CN100514075C

CN100514075C - DC electric filed detection method of insulator for high-voltage DC transmission line

Info

Publication number: CN100514075C
Application number: CNB2006100897690A
Authority: CN
Inventors: 程养春; 李成榕; 唐志国; 王伟; 郑书生
Original assignee: North China Electric Power University
Current assignee: North China Electric Power Research Institute Co Ltd; North China Electric Power University
Priority date: 2006-07-14
Filing date: 2006-07-14
Publication date: 2009-07-15
Anticipated expiration: 2026-07-14
Also published as: CN1924593A

Abstract

The invention discloses a method for measuring a DC electric field of an insulator of a high-voltage direct current transmission line, which belongs to the field of live detection of an insulator of a high-voltage direct current transmission line in a power system. An integrating circuit is used to measure the DC electric field strength by measuring the amount of electrostatically induced charges on two metal conductors in the space electric field. The advantages of the present invention are that the device used is simple and low in cost, and only needs a metal plate and an integrator circuit; it is easy to operate, and the measurement of the entire DC electric field distribution can be completed by simply moving the device to the front of the insulator and sliding along the insulator, without There are shortcomings of the above-mentioned various methods, accurate and reliable.

Description

DC electric filed detection method of insulator for high-voltage DC transmission line

Technical field

The invention belongs to electric system mesohigh transmission line insulator live detection range, a kind of DC electric filed detection method of insulator for high-voltage DC transmission line particularly is provided.

Technical background

China super high voltage direct current electricity transmission system send passage as the east of a large amount of water power in western part, and the power of its carrying is very big, understands oepration at full load usually, in case straight-flow system has an accident, will produce great impact to electrical network.Behind the dc system fault,, cause system frequency to raise because a large amount of power delivery is not gone out; The transfer of a large amount of power makes the part circuit particularly net the serious overload of interconnection between province, and whole power network safety operation is caused great impact; Dc system fault is frequent, and particularly straight-flow system continuous several times fault happens occasionally, the stable operation of serious threat security of system.DC power transmission line is the important component part of DC transmission system, because of transmission line malfunction and maintenance cause whole DC transmission system example out of service to happen occasionally.

For super high voltage direct current electricity transmission line, major accident is insulator flashover and pollution flashover takes place when being struck by lightning; Main maintenance work is to detect low zero resistance insulator, inferior insulator and removing filth.The thousands of easily kilometers of super high voltage direct current electricity transmission line, the insulator consumption is huge, and maintenance work is particularly wasted time and energy.Yet the research of direct current transportation aspect at present mainly concentrates on the power station equipment, and to the consumption maximum, directly to influence the line insulator and the runnability research thereof of circuit reliability less.A lot of 500kV have taken place and have exchanged the composite insulator accident in China, and the running environment of D.C. isolation is more more abominable than the running environment that exchanges insulator, and the probability that has an accident is higher.Show according to document announcement and correlative study, similar geographical environment, all to do the time spent than ac high voltage even more serious for the metal termination burn into pollution level of insulator under the high direct voltage effect, and the spoilage of insulator is also higher.

Electric field method is a kind ofly to utilize Electric Field Distribution curve around the insulator to judge defective, detect the high-voltage transmission line insulator live detection method of low zero resistance insulator, whether its principle is distorted a Electric Field Distribution around the insulator of defective, distort according to the Electric Field Distribution curve and judge low null value porcelain suspended insulator and defective composite insulator.Insulator charged detection instrument based on this principle is applied at the high-voltage AC transmission circuit.But the difficulty of dc electric field measurement technology far surpasses AC field, requires the input impedance infinity of surveying instrument, makes that directly the measurement DC electric field is unlikely.Measure extra high voltage network insulator DC electric field on every side difficulty more, not only require the surveying instrument volume little, in light weight, and easy and simple to handle.The method that is used for the insulator dc electric field measurement at present mainly contains the photoelectric effect method, rotation electrode electrostatic induction method, ball crack and voltage divider method four big classes, and wherein back two classes can only be used for porcelain insulator and glass insulator.

