CN100470987C - Method for raising measuring precision of microcomputer protective relay device - Google Patents

Abstract

Characters of the invention are that using divider circuit implements protection in two segments corresponding to large and small measured current for the protection current in order to raise precision; carrying out seamless fitting for data sampled from same protection current in segments; according to rated value and actual value, software layer carries out correction of amplitude and correction of phase for each channel of protection current at same time. The invention reflects real change of each protected electric quantity correctly. Thus, based on the said real change to carry out correction, the invention raises precision of measurement.

Description

A kind of method that improves measuring precision of microcomputer protective relay device

Technical field

The invention belongs to power system automatic field, relate to the sampling and the signal processing technology of the microcomputer protective relay device of comprehensive automation system of transformer substation.

Background technology

Microcomputer protective relay device is judged the running status of current system mainly according to the variation of protecting electric weight (electric current, voltage, power, impedance and frequency etc.) in the electric power system.When protected electric power system was broken down, microcomputer protective relay device should judge whether for troubles inside the sample space sends trip signal to circuit breaker fault element in time to be isolated from electric power system quickly and accurately.Therefore, the microcomputer protective relay device that uses in the electric power system should satisfy the requirement of reliability, selectivity, sensitivity and quick-action.In the sampling module of microcomputer protective relay device, because voltage transformer (PT) summation current transformer (CT) generates the influence of technology, the property of there are differences between each sampling channel; Because there is sampling time interval in sampling apparatus, inevitably there are amplitude error and phase error between each sampling channel simultaneously.These factors all can influence the sampling and the calculating of protection electric weight.Existing technology generally adopts rheostat to wait and adjusts amplitude, long operational time device aging, produce error thus; And to phase error, also do not have good bearing calibration, the precision of the device that places one's entire reliance upon.Usually, the protective current working range of microcomputer protective relay device is 0.5A to 100A, and requires to have 2.5% the precision that is not more than setting value in whole working range.Under these require, when the protective current of input hour will ask sampling cartridge to be equipped with higher precision; When the protective current higher value of input, need consider the influence of current transformer saturation nonlinearity.Existing technology is handled for whole setting range is unified, and this just must propose higher requirement to current transformer and CT translation circuit.In addition, remote measurement amount (as: voltage, electric current, power, power factor etc.) also has 0.2%-0.5% certainty of measurement requirement, needs to reduce as much as possible to measure the error that the interchannel phase place produces.

Summary of the invention

The objective of the invention is to provide a kind of method that improves microcomputer protective relay device sampling precision and measuring accuracy, the method is carried out amplitude rectification and phasing to each protection electric weight sampling channel at software layer; Adopt segmentation range changing measuring technique that the same protective current signal of importing is carried out seamless match simultaneously behind block sampling, thereby reflect the variation of electric parameters in the electric power system accurately.

The invention is characterized in that this method realizes according to the following steps in microcomputer protective relay device:

Step (1), the value of each parameter below in microcomputer protective relay device, setting:

Measuring voltage amplitude rectification coefficient

Measure the current amplitude correction coefficient

I segment protect current amplitude correction coefficient

II segment protect current amplitude correction coefficient

Measuring voltage phasing coefficient

Measure the phasing coefficient of electric current

I segment protect current phase correction coefficient

II segment protect current phase correction coefficient

Wherein φ represents A, B, C three-phase;

Above-mentioned amplitude rectification coefficient is calculated by following formula:

$K_{U_{\mathrm{\φ}}}=U_e/U_{\mathrm{\φ}};$

$K_{I_{\mathrm{m\φ}}}=I_e/I_{\mathrm{m\φ}};$

$K_{I_{\mathrm{p\φ}\_I}}=I_S/I_{\mathrm{p\φ}\_I};$

$K_{I_{\mathrm{p\φ}\_\mathrm{II}}}=I_S/I_{\mathrm{p\φ}\_\mathrm{II}};$

U wherein _eCPU board A/D in microcomputer protective relay device holds the effective value of the nominal voltage signal of input for relay-protection tester; U _φPass through the effective value of the measuring voltage measured value that obtains after A/D sampling, DFT or FFT handle for described CPU board;

