CN103135023B - The method and apparatus of short circuit is detected in electric power networks - Google Patents

Abstract

The present invention relates to a kind of method and apparatus detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, the method comprises: obtain the first instantaneous current value flowed through as described load supplying branch road, and a time interval of being separated by obtains the second instantaneous current value flowing through described branch road; Judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset; If described default restriction relation is met, then determine to occur short circuit in described electric power networks.Utilize method and apparatus provided by the present invention, can than the short-circuit current doped earlier in network, owing to can compare by means of concrete constraint condition, only the numerical value recorded need be substituted into formula and compare to dope whether there is short-circuit current, so also realize than being easier to.

Description

The method and apparatus of short circuit is detected in electric power networks

Technical field

The present invention relates to a kind of method and apparatus detecting short circuit, particularly relate to and a kind ofly comprising at least one with the method and apparatus detecting short circuit in the electric power networks of electric loading.

Background technology

In electric power networks, isolating switch is usually utilized to carry out short-circuit protection to circuit.In isolating switch, short-circuit current can make the mechanical contact in isolating switch impaired.If short-circuit current is discovered in an early phase, circuit breaker trip can be made before electric current reaches very greatly, thus the damage to isolating switch, the security increasing isolating switch and serviceable life can be reduced.

Zone selective interlock (ZSI) function is one of key character of isolating switch of new generation, effectively can solve the inter-stage selective incubation problem of short-circuit protection, and shortening people is time delay, improves the safety and reliability of power supply-distribution system selective protection.If comparatively fast short-circuit current can be predicted earlier, then can expand its scope of application.

At present, general early stage short-circuit current detection algorithm is this curve criterion (LocusCurveCriteria) of sieve fruit, and its principle is instantaneous value based on short-circuit current and current-rising-rate.But adopt the party's rule to need longer predicted time, even some short-circuit current can not predictedly arrive, and in addition, whether occurs short-circuit current owing to generally needing parallel tables to check, this kind of method implements comparatively complicated.

Summary of the invention

The object of this invention is to provide a kind of can the method and apparatus of short-circuit current efficiently and easily in Sampling network.

The invention provides a kind of method detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, comprising:

Step 101: obtain the first instantaneous current value flowed through as described load supplying branch road, a time interval of being separated by obtains the second instantaneous current value flowing through described branch road;

Step 102: judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset;

Step 103: if described default restriction relation is met, then determine to occur short circuit in described electric power networks.

Described restriction relation be with following at least one or its combine about: the breaking current threshold value preset, adopt highest power factor time electric current and voltage between phase shift, adopt lowest power factor time electric current and voltage between phase shift.

Present invention also offers a kind of device detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, and described device comprises:

An analogue integrator, for according to flow through for described load supplying branch road the first momentary current and be separated by and flow through the second momentary current of described branch road after a time interval, exports the simulating signal of momentary current integrated value in the expression described time interval;

Two analog to digital converters, an analog to digital converter is used for converting described momentary current simulating signal to momentary current digital signal, and another analog to digital converter is for exporting the digital signal of described momentary current integrated value;

A process and detection module, for the digital signal exported according to described two analog to digital converters, judge difference between two instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal occurring short circuit in described electric power networks.

Present invention also offers the device that another detects short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, and described device comprises:

A digital integrator, for according to flow through for described load supplying branch road the first momentary current and be separated by and flow through the second momentary current of described branch road after a time interval, exports the digital signal of momentary current integrated value in the expression described time interval;

An analog to digital converter, for converting described momentary current to corresponding digital signal by simulating signal;

A process and detection module, for the digital signal of the momentary current integrated value that the digital signal that exports according to described analog to digital converter and described digital integrator export, judge difference between described two instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal occurring short circuit in described electric power networks.

Invention further provides a kind of device detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, and described device comprises:

Acquisition module, for obtain flow through for described load supplying branch road the first instantaneous current value and be separated by and flow through the second instantaneous current value of described branch road after a time interval;

Judge module, for judging difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset;

Determination module, for when described default restriction relation is met, exports one and determines the signal occurring short circuit in described electric power networks.

