What is the function of the short circuit ring in lightning protection grounding

The attraction between the moving and static cores changes with the change of alternating current.

This creates variation and noise'Accelerates the wear caused by the contact of the core of the moving and static.

Causes malocclusion. In severe cases, it can also cause contact ablation.

In order to eliminate this drawback. A copper ring is embedded in a part of the end face of the core column.

It is called a short-circuit ring that causes the force of attraction between the moving and static cores to change with the alternating current.

This creates variation and noise'Accelerates the wear caused by the contact of the core of the moving and static.

Causes malocclusion. In severe cases, it can also cause contact ablation.

In order to eliminate this drawback. A copper ring is embedded in a part of the end face of the core column.

It is called a short-circuit ring

Generally, the equipotential connection part of the fixed set. Calculated by location. The effect of equalizing pressure.

Short-circuit ring: The core of the AC contactor is made of silicon steel sheets. , which reduces eddy currents and hysteresis losses in the core of the alternating flux.

When there is an alternating current passing through the solenoid coil. , the attraction of the coil to the armature is also alternating. When the AC current passes through the zero value, the coil magnetic flux becomes zero, and the attraction to the armature is also zero, and the armature will produce a release tendency under the action of the return spring, which makes the force of attraction between the dynamic and static cores change with the change of alternating current, resulting in change and noise'Accelerates the wear caused by the contact of the core of the moving and static.

A lightning arrester is actually a type of lightning arrester. When there is a lightning high voltage, it is broken down (shorted), introducing the high voltage (lightning) into the ground, thus protecting the line from the attack of high voltage. It has both electrical breakdown and thermal breakdown.

It can be recovered when an electrical breakdown occurs. However, it cannot be recovered in the event of a thermal breakdown. After the occurrence of thermal breakdown, it can not play a protective role, and the arrester must be replaced.

The main types of arresters are tubular arresters, valve-type arresters and zinc oxide arresters. The main working principle of each type of arrester is different, but their working essence is the same, all of which are designed to protect communication cables and communication equipment from damage.

Tubular lightning arrester.

The tubular arrester is actually a kind of protection gap with high arc extinguishing ability, which is composed of two series clearances, one gap is in the atmosphere, called the outer clearance, and its task is to isolate the working voltage and avoid the gas production pipe from being burned out by the power frequency leakage current flowing through the pipe; The other is installed in the trachea, called the internal clearance or arc extinguishing gap, and the arc extinguishing capacity of the tubular arrester is related to the size of the power frequency freewheel. This is a kind of protection gap type lightning arrester, which is mostly used in power supply lines for lightning protection.

Valved surge arrester.

The valve-type arrester is composed of a spark gap and a valve resistor, and the valve resistor is made of special silicon carbide. Die resistors made of silicon carbide can effectively protect against lightning and high voltage, and protect equipment. When there is a lightning high voltage, the spark gap is broken down, and the resistance value of the valve resistor decreases, which introduces the lightning current to the earth, which protects the cable or electrical equipment from the harm of lightning current.

Under normal circumstances, the spark gap will not be broken down, and the resistance value of the valve plate resistance is high, which will not affect the normal communication of the communication line.

Zinc oxide arrester.

Zinc oxide arrester is a lightning protection equipment with superior protection performance, light weight, pollution resistance and stable performance. It mainly uses the good nonlinear volt-ampere characteristics of zinc oxide to make the current flowing through the arrester at normal operating voltage very small (micro-ampere or milliampere level); When the overvoltage acts, the resistance drops sharply, dissipating the energy of the overvoltage to achieve the effect of protection. The difference between this arrester and the traditional arrester is that it has no discharge gap, and uses the nonlinear characteristics of zinc oxide to play the role of discharge and breaking.

The above introduces several lightning arresters, each of which has its own advantages and characteristics, and needs to be used for different environments in order to have a good lightning protection effect.

When the arrester is intact and there is no inrush current in the power system, it will not cause the line to be grounded. And when the arrester fails, for example by a permanent breakdown, the line is grounded. Of course, when the arrester discharges the inrush current, it is essentially grounded, and the lightning and inrush energy are discharged into the ground for dissipation, which is allowed.

In the event of a breakdown fault in the arrester or when the voltage used by the arrester exceeds the threshold voltage, it will be directly grounded and discharged; The surface of the arrester is seriously dirty, which will reduce the ground resistance of the line and make it unbalanced. For example: a construction site 10kV power supply system, the cable together with the ring network switchgear insulation resistance test, the test results are low and unbalanced, according to this result does not meet the power transmission conditions, into the ring network switchgear lightning protection surface cleaning and wiping, the final test results meet the requirements.

Therefore, the arrester will not be to the ground under normal circumstances.

When the electrical equipment is working normally, the current in the circuit passes through one end of the power supply and returns to the other end of the power supply to form a closed loop. If the circuit of the current is cut off or the wire is disconnected for some reason, the current in the circuit cannot flow. The circuit cannot form a closed loop, which is called an open circuit.

The two ends of the power supply are directly connected by the wires without passing through any electrical equipment, which is called a short circuit. When a short circuit occurs in a circuit, a very large current will appear in the circuit, which is called a short circuit current. The short-circuit current may increase to far exceed the allowable limit, causing the wire to heat up violently, and even ignite the wire, burn the electrical equipment, and cause disaster.

The so-called grounding protection is a protective wiring method that reliably connects the metal part of the electrical appliance (that is, the metal structure part insulated from the live part) that is not charged under normal circumstances and may be charged after the insulation material is damaged or under other circumstances. Grounding protection is generally used in the power supply system where the neutral point of the distribution transformer is not directly grounded (three-phase three-wire system), so as to ensure that the voltage to the ground generated when the electrical equipment leaks due to insulation damage does not exceed the safety range. If the household appliance does not adopt grounding protection, when a part of the insulation is damaged or a phase wire touches the shell, the shell of the household appliance will be electrified, and the human body will be at risk of electric shock if it touches the shell (frame) of the electrical equipment with damaged insulation.

