CN103645408A - Overhead line short circuit fault identification method and terminal - Google Patents

Abstract

The invention discloses an overhead line short circuit fault identification method and terminal. The method comprises: when the abrupt change value of virtual energy or virtual power of a current overhead line exceeds a threshold, the duration of the abrupt change value exceeds a time interval T, and the voltage and the virtual energy or the virtual power of the current line are zero after the time interval T, determining that a short circuit fault occurs in the current line. By using the method disclosed by the invention, a short circuit fault can be effectively and accurately identified, thus safety performance is improved.

Description

A kind of method of discrimination of overhead transmission line short trouble and terminal

Technical field

The present invention relates to distribution network system field, relate in particular to a kind of method of discrimination and terminal of overhead transmission line short trouble.

Background technology

As everyone knows, fuse can holding circuit be avoided the infringement of short circuit, overcurrent.When its ultimate principle is short circuit or overcurrent, the instantaneous generation thermal energy sudden change of circuit, melts the fuse that broken, thereby cuts off the electricity supply loop.

Yet the method for discrimination accuracy for overhead transmission line short trouble in prior art is lower, cannot carry out accurately the identification of short trouble; Therefore, there is larger potential safety hazard.

Summary of the invention

The method of discrimination and the terminal that the object of this invention is to provide a kind of overhead transmission line short trouble, can be effectively, accurately short trouble is differentiated, thereby improved security performance.

The object of the invention is to be achieved through the following technical solutions:

A method of discrimination for overhead transmission line short trouble, the method comprises:

If the sudden change value of the virtual energy of current overhead transmission line or virtual power surpasses that threshold value, this sudden change value duration exceed time interval T and after the described time interval T voltage of current circuit and virtual energy or virtual power be zero, judge the current circuit fault that is short-circuited.

As seen from the above technical solution provided by the invention, the duration of the sudden change value based on virtual energy or power, this sudden change value and postpone a period of time after the numerical value of virtual energy or power differentiate the current overhead transmission line fault that whether is short-circuited; Its antijamming capability is stronger, and discriminant accuracy is higher.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing of required use during embodiment is described is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, do not paying under the prerequisite of creative work, can also obtain other accompanying drawings according to these accompanying drawings.

The schematic diagram of the method for discrimination of a kind of overhead transmission line short trouble that Fig. 1 provides for the embodiment of the present invention one;

The schematic diagram of a kind of overhead transmission line short trouble sense terminals that Fig. 2 provides for the embodiment of the present invention two.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Based on embodiments of the invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to protection scope of the present invention.

Embodiment mono-

Be illustrated in figure 1 the schematic diagram of the method for discrimination of a kind of overhead transmission line short trouble that the embodiment of the present invention provides.The method mainly comprises:

If the sudden change value of the virtual energy of current overhead transmission line or virtual power surpasses that threshold value, this sudden change value duration exceed time interval T and after the described time interval T voltage of current circuit and virtual energy or virtual power be zero, judge the current circuit fault that is short-circuited.

Above-mentioned threshold value and time interval T can be according to the actual requirements or experience set.

For the instantaneous value computing method of virtual energy and virtual power, do detailed introduction below.

Energy on line of electric force transmits and comprises meritorious and idle two parts, and resistive component is consumed by resistor-type equipment, and reaction component is for energy exchange, complete by electric energy and be converted to magnetic energy, then be converted to electric energy by magnetic energy, go round and begin again, be transmitted to back and forth on line of electric force, be not consumed.The embodiment of the present invention is mainly considered the calculating of resistive component energy.

If overhead transmission line is i (t) at t electric current constantly, the equivalent resistance of overhead transmission line is R, and the active power that this overhead transmission line consumes constantly at t is:

P(t)＝i ²(t)R。

For the ease of calculating, can suppose the equivalent resistance R=1 Ω (not considering the reactive power that reactance and reactance produce herein) of this circuit, above formula can be exchanged into:

P(t)＝i ²(t)。

In fact, the R of circuit might not be 1 Ω, just finds out a kind of benchmark of comparison by this calculating, and therefore, this power is virtual power.

According to this virtual power, can calculate one-period (0, T ₀) in, the energy consuming:

$E\left(t\right)={\∫}_0^{T_0}P\left(t\right)\mathrm{dt};$

Wherein, t ∈ (0, T ₀).Above-mentioned energy is to calculate and get based on virtual power, is therefore virtual energy.Because p (t) changes, thereby the energy that different cycles calculates also changes.

When circuit is short-circuited, virtual energy can increase rapidly, produces sudden change.When Sudden Changing Rate increases to certain limit value, can cause circuit tripping operation, cause line voltage distribution be 0 and follow-up measured nominal energy be 0.

