CN105655993A - Current differential protection method adopting Apollonius theorem - Google Patents

Abstract

The invention relates to a current differential protection method adopting the Apollonius theorem. The current differential protection method comprises the following steps: acquiring phasors of three-phase current on two sides of a power transmission line as shown in the specification; mapping a current differential protection criterion on a current complex plane; according to the Apollonius theorem, adjusting the position of an acting circle to obtain the current differential protection criterion on the current complex plane; and converting the current differential protection criterion to a phasor form. According to the technical scheme provided by the invention, a current differential protection movement range is determined by using the Apollonius theorem, so that the range of a current differential protection acting region is expanded, and the sensitivity of current differential protection is improved when faults occur in the region; and meanwhile, the reliability of the current differential protection is not reduced when faults occur outside the region.

Description

A kind of current differential protection method utilizing A Shi circle theorem

Technical field

The present invention relates to relay protection field, be specifically related to a kind of current differential protection method utilizing A Shi circle theorem.

Background technology

Current differential protection is widely used in whole world electrical network as the main protection of ultra-high/extra-high voltage transmission line of electricity. The current differential protection principle that route protection adopts both at home and abroad at present, including steady-state quantity differential protection, Sudden Changing Rate differential protection, sampling value differential protection etc. The many employings of estimated current differential protection criterion and difference criterion, change the sensitivity of current differential protection, but in heavy load situations, load current affect the braking amount of current differential protection so that it is sensitivity decrease by adjusting restraint coefficient.

Summary of the invention

It is an object of the invention to provide a kind of current differential protection active region defining method utilizing A Shi circle theorem and current differential protection criterion, improve the sensitivity of current differential protection during troubles inside the sample space, and do not reduce the reliability of current differential protection.

For achieving the above object, the present invention by the following technical solutions: a kind of current differential protection method utilizing A Shi circle theorem, including:

Gather transmission line of electricity both sides each three-phase current sampled value, the phasor of computing electric power line both sides three-phase currentWithRelativelyWithSize, when $\left|{\stackrel{\·}{I}}_M\right|>\left|{\stackrel{\·}{I}}_N\right|$ Time, order $\stackrel{\·}{\mathrm{\ρ}}={\stackrel{\·}{I}}_N/{\stackrel{\·}{I}}_M;$ When $\left|{\stackrel{\·}{I}}_M\right|>\left|{\stackrel{\·}{I}}_N\right|$ Time, order $\stackrel{\·}{\mathrm{\ρ}}={\stackrel{\·}{I}}_M/{\stackrel{\·}{I}}_N;$

Current differential protection criterion is mapped on electric current complex plane; Current differential protection criterion is mapped in the region on electric current complex plane:Wherein, �� is restraint coefficient.

The position of current differential protection action circle is adjusted, it is determined that the actuating range of protection according to A Shi circle theorem;

It is converted into the phasor form of current differential protection again.

WhenTime, for external area error; WhenTime, for single supply troubles inside the sample space.

Adjust the action circle of current differential protection criterion according to A Shi circle theorem, make it surround the initial point of electric current complex plane.

When k is 0.35, obtain the current differential protection criterion on electric current complex planeIt is denoted as phasor form: $\left|{\stackrel{\·}{I}}_M+{\stackrel{\·}{I}}_N\right|>\mathrm{\λ}\left|0.35{\stackrel{\·}{I}}_M-{\stackrel{\·}{I}}_N\right|.$

With immediate prior art ratio, the present invention provides technical scheme to have following excellent effect

1, technical solution of the present invention improves the active region of current differential protection;

2, when technical solution of the present invention improves troubles inside the sample space, the sensitivity of current differential protection, does not reduce the reliability of protection during external area error simultaneously;

3, technical solution of the present invention is applicable to heavy-haul line.

Accompanying drawing explanation

Fig. 1 is the current differential protection operating space schematic diagram at complex plane of the embodiment of the present invention;

Fig. 2 is that the K in Fig. 1 takes when 0.35 current differential protection in the acting characteristic area schematic of complex plane.

