CN106291076B - A kind of double difference fraction D-dot overvoltage sensors and measuring system - Google Patents

Abstract

The present invention relates to a double-differential D-dot overvoltage sensor and a measurement system. The double-differential D-dot overvoltage sensor includes a first unipolar D-dot sensor and a second unipolar D-dot sensor, and the first The unipolar D-dot sensor and the second unipolar D-dot sensor are arranged symmetrically up and down; the first unipolar D-dot sensor and the second unipolar D-dot sensor both include a metal hemispherical shell body, the outer surface of the metal hemispherical shell body An outer layer electrode is arranged, an inner layer electrode is arranged on the inner surface of the metal hemispherical shell body, and the outer layer electrode and the inner layer electrode are connected through an insulating filler. The outer and inner electrodes of the double-differential D-dot overvoltage sensor rely on electric field coupling to induce charges, output differential voltage signals, and realize non-contact measurement of the measurement system, improving the response speed, anti-interference ability and sensitivity of the measurement. The overvoltage measurement system processes the differential voltage signal output by the double differential D-dot overvoltage sensor, and automatically identifies the overvoltage signal.

Description

A double-differential D-dot overvoltage sensor and measurement system

technical field

The invention relates to the technical field of smart grid overvoltage monitoring, in particular to a double-differential D-dot overvoltage sensor and a measurement system.

Background technique

Overvoltage refers to the phenomenon of voltage rise and potential rise that is dangerous to insulation in the power system under certain conditions. It belongs to an electromagnetic disturbance phenomenon in the power system, including external overvoltage and internal overvoltage. External overvoltage includes lightning overvoltage and atmospheric overvoltage. External overvoltage will destroy the insulation of electrical facilities, cause short-circuit grounding fault, and will also propagate along the line in the form of flowing waves, invading substations and causing insulation damage accidents; internal overvoltage is the power Overvoltage caused by changes in the internal operation mode of the system, including transient overvoltage and operating overvoltage. Overvoltage will cause a series of accidents such as breakdown, discharge, flashover and explosion of power equipment.

The acquisition of overvoltage signals is mainly realized by sensors. At present, it is mainly a non-contact capacitive voltage divider sensor. The stray capacitance C1 is used as the high-voltage arm capacitance, and a fixed-value capacitor with a capacitance of C2 is connected directly under the sensing metal plate as the low-voltage arm capacitance. The overvoltage signal is drawn from the sensing metal plate through the matching resistor and transmitted to the external through the coaxial cable. For the data acquisition system, the entire sensor is installed in a metal shielding case to shield the interference of other non-measurement items.

However, the overvoltage signal collected by the current sensor is easily affected by the complex electromagnetic environment, the anti-interference ability is low, the sensitivity of the sensor is low, resulting in low measurement accuracy, and the overvoltage signal is often not captured.

Contents of the invention

In order to overcome the problems of low anti-interference ability and low sensitivity of the overvoltage sensor in the related art, and often fail to capture the overvoltage signal, the present invention provides a double-differential D-dot overvoltage sensor and a measurement system.

In order to solve the above technical problems, the present invention provides the following technical solutions:

The double differential D-dot overvoltage sensor provided by the present invention includes a first unipolar D-dot sensor and a second unipolar D-dot sensor, wherein,

The first unipolar D-dot sensor and the second unipolar D-dot sensor are arranged symmetrically up and down;

Both the first unipolar D-dot sensor and the second unipolar D-dot sensor include a metal hemispherical shell body, the outer surface of the metal hemispherical shell body is provided with an outer layer electrode, and the inner surface of the metal hemispherical shell body is provided with Inner electrode;

An insulating filler is provided between the outer electrode and the inner electrode, and the outer electrode and the inner electrode are connected through the insulating filler.

Preferably, in the above-mentioned double-differential D-dot overvoltage sensor, the outer electrode and the inner electrode are both hemispherical shell-shaped PCB boards.

Preferably, in the above double differential D-dot overvoltage sensor, the insulating filler includes epoxy resin.

Preferably, in the above-mentioned double-differential D-dot overvoltage sensor, the same end of the outer layer electrode and the inner layer electrode are respectively provided with output ends.