The photoelectric effect method utilizes pockels effect, kerr effect, optical waveguide, the electricity of some photoelectric crystals to cause light absorption, piezoelectricity elasto-optical effect, is subjected to the light signal of electric field intensity modulation to obtain electric field intensity information by measurement.Be subjected to optical crystal machining accuracy requirement height in the reality, had a strong impact on by temperature, stress and natural birefringence, the electro-optic crystal price is more expensive, and optical detection device requires the restriction of very sensitive factor such as accurately.The bigger difficulty that runs in dc electric field measurement is, requires the conductivity of electro-optic crystal and specific inductive capacity as far as possible little in the electric field measurement, and the electrooptical coefficient of the little crystal of specific inductive capacity is often also less; Migration of crystals ion and space charge are after assembling on the sensor, and former space electric field is changed; The optical fiber that connects probe and optical instrument has plastic peel usually, also can fetter a large amount of space charges, causes space electric field to change.Therefore this class measuring method is not used widely.

Rotation electrode electrostatic induction method is utilized a pair of counterrotating impeller shape electrode, and the charge signal that the space DC electric field is sensed on electrode is modulated into ac current signal and measures, and has reduced the requirement of subsequent process circuits such as pair amplifier.If this rotation electrode is put into DC electric field, and make pole plate vertical with direction of an electric field, then the electric charge of assembling on the pole plate also changes by the near sinusoidal rule.If two-plate is linked to each other by resistance, then have the near sinusoidal electric current on the resistance and flow, the resistance two ends also produce alternating voltage.Obviously, the size of this alternating voltage is directly proportional with the size of DC electric field.Surveying instrument based on these class methods exists mechanical rotation mechanism or vibrating mechanism, and is comparatively complicated, bulky, is unfavorable for the insulator accurate measurement of severe non-uniform electric field on every side.The more important thing is, draw comparatively difficulty of signal, must solve " being association of activity and inertia " problem from the electrode of high speed rotating or vibration.Employed brush structure is is often worn and torn, and contact resistance comes and go, and makes signal stable inadequately.I find in actual measurement, have a large amount of higher hamonic waves on the super high voltage direct current electricity transmission line, and the frequency of the ac modulation signal of DC electric field sensor output usually is between the harmonic frequency, am difficult to extract.Harmonic electric field also can be rotated the electrode modulation, causes powerful interference.

Ball crack method and voltage divider method all design at the voltage of bearing on the monolithic insulator in the porcelain suspension insulator string.Ball crack method is placed on two prills respectively on the steel cap and steel pin of insulator to be measured, and then the DC voltage of bearing on the insulator also is applied on the clearance between two balls, and the voltage breakdown in ball crack is exactly the voltage of bearing on the insulator.The voltage divider method utilizes a series of serial resistances to produce various known potential, and current potential to be measured in the insulator chain is connected with galvanometer on each joint of voltage divider, and when the galvanometer no current, current potential to be measured is consistent with the current potential of this joint of voltage divider.These two kinds of methods can only be used for laboratory study, can not be used for the measurement that the insulator DC electric field distributes on the actual track.And because of ball crack voltage breakdown dispersiveness is big, voltage divider and galvanometer lead effect Electric Field Distribution error are bigger.

Summary of the invention

The object of the present invention is to provide a kind of DC electric filed detection method of insulator for high-voltage DC transmission line, realized easier, practical, dc electric field measurement around the HVDC (High Voltage Direct Current) transmission line insulator accurately, not only can realize the charged detection problem of D.C. isolation, and can provide scientific basis for the design and the maintenance of D.C. isolation.

The present invention adopts integrating circuit, and the quantity of electric charge by electrostatic induction electric charge on two metallic conductors in the measurement space electric field reaches the purpose of measuring DC electric field intensity, as shown in Figure 1.

1, metallic conductor can be made up of two metal polar plates that are parallel to each other 1 and 2; These two pole plates are connected respectively to the positive input terminal and the negative input end of operational amplifier 3, and utilize the characteristic of operational amplifier intrinsic " positive-negative input end voltage is zero ", make metal polar plate 1,2 keep same current potential;

2, operational amplifier 3 constitutes integrating circuit 5 with capacitor 4, and the electric current I from pole plate 1 and 2 is carried out integration.Metal polar plate 1,2 and integrating circuit 5 from the place of space DC electric field less than 1kv/m, are moved to insulator surface; Electrostatic induction electric charge Q in the process that moves on the pole plate increases with the enhancing of DC electric field E, and forms electric current I between two metal polar plates; Electric current I is integrated 5 integrations of circuit, and makes integrating circuit 5 output voltage U; Then voltage signal U is directly proportional with tested DC electric field intensity E.By demarcating the scale-up factor that to obtain U and E.If metal polar plate 1,2 and integrating circuit 5 are slided along insulator surface, then along with the variation of space, metal polar plate place of arrival DC electric field E, the size of electrostatic induction electric charge Q changes thereupon on the pole plate, then has corresponding electric current I to flow between two-plate, and then integrator output voltage U changes thereupon.Integrator output voltage U can utilize common single chip circuit collection and store.The Changing Pattern of final U is exactly the regularity of distribution of E along insulator.