I _eHold the effective value of the rated current signal of input for the CPU board A/D of relay-protection tester in microcomputer protective relay device; I _{M φ}Pass through the effective value of the measurement current measurement value that obtains after A/D sampling, DFT or FFT handle for described CPU board;

I _SFor holding the effective value of the protection test current signals of input by the CPU board A/D of relay-protection tester in microcomputer protective relay device; I _{P φ _ I}, I _{P φ _ II}The effective value of the protective current measured value that obtains at I section sampling channel and II section sampling channel respectively after handling through A/D sampling, DFT or FFT for described CPU board;

Each protects the phasing coefficient of electric weight to be drawn by following formula:

$e^{\mathrm{j\Δ}{\mathrm{\θ}}_{\mathrm{\φ}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\θ}}_{\mathrm{\φ}})};$

$e^{\mathrm{j\Δ}{\mathrm{\α}}_{\mathrm{m\φ}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\α}}_{\mathrm{m\φ}})};$

$e^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\β}}_{\mathrm{p\φ}\_I})};$

$e^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}})};$

θ wherein _AThe phase place of the A phase measuring voltage that obtains after handling through A/D sampling, DFT or FFT for described CPU board, θ _φPass through the phase place of each the phase measuring voltage that obtains after A/D sampling, DFT or FFT handle for described CPU board; α _{M φ}For each that obtains after described CPU board process A/D sampling, DFT or the FFT processing measured the phase place of electric current mutually; β _{P φ _ I}, β _{P φ _ II}Each the phase protective current that obtains after handling through A/D sampling, DFT or FFT for described CPU board is respectively in the phase place of I section sampling channel and II section sampling channel measured value;

Described I segment protect electric current and II segment protect electric current come from two outputs of a protective current block sampling circuit respectively, this sample circuit is by the measurement current transformer (CT) in the electric weight conditioning plate in the microcomputer protective relay device, be parallel to this instrument transformer (CT) output by resistance (R1), (R3) serial connection back ground connection and the resistor voltage divider circuit that forms mutually successively, be parallel to resistance (R3) two ends and by resistance (R4), the capacitance-resistance serial connection branch road that electric capacity (C2) constitutes is serially connected with between resistance (R1) end and the ground by resistance (R2), the capacitance-resistance serial connection branch road that electric capacity (C1) serial connection constitutes constitutes; I section sample rate current comes from the output of electric capacity (C1), in hour employing of measurement current signal of current transformer (CT) output; II section sample rate current comes from the output of electric capacity (C2), adopts when selected measurement current signal is big;

Step (2), respectively protect electric weight by described electric weight conditioning plate to described CPU board input:

Three-phase measuring voltage before not proofreading and correct

Output to the A/D signal input part of this CPU board successively behind the sampling channel that forms by the series connection of voltage transformer (PT), voltage filter amplifier in this electric weight conditioning plate, wherein:

${\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}};$

Three-phase before not proofreading and correct is measured electric current

Output to the A/D signal input part of this CPU board successively behind the sampling channel that forms by the series connection of current transformer (CT), current filtering amplifier in this electric weight conditioning plate, wherein:

${\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

Three-phase protective electric current before not proofreading and correct

Output to protective current I section, the II section sampling channel of the A/D signal input part of this CPU board successively behind the block sampling passage that forms by the series connection of current transformer (CT), current filtering amplifier in this electric weight conditioning plate, wherein:

The protective current of I section sampling channel: ${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

The protective current of II section sampling channel: ${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

Step (3), the electric weight of respectively protecting that described CPU board is imported step (2) carries out DFT or FFT conversion;

Step (4), described CPU board is carried out amplitude rectification to the electric weight of respectively protecting of step (3) output by following formula, obtains the measured value behind the amplitude rectification:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}=K_{U_{\mathrm{\φ}}}{\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}};$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}=K_{I_{\mathrm{m\φ}}}{\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}=K_{I_{\mathrm{p\φ}\_I}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}=K_{I_{\mathrm{p\φ}\_\mathrm{II}}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}};$

