The power quality analyzer is a special portable product that detects and analyzes the quality of power grid operation. It can provide harmonic analysis and power quality analysis in power operation, and can perform long-term data acquisition and monitoring of power grid operation. At the same time, it is equipped with power quality data analysis software to perform various analyses on the measurement data uploaded to the computer.
Electricity is now widely used by people. Electricity has become the most common source of energy for people. Electricity is also an important indicator of a country’s overall national strength and development level. Guaranteeing the stable supply of electrical energy is related to people's normal life and production. The operation of the national economy and the safety of electrical equipment in the power grid are of great significance. The issue of power quality has received widespread attention from people. The quality standards for electric energy have also been promulgated. However, compared with developed countries such as Europe, the United States, Japan, and Japan, we still have a certain gap. We haven't systematically studied the voltage problem. The understanding of electric energy still stays in the traditional voltage and frequency deviations.
Second, the power quality analyzer causes the voltage drop
An important indicator in the energy index is the voltage dip. Voltage sag is an important part of the energy index. The definition of voltage dips in the Institute of Electrical and Electronics Engineers is that the effective rms voltage of a voltage in a power supply system suddenly drops to 10% - 90% of its rated value and returns to normal within a short period of 1min thereafter Working status.
There are many factors that cause voltage dips, mainly due to the sudden start-up or loading of high-power electrical equipment, lightning strikes on the power system network, short circuits in the circuit, and failures in circuit protection measures. Compared with the blackout of power lines, the phenomenon of voltage dips frequently occurs, and it is difficult for people to notice them. Therefore, it is relatively difficult to handle them.
Third, the voltage caused by the sudden drop
Because the voltage drop phenomenon occurs frequently, it is the main factor affecting the power system power quality, which can affect every power user in the power system. The dangers of the sudden drop of power in the power system mainly include: First, the information industry has a huge impact, the misoperation of automatic control devices, and the failure of computer systems. Second, the hazards caused to sensitive machinery and equipment, such as hazards to the DC generator, when the voltage is lower than the normal 80%, circuit tripping accidents are most likely to occur. For the PLC controller, each voltage dips or circuit Short circuit will cause the disorder of the control program to occur, and for the frequency converter, when the voltage is continuously lower than 70% within 120s, it will be out of operation. Fourth, it affects people's normal production and life. Fifth, every time the voltage swells or the voltage fluctuates, the national economy will have at least 100,000 to 200,000 yuan in economic losses, and many will reach millions of economic losses.
Fourth, solve the voltage dips
From the above, it can be seen that the voltage sag brings a lot of harm to our lives. Therefore, measures must be taken to resolve the losses caused by the voltage sag. To solve the problem of voltage dips generally take the following measures:
(I) Reduce the frequency of voltage sags and reduce the time for circuit troubleshooting. Reducing the time for circuit troubleshooting is also to reduce the duration of voltage sags and reduce the impact of voltage sags on machine equipment, thereby reducing the economic losses caused. In order to reduce the time for troubleshooting, the general circuit uses static short-circuit and current-limiting fuses.
(b) Change the system design of the circuit network to avoid or reduce voltage disturbances. This measure is mainly to change the wiring, use special transformers, such as the k-type transformer, improve the performance of equipment, bold wires, sensitive anti-interference protection measures for sensitive equipment and equipment, use an independent loop, reduce the resistance of grounding, Arrester configuration and parameters are improved.
(c) Improve the ability of circuit equipment to withstand voltage sags. For example, using a motor generator set (MG), the inertia of the motor can be used to keep the voltage of the generator stable when the voltage dip occurs, and the circuit transformer uses a magnetic resonant transformer (CVT) when the circuit voltage suddenly drops to 70% of the normal voltage. It is still able to provide a smooth voltage, the only drawback is that it is slightly larger than a normal transformer.
(d) Installation of voltage compensation devices in the circuit. The most typical installation of voltage compensation devices in the circuit is the installation, dynamic voltage recovery period (DVR) and uninterruptible power supply (UPS). The grid voltage is output to the DC-AC inverter through the AC-DC inverter output DC voltage, and a stable AC voltage is output to the load. At the same time, the grid voltage charges the energy storage battery. When the power grid undervoltages or suddenly loses power, the UPS power supply starts to work and the energy storage battery supplies the power required by the load to maintain normal production. Due to production needs, when the load is heavily overloaded, the UPS can directly supply power to the load by rectifying the grid voltage, which can effectively solve problems such as voltage dips and short-term power supply interruptions. In addition, the full power of the load is provided after the conversion by the UPS, which increases system losses and reduces efficiency.
When the DVR is connected in series with a sensitive load and a voltage dip occurs, the DC-AC inverter with pulse width modulation will synthesize a voltage with a controlled amplitude, frequency, and waveform. This voltage is added through a series-connected step-up transformer. On the line voltage, the voltage dips can be reacted within 1/4 cycle, that is, the output voltage is raised to the voltage level required by the system. The reference source of the PWM modulation wave of the inverter is a standard sine wave. By comparing the acquisition voltage waveform with the standard wave, voltage harmonics can be effectively compensated. The voltage boosting energy is supplied by the DC capacitor.
DVR is currently the most concerned device to solve the voltage drop. Although the DVR is operated in series on the line, it only needs to compensate for the energy of the voltage dips. Therefore, its design power is only 1/5 to 1/3 of the total capacity of the load. The price is better than the UPS with the same capacity, and the loss is far. Lower than the latter, with significant technological advancement.
to sum up:
From the above, it can be seen that the voltage sag in the power quality problem is a particularly prominent problem. The key to reducing the power system losses lies in the fact that when the voltage sag occurs, it can be quickly and effectively controlled and processed in a timely manner. The voltage quality inspection network must be continuously improved, and the comprehensive inspection capability of the power quality should be improved, and the power users should be aware of the problem of voltage dips. The power users who are more sensitive to the problem of power dips should help improve the circuit and reduce the voltage dips. The harm caused. Reducing the voltage sag is not only of great importance to the safety of the power grid, but also important to the economic operation of the country.
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