Present invention also offers a kind of machine readable media, store a programmed instruction that can run, described instruction operation, when a digital processing system, can make described system perform the method for any one detection electric power networks short circuit currents of the present invention.

Present invention also offers a kind of computer program, comprise a machine readable media, the programmed instruction that described media storage one can run, described instruction operation, when a digital processing system, can make described system perform the method for any one detection electric power networks short circuit currents of the present invention.

The method detecting short circuit in electric power networks, device, machine readable media and the computer program that utilize the embodiment of the present invention to provide, can than the short-circuit current doped earlier in network, owing to can compare by means of concrete constraint condition, only the numerical value recorded need be substituted into formula and compare to dope whether there is short-circuit current, so also realize than being easier to.In addition, due to the short-circuit current in network can be doped earlier, also just expand the scope of application of zone selective interlock technology, alleviate the pressure of contact and isolating switch simultaneously.

Accompanying drawing explanation

Hereafter also come by reference to the accompanying drawings to be further described the above-mentioned characteristic of the present invention, technical characteristic, advantage and implementation thereof by description of a preferred embodiment by clearly understandable mode, wherein:

Fig. 1 is the equivalent-circuit model that the present invention's embodiment of the method adopts.

A kind of process flow diagram detecting the method for short circuit in electric power networks that Fig. 2 provides for an embodiment.

A kind of process flow diagram detecting the method for short circuit in electric power networks that Fig. 3 provides for another embodiment.

The schematic diagram detecting the device of short circuit in electric power networks that Fig. 4 provides for an embodiment.

The schematic diagram detecting the device of short circuit in electric power networks that Fig. 5 provides for an embodiment

The schematic diagram detecting the device of short circuit in electric power networks that Fig. 6 provides for another embodiment

Label declaration:

10 voltage sources

12 isolating switchs

31 analogue integrators

32A, 32B analog to digital converter

5 sensors

33 process and detection modules

51 digital integrators

52 analog to digital converters

53 process and detection modules

401 acquisition modules

402 judge modules

403 determination modules

Embodiment

In order to the technical characteristic to invention, object and effect have understanding clearly, now contrast accompanying drawing and the specific embodiment of the present invention is described, label identical in the various figures represents identical part.

Introduce the inventive method embodiment by Fig. 1 now.

In FIG, electric power networks involved in the present invention comprises voltage source 10, inductance component L and resistive element R.Voltage source 10 can be one and have given frequency (such as 50 hertz) and known peak value (such as volt) sine-wave generator or sine wave generator (sinusoidalgenerator).Although the voltage source 10 in Fig. 1 is expressed as voltage generator, in fact this sketch can represent different power supply in real network or generator.Electric power networks can be then single-phase, three-phase or polyphase network, when electric power networks is three-phase power network, respectively mutually in electric current can be understood as a momentary current.

In the embodiment of the present invention, between voltage source 10 and load (remainder in network is load), be connected in series with an isolating switch 12, electric power networks then by a power supply branch road for load is powered.Controlled the disjunction of isolating switch 12 by certain circuit (not shown), this circuit can comprise suitable sensor and use the method for the detection short-circuit current introduced in the embodiment of the present invention.

Specifically, in order to predict short-circuit current, key is to judge prospective current I _pwhether be greater than breaking current threshold value I _rif, prospective current I _pbe greater than breaking current threshold value I _r, then short-circuit current can be there is in prediction circuit.

As shown in Figure 2, present invention proposes a kind of method detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, comprising:

Step 101: obtain the first instantaneous current value flowed through as described load supplying branch road, a time interval of being separated by obtains the second instantaneous current value flowing through described branch road;

Step 102: judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset;

Step 103: if described default restriction relation is met, then determine to occur short circuit in described electric power networks.

Below for the example that a concrete restriction relation is derived, in this example, consider default tripping current threshold value, the possible range of power factor, i.e. most high threshold and minimum threshold.

