Power quality monitoring device APview500 voltage flicker monitoring

Ankrui manufacturer Shi Lihua 18706162823 (same WeChat account)

The development of modern society cannot be separated from the support of electricity, and the stability and quality of electricity will greatly affect people's lives and work. Higher quality electricity is very important for people's production and life. The online detection system for power grid energy can provide real-time monitoring and data recording of the actual application of power grid energy during the application process. Technical personnel can analyze the data to determine the actual application of power grid energy, identify malfunctioning equipment, and replace and repair them to ensure the quality of power grid energy. The detection indicators of the power grid power quality detection system are important standards for technical personnel to judge the quality of power and the operation quality of the power grid. Technical personnel can also analyze these indicators to determine whether the power grid power quality meets the actual requirements of China for power grid power quality. At present, the indicators used in the process of power grid quality testing in China include voltage deviationFrequency deviationHarmonicsVoltage fluctuations, flickerThree phase voltage imbalance, etc.

Power quality monitoring device APview500 voltage flicker monitoring

1. Overview

Ankerui APView500Power quality monitoring deviceIt is a device that monitors power quality indicators by analyzing and processing the introduced voltage and current signals. Suitable for situations where accurate measurement of power quality indicators is required, such as resolving power quality disputes as stipulated in power supply contracts, or verifying compliance with relevant power quality standards. The main functions and accuracy of the device are shown in the table below.

2. Functional characteristics of the device

Web access function:Web Service technology enables different applications running on different machines to exchange data or integrate with each other without the need for additional, specialized third-party software or hardware. Applications implemented according to the Web Service specification can exchange data with each other regardless of the language, platform, or internal protocol they use. With this feature, we can display the data monitored by the APView series power quality online monitoring device in real-time on computers within the same local area network.

Connect the computer to the power quality online monitoring device through a network cable (using the network port on the back of the device), check the device's IP address and record it.

The device integrates embedded Web Server functionality internally, supporting users with different levels of permissions to log in and access. Users of different levels use different 8-digit passwords to log in, namely "tourists"; Administrator; Debugging personnel. Users can directly connect to the device through a browser and view real-time power quality data and tuning device parameters.

Wave recording file analysis:COMTRADEIt is a data file format suitable for obtaining transient waveforms and events from power system models. The waveform recording file of the APView series power quality online monitoring device COMTRADE consists of a configuration file (. CFG) and a data file (. DAT). The configuration file (. CFG) contains the information required to correctly parse the data file (. DAT) using a computer program. This information entry includes: sampling rate, number of channels, grid frequency, channel information, etc. The data file (. DAT) contains the values of each input channel and sample in the transient record. The sampled values are stored in binary format as converted values of the waveform sampling input.

Ankrui manufacturer Shi Lihua 18706162823 (same WeChat account)

Power quality monitoring device APview500 voltage flicker monitoring

3. Common power quality analysis

voltage deviationThe relative deviation between the actual operating voltage and the nominal voltage of the system at a certain testing point during the transportation of electrical energy in the power grid, including overvoltage and undervoltage. Overvoltage refers to the phenomenon of long-term voltage fluctuations under power frequency, where the root mean square value of the AC voltage increases by more than 10% of the nominal value and lasts for more than 1 minute. Overvoltage is an electromagnetic disturbance phenomenon in the power system. On the one hand, the insulation of power equipment can withstand the working voltage for a long time, and at the same time, it needs to be able to withstand a certain degree of overvoltage in order to ensure the safe and reliable operation of the power system. On the other hand, during system operation, it is necessary to ensure that the equipment operates within the upper limit of the allowable voltage deviation range to avoid damage to the insulation of electrical equipment. Overvoltage may arise from cutting off a large load or changes in reactive power compensation in the system, such as adding a set of capacitors. Poor system voltage regulation or control capability may lead to overvoltage. Incorrect adjustment of transformer taps can also lead to system overvoltage. Low voltage refers to a long-term voltage fluctuation phenomenon where the root mean square value of the AC voltage decreases below the nominal value by 10% and lasts for more than 1 minute at the power frequency. The cause of low voltage is opposite to overvoltage. Placing a large load or disconnecting a capacitor bank can cause low voltage, which can be returned to normal voltage levels through the system voltage regulation device. Overloading of power transmission and transformation equipment can also lead to system overvoltage. The national standard GB/T12325-2008 for power quality specifies the voltage deviation for different voltage levels: the sum of positive and negative deviations for power supply voltages of 35kV and above shall not exceed 10% of the nominal voltage; The deviation of three-phase power supply voltage of 20kV and below is ± 7% of the nominal voltage; The voltage deviation of 220V single-phase power supply is+7% and -10% of the nominal voltage.

frequency deviationIt is the difference between the actual value and the nominal value of the system frequency. The change in active power of the system is the fundamental cause of frequency deviation. The steady-state power system frequency is directly related to the generator speed of the system. At any given moment, the frequency depends on the balance between the (total) load and the instantaneous (total) power generation output. With this dynamic change in balance, there will be slight variations in frequency. These slight changes can be automatically adjusted through the speed control device of the generator, and the power generation system generally does not have a significant impact. The frequency variation of the power system deviates from the normal allowable range, usually caused by the disconnection of large capacity loads or the disconnection of large capacity generators during transmission system failures. Due to its limited power supply capacity, island systems can only tolerate relatively slight frequency changes. The national standard GB/T15945-2008 for power quality specifies that the frequency deviation limit for power systems under normal operating conditions is ± 0.2Hz. When the system capacity is small, the deviation limit can be relaxed to ± 0.5Hz.

