Vacuum Interrupter
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Shaanxi huadian electric co., Ltd. It is located in Baoji high-tech development zone, Shaanxi province. A modern high-tech enterprise specializing in integrating research and development, manufacturing, and sales of vacuum circuit breakers.
Shaanxi huadian has nearly 10,000 square meters of circuit breaker production workshop, and has a fully automated control assembly line and a full set of imported circuit breaker testing equipment, with an annual production capacity of 10,000 units.
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In electrical engineering, a vacuum interrupter is a switch which uses electrical contacts in a vacuum. It is the core component of medium-voltage circuit-breakers, generator circuit-breakers, and high-voltage circuit-breakers. Separation of the electrical contacts results in a metal vapour arc, which is quickly extinguished. Vacuum interrupters are widely used in utility power transmission systems, power generation unit, and power-distribution systems for railways, arc furnace applications, and industrial plants.
Since the arc is contained within the interrupter, switchgear using vacuum interrupters are very compact compared with switchgear using air, sulfur hexafluoride (SF6) or oil as arc-suppression medium. Vacuum interrupters can be used for circuit-breakers and load switches. Circuit-breaker vacuum interrupters are used primarily in the power sector in substation and power-generation facilities, and load-switching vacuum interrupters are used for power-grid end users.
Benefits of Vacuum Interrupter
Long Life, High Reliability — Vacuum interrupters can be expected to last the life of the equipment in which they are installed
Controlled contact erosion results in virtually maintenance-free operation
Fast Interrupting Speed — The interruption mechanism is independent of current magnitude, so interruption can normally be anticipated at the first current zero with no restriking
Rapid Dielectric Recovery — The dielectric strength of the contact gap recovers more rapidly than the recovery voltage can rise, eliminating restriking
High Cycle Withstand Voltages
Robust, Compact Design — Vacuum dielectric enables contacts to be arranged close together so circuit interruptions can be designed in a smaller envelope
Environmentally Friendly — Current interruption occurs in a vacuum, so there is no emission of greenhouse or toxic gases
Atmospheric Contact Contamination Is Eliminated— Oxides and corrosion layers cannot form in the vacuum environment
Noise-free And Flash-free — All arcing is confined within the vacuum interrupter body
Types of Vacuum Interrupter
Glass ( Or Ceramic ) Vacuum Interrupter For Circuit Breaker
This series of vacuum interrupter adopt ceramic insulating envelope , cup shaped axial magnetic field ,intermediate sealing shield structure , Cu - Cr contact materials . It has the features of large switching capacity , high insulating levels , strong arc - quenching capability and long life , etc . Vacuum circuit breaker matched with it has the advantages of simple maintenance , no risk of explosion , no pollution and low noise , etc ., and it can be widely used in the electric power , mechanical , metallurgy , chemical and mine department , etc ., to control and protect the transmission and distribution system .
Glass ( Or Ceramic ) Envelope Vacuum Interrupter For Load Switch
This series of vacuum interrupter adopt ceramic insulating envelope , and WCu contact materials with low chopping value and long life . This kind of product has the features of smal size , long life , high insulatinc levels and reliable performance . Load switch matched with it has the advantages of simple maintenance , no risk of explosion , no pollution and low noise , etc ., it can be widely used in the electric power , mechanical , metallurgical , chemical and mine department , etc ., to control the transmission and distribution system .
Ceramic Envelope Vacuum Interrupter For Contactor
This series of vacuum interrupter adopt ceramic insulating envelope and Cu ( W + WC ) contact materials with low chopping value . This kind of product has the features of reliable performance , long life and smal size , etc . Contactor matched with it has the advantages of simple maintenance , no risk of explosion , no pollution and low noise , etc ., it can be widely used in the electric power , mechanical , metallurgical , chemical and mine department , etc ., to control and protect the transmission and distribution system . It is especially suitable for frequent operation of cutting off inductive load and used in the places where it is operated frequently .
Vacuum Interrupter For Railway Circuit Breaker
This series of vacuum interrupter adopt long distance ceramic insulating envelope with shed , intermediate sealing shield , cup shaped axial magnetic field structure and Cu - Cr contact materials . It has the features of large switching capacity , high insulating levels and strong arc - quenching capability , etc . Railway circuit breaker matched with it has the advantages of simple maintenance , no risk of explosion , no pollution and low noise , etc . It can be met with the use requirements at high altitudes ( up to 4000m), and can be used incontroling and protecting electrified railway lines .
