CN101625382B - Method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil - Google Patents

Abstract

The present invention is a kind of method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil, is suitable for the lower pure cable power grid of power grid nature degree of asymmetry or cable overhead line mixing power grid. It by the consecutive variations of the amplitude of monitoring power grid residual voltage and phase can capacitance current (taking off humorous electric current) component to power grid single-phase-to-ground current and watt current (damping current) component carry out continuously tracking and monitoring, theoretical measurement error is not more than The invention is simple and feasible, only need to detect that two parameters that monitoring meets arc suppression coil automatic tracking and compensating controller needs can be continuously tracked in an electrical parameter, very easy-to-use chip microcontroller, it does not need to carry out any operation to arc suppression coil, the normal operation of power grid is not influenced, post-set arc suppression coils are not only suitable for, the tuning control of preset arc suppression coil is also applied for, is a kind of universal measurement method of grounding current of automatic compensating device of arc suppression coil.

Description

Method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil

Technical field

What the present invention relates to is a kind of measuring method of technical field of electricity, specifically is the power distribution network ground current automatic tracing and measuring technology that is used for Arc Suppression Coil Control.

Background technology

Existing multiple arc suppression coil tuning control method: displacement voltage maximum value method, triangle of impedance method, phase place tuning methods, 2 analytical methods, resonance method binding curve fitting process etc., they respectively have its characteristics.As: displacement voltage maximum value method, triangle of impedance method, phase place tuning methods need arc suppression coil constantly to transfer the files when tuning, this will shorten the life-span of used mechanical organ (as the loaded switch) of transferring the files greatly, and, only be applicable to " preset adjustment " arc suppression coil, can not provide and take off the humorous electric current or the value of capacitance current; 2 analytical methods, resonance method binding curve fitting processs are directly measured the earthing capacitance current of electrical network, therefore both applicable to " with tuning ", also applicable to the control of " preset adjustment " arc suppression coil, but also require the arc suppression coil multi-pass operations when tuning, can shorten the life-span of the used mechanical organ of transferring the files equally, and can not monitor the humorous electric current of taking off of electrical network or the value of capacitance current continuously, therefore, tuning measurement mechanism needs a correct judgement to the variation of electrical network Zero sequence parameter (line loop operation), so that remeasure; More than tuning measuring method be applicable to the pole line or the pole line cable mixing electrical network of nature degree of asymmetry higher (more than 0.5%), and the natural degree of asymmetry of pure cable electrical network (as the colliery) is lower, generally below 0.5%, some colliery electrical network has only 0.02%.For these electrical networks, the arc suppression coil of above tuning manner control will add an imbalance to electrical network when installing, and will be uneven or at the electric capacity of a certain addition of electrical network etc. as grounding transformer three phase windings.

Summary of the invention

Technical matters: the present invention is directed to the existing deficiency that is used for the capacitive earth current measuring method of Arc Suppression Coil Control, proposed a kind of simple and reliable method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil.

Technical scheme: the present invention and phase method are measured the tuning essential distinction that has, it more accurately Continuous Tracking measure capacitance current (or taking off humorous electric current) component of earth-fault current, and can also Continuous Tracking measure active current (damping current) component of earth-fault current.Not only avoided the shortcoming of existing measuring method in its implementation process, and the variation that only need monitor an electric weight of electrical network just can be continuously carried out tracking and monitoring to the earth-fault current of electrical network, simple, measuring accuracy is high, do not need arc suppression coil is carried out any operation, do not influence the normal operation of electrical network, be more suitable for being used for the measurement of the online in real time Continuous Tracking earth-fault current of Arc Suppression Coil Control.The present invention is applicable to that the nature degree of asymmetry is lower, and is general at pure cable below 0.5% or cable trough ceases to be busy mixing electrical network.