According to the equivalent-circuit model of Fig. 1, according to Ohm law, can obtain:

Wherein, V _mbe the maximum voltage of power supply, w is the supply frequency in units of radian RAD, be connect angle, i is instantaneous current value, and i ' is i.e. di/dt, is the first order derivative of electric current;

$\tan \mathrm{\θ}=\frac{\mathrm{wL}}{R};$

$\cos \mathrm{\θ}=\frac{R}{\sqrt{R^2+{\left(\mathrm{wL}\right)}^2}};$

Wherein, cos θ is power factor, is determined by the inductance L in model and resistance R; θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage;

According to Ohm law, the maximum current of expection is

$I_p=\frac{V_m}{\sqrt{{2R}^2+2{\left(\mathrm{wL}\right)}^2}};---\left(1.1\right)$

Integral and calculating is carried out to formula 1.0, just can obtain formula 1.2,

Here, the embodiment of the present invention introduces two parameter X and Y, wherein:

$X=\frac{i\left(t\right)-i\left(0\right)}{I_r},$ $Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt}---\left(1.3\right)$

Can find out, instantaneous current value when i (0) is initial, it is instantaneous current value after the time window of t that i (t) is then through a length, due to I _rbreaking current threshold value, i.e. I _rbe a constant, then X can be regarded as a parameter about instantaneous current value.And simultaneously, because w is the supply frequency in units of radian RAD, be also a constant, so Y can be regarded as a parameter about current integration values.

Can according to connection angle during short circuit a current threshold X is determined with power-factor cos θ _thwith a current integration values threshold value Y _th, when the parameter X about instantaneous current value exceedes this current threshold X _thtime, namely

$|X=\frac{i\left(t\right)-i\left(0\right)}{I_r}|>X_{\mathrm{th}}---\left(A\right)$

I.e. prospective current I _pexceed breaking current threshold value I _r, due to I _p> I _r, just can predict and there will be short-circuit current.

When the parameter Y about current integration values exceedes this integrated value threshold value Y _thtime, namely

$|Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt}|>Y_{\mathrm{th}}---\left(B\right)$

Also I can be obtained _p> I _r, namely prediction there will be short-circuit current.

Meanwhile, consider

We can be out of shape formula 1.2, obtain following formula:

Clearly, if θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage, for given θ ₁and θ ₂, just can obtain two constant R _th1and R _th2as threshold value, namely

$R_{\mathrm{th}1}=\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right),$ $R_{\mathrm{th}2}=\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$

In conjunction with formula 1.4, we just can draw,

|Y+tan(θ ₁)X|＞R _th1(C)

Or

|Y+tan(θ ₂)X|＞R _th2(D)

Time, I _p> I _r, just likely there will be short-circuit current.

If in order to improve accuracy, can also require

| Y+tan (θ ₁) X| > R _th1and | Y+tan (θ ₂) X| > R _th2(E)

Time, at this moment owing to meeting two constraint conditions simultaneously, so can predict more accurately and there will be short-circuit current.To sum up, can find out there is multiple possible restriction relation, and when meeting formula (A) | X| > X _thtime, or meet formula (B) | Y| > Y _thtime, or meet formula and meet formula simultaneously time, can predict in network and occur short-circuit current.

And, because X is a formula about instantaneous current value, Y is a formula about current integration values, the long-pending of the two then can be expressed as the result relevant to the energy size that contact of breaker bears, so utilize X and Y to predict the short-circuit current in network, than utilizing the derivative of electric current to predict that the methods such as short-circuit current more tally with the actual situation.

In the above-mentioned methods, can measure in different sampling instants when measuring instantaneous current value, such as constantly, constant duration instantaneous current value is measured.The integrated value of the electric current needed for determining step can according to measuring the instantaneous current value that obtain and time interval calculation out, and the definition that concrete computing method can refer to integration obtains, and also can directly adopt existing computing method, repeat no more here.

Due to the various factors existed in reality, sometimes once judge just to conclude that it is inaccurate for there occurs short circuit according to above-mentioned constraint condition, in order to improve the reliability of short-circuit detecting further, whether some embodiments of the present invention there is short circuit according to the judged result determination circuit of continuous print repeatedly (at least twice).Continuous print number of times can preset, and such as, when the result to judge for continuous 3 times all represents and occurred short circuit, then determines to have occurred short circuit.

