CN103364604B - Capacitance type potential transformer and measuring method suitable in high-voltage harmonic measurement - Google Patents

Abstract

The present invention relates to a kind of capacitance type potential transformer suitable in high-voltage harmonic measurement and measuring method.The low-voltage capacitance branch road of capacitive divider and intermediate transformer branch road of capacitance type potential transformer are connected respectively a current transformer, the present invention adds two conventional current transformers in conventional condenser voltage transformer, utilizes the electric current that the two mutual inductor measuring measures can calculate size and the phase place of high-pressure system harmonic voltage.Therefore, present invention have the advantage that simple in construction, it is achieved convenient, measure voltage harmonic precision high, and not by the impact of capacitance type potential transformer load, the occasion at high voltage harmonic voltage measurement has significantly high using value and marketing prospect.

Description

Capacitance type potential transformer and measuring method suitable in high-voltage harmonic measurement

Technical field

The present invention relates to a kind of capacitance type potential transformer and measuring method, especially relate to a kind of capacitance type potential transformer suitable in high-voltage harmonic measurement and measuring method.

Background technology

Nonlinear-load application in power system is increasing causes that the voltage distortion problem of high-voltage electric power system is increasingly severe.Power supply department and scientific research institution, in the urgent need to the voltage harmonic of high-voltage electric power system is measured, to understand the voltage harmonic situation of high-pressure system, make harness of harmonic wave targetedly.

But in currently used high pressure harmonic measuring method and equipment, adopt the scheme of resistor divider and capacitor dividing potential drop to need to adopt special equipment, and these equipment volume are big, expensive.Capacitance type potential transformer is because of its volume is little, lightweight, maintenance workload is few, electric field intensity nargin is big, insulating reliability is high advantage; and derided capacitors can double as coupling capacitor for radio frequency carrier channel, be widely used in 110kV(even 35kV) and the voltage measurement of above high voltage solidly earthed neutral system, high frequency communications and relay protection in.Thus according to the actual fact, capacitance type potential transformer is adopted to carry out the method that high pressure harmonic measure is most convenient economy, but owing to capacitance type potential transformer internal resonance condition under harmonic condition will be destroyed, measure harmonic wave and will appear from bigger error, it is impossible to directly application conventional capacitive-type voltage transformer carries out high pressure harmonic measure.

Currently also there is the frequency response characteristic having researched and analysed capacitance type potential transformer, after utilizing this frequency response characteristic that capacitance type potential transformer double measurement voltage is modified, derive on high-tension side voltage harmonic.But this scheme needs the frequency response characteristic of the various dissimilar capacitance type potential transformer of off-line analysis, it is to be appreciated that the detailed construction of capacitance type potential transformer and element parameter, and the frequency response characteristic under different loading conditions is also different, therefore this method realizes complex, limits its application.

Therefore, if capacitance type potential transformer simply can be transformed, design a kind of scheme being applicable to high pressure harmonic measure based on capacitance type potential transformer, it is possible under measuring the high-tension situation of power frequency, provide high-precision high pressure harmonic measure simultaneously.Thus for realizing the scheme that high pressure harmonic voltage measurement provides a kind of cost performance significantly high, having great practical value and marketing prospect.

Summary of the invention

The present invention mainly solves the technical problem existing for prior art；Provide a kind of simple in construction, it is convenient to realize, measure voltage harmonic precision high, and not by the impact of capacitance type potential transformer load, the occasion at high voltage harmonic voltage measurement has the capacitance type potential transformer being applicable to high-voltage harmonic measurement and the measuring method of significantly high using value and marketing prospect.

The above-mentioned technical problem of the present invention is addressed mainly by following technical proposals:

A kind of capacitance type potential transformer suitable in high-voltage harmonic measurement, it is characterized in that, the low-voltage capacitance branch road of capacitive divider and intermediate transformer branch road of capacitance type potential transformer are connected respectively a current transformer, it may be assumed that the high-voltage capacitance of the capacitive divider of definition capacitance type potential transformer is high-voltage capacitance C_HAnd the low-voltage capacitance of capacitive divider is low-voltage capacitance C_L；The series compensation reactor of capacitance type potential transformer is series compensation reactor L_f；The intermediate transformer of capacitance type potential transformer is intermediate transformer T；Wherein low-voltage capacitance C_LBranch road in connect ground connection after a current transformer S1, S2 connects ground connection after a current transformer S2 in the branch road of intermediate transformer T.