Method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil may further comprise the steps:

1. relatively meet a little electric capacity Δ C at the A of electrical network;

2. obtain residual voltage at voltage transformer pt secondary open delta

With " accordingly " line voltage promptly get B mutually with C top-stitching voltage mutually

:

3. continuous monitoring residual voltage

Amplitude and phase place with respect to the line voltage phasor

Variation, available following formula calculates:

The ground current capacitance current component that is used for the control of " with mode " arc suppression coil:

$I_C=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}+I_L$ 1 formula

The ground current that is used for the control of " presetting system " arc suppression coil takes off humorous current component:

$I_v=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}$ 2 formulas

Active current component in the ground current:

$I_d=(g_{\mathrm{\Σ}}+g_L)U_{\mathrm{\φN}}=\mathrm{\ω\ΔC}\frac{\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}$ 3 formulas

In the formula: $U_0^{*2}=U_0^2/U_{\mathrm{\φN}}^2;$ $\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}};$ $\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}}$

$\left\{\begin{array}{c}\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\cos (\mathrm{k\ω}/T)\\ \mathrm{Im}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\sin (\mathrm{k\ω}/T)\end{array}\right.;$

u ₀(k) be the sampled value of electrical network residual voltage; N is the sampling number of a power frequency period T; U _{φ N}Be the specified phase voltage of electrical network; I _L=U _{φ N}/ ω L; Equivalent inductance value when L is the current output offset current of arc suppression coil; ω is the electrical network angular frequency; C _∑=C _A+ C _B+ C _C, C _A, C _BAnd C _CBe respectively the electrical network three-phase ground capacitance; g _∑For the relatively total electricity of electrical network three is led, $g_{\mathrm{\Σ}}=\frac{1}{r_A}+\frac{1}{r_B}+\frac{1}{r_C},$ r _A, r _BAnd r _CBe respectively electrical network three-phase insulation against ground resistance; g _LThat lead for arc suppression coil loss equivalent conductance and preset arc suppression coil damping electricity and.

The little electric capacity Δ C of described step in 1. should select by the following formula requirement:

To post-set arc suppression coils $\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_C-I_L}{\mathrm{\ω}{U}_{\mathrm{\φN}}};$ To preset arc suppression coil: $\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_d}{\mathrm{\ω}{U}_{\mathrm{\φN}}},$ Wherein:

Be the natural unbalance voltage perunit value of electrical network, I _CBe power-to-ground capacitance electric current, I _LBe the offset current lower limit of arc suppression coil output, I _dThe real component of electrical network ground current, δ is the maximum relative measurement error that allows.

Described step 1. with step 2. in, little electric capacity Δ C added certain with the line voltage phasor of being got one " accordingly " relation is arranged, if A relatively meets a little electric capacity Δ C, then get B mutually with C top-stitching voltage mutually

, if B relatively meets a little electric capacity Δ C, then get C mutually with A top-stitching voltage mutually , if C relatively meets a little electric capacity Δ C, then get A mutually with B top-stitching voltage mutually

Described step 3. in, the theoretical measuring relative errors of the damping current component that takes off humorous electric current and 3 formulas in the capacitance current in 1 formula, 2 formulas can have following formula to represent:

The theoretical measuring relative errors of 1 formula and 2 formulas ${\mathrm{\δ}}_v=\frac{\mathrm{\Δ}{I}_v}{I_v}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

The theoretical measuring relative errors of 3 formulas ${\mathrm{\δ}}_d=\frac{\mathrm{\Δ}{I}_d}{I_d}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

Wherein: $U_{00}^{*}=U_{00}/U_{\mathrm{\φN}},$ $U_0^{*}=U_0/U_{\mathrm{\φN}}$ For electrical network normally moves, the unbalance voltage perunit value of electrical network when promptly measuring capacitance current or taking off humorous current component, U ₀₀Be the natural asymmetrical voltage of electrical network, U ₀Asymmetrical voltage when normally moving for electrical network; Δ I _vFor taking off the absolute error of humorous current measurement; Δ I _dThe absolute error that damping current is measured.