On the contrary, if the electrical equipment is grounded for protection, the single-phase grounding short-circuit current will flow along the two parallel branches of the grounding device and the human body. Generally speaking, the resistance of the human body is much greater than that of the grounding body, so the current flowing through the human body is very small, and the current flowing through the grounding device is very large. In this way, the risk of electric shock to the human body after the leakage of electrical equipment is reduced.

Generally, the equipotential connection part of the fixed set. Calculated by location. The effect of equalizing pressure.

Short-circuit ring: The core of the AC contactor is made of silicon steel sheets. , which reduces eddy currents and hysteresis losses in the core of the alternating flux.

When there is an alternating current passing through the solenoid coil. , the attraction of the coil to the armature is also alternating. When the AC current passes through the zero value, the coil magnetic flux becomes zero, and the attraction to the armature is also zero, and the armature will produce a release tendency under the action of the return spring, which makes the force of attraction between the dynamic and static cores change with the change of alternating current, resulting in change and noise'Accelerates the wear caused by the contact of the core of the moving and static.

1. The lightning protection of the factory is divided into the overall structure lightning protection, that is, the lightning protection of the main plant, and the main foundation is grounded and grounded to form a grounding network, and the grounding resistance is less than 10 ohms. Then it is connected with the main body of the steel bar or steel structure of the main plant. The cement concrete roof is connected to the lightning belt or lightning rod, and the ground outside the wall must also have a grounding test point, and the steel structure should be directly led to the roof with galvanized flat iron.

2. The grounding of the power supply system is divided into protective grounding and working point grounding, and the protective grounding is the grounding of the shell of the live equipment. The grounding of the working point refers to the grounding of the zero line, and the grounding network is the same as the lightning protection grounding method, and the grounding resistance is less than 4 ohms. If the requirements are not met, the grounding electrode should be added, and if the conditions are not good, electrolyte should be added and/or the soil should be replaced.

The working grounding and protective grounding are independently led out in the distribution room, and the system can be one. The way of working, such as the separation of the ground and neutral wires, can also be combined into one and lead to the electrical system (or equipment). The grounding system must be grounded repeatedly.

There is also an independent and separate way, the TN-S system. Ground zero can no longer be one.

3. Instrumentation grounding system. The grounding resistance of the system is less than 1 ohm and cannot be connected to the lightning protection grounding.

Fourth, anti-static grounding, such as tubing, etc., every 35 meters (elbow) must have a reliable grounding (the system can also be independent), the resistance is less than 30 ohms.

Partial concept of lightning protection grounding device:

1) Lightning receiving device: a metal rod (lightning receiver) that directly or indirectly receives lightning, such as lightning rods, lightning belts (nets), and overhead ground.

wire and lightning arrester, etc.

2) Down lead: The conductor used to conduct lightning current from the lightning receiver to the grounding device.

3) Grounding wire: a metal conductor that does not carry current under normal circumstances when the grounding terminal of electrical equipment and tower is connected with the grounding body or neutral wire.

4) Grounding body (pole): A metal conductor buried in the soil and in direct contact with the earth, called a grounding body. It is divided into vertical ground body and horizontal grounding body.

5) Grounding device: a general term for grounding wire and grounding body.

6) Grounding grid: a mesh grounding device composed of vertical and horizontal grounding bodies with the effect of discharge and equalization.

7) Grounding resistance: the sum of the grounding resistance of the grounding body or the natural grounding body becomes the grounding resistance of the grounding device, and its value is equal to the ratio of the grounding voltage of the grounding device to the current flowing into the ground through the grounding body. At the same time, the grounding resistance is also a sign of the level of the constant grounding device. ‍‍

Lightning protection grounding is divided into two concepts, one is lightning protection, to prevent damage caused by lightning strikes; The second is electrostatic grounding to prevent static electricity from harming. With the increasingly extensive application of cathodic protection in storage tanks, its protection effect has attracted more and more attention, and the contradiction between lightning protection and grounding specifications and cathodic protection specifications has become more and more prominent.

1) Category 1: manufacturing and storage of pyrotechnics, etc., caused by sparks, causing great damage and personal damage; Buildings with Zone 0 or 20** hazardous locations; Has a Zone 1 or Zone 21** hazardous location.

2) Category II: National Key Cultural Relics Units; national buildings and large-scale buildings; National special and first-class large gymnasiums; Dangerous buildings that manufacture and store explosives and their products, and electric sparks are not easy to cause or cause great damage to people; Those who have Zone 1 or 21** dangerous places, and electric sparks are not easy to cause ** or will not cause huge damage and personal **; Have a Zone 2 or Zone 22** hazardous location; Possess ** dangerous open-air steel closed gas tank.

3) Category III: Exception.

Categories 1 and 2 are the third category

Combine the lightning protection grounding electrode and the cathodic protection anode into one: in the sacrificial anode cathodic protection, the grounding resistance of the anode is required to be as low as possible, which is consistent with the requirements of lightning protection and grounding. If the cross-sectional area of the anode connection cable is increased to meet the requirements of lightning protection and grounding, it is generally believed that the lightning protection grounding system can be replaced by the sacrificial anode system, so that the sacrificial anode plays the dual role of cathodic protection and lightning protection.

Install the grounding battery between the grounding wire or the grounding grid of the storage tank, the grounding battery is made of double zinc rods, and the double zinc rods are usually in an open circuit state, when there is a lightning strike or fault voltage, the fault current is introduced into the grounding network through the double zinc rods, which plays a role in safety protection for the storage tank. ‍‍