1. Definition Description Voltage Sag refers to the phenomenon that the supply voltage suddenly drops in a short period of time. The typical duration of the gas is 0.5 to 30 cycles, usually no more than 1 second.
1. Definition Description Voltage Sag refers to the phenomenon that the supply voltage suddenly drops in a short period of time. The typical duration of the gas is 0.5 to 30 cycles, usually no more than 1 second.
Voltage sag is usually described in two variables in engineering: Sag Magnitude and Duration Time. In general, the voltage sag is deep and the duration is short; the amplitude is shallow and the duration is long.
Voltage sag belongs to the category of power quality. Power Quality refers to the voltage, current or frequency condition that guarantees the normal operation of electrical equipment. According to the statistics of the American Academy of Electric Power (EPRI), more than 90% of the power quality problems are caused by Voltage Sag and Voltage Swell, where voltage sag is the main cause of the accident.
The power quality is different from the reliability of the power supply. The reliability of the power supply is defined by the ratio of the actual power supply time to the power supply time. We take the reliability of power supply as 99.99999% as an example (it is very difficult to achieve seventy-nine high reliability in actual power supply). According to the calculation of 365 days a year, the accumulated power outage time is 3.1536 seconds per year, however, despite With such high reliability, the voltage sag can still reach an average of 10 to 12 times per year.
2, the cause of the voltage sag is very complicated, there are natural factors, there are also human factors, there are factors in the system protection of the power supply department, as well as equipment reasons and misoperations within the enterprise.
Natural factors, such as lightning strikes, strike on the power line or insulator, and the strong wind causes the power line to dance, and the debris hits the power line to cause a short circuit, thereby causing the protection setting action.
Human causes, such as the collapse of power transmission poles caused by vehicles, and the destruction of buried lines caused by construction.
Reasons for the power supply department, such as reclosing.
Internal reasons, such as the start of the induction motor, the current drawn from the power supply can reach 500% to 600% of the full load. When such a large current passes through the impedance, the voltage suddenly drops; misoperation short circuit may cause the system to be far away. The terminal supply voltage is more severely dropped.
The impact between enterprises, the voltage sag generated inside an enterprise, feedback back to the grid, thus affecting the voltage of other enterprises.
A certain point produces a voltage sag (the source of occurrence), and the voltage sag will propagate in the transmission network with varying amplitude and time. The farthest transmission distance can reach one or two hundred kilometers. The closer to the source, the greater the impact. . With the increase of enterprise density in the same region, the capacity of various electrical equipment within the enterprise increases, and the voltage sag between enterprises has an increasing trend.
3, the impact of many accidents even when the fluorescent lights are not flashing, people are inexplicable, most of the machines are still working, and some machines are indeed down, although such accidents are not particularly large, but on average every month occurs 1 ~ Two times, it is such a situation that the direct and indirect economic losses caused each year are hard to estimate.
In the current industrial production, electronic power equipment is widely used, such as PLC, frequency converter, bus, contactor, relay, controller, etc., and these components are sensitive to voltage sag, but once these components are due to voltage If the sag stops working, the entire equipment or assembly line will be affected.
In the semiconductor industry, the production process, environment (such as temperature, air cleanliness, etc.) are very demanding, and the semiconductor factory is an interconnected system. If there is a problem in any link, the entire process production line must stop. If the chiller stops due to voltage sag, the temperature will not meet the production requirements, and other processes will stop due to cascading failure. Products being processed (such as wafers) are scrapped, and it takes a long time (at least half an hour) to restart production requirements.
The automobile manufacturing industry, such as the paint shop, has high requirements for temperature, humidity, inlet and outlet pressure and process requirements (electrophoresis, drying, etc.), and these factors are interlocked once, once the drying furnace (control temperature) is shut down, the whole The production line should be stopped, and the body that is being painted and dried by electrophoresis is scrapped. It takes 1~2 hours to restart the production requirements.
In the tire manufacturing industry, if the boiler that supplies steam for the vulcanization process is shut down due to power quality problems, the restart recovery time is more than half an hour, resulting in the scrapping of all products of the vulcanization process.
The voltage sag causes the equipment to stop and stop production, which will lead to product scrapping, equipment tool damage, and the impact is greater, it takes a long time to restart the conditions required for production.
The voltage sag problem will affect many industries, but the damage will be different. In the assessment, one must consider the voltage sag caused by the shutdown, the loss of some or all of the products being processed, the damage of the processing equipment, and the time to go through the equipment to restart the conditions necessary to meet the production requirements. This part is the loss of normal production.
4. Governance plan
The ZIGOR AVC fast voltage regulator is an innovative system developed and manufactured by Zigor, Spain for voltage sags. Founded in 1998, Zigor is part of a large Spanish industrial group and is a leading multinational company in the power electronics and renewable energy industries. Zigor has highly qualified and experienced R&D talents, leading the technology and leading the way in power quality, photovoltaic solar systems and power electronics customization solutions.
The ZIGOR AVC Fast Voltage Regulator is a high performance, continuous online voltage sag regimen. It uses the latest microprocessor control and IGBT inverter switching technology. The ZIGOR AVC fast voltage regulator monitors the input supply voltage at all times. Once the voltage deviates from the set value, within 3 milliseconds, it controls the IGBT inverter to add an appropriate compensation voltage to the main circuit through the series injection transformer, which will extremely quickly The output voltage is adjusted to a set value, eliminating the effects of voltage dips from the input of the grid on the load. The ZIGOR AVC fast voltage regulator does not contain any energy storage unit, and the energy required for voltage sag compensation is obtained from the grid.
ZIGOR AVC fast voltage regulator advantages:
Ø Strong compensation ability, three-phase as low as 50%, single-phase as low as 40% complete compensation, maintaining 30 seconds;
Ø The main circuit has only one set of coil windings, does not contain any power electronic devices, and has very high reliability;
Ø The response speed is extremely fast, and the compensation is completed within 3 milliseconds;
Ø No energy storage unit, maintenance-free, small footprint, high cost performance, high return on investment;
Ø Operating efficiency is much higher than UPS, up to 98%;
Ø Strong overload capability, 150% maintained for 30 seconds;
Ø Capacity 50-9000kVA, suitable for medium voltage protection.
Power quality control, power quality analyzer, power quality monitor, voltage sag, more exciting in Shanghai Jingneng Power, please go to http:// for details
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A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check Valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with Ball Valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve or tilting disc check valve is check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains open until the tank Drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in applications such firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure. Another example is the backwater valve (for sanitary drainage system) that protects against flooding caused by return flow of sewage waters. Such risk occurs most often in sanitary drainage systems connected to combined sewerage systems and in rainwater drainage systems. It may be caused by intense rainfall, thaw or flood.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
An in-line check valve is a check valve similar to the lift check valve. However, this valve generally has a spring that will 'lift' when there is pressure on the upstream side of the valve. The pressure needed on the upstream side of the valve to overcome the spring tension is called the 'cracking pressure'. When the pressure going through the valve goes below the cracking pressure, the spring will close the valve to prevent back-flow in the process.
A duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow.
A pneumatic non-return valve.
Multiple check valves can be connected in series. For example, a double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.
Check Valves, Water Check Valves, Brass Check Valves, Sanitary Check Valves
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