Step (5), the described CPU board electrical measurement value of respectively protecting after to each amplitude rectification of step (4) output is carried out phasing, obtains the measured value behind the phasing:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′\′}={\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\θ}}_{\mathrm{\φ}}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j({\mathrm{\θ}}_{\mathrm{\φ}}+\mathrm{\Δ}{\mathrm{\θ}}_{\mathrm{\φ}})};$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\α}}_{\mathrm{m\φ}}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j({\mathrm{\α}}_{\mathrm{m\φ}}+\mathrm{\Δ}{\mathrm{\α}}_{\mathrm{m\φ}})};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_I}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I})};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}})};$

Afterwards will be in described step (5) by following formula to I segment protect electric current

II segment protect electric current

Carry out piecewise fitting, to overcome non-linear effects;

In the formula, I _sFor carrying out the selected system parameters of piecewise fitting; Generally be chosen for the 80%-90% of the maximum range of I section sampling channel.

Through test, use the microcomputer protective relay device of this method, its voltage, current protection precision are all less than 2.5%; Voltage, current measurement precision are all less than 0.4%.

Description of drawings

Fig. 1. protective current block sampling circuit theory diagrams;

Fig. 2. protective current is chosen I section sampling channel schematic diagram;

Fig. 3. protective current is chosen II section sampling channel schematic diagram;

Fig. 4. before the graph of a relation of amplitude rectification fore-and-aft survey value and actual value: a. proofreaies and correct, after b. proofreaies and correct;

Fig. 5. protective current I, II section are measured the relation curve of effective value and actual effective value before and after the amplitude rectification: before a. proofreaies and correct, after b. proofreaies and correct;

Fig. 6. the system hardware theory diagram;

Fig. 7. electric weight conditioning plate theory diagram;

Fig. 8. demarcate the connection diagram of the test method of every correction parameter;

Fig. 9. sampling channel amplitude rectification coefficient calculations flow chart;

Figure 10. sampling channel phasing coefficient calculations flow chart;

Figure 11. measuring voltage trimming process schematic diagram;

Figure 12. measure current correction process schematic diagram;

Figure 13. protective current trimming process schematic diagram.

Embodiment

Below in conjunction with accompanying drawing the present invention is done and to be described in further detail.The present invention includes:

(1) the block sampling technology of microcomputer protecting device range changing measurement

The present invention adopts the range changing measuring technique that the same protective current signal of importing is carried out block sampling.Can divide the multistage sampling in theory, the present invention adopts two sections samplings of branch, promptly to same protective current signal, adopts two sampling channels to sample simultaneously, is called I section sampling channel and II section sampling channel, and its circuit theory diagrams as shown in Figure 1.

Wherein I section sampling channel range is less, and the precision height can effectively improve input signal signal to noise ratio hour; II section sampling channel range is bigger, can overcome the saturated influence that brings of I section sampling channel effectively.When input signal hour, adopt the data of I section sampling channel, to obtain higher sampling precision, as shown in Figure 2; When input signal was big, I section sampling channel occurred saturated, thus adopt the data of II section sampling channel, to obtain to satisfy the measurement range of required precision, as shown in Figure 3.

(2) the software layer amplitude rectification and the approximating method of sampling channel

The present invention carries out amplitude rectification to all sampling channels at software layer; Simultaneously on the basis of amplitude rectification, I, the II section sampling channel of same protective current signal carried out seamless match.The measured value and the actual value of protection electric weight exist than mistake on amplitude before not proofreading and correct.With the three-phase measuring voltage is example, and measured value and actual value vector correlation be not shown in Fig. 4 a before not proofreading and correct; The latter two concern shown in Fig. 4 b through amplitude rectification.Among the figure,

Be actual value,

Be measured value, φ represents A, B, C phase.Setting the measured value of not proofreading and correct the three-phase measurement voltage signal is:

${\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}}$

The measured value that three-phase is measured current signal is:

${\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

Three-phase protective current signal I section measured value is:

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

Three-phase protective current signal II section measured value is:

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

In the following formula, U _φ, I _{M φ}, I _{P φ _ I}, I _{P φ _ II}Be effective value.

