Necessity and method of power quality monitoring
Foreword: With the development of modern industrial technology, there are more and more types of electric load, and the impact and non-linear loads such as electrified railways, electric arc furnaces and rolling mills are increasing in capacity and quantity; rectification and inverter devices and The non-linear load such as the frequency conversion adjustment device is increasing, which causes the power quality to deteriorate frequently, and even causes network power accidents and abnormal production equipment, including increased loss of power equipment, shortened life, and degraded operation performance.
Analysis of the necessity of power quality monitoring
With the development of computer technology, the emergence and input of sensitive loads such as computer-based control systems and electronic devices have caused temporary overvoltage, transient overvoltage, voltage sag and short interruptions. The economic losses caused by power quality problems are increasing. For example, a semiconductor chip factory, tens of milliseconds of voltage sag and short-term interruptions, and other economic losses caused by power quality problems that have not been valued by people have been increasing. For example, a semiconductor chip factory, tens of milliseconds of voltage sag will cause hundreds of millions of dollars in economic losses. Therefore, it is imperative to strengthen the management of power quality and to carry out the work of power quality waking, monitoring, research and governance.
Analysis of power quality monitoring methods
In today's highly developed computer technology, on the one hand, the test data of portable devices can be imported into the power quality monitoring platform; on the other hand, more and more special tests are carried out using multiple power quality analyzers at the same time (network structure dynamic adjustment), Movement and fixation become relative concepts. As far as the current power quality measurement is concerned, it can be divided into the following three categories.
(1) Online monitoring. Installed on site using a stationary power quality monitoring device. It is mainly applicable to real-time monitoring of power quality indicators of large non-linear load access points and power grid substations.
(2) General survey. Using portable power quality analyzer to carry out 1-2 days of power quality testing for each monitoring point, mainly for monitoring methods that need to master the power quality indicators without continuous monitoring, to determine the power quality indicators of the grid. The background level, the actual level of power quality pollution.
(3) Special monitoring. Use power quality analyzer (or analysis system) to test specific problems, mainly for fault analysis; before and after non-linear equipment access to the grid (or expansion and expansion); find grid power quality pollution sources; understand some special loads or users Impact on grid power quality indicators and reactive power compensation equipment.
Selection of power quality monitoring equipment
According to different monitoring methods, power quality monitors can be divided into power quality remote monitors, portable multi-function power quality analyzers and handheld harmonic analyzers.
(1) Power quality remote monitor
Main functions and features: Continuous monitoring of voltage deviation of common power supply point, three-phase voltage unbalance, voltage harmonics, frequency deviation, and harmonic current and negative sequence current injected into the grid by the user; power quality indicator over-limit alarm and data record Wave; perfect network communication function; realize two-way supervision of power supply and electricity, and analysis and recording of electrical energy faults.
Applicable monitoring methods: continuous monitoring of power quality at public power supply points; multi-point monitoring constitutes regional power quality monitoring network.
(2) Portable multifunctional power quality analyzer
There are many input channels, large dynamic range, and multiple trigger modes; all indicators for analyzing power quality can be recorded, multiple working modes can be selected, and the amount of memory is large; advanced data signal processing methods such as FFT with variable window width and wavelet transform are applied; A good software platform with rich development software capabilities and convenient operation interface.
Applicable methods: Special test, monitoring of interference source equipment before and after grid (or capacity change); filter device height and function evaluation test; scientific research test; on-site timing test.
(3) Handheld harmonic analyzer
Handheld harmonic analyzer: single-phase voltage and current input; test and analysis voltage, fundamental RMS of current, true RMS, 2~50 harmonics, active power, power factor; waveform storage, playback, communication interface And software.
Applicable monitoring methods: On-site periodic inspection, non-linear power equipment debugging.