A kind of high-voltage harmonic measurement method based on capacitance type potential transformer, utilizes the electric current that two current transformer S1 summation current transformer S2 measurements obtain and the high-voltage capacitance C of capacitive divider_HLow-voltage capacitance C with capacitive divider_LCapacitance can either obtain the on high-tension side harmonic voltage of capacitance type potential transformer.

In a kind of above-mentioned high-voltage harmonic measurement method based on capacitance type potential transformer, concrete acquisition methods is as follows:

Step 1, the secondary current obtained according to current transformer S1 measurement and no-load voltage ratio thereof obtain low-voltage capacitance C_LThe electric current i of branch road_CL；The secondary current obtained according to current transformer S2 measurement and no-load voltage ratio thereof obtain the electric current i of intermediate transformer T branch road_CT

Step 2, based on i_CH=i_CL+i_CT, it is thus achieved that high-voltage capacitance C_HThe electric current i of branch road_CH；

Step 3, decomposites electric current i based on Fourier transformation_CLAnd i_CHIn harmonic current components, it may be assumed that

$i_{\mathrm{CH}}=\sqrt{2}\·\underset{h=1}{\overset{n}{\mathrm{\Σ}}}(I_{\mathrm{CH}\left(h\right)}\·\sin (2\mathrm{\π}\·f\·h\·t+{\mathrm{\θ}}_{\mathrm{CH}\left(h\right)}))$

$i_{\mathrm{CL}}=\sqrt{2}\·\underset{h=1}{\overset{n}{\mathrm{\Σ}}}(I_{\mathrm{CL}\left(h\right)}\·\sin (2\mathrm{\π}\·f\·h\·t+{\mathrm{\θ}}_{\mathrm{CL}\left(h\right)}))$

Wherein: h is overtone order, n is the most higher harmonics number of times paid close attention to；F is power frequency,；T is the time；I_CH(h)And θ_CH(h)Respectively electric current i_CHIn the virtual value of h subharmonic and phase angle；I_CL(h)And θ_CL(h)Respectively electric current i_CLIn the virtual value of h subharmonic and phase angle；

Electric current i_CHAnd i_CLIn h subharmonic be respectively as follows:

${\stackrel{\·}{I}}_{\mathrm{CH}\left(h\right)}=I_{\mathrm{CH}\left(h\right)}\∠{\mathrm{\θ}}_{\mathrm{CH}\left(h\right)},$ ${\stackrel{\·}{I}}_{\mathrm{CL}\left(h\right)}=I_{\mathrm{CL}\left(h\right)}\∠{\mathrm{\θ}}_{\mathrm{CL}\left(h\right)};$

Step 4, based on the data that step 3 obtains, it is possible to obtain

${\stackrel{\·}{U}}_{S\left(h\right)}={\stackrel{\·}{I}}_{\mathrm{CL}\left(h\right)}\·\frac{1}{j\·2\mathrm{\π}\·f\·h\·C_L}+{\stackrel{\·}{I}}_{\mathrm{CH}\left(h\right)}\·\frac{1}{j\·2\mathrm{\π}\·f\·h\·C_H}$ Formula one；

Wherein, C_HAnd C_LIt is the high-voltage capacitance C of capacitive divider respectively_HLow-voltage capacitance C with capacitive divider_LCapacitance be the value of low pressure and high-voltage capacitance；

Then, to all subharmonic (h=1,2 ..., n) all carry out the calculating shown in formula one, high-voltage system voltage u can be calculated_SEach harmonic voltage, namely these voltages are by the value required for frequency analysis.

Therefore, present invention have the advantage that and only need to add two conventional current transformers in conventional condenser voltage transformer, utilize the electric current that the two mutual inductor measuring measures can calculate size and the phase place of high-pressure system harmonic voltage.Present configuration is simple, it is achieved convenient, measures voltage harmonic precision high, and not by the impact of capacitance type potential transformer load, the occasion at high voltage harmonic voltage measurement has significantly high using value and marketing prospect.

Accompanying drawing explanation

Fig. 1 is a kind of high-voltage harmonic measurement electrical block diagram based on capacitance type potential transformer of the present invention.

Detailed description of the invention

By the examples below, and in conjunction with accompanying drawing, technical scheme is described in further detail.

