CN1797887A - Method for starting up and protecting sampling values in three phases at same time - Google Patents

Abstract

Starting up and protecting method by sampling values in three phases at same time includes steps: sampling circuit samples difference value of currents between phases; relation between positive and negative sequence currents is obtained from the difference values, and then effective value of negative sequence current is calculated and stored in memory; when calculating effective value of negative sequence current, the method magnifies negative sequence current by using data character of spanning windows; using positive sequence current to carry out brake, prevents error start-up caused by unbalanced negative sequence current; based on whether static stable state is destroyed, the method determines to use high or low threshold values, and uses floating threshold to prevent error start-up caused by system oscillation and frequency shift. Comparing with prior art, the invention raises sensitivity and reliability, suitable to relay protection for digital high-tension transmission line.

Description

A kind of method for starting up and protecting sampling values in three phases at same time

Technical field

The present invention relates to electricity field high-voltage fence technical field of relay protection, relate in particular to a kind of method for starting up and protecting sampling values in three phases at same time, the feature when utilizing data to stride window is amplified the startup amount, the sensitivity of responsiveness and action during with the raising fault.

Background technology

In the Microcomputer Protection of supertension line, the effect that starting component mainly plays locking and enters malfunction routine.Latch-up protection when system normally moves the generation abnormal conditions even the measuring component malfunction also can guarantee to protect not mistrip, has improved the reliability of device work; Simultaneously, when fault, start a whole set of protection, remove out atretostomia.If starting component is failure to actuate when fault, can cause protecting tripping, cause upper level protection overstep tripping, will run counter to rapidity of relay protection and optionally requirement simultaneously.Starting component requires and can fast, reliably react various types of short troubles, then can not error starting to misoperation situations such as system oscillation and frequency shift (FS)s.At present; the internal microcomputer line protective devices generally adopt difference of phase currents or the phase current difference sudden change amount startup amount as starting component; and provide height definite value starting component: the low definite value starting component of phase current is in order to start posting a letter of enclosed type direction protection; but it still enters normal working procedure after starting, and the action of high-set setting starting component then enters exception handles." wavelet packet analysis of system microcomputer protection starting component " that Zheng Deshan, Yang Deqiang, Shi Xinling deliver on " electrotechnics " 2003 (7) introduced the essential structure principle of wavelet packet and the problem that the electric power system microcomputer protective relay exists, and carried out the wavelet packet analysis of starting component.Liu Huanzhang, Li Xiaohua, Yin Xianggen, Chen Deshu are in " Automation of Electric Systems " 2003; " the highly sensitive starting component of sampling values in three phases at same time " delivered on 27 (19) discloses a kind of starting algorithm based on the sampled value of three phases at same time of microcomputer based relay protective device starting component; this algorithm is not subjected to the influence of system frequency deviation, breaking down in vibration does not need to increase assistant criteria and just can reflect various fault types delicately; but be subjected to the influence in system oscillation cycle, cycle of oscillation too weak point may be when system's fault-free error starting.The weak point of such starting component is when system's generation quick oscillation may error starting, if increase the out-of-step blocking element again, breaking down in vibration then may tripping again, has also increased the complexity that starts; Simultaneously, start the sensitivity deficiency when starting component of kinetic current sudden change amount in system slow developing fault and high resistance earthing fault takes place, so also set up the zero-sequence current starting component in the protective device.

Summary of the invention

In order to overcome the deficiencies in the prior art, the object of the present invention is to provide a kind of method for starting up and protecting sampling values in three phases at same time, the feature when utilizing data to stride window is amplified the startup amount, the sensitivity of responsiveness and action during with the raising fault.

For finishing above-mentioned purpose, the overall technological scheme that the present invention takes is: a kind of method for starting up and protecting sampling values in three phases at same time, and the formation Automation of Electric Systems fault judgement and the protection system of computer, sample circuit, relay, this method may further comprise the steps:

Step 1, each the phase current instantaneous sampling value that obtains according to the protective device sample circuit are asked for the difference of three-phase current;

Step 2, computer obtain the relation of itself and positive and negative preface electric current by the three-phase current value difference, calculate the effective value of negative-sequence current, and this effective value is stored in the computer storage;

Step 3, when asking for the negative-sequence current effective value, utilize data to stride the feature of window, amplify negative-sequence current;

Step 4, brake, prevent that the negative phase-sequence unsymmetrical current from causing the starting component error starting with the forward-order current amount;

Step 5, protection determine to adopt high and low threshold definite value, and prevent that with floating threshold system oscillation and frequency shift (FS) from causing error starting according to the quiet judgement that surely whether destroys.

