CN105116201A - Measuring device and method for return voltage parameter - Google Patents

Abstract

The invention discloses a measuring device for a return voltage parameter, which comprises a capacitor; the capacitor is provided with an upper terminal at an upper polar plate and a lower terminal at a lower polar plate; the lower terminal is connected with a microcurrent tester in series; an output interface of the microcurrent tester is connected with a data acquisition card; the capacitor is arranged in a sealed container, and the upper terminal and the lower terminal extend out of the sealed container communicated with a vacuumizing device. Compared with the prior art, the measuring device has the following advantages: (1) an evaluation parameter of a return voltage is directly obtained by measuring a charging and discharging current on the polar plates of the capacitor, influence of a leakage current on voltage measuring is avoided, and the evaluation parameter acquired by the current is more convenient and accurate; (2) a shell of the measuring device adopts a high-low concave-convex smocking type design, thus increasing a creepage distance of the surface leakage current and reducing errors caused by the leakage current; (3) the interior of the measuring device is in a vacuum state, and can eliminate the influence of factors such as humidity in air and the like.

Description

The measurement mechanism of return voltage parameter and measuring method

Technical field

The present invention relates to a kind of measurement mechanism of return voltage parameter.The invention still further relates to a kind of method using described measurement mechanism to carry out return voltage parameter measurement.

Background technology

In modern power systems, electric energy safe, supply that is reliable and high-quality are the most basic requirements.In electric system, transformer is whole electrical grid transmission electric energy and the key equipment distributing electric energy.Therefore, whether good reliable, the stable operation directly having influence on whole electric system of transformer.Transformer insulated partial properties declines, and especially, insulation degradation damages, and directly can cause Power Transformer Faults.Up to now, the monitoring method of transformer insulation state mainly can be divided into chemical method, method for electrically and other diagnostic method.Wherein chemical method comprises furfural content analysis, water trace analysis, dissolved gas analysis etc. in insulation paper polymerization degree test, oil, and method for electrically comprises dielectric response method (time domain, frequency domain) and traditional electric test method.

Return voltage method (Returnvoltagemethod, RVM) based on dielectric response basis starts from the nineties in 20th century, is a kind of nondestructive testing method being obtained Solid Insulation of Power Transformer state by impressed voltage.Its advantage is that antijamming capability is strong, the initial slope S of its return voltage curve _i, centre time constant t _domclosely related etc. moisture etc. in the degree of aging of parameter and transformer, paper; The field monitoring of transformer can also be advantageously used in simultaneously.In recent years along with transformer insulation state detects the development in harmless state of insulation testing research, return voltage method comes into one's own gradually.

The method of testing of current return voltage is directly at tested object two ends access voltage test device, but the method is when carrying out return voltage test: one is the equivalent inpnt resistance of test branch road in the two ends parallel connection of tested object, equivalent inpnt resistance is often much smaller than the insulation resistance of tested object self, therefore the access of equivalent inpnt resistance makes the free charge producing return voltage have new leak path, accelerate the leakage rate of free charge, make the return voltage curve obtained have very large error, the status assessment data obtained is inaccurate; Two is in data processing, voltage test device continuous coverage sample obtains return voltage numerical value, return voltage curve is obtained again by its numerical value of matching, finally to return voltage curve carry out numerical analysis obtain evaluate parameter, process comparatively loaded down with trivial details and also there will be in fit procedure the data precision decline problem.

Summary of the invention

First technical matters to be solved by this invention, is just to provide a kind of measurement mechanism of return voltage parameter.

Second technical matters to be solved by this invention, is just to provide a kind of measuring method of return voltage parameter.

Adopt apparatus and method of the present invention, directly can obtain the return voltage parameter of assessment transformer oil paper insulation state, thus avoid the defect that existing return voltage testing apparatus Leakage Current causes error, improve the accuracy rate of measurement, simplify loaded down with trivial details evaluate parameter computation process simultaneously, make measurement more convenient.