A double differential D-dot overvoltage sensor provided by the present invention includes a first unipolar D-dot sensor and a second unipolar D-dot sensor, wherein the first unipolar D-dot sensor and the second unipolar The polar D-dot sensor is arranged symmetrically up and down; the first unipolar D-dot sensor and the second unipolar D-dot sensor both include a metal hemispherical shell body, and the outer surface of the metal spherical shell body is provided with an outer layer electrode, An inner layer electrode is arranged on the inner surface of the metal hemispherical shell body; an insulating filler is arranged between the outer layer electrode and the inner layer electrode, and the outer layer electrode and the inner layer electrode are connected through the insulating filler. The double differential D-dot overvoltage sensor provided by the present invention is placed in the electric field to collect voltage signals to realize non-contact measurement; the insulating filler not only supports the internal structure of the sensor, but also regulates the electric field around the sensor , to improve the insulation capability of the entire sensor; the D-dot sensor has a large measurement bandwidth; the first unipolar D-dot sensor and the second unipolar D-dot sensor arranged symmetrically up and down are used to collect potential signals at different positions, Output different voltage signals to improve the measurement accuracy and sensitivity of the sensor.

Based on the double differential D-dot overvoltage sensor provided by the invention, the invention also provides an overvoltage measurement system.

The overvoltage measurement system provided by the present invention includes a double differential D-dot overvoltage sensor, an amplification circuit, a signal conditioning circuit, a high-speed acquisition circuit and an overvoltage self-identification module, wherein,

The output end of the double differential D-dot overvoltage sensor is electrically connected to the input end of the amplifying circuit;

The output end of the amplifying circuit is electrically connected to the input end of the signal conditioning circuit;

The output terminal of the signal conditioning circuit is electrically connected to the input terminal of the high-speed acquisition circuit;

The output end of the high-speed acquisition circuit is electrically connected to the overvoltage self-identification module.

Preferably, in the above overvoltage measurement system, the amplifying circuit is a two-stage differential amplifying circuit.

Preferably, in the above overvoltage measurement system, the signal conditioning circuit includes a filter circuit.

The overvoltage measurement system provided by the present invention includes a double differential D-dot overvoltage sensor, an amplifying circuit, a signal conditioning circuit, a high-speed acquisition circuit and an overvoltage self-identification module, wherein the double differential D-dot overvoltage sensor, an amplifying circuit , the signal conditioning circuit, the high-speed acquisition circuit and the overvoltage self-identification module are electrically connected in series in sequence. The double-differential D-dot overvoltage sensor collects potential signals at different electric field positions and outputs differential voltages; the amplifier circuit amplifies the output voltage signals; the signal conditioning circuit further processes the amplified signals to remove interference signals; the high-speed acquisition circuit will simulate The signal is converted into a digital signal, which is convenient for comparison and identification; the overvoltage self-identification module identifies the overvoltage signal by comparison. The overvoltage measurement system provided by the invention automatically identifies overvoltage signals through a series of circuit processing, has wide measurement bandwidth, strong anti-interference ability and high sensitivity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings without paying creative labor.

Fig. 1 is the structural representation of a kind of non-contact capacitive pressure divider sensor that prior art provides;

Fig. 2 is the structural representation of a kind of unipolar D-dot sensor provided by the present invention;

Fig. 3 is the structural representation of a kind of double differential D-dot overvoltage sensor provided by the present invention;

Fig. 4 is a structural schematic diagram of an overvoltage measurement system provided by the present invention;

The symbols in Figure 1-Figure 4 indicate:

01-upper electrode, 02-lower electrode, 1-first unipolar D-dot sensor, 11-outer electrode, 12-inner electrode, 13-insulation filler, 2-second unipolar D-dot sensor, 3-amplification circuit, 4-signal conditioning circuit, 5-high-speed acquisition circuit, 6-overvoltage self-identification module.

Detailed ways

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with aspects of the invention as recited in the appended claims.

The unipolar D-dot sensor measures the lightning impulse voltage signal by measuring the rate of change of the electric displacement vector. When the lightning strikes the ground on or near the wire to be tested, the upper electrode 01 and the lower electrode 02 of the sensor will pass through The electric field coupling induces charges, and when the changing induced charges flow through the measuring resistor R _m connected to the electrodes, a resistance voltage drop is generated. At this time, the measured difference between the floating potential of the upper electrode 01 and the lower electrode 02 is used as the difference of the sensor Output, the equivalent principle of the electric field measured by the upper electrode 01 and the lower electrode 02 is shown in Figure 2:

If the unipolar D-dot sensor is placed in the space where the electric field strength is E(r,t), the surface of the metal electrode will have an induced charge due to the principle of electrostatic induction, and its size is q, which is obtained by Gauss' theorem:

In the above formula, the right side of the equation indicates that the electric field strength E(r, t) produces a linear superposition of charges on each micro-element on the conductor surface, so the induced charge is proportional to the electric field strength E(r, t).