Detailed description of the invention

Below in conjunction with embodiment, the invention will be described in further detail.

Embodiment 1:

A kind of current differential protection method utilizing A Shi circle theorem of invention of this example, including:

1) gather circuit both sides each three-phase current sampled value, utilize fourier algorithm to calculate phasor, can obtain

2) compareWithSize, when $\left|{\stackrel{\&CenterDot;}{I}}_M\right|>\left|{\stackrel{\&CenterDot;}{I}}_N\right|$ Time, order $\stackrel{\&CenterDot;}{\mathrm{\&rho;}}={\stackrel{\&CenterDot;}{I}}_N/{\stackrel{\&CenterDot;}{I}}_M;$ When $\left|{\stackrel{\&CenterDot;}{I}}_M\right|<\left|{\stackrel{\&CenterDot;}{I}}_N\right|$ Time, order $\stackrel{\&CenterDot;}{\mathrm{\&rho;}}={\stackrel{\&CenterDot;}{I}}_M/{\stackrel{\&CenterDot;}{I}}_N;$

3) acting characteristic of current differential protection is represented on a complex plane;

4) K=0.35 is chosen. Obtaining current differential protection criterion on a complex plane is

5) will $\left|1+\stackrel{\&CenterDot;}{\mathrm{\&rho;}}\right|>\mathrm{\&lambda;}\left|0.35-\stackrel{\&CenterDot;}{\mathrm{\&rho;}}\right|$ Being expressed as phasor form is $\left|{\stackrel{\&CenterDot;}{I}}_M+{\stackrel{\&CenterDot;}{I}}_N\right|>\mathrm{\&lambda;}\left|0.35{\stackrel{\&CenterDot;}{I}}_M-{\stackrel{\&CenterDot;}{I}}_N\right|.$

Performance compares:

Conventional current differential protection criterion is:

$\left|{\stackrel{\&CenterDot;}{I}}_M+{\stackrel{\&CenterDot;}{I}}_N\right|>\mathrm{\&lambda;}\left|{\stackrel{\&CenterDot;}{I}}_M-{\stackrel{\&CenterDot;}{I}}_N\right|$

For identical restraint coefficient ��, the current differential protection criterion actuating range that this patent proposes is relatively big, on the other hand, it is easier to improve the restraint coefficient �� of current differential protection.

Finally should be noted that: above example is only in order to illustrate that technical scheme is not intended to limit; although those of ordinary skill in the field with reference to above-described embodiment it is understood that still the specific embodiment of the present invention can be modified or equivalent replace; these are without departing from any amendment of spirit and scope of the invention or equivalent replace, all within the claims of the present invention.

Claims (7)

1. the current differential protection method utilizing A Shi circle theorem, it is characterised in that: including:

The phasor of computing electric power line both sides three-phase currentWith

RelativelyWithSize; WhenTime, orderWhenTime, order $\stackrel{\&CenterDot;}{\mathrm{\&rho;}}={\stackrel{\&CenterDot;}{I}}_M/{\stackrel{\&CenterDot;}{I}}_N;$

Current differential protection criterion is mapped on electric current complex plane;

Adjust the position of current differential protection action circle according to A Shi circle theorem, it is determined that the actuating range of protection, then be converted into the phasor form of current differential protection.

2. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 1, it is characterised in that: gather transmission line of electricity both sides each three-phase current sampled value, utilize fourier algorithm to calculate the phasor of three-phase currentWith

3. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 1 or 2, it is characterised in that: current differential protection criterion is mapped in the region on electric current complex plane and is:Wherein, �� is restraint coefficient.

4. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 3, it is characterised in that: whenTime, for external area error; WhenTime, for single supply troubles inside the sample space.

5. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 1, it is characterised in that: adjust the action circle of current differential protection criterion according to A Shi circle theorem, make it surround the initial point of electric current complex plane.

6. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 5, it is characterised in that: when k is 0.35, obtain the current differential protection criterion on electric current complex plane

7. a kind of current differential protection method utilizing A Shi circle theorem as claimed in claim 6, it is characterised in that: described current differential protection criterion phasor form is: