CN102928701A - Measuring system for measuring ion current field distribution characteristics under direct current transmission - Google Patents

Abstract

The invention relates to a measurement system for measuring the distribution characteristics of ion flow field under direct current transmission. The system includes a direct current electric field strength sensor, an ion flow collection sensor, a meteorological parameter sensor and a multi-channel real-time synchronous control device. The direct current electric field strength Sensors, ion current collection sensors and meteorological parameter sensors are evenly distributed on the measurement site, and the multi-channel real-time synchronous control device is connected to the DC electric field strength sensor, ion current collection sensor and meteorological parameter sensor respectively, and receives the direct current electric field strength sensor, ion current Collect the data collected by sensors and meteorological parameter sensors, and perform characteristic analysis and storage on the data. Compared with the prior art, the present invention has the advantages of realizing real-time measurement of multi-parameters and multi-channels, high measurement accuracy and the like.

Description

Measuring System for Measuring Distribution Characteristics of Ion Flow Field under DC Transmission

technical field

The invention relates to a power measurement system, in particular to a measurement system for measuring the distribution characteristics of ion flow field under direct current transmission.

Background technique

As my country's UHV power grid construction is approaching vigorously, the formulation of relevant standards for UHV transmission technology is becoming increasingly urgent. Among them, the measurement method of the ion flow field of the UHV DC transmission and the calibration method of the instrument are the important foundation and direct basis for the electromagnetic environment evaluation of the UHV DC transmission project. Different from the electromagnetic environment of the AC transmission line, the DC electromagnetic environment is directly related to the corona characteristics of the transmission line and the electric field effect caused by it. Line corona refers to a luminous discharge phenomenon caused by the ionization of the air around the wire after the surface potential gradient of the wire exceeds a certain critical value. Due to the different voltage properties of DC lines and AC lines, the development process of DC corona is very different from that of AC corona. When corona occurs on the AC line, due to the periodic change of the polarity of the conductor voltage, the ions generated by the air ionization of the corona discharge in the first half cycle are almost all pulled back to the conductor due to the change of the voltage polarity in the second half cycle. The ionized ions are basically bound near the wire, and there are no charged ions in the vast space between the polar wire and the ground.

The DC line is different, the voltage polarity of the wire is fixed, a relatively stable free layer will be formed around the wire, and there are a large number of ions with the same polarity as the wire outside the free layer. The presence of these space charges distorts the electric field in the absence of space charges. The space charge also continuously migrates to the surroundings and the ground due to the action of the electric field force. The space charge itself generates an electric field, which will greatly strengthen the electrostatic field (also known as the nominal electric field) generated by the surface charge of the wire. Space charges move under the action of an electric field, forming an ionic current. This electric field under the joint action of space charge and original wire charge is called synthetic electric field. The effect of space charge is particularly prominent when the development of wire corona is serious. In some cases, the ground synthetic electric field can even reach 2 to 3 times the nominal field. Therefore, the increase of ground field strength and the appearance of ionic currents are one of the important characteristics that distinguish the electromagnetic environment problems of DC transmission lines from those of AC lines.

Humans have different feelings on AC and DC currents. Research by the Electric Power Research Institute (EPRI) in the United States has shown that to obtain the same degree of feeling, the DC current flowing through is more than five times larger than that of AC. The Dallas (Dallas) Test Center in the United States has done a human experience test under the high-voltage DC bus, and the perceivable field strength under the DC transmission line is much higher than that of the AC.

The electric field effect under high-voltage direct current (HVDC) transmission lines is very different from that of alternating current, so the same standard cannot be used to measure the electromagnetic environment impact of the two. Countries do not have uniform regulations on the limits of ground synthetic electric field and ion current density under DC transmission lines. Our country has also carried out relevant research and published the industry standard DL436-2005 "Technical Guidelines for High Voltage DC Overhead Transmission Lines", which was implemented on June 1, 2006. It stipulates that the maximum synthetic field strength on the ground under the DC line should not exceed 30kV/m, and the maximum ion current density should not exceed 100nA/m2. According to the recently released DL/T 1088-2008 "Limits of Electromagnetic Environmental Parameters for ±800kV UHV DC Lines", when the line is close to a residential house, the combined field strength limit on the ground at the residential house is 25kV/m, and 80% of the measured The value shall not exceed 15kV/m, the combined field strength limit of the line crossing farmland, roads and other areas that are easily accessible to personnel is 30kV/m, and the ion current density limit under the line is 100nA/m2. It is very urgent and necessary to study the measurement of various corona parameters off-line, so as to provide a strong scientific basis for the electromagnetic environment assessment of the UHV DC transmission line corridor.