If the electric field changes with time, the induced charge will also change with time, and formula (1) becomes:

The current generated by the changing charge will flow through the resistor R _m , then the voltage drop V _o (t) on the resistor R _m is:

It can be seen from the above formula that the output voltage signal V _o (t) of the D-dot sensor is proportional to the differential value of the electric field intensity.

The electric potential on the outer surface of the conductor is distributed according to the function f(r′), r′ is the position vector at the source point of the conductor, r is the position vector at the field point, E(r) is the electric field intensity at this point, and there is no free charge in the Ω region , that is, ρ(r′)=0, F(r) is a constant, which can be obtained through formula derivation:

Through formula (3) and formula (4), the relationship between the potential value of the transmission line and the output voltage signal of the D-dot sensor can be obtained as follows:

After derivation, the relationship expression between D-dot sensor input and output is:

Among them, V _o (t) - the output voltage signal of the D-dot sensor;

R _m - measuring resistance;

A _eq - the equivalent area of the sensor;

It can be seen from formula (6) that by integrating the output voltage signal of the D-dot sensor, the voltage signal proportional to the electric field intensity at the measurement point in the space area can be obtained, and after being corrected by the corresponding proportional correction coefficient, it can be obtained The value of the electric field at that point.

The D-dot sensor relies on the electric field coupling method to measure the conductor potential. It is based on the principle that the electric field value around the conductor is proportional to the conductor's own potential. By introducing the sensor into the electric field generated around the measured conductor, the electric field value versus time differential value proportional to the voltage signal. There is no direct electrical connection between the D-dot sensor and the conductor. It only indirectly measures the conductor potential by measuring the electric field strength around the conductor. There is no direct energy transfer in the process. Since there is no winding and iron core structure, while avoiding waveform distortion, a larger measurement dynamic range can be obtained by virtue of the linear medium between the conductor and the sensor. Moreover, its structure is simple, and the characteristics of non-contact measurement make it possible to reduce the insulation structure, and the lower output voltage range also realizes the miniaturization and digitization of the sensor.

Referring to FIG. 3 , this figure shows the basic structure of the double-differential D-dot overvoltage sensor provided by the embodiment of the present invention.

Based on the measurement principle of the above-mentioned unipolar D-dot sensor, the double differential D-dot overvoltage sensor provided by the present invention includes a first unipolar D-dot sensor 1 and a second unipolar D-dot sensor 2, wherein:

The first unipolar D-dot sensor 1 and the second unipolar D-dot sensor 2 have the same structure and are arranged symmetrically up and down, so they can measure electric field signals at different positions and output voltage signals U ₁ and U ₂ respectively, which can improve measurement accuracy , to reduce the impact of signal errors on measurement accuracy.

The first unipolar D-dot sensor 1 and the second unipolar D-dot sensor 2 both include a metal hemispherical shell body, the outer surface of the metal hemispherical shell body is provided with an outer layer electrode 11, and the inner surface of the metal hemispherical shell body is provided with an inner layer electrode 12. Both the first unipolar D-dot sensor 1 and the second unipolar D-dot sensor 2 adopt a metal hemispherical shell structure. The reason is that the spherical structure is similar to the equipotential surface of the electric field around the measured conductor, which can make the charge distribution on the electrode even , reduce the maximum value of the local electric field intensity at the boundary and inside of the sensor, effectively reducing the reliability of the sensor for insulation breakdown. Moreover, in this case, the direction of the electric field intensity vector uniformly points to the radial direction, and no bending of electric field lines occurs, which can minimize the edge effect and achieve the purpose of weakening the original electric field distortion caused by the intervention of the sensor. Preferably, both the outer layer electrodes 11 and the inner layer electrodes 12 are hemispherical shell-shaped PCB boards.

An insulating filler 13 is provided between the outer electrode 11 and the inner electrode 12 , and the outer electrode 11 and the inner electrode 12 are connected through the insulating filler 13 . The insulating filler supports the internal structure of the entire D-dot sensor, and also plays a role in regulating the electric field around the sensor, so that the strong electric field is concentrated in the insulating filler bracket with a high critical electric field strength, thereby reducing the impact of the external electric field. Finally, the purpose of improving the insulation capacity of the entire sensor is achieved, and at the same time the output power of the sensor is reduced, so that it can meet the requirements of the low-power drive of the secondary measurement device. Preferably, epoxy resin is used for the insulating filler 13 in the double differential D-dot overvoltage sensor provided by the present invention.