The three-phase current value difference in the described step 2 and the relation of positive and negative preface electric current adopt following formula:

$i\left(t\right)={[i_a\left(t\right)-i_b\left(t\right)]}^2+{[i_b\left(t\right)-i_c\left(t\right)]}^2{+[i_c\left(t\right)-i_a\left(t\right)]}^2$

Wherein: I _1mBe forward-order current amplitude, I _2mBe the negative-sequence current amplitude.

The effective value that obtains negative-sequence current in the described step 2 further may further comprise the steps:

Step 21, computer utilization to following formula differential, take absolute value, get again the T/4 interval integral,

Obtain:

df(t)＝9I _1mI _2mcos(2ωt+)d2ωt

$2I_1{I}_2=I_{1m}{I}_{2m}=\frac{1}{18}{\∫}_{t_0}^{t_0+T/4}\left|f^{\′}\left(t\right)\right|\mathrm{dt}=K_1$

Step 22, computer are got the T/2 interval integral to The above results, ask for DC component

${\∫}_{t_0}^{t_0+T/2}f\left(t\right)\mathrm{dt}=\frac{9}{4}(I_{1m}^2+I_{2m}^2)T;$ $I_1^2+I_2^2=\frac{1}{2}(I_{1m}^2+I_{2m}^2)=\frac{2}{9T}{\∫}_{t_0}^{t_0+T/2}f\left(t\right)\mathrm{dt}=K_2$

Step 23, computer are obtained the effective value of positive and negative electric current:

$I_1=\frac{1}{2}(\sqrt{K_2+K_1}+\sqrt{K_2-K_1});I_2=\frac{1}{2}(\sqrt{K_2+K_1}-\sqrt{K_2-K_1})$

Amplification negative-sequence current in the described step 3 is meant the integrating range of interior preceding T/2 period of a power frequency period T as asking function, and the back T/4 period is as the integrating range of the derived function absolute value of being asked.

Positive sequence braking amount in the described step 4 is the smaller in current amount and all preceding amounts.

Described actuating quantity is the sudden change amount of negative-sequence current, actuating quantity (Δ Δ I2)=|| before current (I2)-half cycle (I2) |-| (I2)-one is before week (I2) before the half cycle ||.

Value when the low definite value threshold definite value in the described step 5 refers to that system normally moves, do not have quiet steady destroy.

High-set setting threshold in the described step 5 refers to protect judges quiet steady destruction, the definite value when vibration takes place in system, after system vibrates, reduces the action sensitivity of starting element, the Fraquent start of starting element when preventing to vibrate.

The present invention has following advantage: the present invention has constructed the function of three-phase current sampling value difference, and three alternate current sample differences are handled by this function, obtain the negative-sequence current effective value, the feature of utilizing data to stride window is amplified the startup amount, the purpose of responsiveness and action sensitivity when reaching the raising fault.With floating threshold, forward-order current braking and the quiet steady method that the action threshold value is improved in the back of destroying, the error starting phenomenon when preventing the locking system quick oscillation, effectively improved the action sensitivity and the reliability of starting component.Starting component provided by the invention is not subjected to the influence of system operation mode, is not subjected to the influence of ground connection transition resistance, and no matter the length in system oscillation cycle all can reliably start when the fault of system's generation any kind, and must not establish the assistant starting element in addition.

Description of drawings

Fig. 1 is a main flow chart of the present invention;

Fig. 2 is that the data window when asking for the negative-sequence current effective value is arranged schematic diagram.