Embodiment:

Accompanying drawing 1 is the structure chart of a kind of high-voltage harmonic measurement scheme based on capacitance type potential transformer.C in figure_HAnd C_LThe respectively high-voltage capacitance of the capacitive divider of conventional capacitive-type voltage transformer and low-voltage capacitance；L_fSeries compensation reactor for conventional capacitive-type voltage transformer；T is the intermediate transformer of conventional capacitive-type voltage transformer；Z_LLoad (not being the ingredient of capacitance type potential transformer) for capacitance type potential transformer.The classical tandem current transformer that S1 and the S2 respectively present invention is affiliated, wherein S1 is connected on low-voltage capacitance C_LBranch road in, S2 is connected in the branch road of intermediate transformer T.Should be noted that current transformer S1 and S2 need to respectively close to low-voltage capacitance C in order to reduce the insulating requirements to current transformer S1 and S2 simultaneously_LThe earth point of branch road and intermediate transformer T branch road.Here, it is to be noted that S1 and S2 is connected in branch road is essentially optional position, without influence on the size measuring electric current, but if it is considered that insulating requirements, it is different that S1 and S2 is connected on the voltage of difference, therefore, being connected between the primary side of intermediate transformer and earth point by S1, S2 is connected between low-voltage capacitance and earth point.

The secondary current and the no-load voltage ratio thereof that obtain according to current transformer S1 measurement can calculate low-voltage capacitance C_LThe electric current i of branch road_CL；The secondary current obtained according to current transformer S2 measurement and no-load voltage ratio thereof can calculate the electric current i of intermediate transformer T branch road_CT；According to Kirchhoff's current law (KCL), high-voltage capacitance C_HThe electric current i of branch road_CHMeet:

i_CH=i_CL+i_CT(1)

Utilize ripe Fourier Transform Technique, electric current i can be decomposited respectively_CLAnd i_CHIn harmonic current components:

$i_{\mathrm{CH}}=\sqrt{2}\·\underset{h=1}{\overset{n}{\mathrm{\Σ}}}(I_{\mathrm{CH}\left(h\right)}\·\sin (2\mathrm{\π}\·f\·h\·t+{\mathrm{\θ}}_{\mathrm{CH}\left(h\right)}))---\left(2\right)$

$i_{\mathrm{CL}}=\sqrt{2}\·\underset{h=1}{\overset{n}{\mathrm{\Σ}}}(I_{\mathrm{CL}\left(h\right)}\·\sin (2\mathrm{\π}\·f\·h\·t+{\mathrm{\θ}}_{\mathrm{CL}\left(h\right)}))---\left(3\right)$

Wherein: h is overtone order, n is the most higher harmonics number of times (generally taking 40 times enough) paid close attention to；F is power frequency, and China is 50Hz；T is the time；I_CH(h)And θ_CH(h) respectively electric current i_CHIn the virtual value of h subharmonic and phase angle；I_CL(h)And θ_CL(h)Respectively electric current i_CLIn the virtual value of h subharmonic and phase angle.

By electric current i_CHAnd i_CLIn h subharmonic be written as phasor form respectively:

${\stackrel{\·}{I}}_{\mathrm{CH}\left(h\right)}=I_{\mathrm{CH}\left(h\right)}\∠{\mathrm{\θ}}_{\mathrm{CH}\left(h\right)}---\left(4\right)$

${\stackrel{\·}{I}}_{\mathrm{CL}\left(h\right)}=I_{\mathrm{CL}\left(h\right)}\∠{\mathrm{\θ}}_{\mathrm{CL}\left(h\right)}---\left(5\right)$

Need the high-voltage system voltage u measured_SH subharmonic can pass through following formula calculate obtain:

${\stackrel{\·}{U}}_{S\left(h\right)}={\stackrel{\·}{I}}_{\mathrm{CL}\left(h\right)}\·\frac{1}{j\·2\mathrm{\π}\·f\·h\·C_L}+{\stackrel{\·}{I}}_{\mathrm{CH}\left(h\right)}\·\frac{1}{j\·2\mathrm{\π}\·f\·h\·C_H}---\left(6\right)$

To all subharmonic (h=1,2 ..., n) all carry out the calculating shown in formula (6), high-voltage system voltage u can be calculated_SEach harmonic voltage, namely these voltages are by the value required for frequency analysis.

The present invention seals in conventional current transformer respectively in the low-voltage capacitance branch road and intermediate transformer branch road of the capacitive divider of conventional capacitive-type voltage transformer, utilize the electric current measuring low-voltage capacitance branch road and the intermediate transformer branch road obtained, in conjunction with high pressure and the low tension capacitance of capacitive divider, the harmonic content of high-voltage system voltage can be calculated.The high-voltage harmonic measurement scheme based on capacitance type potential transformer of the present invention only simply need to be improved on the basis of conventional capacitive-type voltage transformer, realize simple, provide important technological means for realizing accurately measuring of high pressure harmonic voltage, there is significantly high practical value and wide marketing application prospect.