In order to facilitate the output voltage signal of the sensor, the same end of the outer layer electrode 11 and the inner layer electrode 12 are respectively provided with an output end, and the output voltage of the first unipolar D-dot sensor 1 is U ₁ , and the output voltage of the second unipolar D-dot sensor 2 is U 1 . The output voltage of is U ₂ , and the output voltage is subsequently processed.

The outer electrode 11 and the inner electrode 12 are concentric rings with different radii, for example, the outer electrode 11 has a radius of 5 cm, and the inner electrode 12 has a radius of 7 cm.

The double differential D-dot overvoltage sensor provided by the embodiment of the present invention includes a first unipolar D-dot sensor 1 and a second unipolar D-dot sensor 2, and the first unipolar D-dot sensor 1 and the second unipolar D-dot sensor The polar D-dot sensor 2 is arranged symmetrically up and down; the first unipolar D-dot sensor 1 and the second unipolar D-dot sensor 2 both include a metal hemispherical shell body, and an outer layer electrode 11 is arranged on the outer surface of the metal hemispherical shell body, and the metal hemispherical shell body The inner surface of the hemispherical shell body is provided with an inner layer electrode 12, and the outer layer electrode 11 and the inner layer electrode 12 are connected by an insulating filler 13, and the unipolar D-dot sensor senses the charge, the output differential voltage. The double-differential D-dot overvoltage sensor provided by the embodiment of the present invention has a simple structure, realizes non-contact measurement, and has fast response speed and high sensitivity.

Based on the double differential D-dot overvoltage sensor provided by the present invention, the present invention also provides an overvoltage measurement system, as shown in FIG. 4 .

The overvoltage measurement system provided by the embodiment of the present invention includes a double differential D-dot overvoltage sensor, an amplification circuit 3, a signal conditioning circuit 4, a high-speed acquisition circuit 5 and an overvoltage self-identification module 6, wherein:

The double differential D-dot overvoltage sensor obtains the voltage signal of the electric field around the transmission line under test, and the output end of the double differential D-dot overvoltage sensor is electrically connected to the input end of the amplifier circuit 3, and the double differential D-dot overvoltage The sensor outputs a differential voltage and transmits it to the amplifying circuit 3 . The double-differential D-dot overvoltage sensor is placed in the electric field near the transmission line under test, and the charge is induced by electric field coupling, and the differential output voltage U ₁ , U ₂ is amplified by the amplifier circuit 3 to output the differential voltage U _o .

In order to amplify the differential output voltage of the double-differential D-dot overvoltage sensor, the amplifying circuit 3 adopts a two-stage differential amplifying circuit. The differential output voltages U ₁ and U ₂ of the double differential D-dot overvoltage sensor are:

After the first-stage differential amplifier circuit, the output voltages U _o1 and U _o2 are respectively:

U _o1 =k ₁ U ₁ U _o2 =k ₁ U ₂

Among them, k ₁ ——the differential mode amplification factor of the first stage differential circuit.

After the second stage differential amplifier circuit, the output voltage U _o is:

U _o ＝k ₂ (k ₁ U ₁ -k ₁ U ₂ ) (9)

Among them, k ₂ ——the differential mode amplification factor of the second stage differential circuit.

In a general two-stage differential amplifier circuit, k is the overall differential amplification factor, uniformly k=k ₁ k ₂ , and the value ranges of k ₁ and k ₂ are between 3-20. The two hemispherical electrodes in the double differential D-dot overvoltage sensor can be regarded as R _m1 =R _m2 , A _eq1 =A _eq2 , which are unified as R _m , A _eq . Derived from formula (7), formula (8) and formula (9), the amplified output voltage U _o is:

The common-mode rejection ratio of a single-stage differential amplifier circuit is the absolute value of the ratio of the differential-mode voltage amplification factor to the common-mode voltage amplification factor, and the common-mode rejection ratio of a two-stage differential amplifier circuit is the common-mode rejection ratio of a single-stage differential amplifier circuit. square, so the common mode rejection ratio of the amplifying circuit 3 is the square of a single differential amplifier circuit, roughly on the order of 10 ¹⁶ -10 ²⁰ , and the differential mode signal amplification capability is also the product of a single-stage differential amplifier circuit, which is about 9-400 times. The voltage signal collected by the double-differential D-dot overvoltage sensor is processed by the amplifier circuit 3, which greatly improves the common mode suppression ability, improves the signal-to-noise ratio, removes part of the interference signal, and has better overvoltage detection ability.