Beneficial effect: the invention provides a kind of method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil, it both carried out tracking measurement to the power-to-ground capacitance electric current, be used for being transferred the control of arc suppression coil, go back tracking measurement simultaneously and go out real component in the electrical network earth-fault current, more help accurately to judge the size of ground current, arc extinguishing condition when more helping to understand singlephase earth fault more helps to improve the success ratio of arc suppression coil action.It both can be used for " with mode " arc suppression coil as " capacitor tuning type ", " magnetic biasing type ", " phase control type ", " three phase five post direct adjusting inductor type " etc., also can be used for of the tuning control of " presetting system " arc suppression coil as " adjustable air gap formula ", " turn-adjusting ", " three-phase five-limb " etc., be the general method for continuously tracking and measuring grounding current of a kind of arc suppression coil earthing system in essence, be applicable to the tuning control of the arc suppression coil that different manufacturers produce.And it is the measurement of humorous electric current of taking off of arc suppression coil earthing system and damping current in essence, therefore, can be used for the measurement of many arc suppression coils with the tuning control of net parallel running.It has measure tuning principle clear thinking, calculate simple, do not need when measuring arc suppression coil is carried out any operation, the normal operation of electrical network do not produced advantages such as any influence, very easy-to-use chip microcontroller, used expense be low.

Description of drawings

Fig. 1 is an arc suppression coil earthing electric network equivalent circuit synoptic diagram.

Fig. 2 is residual voltage and " accordingly " line voltage phasor synoptic diagram.

Embodiment

A kind of method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil of the present invention may further comprise the steps:

1. meet a little electric capacity Δ C over the ground in a certain phase of electrical network (generally can in the A phase);

2. obtain residual voltage at voltage transformer pt secondary open delta

With " accordingly " line voltage (relatively meet a little electric capacity Δ C as A, then get B mutually with C top-stitching voltage mutually

);

3. continuous monitoring residual voltage

Amplitude and with respect to the line voltage phasor The variation of phase place, available following formula calculates:

Capacitance current component in the ground current (being used for the control of " with mode " arc suppression coil):

$I_C=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}+I_L$ 1 formula

Take off humorous current component (being used for the control of " presetting system " arc suppression coil) in the ground current:

$I_v=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}$ 2 formulas

Meritorious (damping) current component in the ground current:

$I_d=(g_{\mathrm{\Σ}}+g_L)U_{\mathrm{\φN}}=\mathrm{\ω\ΔC}\left[\frac{\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}\right]U_{\mathrm{\φN}}$ 3 formulas

In the formula:: $U_0^{*2}=U_0^2/U_{\mathrm{\φN}}^2;$ $\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}};$ $\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}}$

$\left\{\begin{array}{c}\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\cos (\mathrm{k\ω}/T)\\ \mathrm{Im}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\sin (\mathrm{k\ω}/T)\end{array}\right.;$ ；

u ₀(k) be the sampled value of electrical network residual voltage; N is the sampling number of a power frequency period T; U _{φ N}Be the specified phase voltage of electrical network; I _L=U _{φ N}/ ω L; Equivalent inductance value when L is the current output offset current of arc suppression coil; ω is the electrical network angular frequency; C _∑=C _A+ C _B+ C _C, C _A, C _BAnd C _CBe respectively the electrical network three-phase ground capacitance; g _∑For the relatively total electricity of electrical network three is led, $g_{\mathrm{\Σ}}=\frac{1}{r_A}+\frac{1}{r_B}+\frac{1}{r_C},$ r _A, r _BAnd r _CBe respectively electrical network three-phase insulation against ground resistance; g _LThat lead for arc suppression coil loss equivalent conductance and preset arc suppression coil damping electricity and.