Solve above-mentioned first technical matters, the present invention adopts following technical scheme:

A kind of measurement mechanism of return voltage parameter, it is characterized in that: comprise a capacitor, the top crown of described capacitor is provided with terminals, bottom crown is provided with lower terminals, described lower terminals are connected in series with a Micrometer of current, and the output interface of described Micrometer of current is connected with a data collecting card; Described capacitor is placed in an airtight container, and described upper terminals, lower terminals reach outside airtight container, and described airtight container is connected with a vacuum extractor.。

Further, described capacitor is plane-parallel capacitor, described upper terminals are upper metal guide rod, described lower terminals are lower metal guide rod, described upper metal guide rod is provided with external thread, described airtight container has a threaded hole coordinated with upper metal guide rod, it is outer and by rotating the distance that upper metal guide rod comes regulating capacitor two-plate that described upper metal guide rod stretches out airtight container through threaded hole, and described lower metal guide rod to be fixedly located on airtight container and to stretch out outside airtight container.

As a kind of embodiment of the present invention, the wall of described airtight container is concavo-convex plaited skirt shape.

Described airtight container is formed by high resistivity insulating material (SMC plate) manufacture.

Described vacuum means is set to vacuum air pump, and it is arranged on the wall of airtight container.

Described plane-parallel capacitor is formed by the manufacture of red copper material.

Solve above-mentioned second technical matters, the present invention adopts following technical scheme:

A measuring method for return voltage parameter, is characterized in that comprising the following steps:

Direct supply is connected with the positive and negative terminals of transformer high-low-voltage winding by S1, and utilize direct supply to charge to the insulation resistance Rg of transformer high-low-voltage winding and geometric capacitance Cg, the duration of charging is T _c;

S2 disconnects direct supply, and be directly connected by the positive and negative terminals of transformer high-low-voltage winding, the geometric capacitance Cg of transformer high-low-voltage winding discharges, and discharge time is T _d;

The positive and negative terminals of transformer high-low-voltage winding disconnect by S3, the upper terminals of described measurement mechanism are connected with the positive terminals of transformer high-low-voltage winding, lower terminals are connected with the negative terminals of transformer high-low-voltage winding, obtain the current i on capacitor plate by Micrometer of current _c, and the current data of Micrometer of current acquisition is collected with data collecting card.

Compared with prior art, inventive article has the following advantages:

1) directly obtained the evaluate parameter of return voltage by the charging and discharging currents measured on capacitor plate, avoid leakage current on the impact of voltage measurement, the evaluate parameter simultaneously obtained by electric current is convenient, accurate;

2) shell of measurement mechanism adopts the concavo-convex clothing pleat design of height, adds the creepage distance of surface leakage current, decreases the error that leakage current causes;

3) measurement mechanism inside is in vacuum state, can eliminate the impact that in air, the factor such as humidity is brought.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of measurement mechanism of the present invention;

Fig. 2 is the use schematic diagram of measurement mechanism of the present invention;

Fig. 3 is the return voltage curve map that the present invention measures.

In figure: 1-airtight container, 2-vacuum air pump, 3-top crown, 4-bottom crown, 5-threaded hole, the upper metal guide rod of 6-, metal guide rod under 7-, 8-Micrometer of current, 9-data collecting card, 10-capacitor.

Embodiment

Below in conjunction with accompanying drawing, by embodiment, the invention will be further described.

As shown in Figure 1, 2, the measurement mechanism embodiment of return voltage parameter of the present invention, comprise a capacitor 10, capacitor 10 is placed in an airtight container 1, airtight container 1 is connected with a vacuum extractor, wherein vacuum means is set to vacuum air pump 2, and it is arranged on the wall of airtight container 1, and capacitor 10 is in the working environment of vacuum can eliminate the impact that in air, the factor such as humidity is brought;

The top crown 3 of capacitor 10 is provided with terminals, bottom crown 4 is provided with lower terminals, lower terminals are connected in series with a Micrometer of current 8, the output interface of Micrometer of current 8 is connected with a data collecting card 9, the evaluate parameter of return voltage is directly obtained by the charging and discharging currents measured on capacitor plate, avoid leakage current on the impact of voltage measurement, the evaluate parameter simultaneously obtained by electric current is convenient, accurate;

The wall of airtight container 2 is concavo-convex plaited skirt shape, it is formed by high resistivity insulating material (SMC plate) manufacture, the shell of measurement mechanism adopts the concavo-convex clothing pleat design of height, adds the creepage distance of surface leakage current, decreases the error that leakage current causes.