In order to further improve the anti-interference ability, the signal conditioning circuit 4 includes a filter circuit to further filter out the interference signal, improve the signal-to-noise ratio, and prevent the interference signal from affecting the collected voltage signal, thereby affecting the accuracy of measurement.

In order to identify the overvoltage signal, the high-speed acquisition circuit 5 converts the analog signal into a digital signal for easy comparison, that is, converts the amplified voltage signal into a voltage effective value, and transmits the voltage effective value to the overvoltage self-identification module 6 .

In order to further identify overvoltage signals, the overvoltage self-identification module 6 compares the voltage effective value with the preset voltage value, and automatically identifies overvoltage signals such as lightning overvoltage, operating overvoltage, transient overvoltage, and power frequency overvoltage. .

The overvoltage measurement system provided by the embodiment of the present invention includes a double differential D-dot overvoltage sensor, an amplification circuit 3, a signal conditioning circuit 4, a high-speed acquisition circuit 5 and an overvoltage self-identification module 6, wherein the double differential D-dot The overvoltage sensor, amplifier circuit 3, signal conditioning circuit 4, high-speed acquisition circuit 5 and overvoltage self-identification module 6 are electrically connected in series in sequence. The double-differential D-dot overvoltage sensor is placed in the electric field near the transmission line under test, outputs the differential voltage signal of the electric field, and transmits the voltage signal to the amplifying circuit 3; the amplifying circuit 3 performs two-stage differential amplification on the voltage signal, which is convenient Identify the subsequent voltage signal, and transmit the amplified voltage signal to the signal conditioning circuit 4; the signal conditioning circuit 4 further filters the amplified voltage signal to remove the interference signal; the high-speed acquisition circuit 5 converts the filtered voltage signal into a voltage The effective value is convenient for overvoltage signal identification; the overvoltage self-identification module 6 compares the voltage effective value with a preset voltage value to automatically identify the overvoltage signal. The overvoltage measurement system provided by the embodiment of the present invention is applicable to the measurement of various overvoltage signals, has a wide measurement bandwidth, and has strong anti-interference ability.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosure herein. This application is intended to cover any modification, use or adaptation of the present invention, these modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed in the present invention . The specification and examples are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It should be understood that the present invention is not limited to the precise constructions which have been described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (7)

1. A double differential D-dot overvoltage sensor is characterized in that it comprises a first unipolar D-dot sensor (1) and a second unipolar D-dot sensor (2), wherein: The first unipolar D-dot sensor (1) and the second unipolar D-dot sensor (2) are arranged symmetrically up and down; The first unipolar D-dot sensor (1) and the second unipolar D-dot sensor (2) both include a metal hemispherical shell body, and an outer layer electrode (11) is arranged on the outer surface of the metal hemispherical shell body, so An inner layer electrode (12) is arranged on the inner surface of the metal hemispherical shell body; An insulating filler (13) is arranged between the outer layer electrode (11) and the inner layer electrode (12), and the outer layer electrode (11) and the inner layer electrode (12) pass through the insulating filler (13) connect. 2. The double differential D-dot overvoltage sensor according to claim 1, characterized in that, the outer electrode (11) and the inner electrode (12) are hemispherical shell-shaped PCB boards. 3. The double differential D-dot overvoltage sensor according to claim 1, characterized in that the insulating filler (13) comprises epoxy resin. 4. The double-differential D-dot overvoltage sensor according to claim 2, characterized in that, the same ends of the outer layer electrode (11) and the inner layer electrode (12) are respectively provided with output ends. 5. a kind of overvoltage measuring system is characterized in that, comprises double differential type D-dot overvoltage sensor, amplifying circuit (3), signal conditioning circuit (4), high-speed acquisition circuit (5) and overvoltage self-identification module ( 6), where: The output end of the double differential D-dot overvoltage sensor is electrically connected to the input end of the amplifier circuit (3); The output terminal of the amplifying circuit (3) is electrically connected to the input terminal of the signal conditioning circuit (4); The output end of the signal conditioning circuit (4) is electrically connected to the input end of the high-speed acquisition circuit (5); The output end of the high-speed acquisition circuit (5) is electrically connected to the overvoltage self-identification module (6); The double-differential D-dot overvoltage sensor is the double-differential D-dot overvoltage sensor described in any one of claims 1-4. 6. The overvoltage measurement system according to claim 5, characterized in that the amplifying circuit (3) is a two-stage differential amplifying circuit. 7. The overvoltage measurement system according to claim 5, characterized in that the signal conditioning circuit (4) comprises a filter circuit.