Above algorithm pushes away as followsly:

By the equivalent electrical network of Fig. 1 grounding through arc as seen, under the state of nature of electrical network, promptly do not insert little electric capacity Δ C before, the residual voltage of the normal operation of electrical network:

${\stackrel{\·}{U}}_{00}=\frac{\frac{1}{r_A}+\mathrm{j\ω}{C}_A+a^2(\frac{1}{r_B}+\mathrm{j\ω}{C}_B)+a(\frac{1}{r_C}+\mathrm{j\ω}{C}_C)}{g_{\mathrm{\Σ}}+g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}-1/\mathrm{\ωL})}{\stackrel{\·}{E}}_A\≈0$ (1)

When arc suppression coil was installed, the residual voltage after reference phase (A phase) inserts a little electric capacity Δ C was:

${\stackrel{\·}{U}}_0=-\frac{\frac{1}{r_A}+\mathrm{j\ω}(C_A+\mathrm{\ΔC})+a^2(\frac{1}{r_B}+\mathrm{j\ω}{C}_B)+a(\frac{1}{r_C}+\mathrm{j\ω}{C}_C)}{g_{\mathrm{\Σ}}+g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\Δ\ωC}-1/\mathrm{\ωL})}{\stackrel{\·}{E}}_A$ (2)

$=-\frac{\mathrm{j\ω\ΔC}{\stackrel{\·}{E}}_A}{g_{\mathrm{\Σ}}+g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\Δ\ωC}-1/\mathrm{\ωL})}+{\stackrel{\·}{U}}_{00}$

For pure cable electrical network, because

With respect to

Very little, approach zero, can ignore, then:

$\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-1/\mathrm{\ωL}-j(g_{\mathrm{\Σ}}+g_L)=-\mathrm{\ω\ΔC}{\stackrel{\·}{E}}_A/{\stackrel{\·}{U}}_0$ (3)

Getting real part gets:

$\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}}=\mathrm{Re}(-\frac{\mathrm{\ω\ΔC}}{{\stackrel{\·}{U}}_0}{\stackrel{\·}{E}}_A)$

$=-\mathrm{\ω\ΔC}\frac{\mathrm{Re}\left({\stackrel{\·}{E}}_A\right)\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)+\mathrm{Im}\left({\stackrel{\·}{E}}_A\right)\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)}{U_0^2}$ (4)

In the formula: " real part " got in Re () expression; " imaginary part " got in Im () expression.Get

For

With

The reference phasor, see Fig. 2, then:

In advance

90 °, $\mathrm{Re}\left({\stackrel{\·}{E}}_A\right)=0,\mathrm{Im}\left({\stackrel{\·}{E}}_A\right)=E_A,$ Therefore,

$\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}}=-\frac{\mathrm{\Δ\ωC}}{U_0^2}{E}_A\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)$ (5)

Both sides can get 1 formula and 2 formulas with multiply by specified phase voltage.

Equally, (3) are got imaginary part and are got:

$g_{\mathrm{\Σ}}+g_L=\mathrm{Im}\left(\frac{\mathrm{\ω\ΔC}}{{\stackrel{\·}{U}}_0}{\stackrel{\·}{E}}_A\right)$

$=\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{E}}_A\right)\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)-\mathrm{Re}\left({\stackrel{\·}{E}}_A\right)\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)}{U_0^2}$ (6)

$=\mathrm{\ω\ΔC}{E}_A\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)/U_0^2=\mathrm{\ω\ΔCRe}\left({\stackrel{\·}{U}}_0^{*}\right)/U_0^{*2}$

Both sides can get 3 formulas with multiply by specified phase voltage.

Described little electric capacity Δ C should select by the following formula requirement:

To post-set arc suppression coils $\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_C-I_L}{\mathrm{\ω}{U}_{\mathrm{\φN}}};$ To preset arc suppression coil: $\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_d}{\mathrm{\ω}{U}_{\mathrm{\φN}}}.$ Wherein: U ₀₀ ^*Be the natural unbalance voltage perunit value of electrical network, δ is the maximum relative measurement error that allows.