Measured value to all sampling channels carries out amplitude rectification, promptly multiply by the amplitude rectification coefficient, and the measured value that obtains behind the amplitude rectification is:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}=K_{U_{\mathrm{\φ}}}{\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}}$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}=K_{I_{\mathrm{m\φ}}}{\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}=K_{I_{\mathrm{p\φ}\_I}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}=K_{I_{\mathrm{p\φ}\_\mathrm{II}}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

In the formula:

Be three-phase measuring voltage amplitude rectification coefficient;

For three-phase is measured the current amplitude correction coefficient;

Be three-phase protective electric current I section amplitude rectification coefficient;

Be three-phase protective electric current I I section amplitude rectification coefficient;

φ represents A, B, C phase.

After carrying out amplitude rectification, measured value equates that with the effective value of actual value it concerns shown in Fig. 4 b.

For protective current, before not doing amplitude rectification, because the influence of interchannel difference, I section and II section sampling channel measured value are also unequal.Through behind the amplitude rectification, the measurement effective value I of I section sampling channel _{P φ _ I}Measurement effective value I with II section sampling channel _{P φ _ II}Actual effective value I with input signal _{P φ}Relation shown in Figure 5.

In Fig. 5 a, wherein curve 1 is the measurement effective value of I section sampling channel and the proportional curve of actual effective value, and its top is slightly crooked owing to the influence of current transformer saturation nonlinearity; Curve 2 is the measurement effective value of II section sampling channel and the proportional curve of actual effective value; Curve 3 is for ideally measuring the proportional curve of effective value and actual effective value, and slope is 1.Through behind the amplitude rectification, each section curved line relation is shown in Fig. 5 b.

From Fig. 5 b as can be seen, through behind the amplitude rectification,, can behind the software layer phasing, carry out piecewise fitting as follows to the protective current of importing for fear of curve 1 effect of nonlinear:

In the formula, I _sFor carrying out the selected system parameters of piecewise fitting.Generally be chosen for the 80%-90% of the maximum range of I section sampling channel.

(3) the software layer method for correcting phase of sampling channel

Because the difference of device property, except that the error of systematic sampling time-delay, each phase place of sampling between the electric weight also exists error usually, and directly influences the precision of protections such as direction and distance and the precision of remote measurement amount.No matter whether carry out amplitude rectification, the present invention all can carry out phasing at software layer to all sampling channels.With the electric weight behind the amplitude rectification is example, obtains the measured value behind the phasing:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′\′}={\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\θ}}_{\mathrm{\φ}}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j({\mathrm{\θ}}_{\mathrm{\φ}}+\mathrm{\Δ}{\mathrm{\θ}}_{\mathrm{\φ}})}$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\α}}_{\mathrm{m\φ}}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j({\mathrm{\α}}_{\mathrm{m\φ}}+\mathrm{\Δ}{\mathrm{\α}}_{\mathrm{m\φ}})}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_I}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I})}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}})}$

Wherein:

Be three-phase measuring voltage phasing coefficient;

For three-phase is measured the current phase correction coefficient;

Be three-phase protective electric current I section phasing coefficient;

Be three-phase protective electric current I I section phasing coefficient;

φ represents A, B, C phase.

Through behind the phasing; also can there be the error of a conforming system delay in the vector of measured value and actual value in theory; but this error has nothing to do to the various calculating of relaying protection and the certainty of measurement of every remote measurement amount, and protection and the precision of measuring are greatly improved.

(4) test method of the every correction parameter of demarcation

The present invention has designed the test method of demarcating every correction parameter.

1, experimental condition

(1) GB/T 15145-94 computer line protective device general technical specifications is carried out in normal test atmosphere and nominal parameter requirement.

(2) microcomputer protecting device

Microcomputer protective relay device hardware block diagram of the present invention as shown in Figure 6.Protective device mainly is made up of CPU board, electric weight conditioning plate, communication interface, switching value input/output board, demonstration and Keyboard Control plate.

Every electric quantity signal inserts the electric weight conditioning plate in the microcomputer protective relay device.In the electric weight conditioning plate, voltage, current signal is through CT, PT conversion, pass through filter amplifying processing again after, carry out the A/D sampling, as shown in Figure 7.