The sudden change value of virtual energy can be calculated according to t+ Δ t virtual ENERGY E (t+ Δ t) and t virtual ENERGY E (t) constantly constantly, and its formula is:

$\begin{array}{c}\mathrm{\ΔE}=E(t+\mathrm{\Δt})-E\left(t\right)\\ ={\∫}_0^{T_0}{i}^2(t+\mathrm{\Δt})\mathrm{dt}-{\∫}_0^{T_0}{i}^2\left(t\right)\mathrm{dt}\\ ={{\∫}_0^{T_0}(i\left(t\right)+\mathrm{\Δi})}^2\mathrm{dt}-{\∫}_0^{T_0}{i}^2\left(t\right)\mathrm{dt}\\ ={\∫}_0^{T_0}({\mathrm{\Δi}}^2+2i\left(t\right)\mathrm{\Δi})\mathrm{dt}\end{array};$

Wherein, Δ i represents that t is constantly to t+ Δ t curent change value constantly.

On the other hand, can also calculate the average power in one-period according to virtual energy, on the basis of virtual energy divided by time T ₀, be expressed as:

$\stackrel{\‾}{p}=\frac{1}{T_0}{\∫}_0^{T_0}p\left(t\right)\mathrm{dt}=\frac{1}{T_0}{\∫}_0^{T_0}{i}^2\left(t\right)\mathrm{dt}.$

In like manner, the sudden change value of virtual power also can be utilized sudden change value and the time T of virtual energy ₀calculate, its formula is:

$\mathrm{\Δ}\stackrel{\‾}{p}=\frac{\mathrm{\ΔE}}{T_0}=\frac{1}{T_0}{\∫}_0^{T_0}({\mathrm{\Δi}}^2+2i\left(t\right)\mathrm{\Δi})\mathrm{dt}.$

By the above formula, the accuracy of current value will directly affect the accuracy of differentiating result.The embodiment of the present invention can adopt following method to calculate current value: the S on the inductance of continuous sampling and current connection cycle alternating voltage, because voltage waveform in inductance L produces large strange change, has not been sinusoidal waveform; Therefore by the whole zero setting of negative half period alternating voltage in the described S alternating voltage in a cycle, obtain S positive half cycle alternating voltage; Calculate each positive half cycle maximal value alternating voltage, obtain S maximal value; After S maximal value sorted by size, get its intermediate value as the reference data of once surveying 100A correcting current value, obtain with reference to coefficient; With this, with reference to coefficient scale factor calculation, go out current value corresponding to remaining S-1 maximal value.For meeting measuring accuracy and system works speed, the sampling period can be decided to be 0.5ms.Wherein, for the ease of calculating, above-mentioned S can be made as to 5.

This measured value method forms according to development Experience summary for many years, has used for reference median filter method.The benefit of this method is that filter effect is obvious, and calculated amount is little, and speed is fast, and precision is high, current measurement value can be controlled in positive and negative 3% precision, after correcting current, can reach in 2% error.Obvious interference is had to good anti-jamming effectiveness, compared with half-wave integration method measured value precision, improve a lot.

The duration of the sudden change value of the embodiment of the present invention based on virtual energy or power, this sudden change value and postpone a period of time after the numerical value of virtual energy or power differentiate the current overhead transmission line fault that whether is short-circuited; Its antijamming capability is stronger, and discriminant accuracy is higher.

Embodiment bis-

The schematic diagram of a kind of overhead transmission line short trouble sense terminals that Fig. 2 provides for the embodiment of the present invention two.As shown in Figure 2, this terminal mainly comprises:

Successively series connection inductance L, the first resistance R 1, analog/digital converter A/D, single-chip microcomputer, high-voltage measuring circuit and be connected in parallel on the second resistance R 2, capacitor C and the stabilivolt D between the first resistance R 1 and A/D;

Wherein, described single-chip microcomputer, for calculating the sudden change value of virtual energy and virtual power value;

If the sudden change value of the virtual energy of current overhead transmission line or virtual power surpasses that threshold value, this sudden change value duration exceed time interval T and after the described time interval T voltage of current circuit and virtual energy or virtual power be zero, judge the current circuit fault that is short-circuited.

Further, this terminal also comprises:

The power supply and the hardware watchdog that are connected with described single-chip microcomputer.

For the ease of understanding, for its principle of work, do detailed introduction below.

Pole line exchange current produces alternating voltage to inductance L, in order to induce this change in voltage, avoids again not making inductance L magnetic field saturated as far as possible, can be by best wire circle is set after test of many times; Meanwhile, adopt general iron core as induction bar magnet.Resistance R 1 and R2 dividing potential drop, the upper voltage of R2 is as the input of analog quantity/digital quantity converter (A/D).For fear of the saturated input of A/D converter under the large function of current of pole line, R1 and R2 resistance ratio can be by being made as optimal proportion after test of many times.Stabilivolt D and capacitor C play overvoltage protection and filtering interfering effect, avoid A/D conversion to be affected.

Current value by above circuit can utilize respective algorithms to calculate, and the timer of recycling single-chip microcomputer inside can also be obtained two difference of electric current, i.e. Sudden Changing Rates constantly.Thereby can calculate within the cycle of regulation the changes delta E of the virtual energy of circuit.