Vacuum Interrupter For Generator Protection
This series of vacuum interrupter adopt glass ( or ceramic ) insulating envelope , intermediate sealing shield , cup shaped axial magnetic field structure , and Cu - Cr contact materials . It has the features of large switching capacity , high insulating levels and strong arc - quenching capability , etc ., and has the advantages of simple maintenance , on risk of explosion , no pollution and low noise , etc . It can be met with the requirements of generator protection , and is mainly used in generator protection , can be also used in controlling and protecting the transmission and distribution system .
Application of Vacuum Interrupter
Circuit Breakers - Used in circuit breakers in the most demanding electrical circuit protection applications to minimize damage caused by electrical overloads or short circuits.
Load Break Switches - Used in load break switches to connect and disconnect electrical load currents providing limited load switch capacity.
Reclosers - Used in reclosers to automatically open and close distribution circuits in response to transient overload and fault conditions.
Contactors - Used in contactors in demanding applications that require a high number of operations switching a power circuit in electric motors, lighting, heating devices, and capacitor banks.
Tap Changers - Used in tap changers inside transformers to change the winding connections to deliver the required voltage.
Railway Circuit Breakers - Installed in the circuit breaker on top of special locomotives to supply electrical energy to railway locomotives’ electric drive motors.
Components of Vacuum Interrupter
Airtight insulation system
The airtight insulation system consists of an airtight insulating shell, moving end cover plate, fixed end cover plate, and stainless steel bellows made of glass or ceramics. In order to achieve effective airtightness between glass, ceramics, and metals, in addition to using strict sealing techniques, the material's air permeability must be as low as feasible, and the internal outgassing volume must be kept to a minimum.The stainless steel bellows can not only isolate the vacuum state in the vacuum interrupter from the external atmosphere, but they can also move the moveable contact and movable conductive rod within the defined range to perform vacuum switch on and off operations.
Conductive system
The conductive system of the arc extinguishing chamber is made up of the fixed conductive rod, the fixed arc surface, the fixed contact, the moveable contact, the movable arc surface, and the movable conductive rod. The fixed electrode is made up of the fixed conducting rod, the fixed running arc surface, and the fixed contact; the moving electrode is made up of the moving contact, the moving arc surface, and the moving conductive rod. The operational mechanism closes the two contacts through the movement of the movable conductive rod and completes the circuit connection when the vacuum circuit breaker, vacuum load switch, and vacuum contactor assembled by the vacuum interrupter are closed. The vacuum switch is equipped with a guide sleeve at one end of the moving conductive rod and uses a set of compression springs to maintain A rated pressure between the two contacts in order to make the contact resistance between the two contacts as small and stable as possible, and the arc extinguishing chamber has good mechanical strength when it bears dynamic and stable current.The two contacts of the arc extinguishing chamber are separated when the vacuum switch cuts the current, and an arc is formed between them until the arc is extinguished when the current naturally crosses zero, and the circuit breaking is completed.
Shielding system
A shielding cylinder, a shielding cover, and other pieces make up the vacuum interrupter's shielding system. The shielding system's main functions are to:
(1) Prevent the contacts from producing a large amount of metal vapor and droplets splashing during the arcing process, polluting the inner wall of the insulating shell, and causing the insulation strength to decrease or flashover;
(2) Miniaturization of the vacuum interrupter insulation shell is aided by improving the electric field distribution inside the vacuum interrupter, particularly for high-voltage vacuum interrupters.
(3) Capture a portion of the arc's energy and condense the arc products. Most of the heat created by the arc is absorbed by the shielding system, which helps to improve the recovery strength of the medium between the contacts, especially when the vacuum interrupter interrupts the short-circuit current. The bigger the number of arc products absorbed by the shielding system, the more energy it absorbs, which helps to increase the vacuum interrupter's breaking capacity.
Contact system
The contact is where the arc is formed and extinguished, and it has a lot of requirements in terms of materials and construction.