Embodiment

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

See also Fig. 1 main flow chart of the present invention.The formation Automation of Electric Systems fault judgement and the protection system of the computer of tape handling device and memory, sample circuit, relay, the method that sampling values in three phases at same time starts protection is as follows:

At first, according to each phase current instantaneous sampling value ia, ib, ic that the protective device sample circuit obtains, ask for difference ia-ib, ib-ic, the ic-ia of three-phase current.

If have negative phase-sequence, zero sequence composition in the line current, the sampled value of three-phase current can be expressed as:

i _a(t)＝I _1msin(ωft+α)+I _2msin(ωft+β)+I ₀sin(ωft+χ)

i _b(t)＝I _1msin(ωft+α-120°)+I _2msin(ωft+β+120°)+I _0msin(ωft+χ)

i _c(t)＝I _1msin(ωft+α+120°)+I _2msin(ωft+β-120°)+I _0msin(ωft+χ)

Obtain thus:

$i_b\left(t\right)-i_c\left(t\right)=-\sqrt{3}{I}_{1m}\cos (\mathrm{\ωft}+\mathrm{\α})+\sqrt{3}{I}_{2m}\cos (\mathrm{\ωft}+\mathrm{\β})$

${[i_a\left(t\right)-i_b\left(t\right)]}^2+{[i_b\left(t\right)-i_c\left(t\right)]}^2{+[i_c\left(t\right)-i_a\left(t\right)]}^2$

$=\frac{9}{2}[(I_{1m}^2+I_{2m}^2)-{2I}_{1m}{I}_{2m}\cos (2\mathrm{\ωft}+\mathrm{\α}+\mathrm{\β})]$

Wherein: I _1mBe forward-order current amplitude, I _2mFor the negative-sequence current amplitude, make I ₁And I ₂Be respectively positive and negative preface current effective value, then $I_1=I_{1m}/\sqrt{2},$ $I_2=I_{2m}/\sqrt{2}.$

Then, to the function of above-mentioned structure, obtain the effective value of negative-sequence current through a series of derivations.

If f (t) is following expression formula:

For asking for the maximum of two frequency multiplication alternating current components, with its differential, take absolute value, get again the T/4 interval integral

df(t)＝9I _1mI _2mcos(2ωt+)d2ωt

$2I_1{I}_2=I_{1m}{I}_{2m}=\frac{1}{18}{\∫}_{t_0}^{t_0+T/4}\left|f^{\′}\left(t\right)\right|\mathrm{dt}=K_1$

For asking for DC component, it is got the T/2 interval gets integration:

${\∫}_{t_0}^{t_0+T/2}f\left(t\right)\mathrm{dt}=\frac{9}{4}{(I_{1m}^2+I_{2m}^2)T;I}_1^2+I_2^2=\frac{1}{2}(I_{1m}^2+I_{2m}^2)=\frac{2}{9T}{\∫}_{t_0}^{t_0+T/2}f\left(t\right)\mathrm{dt}=K_2$

Solve the effective value of positive and negative electric current:

$I_1=\frac{1}{2}(\sqrt{K_2+K_1}+\sqrt{K_2-K_1});---\left(2\right)$

$I_2=\frac{1}{2}(\sqrt{K_2+K_1}-\sqrt{K_2-K_1})---\left(3\right)$

Because f (t) is to be the function of T/2 in the cycle, the absolute value of the derived function of f (t) is the periodic function of T/4, and the steady-state quantity before the fault or after the fault is quadratured, and is only relevant with the width of separately integrating range, irrelevant with the moment of integration.But be that a part is the data before the fault in the data window in fault, another part is the data after the fault, and this moment, result of calculation had discrepancy.

See also Fig. 2,, moderately amplify negative-sequence current, method arranging data window as shown in Figure 2 in order to improve sensitivity.

Asking for I ₂The time, the data window length of using is 3/4ths cycles, preceding half cycles is used for asking for K ₂, back 1/4th cycles are according to being used for asking for K ₁(k-N/4 in the time of k), asks for K when fault moment is positioned at ₁The time use data after the fault, reflection be reversal long-pending after the fault.K ₂Be with data computation before the fault, reflection be the quadratic sum of the reversal before the fault.Greater than before the fault, dwindled K behind the quadratic sum generic failure of reversal to being equivalent to after the fault ₂Reversal long-pending constant, the quadratic sum of reversal diminishes, and adds that forward-order current generally is not less than the condition of negative-sequence current, has so just amplified negative-sequence current, has dwindled forward-order current.Work as K ₂Contract the too small K of making ₂＜K ₁The time, make K ₂=K ₁To satisfy the domain of definition.