(3) continue and protect the tester mode of connection

The mode of connection of the microcomputer protective relay device and the guarantor's tester that continues as shown in Figure 8.

2, demarcate the method for amplitude rectification coefficient

(1) method of nominal voltage amplitude rectification coefficient

When demarcating the amplitude rectification coefficient,, protect tester by continuing and provide nominal voltage signal for the voltage sample passage ${\stackrel{.}{U}}_e=\sqrt{2}{U}_e{e}^{j0}.$ Microcomputer protective relay device is handled through over-sampling, DFT or fft algorithm.Calculate the measured value of each channel signal:

${\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}}$

Wherein, φ represents A, B, C three-phase.

Actual effective value U with input _eWith measurement effective value U _φCompare, obtain following relational expression:

$U_e=K_{U_{\mathrm{\φ}}}\×U_{\mathrm{\φ}}$

Obtain measuring voltage amplitude rectification coefficient thus:

$K_{U_{\mathrm{\φ}}}=U_e/U_{\mathrm{\φ}}$

(2) method of calibration measurements current amplitude correction coefficient

For all measurement current sample passages, protect the given same rated current signal of tester by continuing ${\stackrel{.}{I}}_e=\sqrt{2}{I}_e{e}^{j0}.$ Microcomputer protective relay device is handled through over-sampling, DFT or fft algorithm, calculates the measured value of measuring current channel:

${\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

Wherein φ represents A, B, C three-phase.

Actual effective value I with input _eWith measurement effective value I _{M φ}Compare, obtain following relational expression:

$I_e=K_{I_{\mathrm{m\φ}}}\×I_{\mathrm{m\φ}}$

Obtain measuring the current amplitude correction coefficient thus:

$K_{I_{\mathrm{m\φ}}}=I_e/I_{\mathrm{m\φ}}$

(3) method of demarcation protective current amplitude rectification coefficient

For the protective current passage, because will carry out match, so the measuring current that the guarantor's tester that continues provides is ${\stackrel{.}{I}}_S=\sqrt{2}{I}_S{e}^{j0}.$

Microcomputer protective relay device is handled through over-sampling, DFT or fft algorithm, calculates the measured value of protective current I and II sampling channel signal:

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

Wherein, φ represents A, B, C three-phase.

Actual effective value I with input _SWith measurement effective value I _{P φ _ I}, I _{P φ _ II}Compare, obtain following relational expression:

$I_S=K_{I_{\mathrm{p\φ}\_I}}\×I_{\mathrm{p\φ}\_I}$

$I_S=K_{I_{\mathrm{p\φ}\_\mathrm{II}}}\×I_{\mathrm{p\φ}\_\mathrm{II}}$

Obtain I section sampling channel and II section sampling channel amplitude rectification coefficient thus:

$K_{I_{\mathrm{p\φ}\_I}}=I_S/I_{\mathrm{p\φ}\_I}$

$K_{I_{\mathrm{p\φ}\_\mathrm{II}}}=I_S/I_{\mathrm{p\φ}\_\mathrm{II}}$

Owing to be at given input I _SThe basis on protective current is done amplitude rectification, and also be I during piecewise fitting _SBe match point, so the piecewise fitting of protective current is continuously (seamless).

Each passage amplitude rectification coefficient computed in software flow chart as shown in Figure 9.

(4) method of demarcation phasing coefficient

When carrying out phasing,, protect the given nominal voltage signal of tester by continuing for all measuring voltage sampling channels ${\stackrel{.}{U}}_e=\sqrt{2}{U}_e{e}^{j0},$ Simultaneously to all current sample passages given one and the synchronous rated current signal of measuring voltage sampling channel ${\stackrel{.}{I}}_e=\sqrt{2}{I}_e{e}^{j0},$ Microcomputer protective relay device is handled through over-sampling, DFT or fft algorithm, obtains respectively:

${\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}}$

${\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

Phase place that in principle can arbitrary electric weight is the phase place of benchmark electric weight, now considers with A phase measuring voltage phase place to be reference phase, phase place and its of each phase is compared can draw each sampling channel and the A phase difference of measuring voltage sampling channel mutually.That is:

Δθ _φ＝θ _A-θ _φ

Δα _mφ＝θ _A-α _mφ

Δβ _{pφ_I}＝θ _A-β _{pφ_I}

Δβ _{pφ_II}＝θ _A-β _{pφ_II}

Obtain the phasing coefficient of each phase voltage thus respectively

Each measures the current phase correction coefficient mutually

Each phase protective current I section phasing coefficient

With protective current II section phasing coefficient

φ represents A, B, C three-phase in the formula.The computed in software flow chart of each sampling channel phasing coefficient as shown in figure 10.