Above example is used for illustrative purposes only, but not limitation of the present invention, person skilled in the relevant technique, without departing from the spirit and scope of the present invention, various conversion or modification can also be made, therefore all equivalent technical schemes also should belong within scope of the invention, should be limited by each claim.

Specific embodiment described herein is only to present invention spirit explanation for example.Described specific embodiment can be made various amendment or supplements or adopt similar mode to substitute by those skilled in the art, but without departing from the spirit of the present invention or surmount the scope that appended claims is defined.

Claims (2)

1. the capacitance type potential transformer being applicable to high-voltage harmonic measurement, it is characterized in that, the low-voltage capacitance branch road of capacitive divider and intermediate transformer branch road of capacitance type potential transformer are connected respectively a current transformer, it may be assumed that the high-voltage capacitance of the capacitive divider of definition capacitance type potential transformer is high-voltage capacitance C_HAnd the low-voltage capacitance of capacitive divider is low-voltage capacitance C_L；The series compensation reactor of capacitance type potential transformer is series compensation reactor L_f；The intermediate transformer of capacitance type potential transformer is intermediate transformer T；At low-voltage capacitance C_LBranch road in connect ground connection after a current transformer S1, ground connection after the current transformer S2 that connects in the branch road of intermediate transformer T；

C_HAnd C_LThe respectively high-voltage capacitance of the capacitive divider of conventional capacitive-type voltage transformer and low-voltage capacitance；L_fSeries compensation reactor for conventional capacitive-type voltage transformer；T is the intermediate transformer of conventional capacitive-type voltage transformer；Z_LLoad for capacitance type potential transformer；Classical tandem current transformer respectively affiliated for S1 and S2, wherein S1 is connected on low-voltage capacitance C_LBranch road in, S2 is connected in the branch road of intermediate transformer T；Should be noted that current transformer S1 and S2 need to respectively close to low-voltage capacitance C in order to reduce the insulating requirements to current transformer S1 and S2 simultaneously_LThe earth point of branch road and intermediate transformer T branch road；Here, it is to be noted that S1 and S2 is connected in branch road is essentially optional position, without influence on the size measuring electric current, but if it is considered that insulating requirements, it is different that S1 and S2 is connected on the voltage of difference, therefore, being connected between the primary side of intermediate transformer and earth point by S1, S2 is connected between low-voltage capacitance and earth point.

2. the high-voltage harmonic measurement method based on the capacitance type potential transformer described in claim 1, it is characterised in that utilize the electric current that two current transformer S1 summation current transformer S2 measurements obtain and the high-voltage capacitance C of capacitive divider_HLow-voltage capacitance C with capacitive divider_LCapacitance can access the on high-tension side harmonic voltage of capacitance type potential transformer；

Concrete acquisition methods is as follows:

Step 1, the secondary current obtained according to current transformer S1 measurement and no-load voltage ratio thereof obtain low-voltage capacitance C_LThe electric current i of branch road_CL；The secondary current obtained according to current transformer S2 measurement and no-load voltage ratio thereof obtain the electric current i of intermediate transformer T branch road_CT

Step 2, based on i_CH=i_CL+i_CT, it is thus achieved that high-voltage capacitance C_HThe electric current i of branch road_CH；

Step 3, decomposites electric current i based on Fourier transformation_CLAnd i_CHIn harmonic current components, it may be assumed that

Wherein: h is overtone order, n is the most higher harmonics number of times paid close attention to；F is power frequency；T is the time；I_CH(h)And θ_CH(h)Respectively electric current i_CHIn the virtual value of h subharmonic and phase angle；I_CL(h)And θ_CL(h)Respectively electric current i_CLIn the virtual value of h subharmonic and phase angle；

Electric current i_CHAnd i_CLIn h subharmonic be respectively as follows:

Step 4, based on the data that step 3 obtains, it is possible to obtain

Wherein, C_HAnd C_LIt is the high-voltage capacitance C of capacitive divider respectively_HLow-voltage capacitance C with capacitive divider_LCapacitance；Then, to all subharmonic (h=1,2 ..., n) all carry out the calculating shown in formula one, high-voltage system voltage u can be calculated_SEach harmonic voltage, namely these voltages are by the value required for frequency analysis.