Ignore the damping of electrical network, promptly think r _A=r _B=r _C=∞, then:

${\stackrel{\·}{U}}_{00}=-\frac{j(\mathrm{\ω}{C}_A+a^2\mathrm{\ω}{C}_B)+\mathrm{a\ω}{C}_C)}{g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}-1/\mathrm{\ωL})}{\stackrel{\·}{E}}_A$ (7)

${\stackrel{\·}{U}}_0=-\frac{\mathrm{j\ω\ΔC}}{g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\Δ\ωC}-1/\mathrm{\ωL})}{\stackrel{\·}{E}}_A+{\stackrel{\·}{U}}_{00}$ (8)

$\left|\frac{g_L+j(\mathrm{\ω}{C}_{\mathrm{\Σ}}-1/\mathrm{\ωL})}{\mathrm{j\ω\ΔC}}\right|\≈\left|\frac{{\stackrel{\·}{U}}_{00}}{{\stackrel{\·}{U}}_0-{\stackrel{\·}{U}}_{00}}\frac{1}{{\stackrel{\·}{U}}_{00}^{*}}\right|=\left|\frac{{\stackrel{\·}{U}}_{00}}{{\stackrel{\·}{U}}_0-{\stackrel{\·}{U}}_{00}}\right|\frac{1}{U_{00}^{*}}=\frac{\mathrm{\δ}}{U_{00}^{*}}$ (9)

To post-set arc suppression coils, g _L≈ 0, should select: $\mathrm{\ω\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}(\mathrm{\ω}{C}_{\mathrm{\Σ}}-\frac{1}{\mathrm{\ωL}}),$ Or: $\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_C-I_L}{\mathrm{\ω}{U}_{\mathrm{\φN}}};$

To preset arc suppression coil, $\mathrm{\ω}{C}_{\mathrm{\Σ}}-\frac{1}{\mathrm{\ωL}}\≈0,$ Should select: $\mathrm{\ω\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}{g}_d,$ g _d=g _∑+ g _L, or:

$\mathrm{\ΔC}=\frac{U_{00}^{*}}{\mathrm{\δ}}\frac{I_d}{\mathrm{\ω}{U}_{\mathrm{\φN}}}.$

For example: a 10kV ground current is about 45A (C _∑=24.8 μ F) distribution, it is 15A " with mode " arc suppression coil that an offset current lower limit is installed, the natural unbalance voltage of electrical network is 0.1%, wishes measuring error in 5%, and is then desirable: $\mathrm{\ΔC}=\frac{0.1}{5}\frac{45-15}{314\×10000/\sqrt{3}}=0.331\left(\mathrm{\μF}\right),$ At this moment, the unbalance voltage perunit value of the normal operation of electrical network is: $U_0^{*}=0.1(1+1/0.05)=2.1,$ The unbalance voltage that is electrical network is 2.1%.For another example: a 10kV ground current is about the distribution of 45A, and it is 15A " presetting system " arc suppression coil that a damping current is installed, and the natural unbalance voltage of electrical network is 0.1%, wishes measuring error in 5%, and is then desirable: $\mathrm{\ΔC}=\frac{0.1}{5}\frac{15}{314\×10000/\sqrt{3}}=0.165\left(\mathrm{\μF}\right),$ At this moment, the unbalance voltage perunit value of the normal operation of electrical network is: $U_0^{*}=0.1(1+1/0.05)=2.1,$ The unbalance voltage that is electrical network is 2.1%.More than two examples also can find out, this measuring method relatively is suitable for the relatively low cable electrical network or the cable trough ceases to be busy mixing electrical network of natural unbalance voltage of electrical network, when natural unbalance voltage in 0.5%, require measuring error 5% with interior condition under, the unbalance voltage of the normal operation of electrical network can be controlled in 10%.The asymmetrical voltage that improves measuring accuracy and reduce electrical network when normally moving is a pair of contradiction, obviously, the nature unbalance voltage is low more to be helped this measuring method more and improves measuring accuracy and reduce electrical network asymmetrical voltage when normally moving, therefore, it is suitable for pure cable electrical network most, also is applicable to cable trough ceases to be busy mixing electrical network.