System can improve the sampling precision of microcomputer protective relay device by amplitude rectification and phasing, and further improves the precision of other remote measurement amount of calculating based on every sampled value.The complete trimming process of measurement voltage signal as shown in figure 11; Measure the complete trimming process of current signal as shown in figure 12; The trimming process of protective current signal integrity, as shown in figure 13.

Claims (1)

1. a method that improves measuring precision of microcomputer protective relay device is characterized in that, this method realizes in microcomputer protective relay device according to the following steps:

Step (1), the value of each parameter below in microcomputer protective relay device, setting:

Measuring voltage amplitude rectification coefficient

Measure the current amplitude correction coefficient

I segment protect current amplitude correction coefficient

II segment protect current amplitude correction coefficient

Measuring voltage phasing coefficient

Measure the phasing coefficient of electric current

I segment protect current phase correction coefficient

II segment protect current phase correction coefficient

Wherein φ represents A, B, C three-phase;

Above-mentioned amplitude rectification coefficient is calculated by following formula:

$K_{U_{\mathrm{\φ}}}=U_e/U_{\mathrm{\φ}};$

$K_{I_{\mathrm{m\φ}}}=I_e/I_{\mathrm{m\φ}};$

$K_{I_{\mathrm{p\φ}\_I}}=I_S/I_{\mathrm{p\φ}\_I};$

$K_{I_{\mathrm{p\φ}\_\mathrm{II}}}=I_S/I_{\mathrm{p\φ}\_\mathrm{II}};$

U wherein _eCPU board A/D in microcomputer protective relay device holds the effective value of the nominal voltage signal of input for relay-protection tester; U _φPass through the effective value of the measuring voltage measured value that obtains after A/D sampling, DFT or FFT handle for described CPU board;

I _eHold the effective value of the rated current signal of input for the CPU board A/D of relay-protection tester in microcomputer protective relay device; I _{M φ}Pass through the effective value of the measurement current measurement value that obtains after A/D sampling, DFT or FFT handle for described CPU board;

I _SFor holding the effective value of the protection test current signals of input by the CPU board A/D of relay-protection tester in microcomputer protective relay device; I _{P φ _ I}, I _{P φ _ II}The effective value of the protective current measured value that obtains at I section sampling channel and II section sampling channel respectively after handling through A/D sampling, DFT or FFT for described CPU board;

Each protects the phasing coefficient of electric weight to be drawn by following formula:

$e^{\mathrm{j\Δ}{\mathrm{\θ}}_{\mathrm{\φ}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\θ}}_{\mathrm{\φ}})};$

$e^{\mathrm{j\Δ}{\mathrm{\α}}_{\mathrm{m\φ}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\α}}_{\mathrm{m\φ}})};$

$e^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\β}}_{\mathrm{p\φ}\_I})};$

$e^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}=e^{j({\mathrm{\θ}}_A-{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}})};$

θ wherein _AThe phase place of the A phase measuring voltage that obtains after handling through A/D sampling, DFT or FFT for described CPU board, θ _φPass through the phase place of each the phase measuring voltage that obtains after A/D sampling, DFT or FFT handle for described CPU board; α _{M φ}For each that obtains after described CPU board process A/D sampling, DFT or the FFT processing measured the phase place of electric current mutually; β _{P φ _ I}, β _{P φ _ II}Each the phase protective current that obtains after handling through A/D sampling, DFT or FFT for described CPU board is respectively in the phase place of I section sampling channel and II section sampling channel measured value;