The concrete grammar of demarcating is: integrating circuit from the place of direct current field intensity less than 1kv/m, is moved in the DC electric field of 50kV/m; When integrating circuit is in the DC electric field of 50kV/m, the numerical value U of integrator output voltage U ₅₀Corresponding to 50kV/m, then the proportionate relationship between U and the E is: E=U* (50/U ₅₀) kV/m.

The invention has the advantages that equipment therefor is simple, with low cost, only need metal polar plate and integrator circuit; Easy and simple to handle, only need device is moved on to the insulator front and can finish the measurement that whole DC electric field is distributed along the insulator slip, and do not have the shortcoming of above-mentioned the whole bag of tricks, accurately and reliably.

Description of drawings

Fig. 1 is a filed detection method schematic diagram of the present invention.Wherein, metal polar plate 1,2, operational amplifier 3, capacitor 4, integrating circuit 5.

Fig. 2 is one embodiment of the present invention synoptic diagram.

The accompanying drawing 3 insulator DC electric field distribution curve for being measured in the embodiments of the present invention, position number are insulator full skirt number, from ground connection side meter.

Specific implementation method

Fig. 1～3 are one embodiment of the present invention.As shown in Figure 2, metal polar plate adopts the parallel rectangular flat board (to be of a size of that 10cm * 5cm), integrating circuit is made up of operational amplifier A D620 and 1 microfarad electric capacity; The single chip circuit of integrating circuit and follow-up responsible record thereof is placed in the rectangle shielding box, and metal polar plate is placed on the shielding box both sides external and insulate with shielding box; Metal polar plate and insulator axis normal can be measured the DC electric field component along axis direction.The axial DC Electric Field Distribution curve that accompanying drawing 3 has provided a 110kV grade composite insulator that this implementation method measured when bearing the 50kV DC voltage, ordinate is the axial DC electric field intensity that is measured among the figure, horizontal ordinate is an insulator full skirt sequence number, from ground connection side meter, up to high-pressure side.As seen, DC electric field distributes and manifests strong, middle weak " saddle " shape distribution in high-pressure side, consistent with theoretical analysis.

Claims

1. A method for measuring the DC electric field of an insulator in a high-voltage DC transmission line, characterized in that: an integrating circuit is used to measure the DC electric field intensity by measuring the amount of charge of the electrostatically induced charge on two metal conductors in the space electric field;

a, the metal conductor that will be made up of two metal pole plates (1,2) parallel to each other; Connect to the positive input terminal and the negative input terminal of operational amplifier (3) respectively, utilize the inherent " positive and negative input terminal voltage of operational amplifier is The characteristic of "zero" keeps the metal plates (1, 2) at the same potential;

B, operational amplifier (3) and capacitor (4) constitute integral circuit (5), the electric current I from metal plate (1,2) is integrated; Metal plate (1,2) and integral circuit (5) Move from a place where the DC electric field is less than 1kv/m to the surface of the insulator; during the moving process, the electrostatically induced charge Q on the plate increases with the increase of the DC electric field E, and a current I is formed between the two metal plates; the current I is drawn The integration of the integral circuit (5) makes the integral circuit (5) output voltage U; the output voltage U is proportional to the measured DC electric field strength E, and the proportional coefficient between U and E is obtained through calibration.

2. The measurement method according to claim 1, characterized in that: the specific method of calibration is: move the integrating circuit from a place where the DC field strength is less than 1kv/m to a DC electric field of 50kV/m; when the integrating circuit When in a DC electric field of 50kV/m, the value U ₅₀ of the output voltage U of the integrator corresponds to 50kV/m, and the proportional relationship is: E=U*(50/U ₅₀ )kV/m.