Overview
With the increase in the degree of automation of factory production, production equipment has become more and more sensitive to voltage sags. Therefore, the requirements for power quality have become higher and higher. The voltage dip problem has caused significant economic losses to important users of continuous production, and has gradually attracted the attention of the power sector and industry users.
According to statistics, a petrochemical industry caused direct losses of up to RMB 8 million due to voltage sags ; a chemical plant suffered a voltage dip loss of RMB 1.6 million; a semiconductor factory lost about US$ 100,000 to US$ 150,000 each time; automotive assembly lines each time It took 45 minutes to shut down and restart , resulting in the loss of 25 vehicles; the production process of integrated circuits was interrupted, and approximately 1 million US dollars was lost to products , and recovery took 30 minutes. It can be seen that the problem of voltage dips has a great impact on the above industries and must be taken seriously.
Causes of voltage sags
Weather-related causes: The most common is a lightning or lightning strike that shorts somewhere on the transmission line to ground, whereupon the protection action is activated, causing a voltage dip in the network around the point of failure. Heavy rain, strong winds, and heavy snow may also cause a short circuit to the ground of the transmission line. Accidents: The vehicle hits a power pole, hoists mechanical contact with overhead lines during construction, digs underground cables for construction damage, and leads to short-circuit faults on animal contact lines. Other reasons: start-up of large motors, equipment short-circuit faults, switch-over operation, and failure of power distribution equipment.Summarizing the above reasons, we can find that these reasons are sudden, inevitable, and mostly unpredictable. Although grid companies invest a lot of resources, they still cannot completely prevent voltage sags. Therefore, for the user, power quality problems will always exist, either tolerate or try to protect sensitive loads internally.
The statistical law of voltage dips
According to the investigation of the EPRI of the United States Academy of Electric Power , more than 92 % of power quality events are voltage dips. Most of the voltage dips are short-term and small. The amplitude of the voltage sag of 10% -30%, about 70% of the sag, the duration of no more than about 90% 1s not exceed about 60% of 0.1s.
It can be seen that choosing a voltage dip solution must consider the dynamic response speed of the control equipment. This is critical. Otherwise, more than half the low voltage is enough to shut down some sensitive equipment. Therefore, an ordinary voltage regulator cannot protect short-term voltage sags. The voltage sags control device is connected in series in the power supply circuit, so its own reliability is particularly important, otherwise it will cause the load to be powered off due to its own fault. Therefore, only the voltage dips control solution with strong compensation ability, fast response speed, high reliability, and low operation and maintenance costs can truly solve the problem and bring investment benefits to the enterprise.
Voltage Slug Reduction Solution: Spanish Zigor Company - AVC Fast Voltage Regulator
The fast voltage regulator is an innovative system developed by Zigor of 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 industry. Zigor has high-qualified and experienced R&D talents, and has a technological advantage that leads the power quality, photovoltaic solar energy system, and customized power electronics solutions. The fast voltage regulator is a high-performance, on-line voltage dip control solution. It uses the latest microprocessor control and IGBT inverter switching technology. The AVC fast voltage regulator constantly monitors the input supply voltage. Once the voltage deviates from the set value, it controls the IGBT inverter to add the appropriate compensation voltage in the main circuit through the series injection transformer within 3 milliseconds. The output will be extremely fast. The terminal voltage is adjusted to the setpoint, thereby eliminating the effect of the voltage dips from the input of the grid on the load. The AVC fast voltage regulator does not contain any energy storage unit and the energy required for voltage sag compensation is obtained from the grid. Fast voltage regulator advantages: strong compensation ability, three-phase as low as 50% , single-phase as low as 40% complete compensation, and maintain for 30 seconds; the main loop has only one set of coil windings, does not contain any power electronics, and the reliability is very high; High response speed, complete compensation within 3 milliseconds; no energy storage unit, maintenance-free, small footprint, high cost performance, high investment return; operating efficiency is much higher than UPS , up to 98% ; strong overload, 150% maintenance 30 seconds; capacity 50-9000kVA , suitable for medium voltage protection.Stone coated metal roofing was refined during and after World War II in the United Kingdom, when the government requested materials that would protect corrugated steel roofs from the harsh climate. A coating of bitumen and subsequent covering by sand, stone or other materials proved effective at protecting the metal roofs and serving as camouflage against potential attack. Now this type roofing sheet is quite popular in the market. Based on this need, we developed stone coated roofing sheet machine, the working speed could reach 25m/min.
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