Next, brake, prevent that the negative phase-sequence unsymmetrical current from causing the starting component error starting with the forward-order current amount.

Above-mentioned what use is the continuous magnitude of current, and what sample in the protection is the sampled value that disperses, and asks for K with discrete sampled value ₁And K ₂Method as follows:

$K_1=\frac{1}{18}\underset{k=-(N/4-1)}{\overset{0}{\mathrm{\Σ}}}|f\left(t_k\right)-f\left(t_{k-1}\right)|$

$K_2=\frac{2}{9N}\underset{k=-(3N/4-1)}{\overset{-N/2}{\mathrm{\Σ}}}f\left(t_k\right)$

Obtain K ₁, K ₂After, use formula (2) respectively, (3) can be in the hope of I ₁And I ₂

The operation equation of starting component is:

ΔΔI ₂＞k ₁·min{I ₁(k-N)，I ₁(k)}+ΔI _ZD (4)

Wherein ${\mathrm{\Δ\ΔI}}_2=\left|\right|I_2\left(t\right)-I_2(t-\frac{N}{2})|-|I_2(t-\frac{N}{2})-I_2(t-N)\left|\right|,$ k ₁Be positive sequence amount restraint coefficient, Δ I _ZDBe fixing threshold.

Δ Δ I ₂Ask in to take the purpose of floating threshold be in order to weaken frequency shift (FS) and the system oscillation influence to this starting component.During normal the operation, because circuit replaces, factors such as three-phase load is asymmetric, system oscillation all can produce negative sequence component, but it is for positive sequence component, therefore just occupy a part seldom, the negative phase-sequence amount causes the starting component error starting when making Brake Energy and effectively prevent from normally to move with the positive sequence amount.In operation equation (2), the smaller in current amount and all preceding amounts is measured in the positive sequence braking, promptly gets min{I ₁(k-N), I ₁(k) }, purpose is in order to reduce the braking amount after fault, to improve the sensitivity of starting component.Actuating quantity is the sudden change amount of negative-sequence current, actuating quantity (Δ Δ I2)=|| before current (I2)-half cycle (I2) |-| (I2)-one is before week (I2) before the half cycle ||.

If continuous 3 sampled points, the operation equation of formula (2) can both satisfy, then the starting component instantaneous starting.

Then, protection decides and adopts high and low threshold definite value according to the quiet judgement that surely whether destroys, and prevents that with floating threshold system oscillation and frequency shift (FS) from causing error starting.

The negative phase-sequence amount I of system oscillation meeting to measuring ₂Produce bigger error, cause the starting component frequent starting during system oscillation easily, therefore after quiet steady destruction is judged in protection, require to improve restraint coefficient and action threshold.

Table 1 coefficient k ₁With fixing choosing of threshold

Positive sequence braking amount	Low definite value		High-set setting
					k 1	ΔI ZD	k 1	ΔI ZD
	800＞I 1≥0	0.03	60	0.04					100
1600＞I≥800					0.04	52	0.05	92
	I 1≥1600	0.05	36	0.06					76

In table 1, low definite value threshold is the value of system when normally moving, not having quiet steady destruction, and the high-set setting threshold is that quiet steady destruction, the definite value when vibration takes place in system are judged in protection.Promptly after system vibrates, require to reduce the action sensitivity of starting component, the frequent starting of starting component when preventing to vibrate.And forward-order current is big more, and the coefficient of forward-order current braking amount is also big more.

This starting component toggle speed is fast, when normal operation is broken down, very high startup sensitivity is arranged; During system oscillation, can error starting, and when vibration is broken down, can reliably start.

