arrester: Generally, the nominal value is between 5-10KA, and they are all voltage limiting types.
Social security electronic lightning arrester is an electrical appliance used to protect various electrical equipment in the power system from damage caused by lightning overvoltage, operating overvoltage, and power frequency transient overvoltage. The main types of lightning protection devices include protective gaps, valve type lightning protection devices, and zinc oxide lightning protection devices. The protection gap is mainly used to limit atmospheric overvoltage, and is generally used for protection of distribution system, line and Electrical substation incoming section. Valve type lightning arrester and zinc oxide lightning arrester are used for the protection of Electrical substation and power plant. They are mainly used to limit atmospheric overvoltage in 500KV and below systems, and also used to limit internal overvoltage or as backup protection for internal overvoltage in ultra-high voltage systems.
Selecting Key Distribution Systems
Firstly, it is important to clarify whether your power distribution system is TT, TN, or IT? Because we have determined the distribution system, we can determine the single-phase, three-phase, wiring method, etc., in order to choose suitable lightning protection products. Most distribution systems in China use TN-S mode.
The main material of social security electronic lightning protection products is zinc oxide Varistor. The quality of its material and the level of its process have a direct impact on whether the product can produce the expected protection effect when struck by lightning. Therefore, you must know the source of the manufacturer's Varistor when selecting lightning protection devices.
Nominal voltage Un: The rated voltage of the protected system matches, and in information technology systems, this parameter indicates the type of protector that should be selected, indicating the effective value of AC or DC voltage.
Maximum continuous working voltage Uc: The maximum voltage effective value that can be applied to the designated end of the protector for a long time without causing changes in the characteristics of the protector or activating the protective element.
Nominal discharge current In: The maximum peak impulse current that the protector can withstand when a standard lightning wave with a waveform of 8/20s is applied to the protector for 10 times.
Maximum discharge current Imax: The maximum peak impulse current that the protector can withstand when a standard lightning wave with a waveform of 8/20s is applied once to the protector.
Voltage protection level Up: The maximum value of the protector in the following tests: 1 kV/s slope of the tripping voltage; Residual voltage of rated discharge current.
According to the principle of three-level lightning protection, the protective measures required for power supply and equipment are divided into three levels. Install the first level lightning arrester in the main distribution cabinet, select a power supply lightning arrester with relatively large current capacity (Imax80KA~160KA depending on the situation), then install the second level power supply lightning arrester (Imax40KA or so) at the distribution box in the subordinate area, and finally install the third level power source lightning arrester (Imax10KA-40KA) at the front end of the equipment.
WPX lightning protection products are welcome to consult and purchase. Lightning protection products should meet the usage requirements specified by the meteorological regulatory agency of the State Council. Lightning protection products should be tested by a testing agency authorized by the competent meteorological agency of the State Council, and can only be put into use after passing the test and meeting relevant requirements. The lightning protection product testing institution authorized by the competent meteorological authority of the State Council shall pass metrological certification and obtain qualification recognition in accordance with relevant national regulations.
The first level lightning arrester can discharge direct lightning current or the huge energy transmitted when the power transmission line is subjected to direct lightning strikes. For places where direct lightning strikes are likely to occur, Class-I lightning protection must be carried out. The second level lightning arrester is a protective device for residual voltage of the previous level lightning arrester and induced lightning strikes in the area. When a large amount of lightning energy is absorbed by the previous level lightning arrester, there is still a considerable amount of energy that will be transmitted to the equipment or the third level lightning arrester, which needs to be further absorbed by the second level lightning arrester. At the same time, the transmission line passing through the first level lightning arrester will also induce lightning Electromagnetic pulse radiation LEMP. When the line is long enough, the energy of induced lightning becomes large enough, and the second level lightning arrester needs to further discharge the lightning energy. The third level lightning arrester is used to protect LEMP and the residual lightning strike energy passing through the second level lightning arrester.
First level protection
The purpose is to prevent surge voltage from directly conducting from LPZ0 zone to LPZ1 zone, limiting surge voltage from tens of thousands to hundreds of thousands of volts to 2500-3000V.
When the power lightning arrester installed at the low-voltage side of the incoming power transformer is used as the first level protection, it shall be a three-phase voltage switch type power lightning arrester, and its lightning current flow shall not be less than 60KA. This level of power lightning arrester should be a large capacity power lightning arrester connected between each phase of the incoming line of the user's power supply system and the ground. Generally, this level of power lightning arrester is required to have a maximum impulse capacity of over 100KA per phase, and the required limiting voltage is less than 1500V, which is called a Class I power lightning arrester. These electromagnetic lightning protectors are designed specifically to withstand high currents caused by lightning and induced lightning strikes, as well as to attract high-energy surges. They can divert a large amount of surge current to the ground. They only provide medium level protection by limiting the voltage (the maximum voltage that appears on the line when the surge current flows through the power supply lightning arrester), because Class I protectors mainly absorb large surge currents, and they alone cannot fully protect sensitive electrical equipment inside the power supply system.
The first level power lightning arrester can prevent 10/350 μ s. A lightning wave of 100KA meets the highest protection standard specified by IEC. Its technical reference is that the lightning current is greater than or equal to 100KA (10/350 μ s) ; The residual voltage value shall not exceed 2.5KV; The response time is less than or equal to 100ns.
Second level protection
The purpose is to further limit the residual surge voltage through the first level lightning arrester to 1500-2000V, and to implement equipotential bonding between LPZ1 and LPZ2.
When the power lightning arrester output from the distribution cabinet line is used as the second level protection, it should be a voltage limiting power lightning arrester with a lightning current capacity of no less than 20KA. It should be installed at the distribution point where important or sensitive electrical equipment is supplied. These power lightning arresters absorb the remaining surge energy passing through the surge arresters at the user's power supply inlet more comprehensively, and have excellent suppression effects on transient overvoltage. The power lightning arrester used here requires a maximum impulse capacity of 45kA or above per phase, and the required limiting voltage should be less than 1200V, which is called a Class II power lightning arrester. The second level protection of the power supply system for general users can meet the requirements for the operation of electrical equipment
The second level power supply lightning arrester adopts a Class C protector for full mode protection of phase to medium, phase to ground, and medium to ground. The main technical parameters are: the lightning current capacity is greater than or equal to 40KA (8/20 μ s) ; The peak residual voltage shall not exceed 1000V; The response time should not exceed 25ns.
Third level protection
The purpose is to ultimately protect the equipment by reducing the residual surge voltage to within 1000V, so that the energy of the surge does not damage the equipment.
The power lightning arrester installed at the incoming end of the AC power supply of electronic information equipment should be a series voltage limiting power lightning arrester as the third level protection, and its lightning current capacity should not be less than 10KA.
The final line of defense can be achieved by using a built-in power lightning arrester in the internal power supply of the electrical equipment to completely eliminate small transient overvoltage. The power lightning arrester used here requires a maximum impulse capacity of 20KA or less per phase, and the required limiting voltage should be less than 1000V. It is necessary to have a third level of protection for some particularly important or sensitive electronic devices, and it can also protect electrical equipment from the transient overvoltage generated within the system.
For the rectifier power supply used by Microwave transmission equipment, mobile station communication equipment and radar equipment, the DC power supply lightning arrester with suitable working voltage should be selected as the final protection according to the protection needs of its working voltage.
Fourth level and above
According to the withstand voltage level of the protected equipment, if two levels of lightning protection can limit the voltage below the withstand voltage level of the equipment, only two levels of protection are needed. If the withstand voltage level of the equipment is low, four or even more levels of protection may be required. The lightning current capacity of the fourth level protection should not be less than 5KA.