CN101242095A - A permanent failure judgement method for power transmission line with parallel reactor - Google Patents

Abstract

The invention relates to the field of power system transmission line relaying protection, in particular to a permanent fault identifying method for the transmission line with collateral reactor. The purpose of this invention is to overcome defects of not effectively using the transmission line with collateral reactor in the present technology. In order to overcome problems in the present technology, the embodiment of this invention is that: a permanent fault identifying method for the transmission line with collateral reactor orderly comprises the following steps: after a single-phase fault is found, the protective device phase-selecting unit confirms the fault phase; configuring the criterion and calculating the action value by using current quantity in the collateral reactor and neutral point small reactor; when the calculated action value is less than the setting value, the fault is identified as instant fault and a superposition valve processes superposition action; when the calculated action value is more than the setting value, the fault is identified as permanent fault and the superposition valve does not process superposition action. This invention has advantages of high identifying precision and reliability.

Description

A kind of permanent failure judgement method for power transmission line with shunt reactor

Technical field:

The present invention relates to power system transmission line relaying protection field, refer more particularly to a kind of permanent failure judgement method for power transmission line with shunt reactor.

Background technology:

The automatic reclosing technology is one of important behave of guaranteeing power system stability and power supply continuity.Especially along with the raising of transmission voltage grade, the increase of phase insulation distance, surpassing 90% in the extra high voltage network fault is single-line to ground fault, and wherein is transient fault more than 80%.Therefore adopt the single-pole reclosing technology for restoring electricity fast and to keep the stability of a system significant.But current single-pole reclosing all is to overlap through the set time, and there is blindness in its action; If coincide with permanent fault, then can bring the impact also more serious to electric power system than normal short circuit, influence the safe and stable operation of electric power system, also seriously threatening the safety of electric equipments simultaneously.The harm that brings to electric power system when coinciding with permanent fault in order to eliminate to the full extent must judge that before overlapping line fault is permanent or instantaneity, overlapped during transient fault, did not overlap during permanent fault, i.e. adaptive reclose.

Pertinent literature has been done research to the permanent failure judgement principle of transmission line single-phase adaptive reclosing.Mainly contain at present based on fault phase voltage characteristic and these two kinds of methods of transient fault arc characteristic, the former has utilized the capacitor coupling voltage characteristic to distinguish transient fault and permanent fault, its sensitivity and anti-transition resistance ability and line length are closely related, and owing to the compensating action of shunt reactor for extra high voltage network, it is lower to disconnect the phase capacitor coupling voltage, line voltage distribution instrument transformer (TV) is difficult to accurately obtain this voltage, causes the voltage method of discrimination effectively to use; The latter mainly utilizes fault transient high-frequency signal feature to distinguish transient fault and permanent fault, the influence of be subject to electric arc blow-out process, high-frequency signal obtaining precision and malfunction, and it is unreliable to differentiate.These two kinds of methods all can not be effective to the transmission line with shunt reactor at present.

Summary of the invention:

The objective of the invention is to provide a kind of permanent failure judgement method for power transmission line, with the shortcoming of can not being effective to that overcomes that prior art exists with the transmission line of shunt reactor with shunt reactor.

For overcoming the problem that prior art exists, technical scheme of the present invention is: a kind of permanent failure judgement method for power transmission line with shunt reactor comprises the steps: successively

1) after single-phase fault takes place, determines the fault phase by the protective device phase selection element;

2) only utilize the magnitude of current of shunt reactor and the little reactor current amount of neutral point to construct criterion, calculate operating value;

3) operating value that calculates then is judged to transient fault, reclosing multiple action during less than setting value; The operating value that calculates then is judged to permanent fault during greater than setting value, and reclosing does not overlap.

Above-mentioned steps 2) in; criterion is a current amplitude than method of discrimination: this method is that shunt reactor A, B, C three-phase current sampled value are obtained in protection according to this side; and then reactor current phasor and the little reactive current phasor of neutral point of being in parallel that must be out of order, and obtain its amplitude ratio.

Above-mentioned steps 2) in, criterion is the spill current method of discrimination: this method is to be computation model with the transient fault model behind the arc extinction, ask for the fault reactor current that is in parallel according to single-end electrical quantity, and calculate the reactor current of asking and the difference of measured current and the ratio of the little reactive current amount of neutral point.