Contents of the invention

The purpose of the present invention is to provide a measurement system for measuring ion flow field distribution characteristics under direct current transmission that can realize multi-parameter multi-channel real-time measurement and high measurement accuracy in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A measurement system for measuring the distribution characteristics of ion flow field under direct current transmission, the system includes a direct current electric field strength sensor, an ion flow collection sensor, a meteorological parameter sensor and a multi-channel real-time synchronous control device, the direct current electric field strength sensor, ion flow The current collection sensors and meteorological parameter sensors are evenly distributed on the measurement site, and the multi-channel real-time synchronous control device is respectively connected to the DC electric field strength sensor, the ion current collection sensor and the meteorological parameter sensor, and receives the direct current electric field strength sensor, the ion current collection sensor and the meteorological parameter sensor in real time. The data collected by the meteorological parameter sensor is analyzed and stored for the characteristics of the data.

The multi-channel real-time synchronous control device includes a portable industrial computer and three data acquisition cards installed in the portable industrial computer, and the three data acquisition cards are respectively connected to a DC electric field strength sensor, an ion current collection sensor and a meteorological parameter sensor.

The portable industrial computer is a computer with LabView programmable data processing function.

The meteorological parameters include wind speed, wind direction, temperature, relative humidity and atmospheric pressure.

The ion current collection sensor includes a connected Wilson ion current collection plate and a digital display microcurrent meter.

Both the DC electric field strength sensor and the ion current collection sensor are provided with an analog output interface, and the analog output interface is connected with a data acquisition card.

There are 10 to 30 direct current electric field strength sensors, and 10 to 30 ion current collection sensors.

Compared with the prior art, the present invention has the following advantages:

1) The multi-channel real-time synchronization control device in the present invention adopts a "pseudo-synchronization" scheme design, a "pseudo-synchronization" scheme;

2) The present invention is equipped with a DC electric field intensity sensor and an ion flow collection sensor at the same time, which can realize the measurement of various ion flow field distribution characteristics under DC transmission, and the measurement accuracy is high.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, a measurement system for measuring the distribution characteristics of ion flow field under DC transmission, the system includes a DC electric field strength sensor 1, an ion flow collection sensor 2, a meteorological parameter sensor 3 and a multi-channel real-time synchronization control device 4 , the DC electric field strength sensor 1, the ion current collection sensor 2 and the meteorological parameter sensor 3 are evenly distributed on the measurement site, and the multi-channel real-time synchronous control device 4 is respectively connected to the DC electric field strength sensor 1, the ion current collection sensor 2 and the Meteorological parameter sensor 3.

The DC electric field strength sensor 1 and the ion current collection sensor 2 are distributed laterally (or in a direction perpendicular to the transmission line) at a certain distance under the transmission line, and the number of sensors can be set according to the area size of the measurement site. In this embodiment, there are 30 DC electric field intensity sensors 1 and ion current collection sensors 2 each. The ion current collection sensor 2 includes a connected Wilson ion current collection plate and a digital display microcurrent meter. The Wilson ion current collector plate is made of copper clad laminate. The conductive metal on its upper surface is divided into two mutually insulated areas. The central area is the effective collection area, and the surrounding edge area is the shielding area, which is directly grounded. The Wilson ion current collector plate The effective collection area has an area of 0.1 m ² . Both the DC electric field strength sensor 1 and the ion current collection sensor 2 are provided with an analog output interface, and the analog output interface is connected with a data acquisition card to realize real-time synchronous data acquisition.

The multi-channel real-time synchronous control device 4 includes a portable industrial computer and three data acquisition cards installed in the portable industrial computer, and the three data acquisition cards are respectively connected to a DC electric field strength sensor, an ion current collection sensor and Meteorological parameter sensor. The portable industrial computer is a computer with LabView programmable data processing function.

The multi-channel real-time synchronous control device 4 of this embodiment adopts the design of the "pseudo-synchronization" scheme (proposed by American NI Corporation) in a parallel manner. The three data acquisition cards described above adopt data acquisition cards produced by NI Corporation: one NI 6250 (16 channels) and two NI6254s (32 channels). The configuration of the portable industrial computer is: CPU Core 2E6300; intel Q965 motherboard; 2GDDRII memory; 80G SATA hard disk; built-in graphics card. WindowsXP operating system.

The scan rate of multi-channel acquisition of NI 625X series data acquisition card is 1MHz, that is, the delay time from the first channel to the thirty-second channel is tens of microseconds. Therefore, the requirement of synchronous sampling for the measurement of the electric field distribution of the ion current under the DC transmission line can be fully satisfied.

NI 6250 has 16 analog input channels, the system is defined as Devl, which is used to collect meteorological parameters, and the wind speed, wind direction, temperature, air pressure and relative humidity correspond to channels AI0~AI4 respectively. The card is directly connected with the signal box of the small mobile weather station with a 68-core cable.

NI6254 has 32 analog input channels, and the two NI 6254 systems default to Dev2 and Dev3 respectively. Dev2 is used to measure the synthetic field strength and connect to the DC field strength meter; Dev3 is used to measure the ion current density and connect to the ion current measuring instrument. The first 30 channels of each card, namely AI0-AI29, correspond to the 30 external sensors in turn.

