Hierarchical protection of surge protectors
Because the kinetic energy of a lightning strike is extremely large, the way of discharging must be classified according to the level, and the kinetic energy of the lightning strike is gradually released to the ground. The first-level surge protector can release the current from the immediate lightning strike, or the great kinetic energy transmitted when the switching power supply transmission route is immediately hit by lightning. It is targeted at areas where there will be an immediate lightning strike. Be sure to carry out CLASS-I lightning protection. The second-level surge protector is a safety protection device for the residual operating voltage of the front surge protector and its residential area magnetic induction due to lightning strikes. When the kinetic energy in the front is greatly digested and absorbed by the lightning strike, there is still some damage to the machinery or equipment. In terms of the third-level surge protector, very great kinetic energy will be transmitted back, and the second-level surge protector must be further digested and absorbed. In addition, the transmission path of the first-level lightning arrester will also magnetically induce the LEMP electromagnetic pulse radiation source. When the route is long enough, the kinetic energy of the magnetic induction lightning will become more and more sufficient, and the second-level lightning arrester must further deal with the kinetic energy of the lightning strike. Perform a bleed. The third-level lightning arrester is to maintain the LEMP and the lightning strike kinetic energy according to the residual of the second-level lightning arrester.
1.First level maintenance
The purpose is to prevent the surge voltage from being immediately transmitted from the LPZ0 area to the LPZ1 area, and limit the surge voltage of hundreds of thousands to hundreds of thousands of volts to 2500-3000V.
The switch surge protector installed on the bottom pressure side of the household distribution transformer should be a three-phase voltage power switch-type switch surge protector for the first-level maintenance, and the total lightning strike flow rate must not be less than 60KA. This level switch surge protector should be a large space switch surge protector connected between the three phases and five wires of the customer's power supply and distribution system channel and the ground. Generally speaking, this level of switch surge protector has a large impact volume of about 100KA per phase, and the specified limited operating voltage is less than 1500V, which is called CLASS I level switch surge protector. This electromagnetic induction lightning arrester is designed to bear the large current of lightning strikes and magnetic induction lightning strikes and attract high-efficiency energy surges, which can separate a lot of surge currents to the ground. They only show the limited working voltage (the larger working voltage appearing on the route when the inrush current passes through the switch surge protector is called the limited working voltage) as medium-level other maintenance. Large surge currents carry out digestion and absorption, and they cannot rely on them to thoroughly maintain the relatively sensitive power-consuming machinery and equipment inside the power supply and distribution system.
The first level switch surge protector can prevent lightning waves of 10 / 350μs and 100KA, exceeding the maximum safety protection specifications required by IEC. Its technical references are: the total lightning strike flow is more than or equal to 100KA (10 / 350μs); the residual voltage is not more than 2.5KV; the response speed is less than or equal to 100ns.
2.Second level security protection
The purpose is to further limit the value of the residual surge voltage of the first-level lightning arrester to 1500-2000V, and perform equipotential bonding on LPZ1-LPZ2.
The switch surge protector that distributes the output of the electrical box route as the second-level maintenance should be a voltage-limiting plate switch surge protector with a lightning strike volume of not less than 20KA. It should be installed to the critical or more sensitive power consumption. Branch power distribution equipment of the power supply system of machinery and equipment. This switching surge protector is based on the surge energy of the household appliances, which is based on the surge energy left by the power supply system. It has a better digestion and absorption effect, and has a good suppression effect against transient overvoltage. The large surge capacity specified for the switch surge protector applied here is about 45kA per phase, and the specified limited operating voltage should be less than 1200V, which is called a CLASS II switch surge protector. The general customer's power supply and distribution system guarantees that the second-level maintenance can exceed the requirements for the operation of power-consuming equipment and equipment.
The second-level switch surge protector uses a C-type protection device to perform phase-neutral, phase-earth, and middle-earth full-mode maintenance. The key performance parameters are: lightning strike current carrying capacity exceeds or is equivalent to 40KA (8 / 20μs); The residual voltage valley value does not exceed 1000V; the response speed does not exceed 25ns.
Third level maintenance
The goal is to finally maintain the machinery and equipment, reduce the value of the residual surge voltage to less than 1000V, and make the kinetic energy of the surge destroy the machinery and equipment.
The switch surge protector installed on the three-phase five-wire end of the AC power supply of electronic information technology equipment should be a series voltage-limiting board switch surge protector when the third-level maintenance is performed, and its lightning current carrying capacity must not be less than 10KA.
The last line of defense can use a built-in switching surge protector in a part of the switching power supply inside the power-consuming equipment to exceed the goal of completely removing subtle transient overvoltages. The larger surge capacity specified for the switch surge protector applied here is 20KA or less per phase, and the specified limited operating voltage should be less than 1000V. Third-level maintenance is necessary for some very critical or sensitive electronic products. In addition, power-consuming equipment can be maintained from transient overvoltage hazards caused by the system software.
For rectifier power supplies for microwave communication equipment, mobile station communication equipment, radar equipment and other applications, it should be considered that the maintenance of its operating frequency must adopt a DC stabilized surge protector that is compatible with the operating frequency as the final stage of maintenance.
4.Fourth level maintenance
According to the withstand voltage test level of the machine and equipment being maintained, if the secondary lightning protection can ensure that the limited working voltage is less than the withstand voltage test level of the machine and equipment, only the second-level maintenance must be performed. If the withstand voltage test level of the machine and equipment is low, the Four or more levels of maintenance would be required. The fourth stage maintains its lightning current carrying capacity not less than 5KA.