(1) Contact material
The contact material has the following requirements:
●High breaking capacity
High electrical conductivity, low thermal conductivity, huge heat capacity, and low thermionic emission capabilities are all required of the material.
●High breakdown voltage
When the breakdown voltage is high, the medium's recovery strength is also strong, which helps with arc extinguishing.
●High electrical corrosion resistance
That is, it can endure arc ablation while evaporating a minimal amount of metal.
●Resistance to fusion welding.
●Low intercept current value, which is required to be below 2.5A.
●Low air content
All materials utilized inside the vacuum interrupter must have a low air content. Copper material, in particular, must be oxygen-free copper processed using a low-gas concentration technique. Silver and copper alloys are necessary for soldering.
●The vacuum interrupter for circuit breakers' contact materials are predominantly copper-chromium alloy, with copper and chromium each accounting for 50% of the total. On the butt surface of the upper and lower contacts, a copper-chromium alloy sheet with a thickness of 3mm is welded. The contact seat, which can be manufactured of oxygen-free copper, is the final component.
(2) Contact structure
The contact structure has a significant impact on the isolated room's breaking capacity. The arc extinguishing effect caused by different structures' connections varies. There are three types of spiral contacts: a cup with a chute, a cup with a longitudinal magnetic field, and a cup with a spiral structure. A longitudinal magnetic field cup is one of them. The contact is primarily in the shape of a structure.
Bellows
The vacuum interrupter's bellows are primarily responsible for ensuring that the movable electrode moves within a particular range and that the vacuum interrupter's function of high vacuum is maintained for a long period, as well as for maintaining the vacuum interrupter's mechanical life. The vacuum interrupter's bellows are a thin-walled stainless steel part with a thickness of 0.10.2mm. The bellows of the arc extinguishing chamber expand and contract during the opening and shutting of the vacuum switch, and the cross section of the bellows is subject to varying tension. As a result, the bellows' life should be calculated based on the amount of repetitive expansion and contraction as well as the operating pressure. The heating temperature of the operating conditions affects the bellows' service life. The leftover heat of the conductive rod is passed to the bellows when the vacuum interrupter breaks the huge short-circuit current, raising the temperature of the bellows. When the temperature rises to a certain point, the bellows will become fatigued and their service life will be shortened.
How to Maintain Vacuum Interrupter
The Vacuum Interrupter Installation Precautions
1.When the vacuum interrupter is in operation, it must have a guiding device. The coaxiality of the whole pipe axis is met by the use of the moving conductive rod, and the bellows is not subject to the torsion.
2.During installation, it is strictly forbidden to hit or knock the pipe casing with hard objects to avoid breakage and air leakage, and prevent the glass casing from being scratched. Otherwise, the glass will be easily broken after being subjected to heat during the breaking process.
3.Pay attention to ensure the coaxiality of the conductive rod of the vacuum interrupter or the perpendicularity with the end face of the fixed end.
4.Be careful not to disassemble the vacuum interrupter repeatedly to prevent the connection of the buckling buckle; nor to twist the conductive rod and excessively compress the bellows to avoid the torque and scratch of the bellows and affect the service life.
The Vacuum Interrupter Use Precautions
1.During use, the vacuum degree of the vacuum interrupter should be checked regularly by the power frequency withstand voltage method.
2.Regularly check the burning condition of the vacuum interrupter contacts. When it reaches the burning mark of the moving conductive rod, or the thickness of the burning loss exceeds the standard value, it indicates that the vacuum interrupter has a life end and should be replaced.
Working Principles of a Vacuum Circuit Breaker
Since circuit breakers typically protect against overcurrent and a short circuit, they use a thermal and magnetic trip to detect each. When the circuit trips, it creates a chain of events inside the insulating medium. In the case of a VCB, the insulating medium is a vacuum.
Once the circuit trips, the actuator mechanism forces the movable contact to break the connection with the fixed contact. The broken connection ionizes metal vapors, creating an electrical arc between the two contacts. This arc can damage equipment and must be extinguished quickly, especially in high-voltage situations.
In a vacuum, the arc extinguishes quickly as a vacuum is an excellent insulator. The ions, vapors, and electrons generate evenly within a vacuum.
The ions condense along the outside of the contacts, and the insulating vessel regains dielectric strength quickly. The arc is extinguished almost immediately after it appears.