The meteorological parameters 3 include wind speed, wind direction, temperature, relative humidity and atmospheric pressure. In this embodiment, the weather parameter sensor 3 selects the small weather station HD2003 produced by Italy delta ohm company. Its most important feature is the measurement of wind speed, which uses ultrasonic wind speed and wind direction measurement technology. This technology can have relatively good wind speed and direction measurement sensitivity at low wind speeds. At the same time, the wind speed and direction measurement mechanism does not have any mechanical device, which avoids various problems caused by mechanical wear and tear, and is a completely maintenance-free wind speed sensor. At the same time, its intelligent control can simultaneously output meteorological parameters such as wind speed, wind direction, temperature, air pressure and humidity in digital and analog form. In this way, on the one hand, we can monitor the meteorological parameters at that time on the industrial computer, and at the same time input the analog quantity to the real-time synchronous data acquisition system and convert the data into the database of the industrial computer at the same time as the synthetic field strength and ion current density.

The working principle of the measurement system used in this embodiment to measure the distribution characteristics of the ion flow field under DC transmission is: the multi-channel real-time synchronous control device 4 receives in real time the ground synthetic field strength data and ion flow data collected by the DC electric field strength sensor 1 through the data acquisition card. Collect the ground ion current density data collected by sensor 2 and meteorological parameter data such as wind speed, wind direction, temperature, relative humidity, and atmospheric pressure collected by meteorological parameter sensor 3, and perform characteristic analysis and storage of the data, and set the sampling interval of each group of data to 1s , sampling time 5min.

Due to the large dispersion of the measured data, it is necessary to use statistical methods for analysis, usually using the following methods:

Arrange the m values in descending order. In this sequence, given an area [max, A] from the maximum value of the queue to the value A, there is a corresponding percentage K of the n values in this area to all m values. , and K=pcqueue(A)=n/m. The statistical significance of this function lies in the ratio of the amount of data greater than the given value A to the total amount of data in a set of data.

In the data measurement of ground synthetic field strength, there will be positive and negative values. The degree of influence of the ground synthetic field strength on the surrounding environment depends on the absolute value of these values. Therefore, in the application, the function pcqueue(A) needs to be modified to some extent. The modified function pcqueue′(A) is defined as:

$\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; pcqueu</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; pcqueue</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; INVpcqueue</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; pcqueu</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; pcqueue</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; INVpcqueue</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>\end{array}\right.$

In the formula, INVpcqueue() is the inverse function of pcqueue().

Example 2

With reference to Fig. 1, the measurement system for the measurement of ion flow field distribution characteristics under DC transmission in this embodiment includes a DC electric field strength sensor 1, an ion current collection sensor 2, a meteorological parameter sensor 3 and a multi-channel real-time synchronous control device 4, Among them, there are ten DC electric field intensity sensors 1 and ion current collection sensors 2 each. All the other are with embodiment 1.

Claims (7)

1. one kind is used for the measuring system that the Ion Flow Field distribution character is measured under the direct current transportation, it is characterized in that, this system comprises the DC electric field intensity sensor, the ion current collecting sensor, meteorologic parameter sensor and hyperchannel real-time synchronization control device, described DC electric field intensity sensor, ion current collecting sensor and meteorological parameter sensors are evenly distributed on measure field, described hyperchannel real-time synchronization control device connects respectively the DC electric field intensity sensor, ion current collecting sensor and meteorological parameter sensors, receive in real time the DC electric field intensity sensor, the data that ion current collecting sensor and meteorological parameter sensors gather, and data are carried out specificity analysis and storage.

2. a kind of measuring system of measuring for Ion Flow Field distribution character under the direct current transportation according to claim 1, it is characterized in that, described hyperchannel real-time synchronization control device comprises a portable industrial pc and the three blocks of data capture cards that are installed in the portable industrial pc, and described three blocks of data capture cards connect respectively DC electric field intensity sensor, ion current collecting sensor and meteorological parameter sensors.

3. a kind of measuring system for Ion Flow Field distribution character measurement under the direct current transportation according to claim 2 is characterized in that, described portable industrial pc is the computing machine with LabView programmable data processing capacity.

4. a kind of measuring system for Ion Flow Field distribution character measurement under the direct current transportation according to claim 1 is characterized in that, described meteorologic parameter comprises wind speed, wind direction, temperature, relative humidity and atmospheric pressure.

5. a kind of measuring system for Ion Flow Field distribution character measurement under the direct current transportation according to claim 1 is characterized in that, described ion current collecting sensor comprises that the Wilson's ion current collecting board and the numeral that are connected show microgalvanometer.

6. a kind of measuring system of measuring for Ion Flow Field distribution character under the direct current transportation according to claim 2, it is characterized in that, be equipped with analog output interface circuit on described DC electric field intensity sensor and the ion current collecting sensor, described analog output interface circuit is connected with data collecting card.

7. a kind of measuring system for Ion Flow Field distribution character measurement under the direct current transportation according to claim 1 is characterized in that, described DC electric field intensity sensor is provided with 10～30, and described ion current collecting sensor is provided with 10～30.

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