Described step is 1. and 2., little electric capacity Δ C added certain with the line voltage phasor of being got one " accordingly " relation is arranged, relatively meet a little electric capacity Δ C as A, then get B mutually with C top-stitching voltage mutually

, if B relatively meets a little electric capacity Δ C, then get C mutually with A top-stitching voltage mutually

, if C relatively meets a little electric capacity Δ C, then get A mutually with B top-stitching voltage mutually

This can find out from (4), for guaranteeing $\mathrm{Re}\left({\stackrel{\·}{E}}_{\mathrm{\φ}}\right)=0,\mathrm{Im}\left({\stackrel{\·}{E}}_{\mathrm{\φ}}\right)=E_{\mathrm{\φ}},$ Wherein φ is A, B and C, must guarantee

In advance with reference to 90 ° of phasors, therefore, must guarantee above " corresponding,, relation, this can be as seen from Figure 2.

Capacitance current or take off humorous current component and the theoretical measuring relative errors of active current or damping current component can have following formula to represent in the ground current of described step described in 3.:

The theoretical measuring relative errors of 1 formula and 2 formulas ${\mathrm{\δ}}_v=\frac{\mathrm{\Δ}{I}_v}{I_v}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

The theoretical measuring relative errors of 3 formulas ${\mathrm{\δ}}_d=\frac{\mathrm{\Δ}{I}_d}{I_d}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

Wherein: $U_{00}^{*}=U_{00}/U_{\mathrm{\φN}},$ $U_0^{*}=U_0/U_{\mathrm{\φN}}$ For electrical network normally moves, the unbalance voltage perunit value of electrical network when promptly measuring capacitance current or taking off humorous current component, U ₀₀Be the natural asymmetrical voltage of electrical network, U ₀Asymmetrical voltage when normally moving for electrical network; Δ I _vFor taking off the absolute error of humorous current measurement; Δ I _dThe absolute error that damping current is measured.

1 formula and 2 formulas are natural asymmetrical voltage U of hypothesis electrical network ₀₀=0, by (2) push away, actual electric network can not absolute symmetry, U ₀₀Can not be zero, therefore, this will produce measuring error.Consider U ₀₀, get by (2):

$\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}}-j(g_{\mathrm{\Σ}}+g_L)=-\mathrm{\ω\ΔC}\frac{{\stackrel{\·}{E}}_A}{{\stackrel{\·}{U}}_0}+\frac{{\stackrel{\·}{U}}_{00}}{{\stackrel{\·}{U}}_0}[\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}}-j(g_{\mathrm{\Σ}}+g_L)]$ (10)

$\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}}-j(g_{\mathrm{\Σ}}+g_L)=-\mathrm{\ω\ΔC}\frac{{\stackrel{\·}{E}}_A}{{\stackrel{\·}{U}}_0}\left(\frac{{\stackrel{\·}{U}}_0}{{\stackrel{\·}{U}}_0-{\stackrel{\·}{U}}_{00}}\right)$ (11)

(11) subtract (3) and get absolute error:

$\mathrm{\Δ}={\mathrm{\Δ}}_v+j{\mathrm{\Δ}}_d=(-\mathrm{\ω\ΔC}\frac{{\stackrel{\·}{E}}_A}{{\stackrel{\·}{U}}_0})\left|\frac{{\stackrel{\·}{U}}_{00}}{{\stackrel{\·}{U}}_0-{\stackrel{\·}{U}}_{00}}\right|$ (12)

${\mathrm{\Δ}}_v\≤-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$ (13)

${\mathrm{\Δ}}_d\≤\mathrm{\ω\ΔC}\frac{\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$ (14)

Take off humorous degree relative error: ${\mathrm{\δ}}_v=\frac{\mathrm{\Δ}{I}_v}{I_v}=\frac{{\mathrm{\Δ}}_v}{\mathrm{\ωC}+\mathrm{\ω\ΔC}-1/\mathrm{\ωL}}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$ (15)

The ratio of damping relative error: ${\mathrm{\δ}}_d=\frac{\mathrm{\Δ}{I}_d}{I_d}=\frac{{\mathrm{\Δ}}_d}{g_{\mathrm{\Σ}}+g_L}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$ (16)。

Claims (3)

1. method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil is characterized in that this method may further comprise the steps:

1. relatively meet a little electric capacity Δ C at the A of electrical network;

2. obtain residual voltage at voltage transformer pt secondary open delta

With " accordingly " line voltage promptly get B mutually with C top-stitching voltage mutually

3. continuous monitoring residual voltage

Amplitude and phase place with respect to the line voltage phasor Variation, available following formula calculates:

The ground current capacitance current component that is used for the control of " with mode " arc suppression coil:

$I_C=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}+I_L$ 1 formula

The ground current that is used for the control of " presetting system " arc suppression coil takes off humorous current component:

$I_v=(\mathrm{\ω}{C}_{\mathrm{\Σ}}+\mathrm{\ω\ΔC}-\frac{1}{\mathrm{\ωL}})U_{\mathrm{\φN}}=-\mathrm{\ω\ΔC}\frac{\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}$ 2 formulas

Active current component in the ground current:

$I_d=(g_{\mathrm{\Σ}}+g_L)U_{\mathrm{\φN}}=\mathrm{\ω\ΔC}\frac{\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)}{U_0^{*2}}{U}_{\mathrm{\φN}}$ 3 formulas

In the formula: $U_0^{*2}=U_0^2/U_{\mathrm{\φN}}^2;$ $\mathrm{Re}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}};$ $\mathrm{Im}\left({\stackrel{\·}{U}}_0^{*}\right)=\mathrm{Im}\left({\stackrel{\·}{U}}_0\right)/U_{\mathrm{\φN}}$

$\left\{\begin{array}{c}\mathrm{Re}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\cos (\mathrm{k\ω}/T)\\ \mathrm{Im}\left({\stackrel{\·}{U}}_0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_0\left(k\right)\sin (\mathrm{k\ω}/T)\end{array}\right.;$

u ₀(k) be the sampled value of electrical network residual voltage; N is the sampling number of a power frequency period T; U _{φ N}Be the specified phase voltage of electrical network; I _L=U _{φ N}/ ω L; Equivalent inductance value when L is the current output offset current of arc suppression coil; ω is the electrical network angular frequency; C _∑=C _A+ C _B+ C _C, C _A, C _BAnd C _CBe respectively the electrical network three-phase ground capacitance; g _∑For the relatively total electricity of electrical network three is led,

r _A, r _BAnd r _CBe respectively electrical network three-phase insulation against ground resistance; g _LThat lead for arc suppression coil loss equivalent conductance and preset arc suppression coil damping electricity and.

2. method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil according to claim 1 is characterized in that, the little electric capacity Δ C of described step in 1. should select by the following formula requirement:

To post-set arc suppression coils To preset arc suppression coil:

Wherein: Be the natural unbalance voltage perunit value of electrical network, I _CBe power-to-ground capacitance electric current, I _LBe the offset current lower limit of arc suppression coil output, I _dThe real component of electrical network ground current, δ is the maximum relative measurement error that allows.

3. method for continuously tracking and measuring grounding current of automatic compensating device of arc suppression coil according to claim 1, it is characterized in that, described step 3. in, the theoretical measuring relative errors of the damping current component that takes off humorous electric current and 3 formulas in the capacitance current in 1 formula, 2 formulas can have following formula to represent:

The theoretical measuring relative errors of 1 formula and 2 formulas ${\mathrm{\δ}}_v=\frac{\mathrm{\Δ}{I}_v}{I_v}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

The theoretical measuring relative errors of 3 formulas ${\mathrm{\δ}}_d=\frac{\mathrm{\Δ}{I}_d}{I_d}\≤\frac{U_{00}^{*}}{U_0^{*}-U_{00}^{*}}$

Wherein:

For electrical network normally moves, the unbalance voltage perunit value of electrical network when promptly measuring capacitance current or taking off humorous current component, U ₀₀Be the natural asymmetrical voltage of electrical network, U ₀Asymmetrical voltage when normally moving for electrical network; Δ I _vFor taking off the absolute error of humorous current measurement; Δ I _dThe absolute error that damping current is measured.

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