Wherein capacitor 10 is plane-parallel capacitor, it is formed by the manufacture of red copper material, upper terminals are upper metal guide rod 6, lower terminals are lower metal guide rod 7, upper metal guide rod 6 is provided with external thread, airtight container 1 has a threaded hole 5 coordinated with upper metal guide rod, it is outer and by rotating the distance that upper metal guide rod comes regulating capacitor two-plate that upper metal guide rod 6 stretches out airtight container 1 through threaded hole 5, and lower metal guide rod 7 to be fixedly located on airtight container 1 and to stretch out outside airtight container.

As shown in Figure 2, above-mentioned measurement mechanism is adopted transformer to be carried out to the concrete steps of the measuring method of return voltage parameter as follows: first Closing Switch J1, direct supply is connected with the positive and negative terminals of transformer high-low-voltage winding, utilize direct supply to charge to the insulation resistance Rg of transformer high-low-voltage winding and geometric capacitance Cg, the duration of charging is T _c; Cut-off switch J1, Closing Switch J2, be directly connected by the positive and negative terminals of transformer high-low-voltage winding, the geometric capacitance Cg of transformer high-low-voltage winding discharges, and discharge time is T _d; Cut-off switch J2, Closing Switch J3, the upper terminals of described measurement mechanism are connected with the positive terminals of transformer high-low-voltage winding, lower terminals are connected with the negative terminals of transformer high-low-voltage winding, regulating the upper and lower polar plate spacing d of the capacitor of measurement mechanism of the present invention by rotating upper metal guide rod, making to meet following relation

$\frac{S}{d}\≤\frac{\mathrm{\ρ}}{100*R_g}---\left(1\right)$

$\frac{S}{d}\≤\frac{C_g}{10*\mathrm{\ϵ}}---\left(2\right)$

In formula, S is the area of vacuum capacitance pole plate, and d is the distance between upper and lower capacitor plate, and ρ is the resistivity between upper and lower capacitor plate, and ε is the specific inductive capacity between capacitor plate;

The data collecting card of measurement mechanism of the present invention is connected with terminal, at this moment can be obtained the current i on capacitor plate by Micrometer of current _c.Finally by data collecting card, the data that Micrometer of current obtains are sent to terminal analysis.

Obtained the parameter of assessment transformer oil paper insulation state by the charging and discharging currents measuring capacitor, we can obtain the relation of return voltage testing evaluation parameter and charging and discharging currents by the following derivation of equation.First, the relation of capacitance voltage and capacitance current is as follows,

$u_C\left(t\right)=\frac{1}{C}{\∫}_{\mathrm{\∞}}^t{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ}=u\left(0\right)+\frac{1}{C}{\∫}_0^t{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ}---\left(3\right)$

According to the decision formula of electric capacity and carry it into formula (3),

$u_C\left(t\right)=u\left(0\right)+\frac{d}{\mathrm{\ϵ}S}{\∫}_0^t{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ}---\left(4\right)$

Gain knowledge according to dependency number known, capacitance voltage initial value u (0) only determines u _cthe upper and lower translation change of (t), and the initial slope S for the major parameter of transformer oil paper insulation state estimation being return voltage _iwith centre time constant t _dom(when return voltage has multiple extreme point, time corresponding to return voltage maximum of points is called main time constant), above parameter and capacitance voltage initial value u (0) have nothing to do.Thus, return voltage u _ret () curve is

$u_{re}\left(t\right)=\frac{d}{\mathrm{\ϵ}S}{\∫}_0^t{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ}---\left(5\right)$

See Fig. 3, initial slope S _ithe initial slope of measuring phases, therefore

$\frac{{\mathrm{du}}_{re}\left(t\right)}{dt}=\frac{d}{\mathrm{\ϵ}S}({{\∫}_0^t{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ})}^{\′}=\frac{d}{\mathrm{\ϵ}S}{i}_C(t)---\left(6\right)$

Thus,

$S_i=\frac{{\mathrm{du}}_{re}\left(t\right)}{dt}{|}_{t=0}=\frac{d}{\mathrm{\ϵ}S}{i}_C\left(0\right)---\left(7\right)$