Or, different numerical value can also be distributed respectively for the judged result of judged result certainly and negative, as 1 and 0, or 1 and-1 etc., the continuous print numerical value that repeatedly judged result is corresponding is added up, judge whether the result added up exceedes this threshold value according to the number of times preset and threshold value, if exceed, then judge to have occurred short circuit.

Again or, can be the numerical value weights assigned factor corresponding to different judged results, judged result is repeatedly weighted and cumulatively obtain weighted sum, judge whether to have occurred short circuit according to weighted sum.Such as, time in satisfied constraint condition with instantaneous current value, then think that the confidence level of this judged result is higher, then distribute higher weighting factor, if only comprise in the constraint condition met $|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$ Or only comprise $|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$ Time, then think that the confidence level of this judged result is relatively lower, then distribute lower weighting factor, etc.

More than just several example, during practical application, can design decision strategy neatly according to specific circumstances.

Particular flow sheet as shown in Figure 3.The process flow diagram of the method for detecting short circuit that Fig. 3 provides for an embodiment, the method comprises the following steps.

Step 301, determines at least two instantaneous current value in different sampling instant (the multiple sampling instant of such as continuous print), chooses at least two instantaneous current value, calculate the integrated value between its difference and two current values;

Step 302, judges whether difference and/or integrated value meet the constraint condition preset, the restriction relation of such as, one or more descriptions in formula (A) (B) (C) (D) (E); If meet, then perform step 303, otherwise return step 301.

Step 303, utilizes judged result to upgrade the judged result sum stored.Such as, the judged result for affirmation and negation arranges different numerical value, can also distribute suitable weight factor for court verdict, is added, obtains new summation with the previous numerical value sum that judged result is corresponding several times continuously stored or weighted sum.

Wherein, can also take some strategies, such as, if once judging to meet constraint condition sum, several times are judging not meet constraint condition continuously again, then judged result sum can be reset.

Step 304, judges whether the summation after upgrading exceedes default threshold value, if exceed, then performs step 305, otherwise return step 301.

Step 305, determines to occur short circuit in network.

The method detecting short circuit in electric power networks utilizing the embodiment of the present invention to provide, can than the short-circuit current doped earlier in network, owing to can compare by means of concrete constraint condition, only the numerical value recorded need be substituted into formula and compare to dope whether there is short-circuit current, so also realize than being easier to.In addition, due to the short-circuit current in network can be doped earlier, also just expand the scope of application of zone selective interlock technology, alleviate the pressure of contactor and isolating switch simultaneously.

Embodiments of the invention additionally provide a kind of short-circuit detecting device, and this device can realize above-mentioned method for detecting short circuit.The schematic diagram detecting the device of short circuit in electric power networks that Fig. 4 provides for an embodiment, in this electric power networks, comprise the branch road that at least one is described load supplying by electric loading and, this device then comprises:

An analogue integrator 31, for according to first momentary current flowing through described branch road such as measured by sensor 5 and the second momentary current flowing through described branch road after the time interval of being separated by, exports the simulating signal of momentary current integrated value in the expression described time interval;

Two analog to digital converter 32A and 32B, analog to digital converter is used for converting simulating signal to digital signal, specifically, one of them analog to digital converter 32A is used for converting instantaneous current value digital signal to by according to a described momentary current simulating signal such as measured by sensor 5, and another analog to digital converter 32B is then for converting the simulating signal of described momentary current integrated value to corresponding digital signal;

A process and detection module 33, for the digital signal exported according to described two analog to digital converter 32A and 32B, judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal S occurring short circuit in described electric power networks.

