What Are The Forms Of Lightning Overvoltage?

Question 1: What are the forms of lightning overvoltage? 1: Direct lightning - also known as direct lightning

The second is: lightning induction - also known as induction lightning

Question 2: What are the types of power system overvoltage? Power system overvoltage is divided into: external overvoltage (lightning overvoltage) and internal overvoltage.The internal overvoltage includes: increased power frequency voltage (power frequency overvoltage), resonance overvoltage and operating overvoltage.

Question 3: The first common form of lightning voltage is: direct lightning - also known as direct lightning

The second is: lightning induction - also known as induction lightning

Question 4: There are generally several methods to prevent lightning overvoltage. In order to analyze the performance of the grounding network of power generation and substations under the action of lightning current, a model that is similar to the node voltage method under power frequency conditions is proposed, and the grounding is calculated with the help of software. Electrical parameters of the grid under lightning current impulse response. This model uses the node voltage method in electrical network theory to consider the impact of soil spark discharge around the grounded conductor on lightning transient effects, nonlinear spark effects and mutual inductance between conductors, and has a positive impact on grounding. The soil discharge breakdown of the conductor establishes an equivalent circuit model based on distributed and time-varying circuit parameters. At the same time, this method provides a thinking method for the dynamic trend prediction of the performance of the grounding grid under the action of large impulse current. Analysis of different grounding grid structures , the impact characteristics of the grounding grid under different lightning current injection points and other factors. When injected at the corners, the potential, scattered current, and axial current around the injection point are all symmetrically distributed about the diagonal of the injection point. When injected at the center point, the ground surface The potential distribution is symmetrical about the center point.

Question 5: The main classification of overvoltage is divided into two categories: external overvoltage and internal overvoltage. External overvoltage is also called lightning overvoltage and atmospheric overvoltage. Caused by thunderclouds in the atmosphere discharging electricity to the ground. It is divided into two types: direct lightning overvoltage and induced lightning overvoltage. The duration of lightning overvoltage is about tens of microseconds and has pulse characteristics, so it is often called lightning shock wave. Direct lightning overvoltage is the overvoltage that occurs when lightning directly strikes the conductive part of electrical equipment. A lightning strike that strikes a live conductor, such as an overhead power line wire, is called a direct lightning strike. Lightning strikes a conductor that is normally grounded, such as a transmission line tower, causing the potential to rise and then discharges the charged conductor, which is called a counterattack. The overvoltage amplitude of a direct lightning strike can reach millions of volts, which will destroy the insulation of electrical facilities and cause short circuit and ground faults. Induced lightning overvoltage is the overvoltage induced on electrical equipment (including secondary equipment and communication equipment) that has not been directly struck by lightning due to the rapid changes in the space electromagnetic field during the discharge process when lightning strikes the ground near electrical equipment. Therefore, overhead transmission lines need to be protected by lightning protection wires and grounding devices. The lightning protection capability of transmission lines is usually expressed by the line lightning resistance level and lightning tripping rate. Internal overvoltage is an overvoltage caused by changes in the internal operation mode of the power system. There are transient overvoltage, operating overvoltage and resonance overvoltage. Transient overvoltage is an overvoltage that occurs when the power system reaches a certain temporary stability after going through a transition process due to the operation of a circuit breaker or the occurrence of a short circuit fault. It is also called an increase in power frequency voltage. Common ones include: ① No-load long-line capacitance effect (Ferranti effect). Under the action of industrial frequency power supply, due to the accumulation of capacitance effect on long-distance no-load lines, the voltage distribution along the line is unequal, with the terminal voltage being the highest. ②Asymmetric short circuit to ground. When phase a of a three-phase transmission line is short-circuited to ground fault, the voltage on phases b and c will increase. ③Load shedding overvoltage. When the transmission line is forced to shed the load suddenly due to a fault, the overvoltage is caused because the power supply electromotive force has not been automatically adjusted in time. Operating overvoltage is an overvoltage with rapid attenuation and short duration caused by circuit breaker operation or sudden short circuit. Common ones are: ① no-load line closing and reclosing overvoltage. ② Cut off the overvoltage of the no-load line. ③ Cut off the overvoltage of the no-load transformer. ④Arc ground overvoltage. Resonance overvoltage is an overvoltage caused by energy storage components such as inductors and capacitors in power systems resonating with the power frequency under certain wiring methods. Generally divided according to the cause: ①Linear resonance overvoltage. ② Ferromagnetic resonance overvoltage. ③Parametric resonance overvoltage.

Question 6: What methods are generally used to control lightning overvoltage 1. Lightning rods and lightning protection wires

2. Lightning arrester

3\Lightning overvoltage of overhead lines

(1) Prevent lightning from directly striking wires

Set up lightning protection wires along the line, and sometimes install lightning rods to match them.

(2) Prevent insulation flashover caused by lightning striking the top of the tower or lightning protection wire

Reduce the grounding resistance of the tower, increase the coupling coefficient, appropriately strengthen the line insulation, use lightning arresters on individual towers, etc.

(3) Prevent lightning flashover from converting into stable power frequency arc

Appropriately increase the number of insulator pieces to reduce the intensity of the power frequency electric field on the insulator string. Use ungrounded or arc-extinguished coil grounding methods in the power grid.

(4) Prevent line interruption of power supply

Use measures such as automatic reclosing, or dual-circuit, ring network power supply, etc.

Question 7: 43. How many forms of overvoltage are there in the power system? Atmospheric overvoltage: caused by direct lightning strikes. It is characterized by short duration and strong impact. It is directly related to the intensity of lightning strike activity and has nothing to do with the voltage level of the equipment. Therefore, the insulation level of systems below 220KV is often determined by preventing atmospheric overvoltage. Power frequency overvoltage: caused by the capacitance effect of long lines and sudden changes in the power grid operation mode. It is characterized by a long duration and a low overvoltage multiple. Generally, it is not dangerous to equipment insulation, but it is certain in ultra-high voltage and long-distance power transmission. Insulation level plays an important role. Operation overvoltage: caused by switch operation in the supply network, it is characterized by randomness, but the overvoltage multiple is high in the most unfavorable circumstances.Therefore, the insulation level of ultra-high voltage systems of 30KV and above is often determined by preventing operating overvoltage.

Question 8: What are the common operating overvoltages? There are many reasons for operating overvoltage in power systems. Generally, there are the following situations: 1. Operating overvoltage caused by cutting off inductive loads. For example, overvoltage caused by cutting off no-load transformers, arc suppression coils, reactors, and motors. 2. Operation overvoltage caused by cutting off the capacitive load. For example, overvoltage caused by cutting off long no-load lines, cable lines or capacitor banks. 3. Operation overvoltage caused by closing the no-load line (including reclosing). For example, during the reclosing process of a system with residual voltage, the reclosing operation overvoltage is caused by recharging. In addition, there are intermittent arc groundings, operating overvoltage caused by sudden load changes in the power system or system disconnection and load shedding. In this case, the system usually starts with an operating overvoltage, followed by longer-duration transient overvoltages.