It should be noted that at last: above embodiment is the unrestricted technical scheme of the present invention in order to explanation only, although the present invention is had been described in detail with reference to the foregoing description, those of ordinary skill in the art is to be understood that: still can make amendment or be equal to replacement the present invention, and not breaking away from any modification or partial replacement of the spirit and scope of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (8)

1, a kind of method for starting up and protecting sampling values in three phases at same time, the formation Automation of Electric Systems fault judgement and the protection system of computer, sample circuit, relay is characterized in that, this method may further comprise the steps:

Step 1, each the phase current instantaneous sampling value that obtains according to the protective device sample circuit are asked for the difference of three-phase current;

Step 2, computer obtain the relation of itself and positive and negative preface electric current by the three-phase current value difference, calculate the effective value of negative-sequence current, and this effective value is stored in the computer storage;

Step 3, when asking for the negative-sequence current effective value, utilize data to stride the feature of window, amplify negative-sequence current;

Step 4, brake, prevent that the negative phase-sequence unsymmetrical current from causing the starting component error starting with the forward-order current amount;

Step 5, protection determine to adopt high and low threshold definite value, and prevent that with floating threshold system oscillation and frequency shift (FS) from causing error starting according to the quiet judgement that surely whether destroys.

2, method for starting up and protecting sampling values in three phases at same time according to claim 1 is characterized in that, the three-phase current value difference in the described step 2 and the relation of positive and negative preface electric current adopt following formula:

$i\left(t\right)={[i_a\left(t\right)-i_b\left(t\right)]}^2+{[i_b\left(t\right)-i_c\left(t\right)]}^2+{[i_c\left(t\right)-i_a]}^2$

Wherein: I _1mBe forward-order current amplitude, I _2mBe the negative-sequence current amplitude.

3, method for starting up and protecting sampling values in three phases at same time according to claim 1 is characterized in that, the effective value that obtains negative-sequence current in the described step 2 further may further comprise the steps:

Step 21, computer utilization to following formula differential, take absolute value, get again the T/4 interval integral,

Obtain:

df(t)＝9I _1mI _2mcos(2ωt+)d2ωt

$2I_1{I}_2=I_{1m}{I}_{2m}=\frac{1}{18}{\∫}_0^{t_0+T/4}\left|f^{\′}\left(t\right)\right|\mathrm{dt}=K_1$

Step 22, computer are got the T/2 interval integral to The above results, ask for DC component,

${\∫}_0^{t_0+T/2}f\left(t\right)\mathrm{dt}=\frac{9}{4}(I_{1m}^2+I_{2m}^2)T;$ $I_1^2+I_2^2=\frac{1}{2}(I_{1m}^2+I_{2m}^2)=\frac{2}{9T}{\∫}_0^{t_0+T/2}f\left(t\right)\mathrm{dt}=K_2$

Step 23, computer are obtained the effective value of positive and negative electric current:

$I_1=\frac{1}{2}(\sqrt{K_2+K_1}+\sqrt{K_2-K_1});$ $I_2=\frac{1}{2}(\sqrt{K_2+K_1}-\sqrt{K_2-K_1})$

4, method for starting up and protecting sampling values in three phases at same time according to claim 1; it is characterized in that; amplification negative-sequence current in the described step 3 is meant the integrating range of interior preceding T/2 period of a power frequency period T as asking function, and the back T/4 period is as the integrating range of the derived function absolute value of being asked.

5, method for starting up and protecting sampling values in three phases at same time according to claim 1 is characterized in that, the positive sequence braking amount in the described step 4 is the smaller in current amount and all preceding amounts.

6, method for starting up and protecting sampling values in three phases at same time according to claim 5; it is characterized in that; described actuating quantity is the sudden change amount of negative-sequence current, actuating quantity (Δ Δ I2)=|| before current (I2)-half cycle (I2) |-| (I2)-one is before week (I2) before the half cycle ||.

7, method for starting up and protecting sampling values in three phases at same time according to claim 1 is characterized in that, the value when the low definite value threshold definite value in the described step 5 refers to that system normally moves, do not have quiet steady destroy.

8, method for starting up and protecting sampling values in three phases at same time according to claim 1; it is characterized in that; high-set setting threshold in the described step 5 refers to protect the definite value when judging quiet steady destruction, system vibration taking place; after system vibrates; reduce the action sensitivity of starting element, the Fraquent start of starting element when preventing to vibrate.

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