Fig. 5 then shows the schematic diagram that another one detects the device of short circuit in electric power networks, and in this electric power networks, comprise the branch road that at least one is described load supplying by electric loading and, this device then comprises:

A digital integrator 51, for according to first momentary current flowing through described branch road such as measured by sensor 5 and the second momentary current flowing through described branch road after the time interval of being separated by, exports the digital signal of momentary current integrated value in the expression described time interval;

Equally also there is the analog to digital converter 52 that simulating signal can be converted to digital signal by, for converting corresponding digital signal to, i.e. the digital signal of the first instantaneous current value and the second instantaneous current value by according to the simulating signal of described first momentary current such as measured by sensor 5 and the second momentary current;

A process and detection module 53, for the digital signal according to the digital signal of described analog to digital converter 52 output and the momentary current integrated value of described digital integrator output, judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal S occurring short circuit in described electric power networks.

Fig. 6 then shows the schematic diagram that another detects the device of short circuit in electric power networks, and in this electric power networks, comprise the branch road that at least one is described load supplying by electric loading and, this device then comprises:

Acquisition module 401, for obtaining the first instantaneous current value flowing through described branch road and the second instantaneous current value flowing through described branch road after the time interval of being separated by;

Judge module 402, for judging difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset;

Determination module 403, for when described default restriction relation is met, exports one and determines the signal S occurring short circuit in described electric power networks.

Acquisition module 401 can also be used for adopting the moment to obtain at least two instantaneous current value in difference, and such as constant duration ground obtains a series of value, therefrom at least chooses two.Judge module 402 can be selected and judge whether each parameter (difference between two instantaneous current value and/or the current integration values in this time interval) obtained meets corresponding restriction relation.

From at least two judged results that judge module 402 obtains, determination module 403 can determine whether described circuit occurs short circuit according to for different sampling instant.Such as, determine that short circuit appears in described circuit according to the judged result of continuous print at least twice; Or, according to presetting continuous print number of times, as 3 times, when the result to judge for continuous 3 times all represents and occurred short circuit, then determine to have occurred short circuit.Or, for the judged result of judged result certainly and negative distributes different numerical value respectively, the continuous print numerical value that repeatedly judged result is corresponding is added up, judges whether cumulative result exceedes default threshold value, if exceed, then judge to have occurred short circuit.Again or, can also be the numerical value weights assigned factor corresponding to different judged results, judged result is repeatedly weighted and cumulatively obtain weighted sum, etc.

Judge module 402 can judge whether the difference between two instantaneous current value and/or the current integration values in this time interval meet the restriction relation relevant with most one of the high threshold and minimum threshold of default trip value, power factor.

No matter the device of the detection short circuit shown in Fig. 4, Fig. 5 or Fig. 6, its restriction relation that will meet can as follows represented by: even

$X=\frac{i\left(t\right)-i\left(0\right)}{I_r},$

$Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt},$

Then described restriction relation can comprise following in one or more:

| X| > X _th; Or

| Y| > Y _th; Or

$|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$ Or

$|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$

Wherein, i (0) is the first instantaneous current value, and i (t) is the second instantaneous current value after elapsed time interval t, I _rfor breaking current threshold value, w is the supply frequency in units of radian RAD, X _thand Y _thfor the constant determined according to connection angle during short circuit and power factor, θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage.

Further, if the restriction relation preset is met, the one or more restriction relations in below namely meeting: meet | X| > X _th; Meet | Y| > Y _th; Or meet and meet simultaneously can predict in network and occur short-circuit current.

The device detecting short circuit in electric power networks utilizing the embodiment of the present invention to provide, can than the short-circuit current doped earlier in network, owing to can compare by means of concrete constraint condition, only the numerical value recorded need be substituted into formula and compare to dope whether there is short-circuit current, so also realize than being easier to.In addition, due to the short-circuit current in network can be doped earlier, also just expand the scope of application of zone selective interlock technology, alleviate the pressure of contact and isolating switch simultaneously.

Present invention also offers a kind of machine-readable storage medium, storing for making a machine perform the instruction detecting the method for short circuit as described herein in electric power networks.Particularly, the system or device of being furnished with storage medium can be provided, store the software program code of the function realizing any embodiment in above-described embodiment on the storage medium, and make the computing machine of this system or device (or CPU or MPU) read and perform the program code be stored in storage medium.

In this case, can realize the function of any one embodiment above-described embodiment from the program code of storage medium reading itself, therefore program code and program code stored storage medium constitute a part of the present invention.