harmonicIt plays a very important role in the process of power grid reference. Harmonics that do not meet the requirements can affect the capacity of transformers, cables, etc. during application, accelerate the aging speed of equipment in the power grid, and even cause damage to power grid equipment in certain situations, affecting the stability of power grid operation and wasting electricity. In the actual use of the power grid, the harmonics generated between adjacent devices will interfere with each other, which will to some extent affect people's electricity quality. At present, devices that generate harmonics during the operation of the power grid include switch mode power supplies, electronic fluorescent lamp ballasts, uninterruptible power supplies, and loads that generate arcs.

three-phase unbalanceIt refers to the difference in amplitude or phase difference between the phase voltage or current of a three-phase system, which is not 120 °. The reasons for user imbalance during use include: uneven distribution of loads among different phases; High harmonic current causes imbalance between phases; Unbalance caused by poor contact between wiring terminals and cables; The occurrence of imbalance caused by external environment (such as line disconnection due to construction, etc.); Long distance overhead transmission and distribution lines that do not switch positions.

voltage fluctuationFlicker refers to a series of random voltage fluctuations or periodic changes in the root mean square value of the power frequency voltage. The evaluation criteria for voltage fluctuations and flicker are based on the GB/T 12326-2008 document on power quality voltage fluctuations and flicker. In the process of detection and evaluation, the main method is to compare the larger value of the flicker during the time period evaluated by the technical personnel with the limit value. If the value is within the flicker limit value, it is considered qualified, while if the flicker value is above its limit value, it is considered unqualified. Voltage fluctuations and flicker can cause the following hazards. 1、 Voltage fluctuations and flicker can cause flickering in lighting equipment to a certain extent, which in turn can cause visual fatigue and affect the quality and efficiency of people's work. 2、 It can also have an impact on devices such as televisions, causing changes in the brightness of television screen images and affecting people's visual sensory experience. 3、 The normal operation of some electric motors is affected, and if this effect persists for a long time, it will greatly damage the service life of the equipment. 4、 The impact on the working conditions of electronic instruments, automation equipment, etc., coupled with China's vigorous development of automation in recent years, has a significant impact on industrial production. Therefore, it is crucial to manage voltage fluctuations and flicker.

Voltage temporary rise, temporary fall, and short-term interruption;Power system failures, equipment malfunctions, and control failures can all cause short-term interruptions. Short term interruption is measured based on the duration when the root mean square value of the voltage is less than 10% of the nominal value. The duration of system failure is determined by the action time of the protective device or the duration of the special event process, and the interruption duration of equipment failure is different. Voltage sag is usually related to system faults and can also be caused by factors such as starting large capacity induction motors or transformer no-load excitation. Voltage sag is usually related to system faults, but the probability of occurrence is much lower than voltage sag. When a single-phase grounding fault occurs in a neutral point ungrounded power system, it can cause an increase in non fault phase voltage. Events such as the withdrawal of large capacity loads, load shedding, or the commissioning of large capacity capacitor banks can also cause voltage spikes.

4. Application Cases

The Ankerui APView500 power quality online monitoring device is widely used in photovoltaic power plants, factories, hospitals and other places. The following are some application cases:

• A monocrystalline silicon rod photovoltaic industry base projectThere are 30 high-voltage incoming lines in the 10/0.4KV user substation of the base, and APView500 is installed at 14 of the incoming lines. The device can monitor the power quality parameters of the incoming line in real time, monitor harmonics and display them in bar charts and tables. It can record transient events such as voltage rise and fall, and has the function of locating the source of voltage drop. It can also generate ITIC and SEMI F47 curves, providing a basis for fault analysis, effectively reducing production line downtime, and improving energy utilization efficiency.

• Photovoltaic project in a certain logistics parkAfter the project was connected to APView500PV, it was successfully discovered that the 5th harmonic current exceeded the limit. By installing a filter in a timely manner, damage to the inverter was avoided. At the same time, based on the recorded wave data, a fault was identified in a certain branch contactor, which was replaced within 2 hours, reducing downtime losses by 300000 yuan. In addition, PQDIF files can be downloaded via USB or FTP, and waveforms can be analyzed using specialized software to facilitate troubleshooting and analysis by maintenance personnel.

• Tesla Factory Distributed Photovoltaic ProjectThe project requires real-time monitoring of power quality such as voltage harmonics and DC components at the grid connection point, and uploading relevant data to the dispatch center. Install one APView500PV in each of the 1 # and 2 # grid connected cabinets to monitor the real-time power quality at the grid connection point. The device ensures the stability and reliability of the power quality of the photovoltaic power generation system, timely detects and solves problems such as voltage fluctuations and harmonic pollution, and provides important basis for the optimization of distributed photovoltaic projects.

• Jinyi Industrial 5MW Distributed Energy Storage ProjectAPView500PV is used in the project to obtain key parameters in the power system in real time, with functions such as harmonic analysis, waveform sampling, voltage sag/sag/interruption monitoring, etc. Users can view real-time waveforms and fault waveforms through the device, conduct fault analysis, optimize power usage, reduce equipment damage risks, and improve the overall operational efficiency and reliability of the power system.

• A heavy industry enterprise's 18MW distributed photovoltaic projectAPView500 is used in the project to collect and monitor harmonic analysis, voltage sag/interruption, flicker monitoring, voltage imbalance, etc. Cooperate with Acrel-1000DP distributed photovoltaic monitoring system to visually display the operating status of distribution lines in the form of a distribution diagram, monitor real-time electrical parameter information of each circuit, dynamically monitor the closing and opening status of circuit breakers and related fault, alarm and other signals, and assist in the coordinated operation of distributed photovoltaics and the power grid.

Ankrui manufacturer Shi Lihua 18706162823 (same WeChat account)