Described I segment protect electric current and II segment protect electric current come from two outputs of a protective current block sampling circuit respectively, this sample circuit is by the measurement current transformer (CT) in the electric weight conditioning plate in the microcomputer protective relay device, be parallel to this current transformer (CT) output by resistance R 1, R3 serial connection back ground connection and the resistor voltage divider circuit that forms mutually successively, the capacitance-resistance serial connection branch road that is parallel to resistance R 3 two ends and is made of resistance R 4, capacitor C 2 is serially connected with between resistance R 1 one ends and the ground and be connected in series the capacitance-resistance that constitutes by resistance R 2, capacitor C 1 and be connected in series branch road and constitute; I section sample rate current comes from the output of capacitor C 1, in hour employing of measurement current signal of current transformer (CT) output; II section sample rate current comes from the output of capacitor C 2, adopts when selected measurement current signal is big;

Step (2), respectively protect electric weight by described electric weight conditioning plate to described CPU board input:

Three-phase measuring voltage before not proofreading and correct Output to the A/D signal input part of this CPU board successively behind the sampling channel that forms by the series connection of voltage transformer (PT), voltage filter amplifier in this electric weight conditioning plate, wherein:

${\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}};$

Three-phase before not proofreading and correct is measured electric current

Output to the A/D signal input part of this CPU board successively behind the sampling channel that forms by the series connection of current transformer (CT), current filtering amplifier in this electric weight conditioning plate, wherein:

${\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}}$

Three-phase protective electric current before not proofreading and correct

Output to protective current I section, the II section sampling channel of the A/D signal input part of this CPU board successively behind the block sampling passage that forms by the series connection of current transformer (CT), current filtering amplifier in this electric weight conditioning plate, wherein:

The protective current of I section sampling channel: ${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}}$

The protective current of II section sampling channel: ${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}$

Step (3), the electric weight of respectively protecting that described CPU board is imported step (2) carries out DFT or FFT conversion;

Step (4), described CPU board is carried out amplitude rectification to the electric weight of respectively protecting of step (3) output by following formula, obtains the measured value behind the amplitude rectification:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}=K_{U_{\mathrm{\φ}}}{\stackrel{.}{U}}_{\mathrm{\φ}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j{\mathrm{\θ}}_{\mathrm{\φ}}};$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}=K_{I_{\mathrm{m\φ}}}{\stackrel{.}{I}}_{\mathrm{m\φ}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j{\mathrm{\α}}_{\mathrm{m\φ}}};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}=K_{I_{\mathrm{p\φ}\_I}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_I}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_I}};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}=K_{I_{\mathrm{p\φ}\_\mathrm{II}}}{\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}};$

Step (5), the described CPU board electrical measurement value of respectively protecting after to each amplitude rectification of step (4) output is carried out phasing, obtains the measured value behind the phasing:

${\stackrel{.}{U}}_{\mathrm{\φ}}^{\′\′}={\stackrel{.}{U}}_{\mathrm{\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\θ}}_{\mathrm{\φ}}}=\sqrt{2}{K}_{U_{\mathrm{\φ}}}{U}_{\mathrm{\φ}}{e}^{j({\mathrm{\θ}}_{\mathrm{\φ}}+\mathrm{\Δ}{\mathrm{\θ}}_{\mathrm{\φ}})};$

${\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{m\φ}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\α}}_{\mathrm{m\φ}}}=\sqrt{2}{K}_{I_{\mathrm{m\φ}}}{I}_{\mathrm{m\φ}}{e}^{j({\mathrm{\α}}_{\mathrm{m\φ}}+\mathrm{\Δ}{\mathrm{\α}}_{\mathrm{m\φ}})};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_I}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_I}}{I}_{\mathrm{p\φ}\_I}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_I}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_I})};$

${\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′\′}={\stackrel{.}{I}}_{\mathrm{p\φ}\_\mathrm{II}}^{\′}{e}^{\mathrm{j\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}}=\sqrt{2}{K}_{I_{\mathrm{p\φ}\_\mathrm{II}}}{I}_{\mathrm{p\φ}\_\mathrm{II}}{e}^{j({\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}}+\mathrm{\Δ}{\mathrm{\β}}_{\mathrm{p\φ}\_\mathrm{II}})}.$

Images