On the quality requirements of power supply in int

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Abstract: by analyzing the main factors affecting power quality, such as voltage fluctuation, frequency fluctuation and transient surge, this paper puts forward some methods to eliminate power pollution, so as to ensure the normal operation of computers and precision electronic equipment in intelligent buildings

key words: intelligent building transient surge electrical interference transient impulse theory power quality requirements in intelligent building with the impact of international information trend and the boiling of microelectronics technology, and the rapid changes in communication, computer and automatic control technology, the building began to move towards the field of high quality and high function, forming a new building form - intelligent buildings. Because many computers and microelectronic devices are used in intelligent buildings, new requirements are put forward for the quality of their power supply. Because the quality of power supply will directly affect the operation stability and reliability of equipment in intelligent buildings, and even lead to major personal and equipment accidents and huge economic losses. This influence not only comes from whether the voltage, frequency, current and other basic elements of the power supply meet the requirements of electrical equipment, but also from the power quality of the power supply. Due to the weakness of low insulation strength, high quality requirements for power supply and poor overvoltage tolerance of electronic computers, microprocessors and other electronic instruments and equipment, these highly sensitive electronic systems often have program operation errors, data errors, time errors, crash, restart without reason or even permanent damage to electrical equipment during operation, causing huge losses to people's daily life. Therefore, in intelligent buildings, it is an inevitable trend to study the quality of power supply and implement effective protective measures, and it has been widely concerned by countries all over the world. 1 technical indicators of power quality the technical indicators for measuring power quality mainly include: voltage fluctuation, frequency fluctuation, harmonic and three-phase imbalance, etc. As we all know, the quality of power supply will be affected by many factors, such as the change of load, the use of a large number of nonlinear loads, the influence of high-order harmonics, the input and cut-off of power factor compensation capacitor, lightning and human faults, public facilities (such as motors, elevators, etc.) will affect the quality of power supply, thus reducing the quality of power supply. 1.1 voltage fluctuation the waveform of sine wave of ideal power supply voltage is continuous, smooth, without distortion, and its amplitude and frequency are stable. When the load changes and the load increases greatly, especially when large equipment nearby is starting, the amplitude of sine wave of power supply is affected and low voltage is generated. When the voltage fluctuation of the power supply exceeds the allowable range, the computer and precision electronic equipment will have errors in calculation, and even the power failure detection circuit of the computer will be mistaken for power failure, resulting in power failure processing signals, affecting the normal work of the computer. The allowable voltage fluctuation range of general computer is: AC 380V, 220V ± 5%. When the voltage of the computer drops to 70% of the rated voltage, the computer is regarded as interrupted. For this reason, the code for design of computer rooms GB 50174-93 (hereinafter referred to as the code) clearly stipulates voltage fluctuations, which are divided into three levels a, B and C (see Table 1). Voltage fluctuation level table 1 voltage level a level B level C

fluctuation range ± 2% ± 5% + 7% ~ -13% 1.2 frequency fluctuation the frequency fluctuation of power supply is mainly caused by the change of generator speed caused by electric overload operation. Most of the external equipment of the computer adopts synchronous motor. Generally, the allowable fluctuation range of the computer frequency is 50Hz ± 1% When the frequency fluctuation of power supply exceeds the allowable range, the frequency of computer information storage will change, resulting in errors, and even information loss. The specification clearly stipulates frequency fluctuation, which is divided into three levels: A, B and C (see Table 2). Frequency fluctuation level table 2 frequency level a level B level C

fluctuation range ± 0.2% ± 5% + 7% at present, Brazil China Sea freight is $5.549/t ~ -13% 1.3 waveforndistortion. The main reason for the power supply voltage waveform distortion is that the nonlinear load in the electricity, especially the existence of some high-power controllable rectifier devices, will produce hydrocarbons on the voltage waveform of the power supply, It will also have an adverse effect on the relative control part of the computer; This waveform distortion will also cause the current on the filter capacitor in the DC power circuit of the computer to increase significantly, and the capacitor will heat up; In addition, because of the appearance of saw waveform, the power failure detection circuit of the computer will mistakenly think of power failure and send out power failure processing signals, which will affect the normal work of the computer. The technical index to measure the waveform distortion is the waveform distortion rate, that is, the percentage of the ratio of the sum of all high-order harmonics of the AC voltage at the input end of the electrical equipment to the effective value of the fundamental wave. The specification specifies the waveform distortion rate as a, B Level C (this revolutionary new product shows the value of an integrated material solution combining comfort, durability and aesthetics to the innovation of important products. See Table 3) waveform distortion rate table 3 waveform distortion level a level B level C

distortion rate (%) 3-5-8 8-101.4 transient surge and transientvoltage surge It means that the sine wave amplitude of power supply voltage increases rapidly within one or several weeks of power frequency. Transient surge is generally expressed by the maximum transient rate. Tran position voltage fall, also known as notch, means that the amplitude of sine wave of power supply voltage drops rapidly within one or several weeks of power frequency. The transient decline is generally expressed by the maximum transient decline rate. Transient surge and transient drop, and the rapid increase or decrease of voltage amplitude within an instant will interfere with the computer system, resulting in its calculation error or damaging the stored data and programs. At present, there is no domestic regulation on large transient rate: (half a week or longer) ≤ 20%; It is reduced to within 15% during recovery, which is 50ms; Then it is reduced to within 6%, which is 0.5s. Maximum allowable transient decline rate: (half a week or longer) ≤ 30%; Recover to within - 20%, 50ms; The tester is mainly used for hydraulic pulse pressure test of steel cylinders, pressure vessels, etc 0.5s for ball disk data within 3%. 1.5 transient voltagepulse, also known as spike or voltage flicker, refers to the narrow pulse superimposed on the electrical ideal sine wave within a time less than half an electrical cycle. There are many reasons for transient pulse, generally mainly from the following aspects: 1.5.1 internalovervoltage

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