Floppy disk, hard disk, magneto-optic disk, CD (as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), tape, Nonvolatile memory card and ROM is comprised for providing the storage medium embodiment of program code.Selectively, can by communication network from download program code server computer.

In addition, be noted that, not only can by performing the program code read-out by computing machine, and by making the operating system etc. of calculating hands-operation carry out practical operation partly or completely based on the instruction of program code, thus the function of any one embodiment in above-described embodiment can be realized.

The present invention relates to a kind of method and apparatus detecting short circuit in electric power networks, described electric power networks comprises at least one and uses electric loading, the method comprises: obtain the first instantaneous current value flowed through as described load supplying branch road, and a time interval of being separated by obtains the second instantaneous current value flowing through described branch road; Judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset; If described default restriction relation is met, then determine to occur short circuit in described electric power networks.Utilize method and apparatus provided by the present invention, can than the short-circuit current doped earlier in network, owing to can compare by means of concrete constraint condition, only the numerical value recorded need be substituted into formula and compare to dope whether there is short-circuit current, so also realize than being easier to.

In this article, " schematically " expression " serves as example, example or explanation ", not should by being described to any diagram of " schematically " in this article, embodiment is interpreted as a kind of preferred or have more the technical scheme of advantage.

A series of detailed description listed is above only illustrating for possible embodiments of the present invention; they are also not used to limit the scope of the invention, all do not depart from the skill of the present invention Equivalent embodiments done of spirit or change all should be included within protection scope of the present invention.

Claims (13)

1. in electric power networks, detect a method for short circuit, described electric power networks comprises at least one and uses electric loading, it is characterized in that, comprising:

Step 101: obtain the first instantaneous current value flowed through as load supplying branch road, a time interval of being separated by obtains the second instantaneous current value flowing through described branch road;

Step 102: judge difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, wherein, order

$X=\frac{i\left(t\right)-i\left(0\right)}{I_r},$

$Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt},$

Then described restriction relation comprise following in one or more:

| X|>X _th; Or

| Y|>Y _th; Or

$|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$ Or

$|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$

Wherein, i (0) is the first instantaneous current value, and i (t) is the second instantaneous current value after elapsed time interval t, I _rfor breaking current threshold value, w is the supply frequency in units of radian RAD, X _thand Y _thfor the constant determined according to connection angle during short circuit and power factor, θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage;

Step 103: if described default restriction relation is met, then determine to occur short circuit in described electric power networks.

2. the method for claim 1, is characterized in that, described default restriction relation is met and comprises the one or more restriction relations met below:

Meet | X|>X _th; Or

Meet | Y|>Y _th; Or

Meet $|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$ And meet simultaneously $|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right).$

3. method according to claim 1, it is characterized in that, described step 101 is specially: carry out continuous sampling to the momentary current flowing through described branch road, and therefrom obtaining at least three instantaneous current value, selection any two instantaneous current value are wherein as described first instantaneous current value and the second instantaneous current value.

4. method as claimed in claim 3, is characterized in that determine whether occur in described electric power networks that the step of short circuit comprises:

Repeat described step 101 and step 102 to obtain at least two judged results;

Determine whether occur short circuit in described electric power networks according to described at least two judged results.

5. method as claimed in claim 4, is characterized in that determine whether occur in described electric power networks that short circuit comprises according to described at least two judged results:

When being judged as meeting restriction relation, arranging judged result is the first numerical value; Otherwise arranging judged result is second value;

Numerical value corresponding for described at least two judged results is added;

If the result be added is greater than default threshold value, then judge to occur short circuit in described electric power networks.

6. method as claimed in claim 5, is characterized in that, is added by numerical value corresponding for described at least two judged results and comprises:

Be that numerical value corresponding to each judged result distributes a weighting factor according to the strategy preset, numerical value corresponding for described at least two judged results is weighted cumulative.

7. the method for claim 1, is characterized in that, described electric power networks is three-phase power network, described first momentary current and the second momentary current be each mutually in electric current.