What Is the Difference Between an Interrupter and a Circuit Breaker?
Interrupters and circuit breakers are both devices used to protect electrical circuits from overloads and short circuits, but they serve slightly different purposes and operate in different ways. Here are the key differences between interrupters and circuit breakers:
Interrupter: An interrupter is a device that is designed to quickly interrupt the flow of current in a circuit when a fault is detected. Interrupters are typically used to protect against short circuits and ground faults.
Circuit breaker: A circuit breaker is a device that automatically interrupts the flow of current in a circuit when it detects an overload or a short circuit. Circuit breakers are designed to protect electrical circuits and the devices connected to them from damage due to excessive current.
Interrupter: Interrupters operate by sensing abnormal current flow in a circuit and opening the circuit to stop the flow of electricity. They are typically fast-acting devices that can quickly disconnect power when a fault occurs.
Circuit breaker: Circuit breakers can be manually operated or automatically tripped when they detect an overload or short circuit. They are designed to trip and open the circuit when the current exceeds a certain threshold to prevent damage to the circuit and connected devices.
Interrupter: Interrupters come in various types, such as arc fault circuit interrupters (AFCIs) and ground fault circuit interrupters (GFCIs). AFCIs are designed to detect and interrupt dangerous electrical arcs that can cause fires, while GFCIs are designed to protect against electric shock in areas where water may be present.
Circuit breaker: Circuit breakers are available in different types based on their applications, such as thermal-magnetic circuit breakers, residual current circuit breakers (RCCBs), and miniature circuit breakers (MCBs). Each type of circuit breaker is designed to provide specific protection against different types of faults.
Vacuum Circuit Breakers Testing Methods
Contact Resistance Test: A micro-ohmmeter is applied to the closed contacts of the VI and the resistance is measured and recorded. The result is compared to the design and/or the average values for the other Vacuum Interrupters in the same run.
High Potential Testing: A high potential voltage is applied across the open contacts of the VI. The voltage is increased to the test value and any leakage current is measured.Factory testing may be done with either AC or DC high-potential test sets . There are a variety of portable test sets available from manufacturers for performing a high-potential test on open vacuum interrupters. The great majority of these test sets are dc test sets, as they are considerably more compact, and hence, more portable, than available ac high-potential test sets.
When a DC test voltage is used, a high field emission current from a microscopic sharp spot on one contact can be misinterpreted as a sign of a vacuum interrupter filled with air. To avoid a misinterpretation of the test result, the vacuum interrupter should always be subjected to both dc voltage polarities. This means the test should be carried out by reversing polarities. A bad interrupter filled with air will have a similarly high leakage current in both polarities.
A good interrupter with a good vacuum level may still have a high leakage current, but this will generally be in only one polarity. An interrupter with a tiny sharp spot on the contact produces a high field emission current only when it is a cathode, not an anode. So repeating the test by reversing the polarities will avoid any misinterpretation of the result. The test voltage to be used for testing a vacuum interrupter is recommended by the manufacturers of vacuum interrupters.
The Leak-rate Test (Mac Test):This test is based on the Penning Discharge Principle which is named after Frans Michael Penning (1894-1953). Penning showed that when a high voltage is applied to open contacts in a gas and the contact structure is surrounded with a magnetic field, the amount of current flow between the plates is a function of the gas pressure, the applied voltage, and the magnetic field strength.
For field testing, the VI is placed in a portable fixed magnetic coil or a flexible cable is wrapped around the test specimen a prescribed number of times. When the test is started, high voltage DC is applied to the VI and the baseline leakage current is measured. Next, a DC voltage pulse is applied to the magnetic field coil during a second application of the high voltage DC and the total current is measured during the pulse. The ion current is calculated as the total current minus the leakage current. Since the magnetic field and the applied voltage are both known, the only variable remaining is the pressure of the gas. If the relationship between the gas pressure and the current flow is known, the internal pressure can be calculated based on the amount of current.
Our Factory
Shaanxi huadian electric co., Ltd. It is located in Baoji high-tech development zone, Shaanxi province. A modern high-tech enterprise specializing in integrating research and development, manufacturing, and sales of vacuum circuit breakers.
