The necessity and method of power quality monitoring
With the development of modern industrial technology, more and more kinds of electric power load, electric railway, arc furnace and rolling mill, impact and nonlinear loads in the capacity, the number is increasing; rectifier and inverter device, frequency adjustment device and nonlinear load increasing, the power quality deterioration in frequency, even cause accidents and abnormal net electricity production equipment and electric equipment, including increased loss of life, performance decline.
Analysis of the necessity of power quality monitoring
With the development of computer technology, based on a computer control system and electronic equipment and other sensitive load and input temporary overvoltage, transient overvoltage, voltage sag and interruption and some have not been caused by power quality problems, people pay more attention to the economic loss increased. For example, a semiconductor chip factory, tens of milliseconds of voltage sags and short interruptions and some other people have not been seriously concerned about the power quality problems caused by the economic losses continue to increase. 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 power quality monitoring, monitoring, research and management.
Analysis of power quality monitoring mode
In the rapid development of computer technology today, on the one hand, the test data of the portable device can import power quality monitoring platform; on the other hand, at the same time the use of multiple power quality analyzer to carry out more and more special test (the dynamic adjustment), mobile and fixed into a relative concept. On the current development of power quality measurement, can be divided into the following three categories.
(1) online monitoring. Fixed power quality monitoring device installed on site. It is mainly suitable for real-time monitoring of power quality indexes of large nonlinear load access point and power grid substation.
(2) survey. Using a portable power quality analyzer for each monitoring point to carry out 1-2 days of power quality testing, mainly applicable to the need to master the power quality index and does not require continuous monitoring of the monitoring methods, the actual level of quality can be used to determine pollution grid power quality index, electrical background.
(3) special monitoring. The use of power quality analyzer (or analysis system) on specific aspects of the test, is mainly applied to fault analysis; nonlinear devices access grid (or expansion) before and after comparison; find the power quality pollution source; understanding of some special loads or user can affect the quality index and the reactive power compensation device in power system.
Selection of power quality monitoring equipment
According to the different monitoring methods, the power quality monitoring instrument can be divided into power quality remote monitor, portable multi-function power quality analyzer and handheld harmonic analyzer.
(1) remote monitoring of power quality
The main functions and features: continuous monitoring of public power supply voltage deviation, three-phase voltage unbalance, the voltage harmonics, frequency deviation, and harmonic current and negative sequence current; power quality indicators and data overrun alarm recorder; improve the function of network communication; to achieve two-way supervision and power power supply side the South fault analysis and recording.
Applicable monitoring mode: continuous monitoring of power quality of public power supply points; multi point monitoring.
(2) portable multi-function power quality analyzer
Input channel, large dynamic range, many kinds of trigger modes can be recorded; analysis of power quality indexes, optional work in various ways, a large amount of memory; the application window of variable width FFT, digital signal processing methods such as wavelet transform; good software platform, with rich software development capabilities and function two convenient operation interface.
Application: special test, interference source equipment involved in the power grid (or capacity change) before and after the monitoring; filter height and function evaluation test; scientific research test; field test.
(3) handheld harmonic analyzer
Portable harmonic analyzer: single-phase voltage and current input; test voltage, current fundamental RMS, RMS, 2 ~50 harmonics, active power, power factor; waveform storage and playback, communication interface and software.
Applicable monitoring mode: on site test, non linear power equipment debugging.
The problems existing in power quality detection and the equipment to solve the problem of power quality problems and equipment selection, as shown in Table 1
Terms of settlement
Harmonic voltage and current waveform
Equipment overheating, malfunction of relay protection
Active power filter, active filter cabinet
Equipment overheating, malfunction of relay protection, communication interference
Static var compensation
Duration and amplitude
Timer timing error
Capacitor, isolated inductor
Wave amplitude, frequency and modulation frequency
Electric arc furnace, motor starting
Servo motor, abnormal operation
Static var compensation
Waveform, peak, duration
Line, charge and capacitor switching
Equipment insulation damage, damage to power electronic equipment
Filter, lightning arrester, isolating transformer
Rise time, peak value, instantaneous value / time