8. in electric power networks, detect a device for short circuit, described electric power networks comprises at least one and uses electric loading, and it is characterized in that, described device comprises:

An analogue integrator (31), for according to flow through for load supplying branch road the first momentary current and be separated by and flow through the second momentary current of described branch road after a time interval, exports the simulating signal of momentary current integrated value in the expression described time interval;

Two analog to digital converter (32A, 32B), one of them analog to digital converter (32A) is for converting described momentary current to corresponding digital signal, and another analog to digital converter (32B) is for converting described momentary current integrated value to corresponding digital signal;

A process and detection module (33), for according to described two analog to digital converter (32A, digital signal 32B) exported, judge difference between two instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal occurring short circuit in described electric power networks.

9. in electric power networks, detect a device for short circuit, described electric power networks comprises at least one and uses electric loading, and it is characterized in that, described device comprises:

A digital integrator (51), for according to flow through for load supplying branch road the first momentary current and be separated by and flow through the second momentary current of described branch road after a time interval, exports the digital signal of momentary current integrated value in the expression described time interval;

An analog to digital converter (52), for converting described momentary current to corresponding digital signal;

A process and detection module (53), for the digital signal of the momentary current integrated value that the digital signal that exports according to described analog to digital converter (52) and described digital integrator (51) export, judge difference between two instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, if described default restriction relation is met, then exports one and determine the signal occurring short circuit in described electric power networks.

10. in electric power networks, detect a device for short circuit, described electric power networks comprises at least one and uses electric loading, and it is characterized in that, described device comprises:

Acquisition module (401), for obtain flow through for load supplying branch road the first instantaneous current value and be separated by and flow through the second instantaneous current value of described branch road after a time interval;

Judge module (402), for judging difference between described first instantaneous current value and the second instantaneous current value and/or in the described time interval, whether momentary current integrated value meets the restriction relation preset, order

$X=\frac{i\left(t\right)-i\left(0\right)}{I_r},$

$Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt},$

Then described restriction relation comprise following in one or more:

| X|>X _th; Or

| Y|>Y _th; Or

$|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$ Or

$|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$

Wherein, i (0) is the first instantaneous current value, and i (t) is the second instantaneous current value after elapsed time interval t, I _rfor breaking current threshold value, w is the supply frequency in units of radian RAD, X _thand Y _thfor the constant determined according to connection angle during short circuit and power factor, θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage;

Determination module (403), for when described default restriction relation is met, exports one and determines the signal occurring short circuit in described electric power networks.

11. devices as claimed in claim 8 or 9, is characterized in that, order

$X=\frac{i\left(t\right)-i\left(0\right)}{I_r},$

$Y=\frac{w}{I_r}\·{\∫}_0^{t}i\left(t\right)\mathrm{dt},$

Then described restriction relation comprise following in one or more:

| X|>X _th; Or

| Y|>Y _th; Or

$|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$ Or

$|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right);$

Wherein, i (0) is the first instantaneous current value, and i (t) is the second instantaneous current value after elapsed time interval t, I _rfor breaking current threshold value, w is the supply frequency in units of radian RAD, X _thand Y _thfor the constant determined according to connection angle during short circuit and power factor, θ ₁for the phase shift between electric current during employing highest power factor and voltage, θ ₂for the phase shift between electric current during employing lowest power factor and voltage.

12. devices as claimed in claim 11, is characterized in that, described default restriction relation is met and comprises the one or more restriction relations met below:

Meet | X|>X _th; Or

Meet | Y|>Y _th; Or

Meet $|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$ And meet simultaneously $|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right).$

13. devices as claimed in claim 10, is characterized in that, described default restriction relation is met and comprises the one or more restriction relations met below:

Meet | X|>X _th; Or

Meet | Y|>Y _th; Or

Meet $|Y+\tan \left({\mathrm{\θ}}_1\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_1\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right)$ And meet simultaneously $|Y+\tan \left({\mathrm{\θ}}_2\right)X|>\frac{2\sqrt{2}}{\cos \left({\mathrm{\θ}}_2\right)}\·\sin \left(\frac{\mathrm{wt}}{2}\right).$