It should be noted that the t=0 moment in formula (7) refers to return voltage detection T in Fig. 3 _pthe initial time in stage (after the charge and discharge stage), namely J3 closed moment.Work as u _re(t)=U _maxtime, derivative value corresponding to this maximum point place is 0, thus

$\frac{{\mathrm{du}}_{re}\left(t\right)}{dt}=\frac{d}{\mathrm{\ϵ}S}{i}_C\left(t\right)=0---\left(8\right)$

I.e. i _c(t _domduring)=0, the corresponding moment is centre time constant.Utilize inverse function, can by t _domshow, namely in practical operation, according to the current data of the return voltage test phase of data collecting card record, in the electric current first time that Micrometer of current detects from just becoming the negative stage, the moment corresponding when electric current registration is 0 is centre time constant t _dom.

Meanwhile, we also can obtain the maximum return voltage U of return voltage curve _max, this parameter also can be used as the supplementary parameter of return voltage testing evaluation state of insulation.For U _maxaccording to formula (5), can obtain,

$U_{\max }=\frac{d}{\mathrm{\ϵ}S}{\∫}_0^{t_{dom}}{i}_C\left(\mathrm{\τ}\right)d\mathrm{\τ}---\left(9\right)$

Wherein, t _domthe data reading that can be obtained by data collecting card.

Claims (7)

1. the measurement mechanism of a return voltage parameter, it is characterized in that: comprise a capacitor (10), the top crown (3) of described capacitor (10) is provided with terminals, bottom crown (4) is provided with lower terminals, described lower terminals are connected in series with a Micrometer of current (8), the output interface of described Micrometer of current (8) is connected with a data collecting card (9); Described capacitor (10) is placed in an airtight container (1), and described upper terminals, lower terminals reach airtight container (1) outward, and described airtight container (1) is connected with a vacuum extractor.

2. the measurement mechanism of return voltage parameter according to claim 1, it is characterized in that: described capacitor (10) is plane-parallel capacitor, described upper terminals are upper metal guide rod (6), described lower terminals are lower metal guide rod (7), described upper metal guide rod (6) is provided with external thread, described airtight container (1) has a threaded hole (5) coordinated with upper metal guide rod (6), described upper metal guide rod (6) stretches out airtight container (1) outward and by rotating the distance that upper metal guide rod (6) comes regulating capacitor (10) two-plate through threaded hole (5), described lower metal guide rod (7) is fixedly located at airtight container (1) and goes up and stretch out outside airtight container.

3. the measurement mechanism of return voltage parameter according to claim 2, is characterized in that: the wall of described airtight container (1) is concavo-convex plaited skirt shape.

4. the measurement mechanism of return voltage parameter according to claim 2, is characterized in that: described airtight container (10) is formed by the manufacture of high resistivity insulating material.

5. the measurement mechanism of return voltage parameter according to claim 2, is characterized in that: described vacuum means is set to vacuum air pump (2), and it is arranged on the wall of airtight container (1).

6. the measurement mechanism of return voltage parameter according to claim 2, is characterized in that: described plane-parallel capacitor is formed by the manufacture of red copper material.

7. the measurement mechanism of the return voltage parameter according to claim 1 to 6 any one carries out a method for return voltage parameter measurement, it is characterized in that comprising the following steps:

Direct supply is connected with the positive and negative terminals of transformer high-low-voltage winding by S1, and utilize direct supply to charge to the insulation resistance Rg of transformer high-low-voltage winding and geometric capacitance Cg, the duration of charging is T _c;

S2 disconnects direct supply, and be directly connected by the positive and negative terminals of transformer high-low-voltage winding, the geometric capacitance Cg of transformer high-low-voltage winding discharges, and discharge time is T _d;

The positive and negative terminals of transformer high-low-voltage winding disconnect by S3, the upper terminals of described measurement mechanism are connected with the positive terminals of transformer high-low-voltage winding, lower terminals are connected with the negative terminals of transformer high-low-voltage winding, obtain the current i on capacitor plate by Micrometer of current _c, and the current data of Micrometer of current acquisition is collected with data collecting card.