High-voltage measuring circuit, for monitoring overhead transmission line high-voltage value, high-voltage value by this circuit measuring out, is measured circuit high pressure simultaneously and is had or not.

According to measured virtual energy with circuit high pressure has or not and the time of time delay, just can accurately judge the circuit fault that whether is short-circuited.

In addition, power supply can adopt power taking technology on hi-line to power to single-chip microcomputer, and the main use of hardware watchdog prevents from crashing and resetting after single-chip microcomputer is interfered.

Wherein, current value Measurement Algorithm can adopt 5 half-wave maximal value median methods.Concrete steps are: 5 cycle alternating voltages in (1) continuous sampling inductance L, because voltage waveform in inductance L produces large strange change, have not been sinusoidal waveforms.By the whole zero setting of all negative half period sampled points, only retain 5 positive half cycle sampled points.(2) obtain each positive half cycle maximal value sampled point.(3) 5 maximal values of sequence.(4) get the 3rd value as the reference data of once surveying 100A correcting current value, other current value is usingd this coefficient and is obtained as scale factor.For meeting measuring accuracy and system works speed, the sampling period is decided to be 0.5ms.

This measured value method forms according to development Experience summary for many years, has used for reference median filter method.The benefit of this method is that filter effect is obvious, and calculated amount is little, and speed is fast, and precision is high, current measurement value can be controlled in positive and negative 3% precision, after correcting current, can reach in 2% error.Obvious interference is had to good anti-jamming effectiveness, compared with half-wave integration method measured value precision, improve a lot.

In addition, concrete judgement and computation process are described in detail in embodiment mono-, therefore repeat no more.

The above; be only the present invention's embodiment preferably, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (8)

1. a method of discrimination for overhead transmission line short trouble, is characterized in that, the method comprises:

If the sudden change value of the virtual energy of current overhead transmission line or virtual power surpasses that threshold value, this sudden change value duration exceed time interval T and after the described time interval T voltage of current circuit and virtual energy or virtual power be zero, judge the current circuit fault that is short-circuited.

2. method according to claim 1, is characterized in that, the computing formula of described virtual power is:

P(t)＝i ²(t)；

Wherein, i represents t current value constantly.

3. method according to claim 1 and 2, is characterized in that, the computing method of described virtual energy comprise:

$E\left(t\right)={\∫}_0^{T_0}P\left(t\right)\mathrm{dt};$

Wherein, p (t) represents virtual power, t and T ₀all represent the time, and t ∈ (0, T ₀).

4. method according to claim 3, is characterized in that, the sudden change value method of calculating virtual energy comprises: utilize t+ Δ t virtual ENERGY E (t+ Δ t) and t virtual ENERGY E (t) constantly constantly to calculate, its formula is:

$\mathrm{\ΔE}=E(t+\mathrm{\Δt})-E\left(t\right){=\∫}_0^{T_0}({\mathrm{\Δi}}^2+2i\left(t\right)\mathrm{\Δi})\mathrm{dt};$

Wherein, Δ i represents that t is constantly to t+ Δ t curent change value constantly.

5. method according to claim 4, is characterized in that, the sudden change value calculating method of described virtual power comprises: sudden change value and the time T of utilizing virtual energy ₀calculate, its formula is:

$\mathrm{\Δ}\stackrel{\‾}{p}=\frac{\mathrm{\ΔE}}{T_0}=\frac{1}{T_0}{\∫}_0^{T_0}({\mathrm{\Δi}}^2+2i\left(t\right)\mathrm{\Δi})\mathrm{dt}.$

6. according to the method described in claim 2-5 any one, it is characterized in that, the method also comprises: the measuring process of current value, and this step comprises:

S on the inductance of continuous sampling and current connection cycle alternating voltage, and by the whole zero setting of negative half period alternating voltage in the described S alternating voltage in a cycle, obtain S positive half cycle alternating voltage;

Calculate each positive half cycle maximal value alternating voltage, obtain S maximal value;

Using the intermediate value in S maximal value as the reference data of once surveying 100A correcting current value, obtain with reference to coefficient;

With this, with reference to coefficient scale factor calculation, go out current value corresponding to remaining S-1 maximal value.

7. an overhead transmission line short trouble sense terminals, it is characterized in that, this terminal comprises: successively series connection inductance, the first resistance, analog/digital converter, single-chip microcomputer, high-voltage measuring circuit and be connected in parallel on the second resistance, electric capacity and the stabilivolt between the first resistance and analog/digital converter;

Wherein, described single-chip microcomputer is for calculating the sudden change value of virtual energy and virtual power value;

If the sudden change value of the virtual energy of current overhead transmission line or virtual power surpasses that threshold value, this sudden change value duration exceed time interval T and after the described time interval T voltage of current circuit and virtual energy or virtual power be zero, judge the current circuit fault that is short-circuited.

8. terminal according to claim 7, is characterized in that, this terminal also comprises:

The power supply and the hardware watchdog that are connected with described single-chip microcomputer.

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