Compared with prior art, the present invention has the following advantages:

1. method of the present invention has been avoided utilizing the disconnection phase voltage that amplitude is little, certainty of measurement is low, has utilized the high shunt reactor magnitude of current of certainty of measurement fully.This mainly is because the current transformer of reactor protection has very high precision when measuring little electric current, has bigger error and measured by the line voltage distribution instrument transformer for the little disconnection phase voltage of amplitude.Therefore, method of discrimination of the present invention adopts the method for voltage, and discrimination precision is high and reliable.

2. the present invention only utilizes this side electric parameters, and the electric parameters of offside is obtained indirectly according to known quantity, has reduced the requirement to signal transmission passage.Simultaneously, utilizing this side electric parameters to find the solution in the process of offside electric parameters, ignoring the influence that disconnects phase, simplifying computational process, can satisfy required precision well differentiating.

3. the invention provides two kinds of method of discrimination based on the shunt reactor magnitude of current.The current amplitude ratio method is used for the permanent failure judgement than short-term road, and discrimination principles is simple, sensitivity and discrimination precision height; Therefore the spill current method is applicable to the permanent failure judgement of the circuit of different length because it has compensated the influence of the distributed capacitance of circuit, and especially it is highly sensitive in the current amplitude ratio method during long transmission line.

4. the present invention is applicable to an end, two ends band shunt reactor circuit, can be used as the nature of trouble discriminating element of a perfect performance of band shunt reactor transmission line single-phase adaptive reclosing.Be not subjected to the influence of line length, position of failure point, transition resistance, load current on the principle.

Description of drawings:

Fig. 1 is the current circuit schematic diagram of transient fault and permanent fault;

Fig. 2 disconnects the π type equivalent circuit of back (behind the arc extinction) mutually for fault under the transient fault;

The flow chart that Fig. 3, Fig. 4 differentiate for single-phase fault character;

Fig. 5 is the hardware block diagram of Microcomputer Protection.

Embodiment:

Below in conjunction with accompanying drawing the present invention is described in further detail.

The current circuit schematic diagram of the disconnection phase that Fig. 1 provides an end band shunt reactor circuit A when mutually single phase ground fault taking place.Wherein

For flowing through the be in parallel electric current of reactor of fault phase A,

For flowing through the electric current of the little reactor of neutral point, C ₀Be the self-induction electric capacity of circuit, L _n, L ₀Be shunt reactor and the little reactor inductance value of neutral point,

N end three-phase voltage during for fault.

The current circuit schematic diagram of Fig. 1 (a) when being depicted as transient fault behind the arc extinction, apparent, this moment, electric current was by shunt reactor A phase, the little reactor of neutral point and M end A electric capacity formation relatively loop; And for the permanent fault current circuit schematic diagram shown in Fig. 1 (b), electric current forms the loop by the transition resistance at shunt reactor A phase, the little reactor of neutral point and place, fault point.

1, the method for discrimination of current amplitude ratio

Current amplitude is applicable to differentiation than the single-phase fault character of short-term road than method of discrimination, and this moment, the influence of distributed capacitance of circuit can be ignored.

When metal ground connection, ${\stackrel{\·}{U}}_{\mathrm{na}}=0,\left|\frac{{\stackrel{\·}{I}}_{\mathrm{nax}}}{{\stackrel{\·}{I}}_{\mathrm{no}}}\right|=\frac{X_0}{X_n}---\left(1\right)$

Wherein, X _n, X ₀Be shunt reactor and the little reactor induction reactance of neutral point.

In like manner, when passing through transition resistance R _FDuring ground connection, can equivalence be:

$\left|\frac{{\stackrel{\·}{I}}_{\mathrm{nax}}}{{\stackrel{\·}{I}}_{\mathrm{no}}}\right|=\frac{X_0}{\sqrt{{X_n}^2+{R_F}^2}}---\left(2\right)$

By formula (2) as can be known, along with transition resistance R _FIncrease, $\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|$ Value reduce gradually, work as R _FDuring → ∞, can be considered transient fault, $\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|$ It is minimum that value is reduced to.

During therefore with transient fault $\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|$ Value is as setting value K _DZ1, consider the influence of factors such as model simplification, the error of calculation, determine setting value by following formula,

$K_{\mathrm{DZ}1}=K_{k1}\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|,---\left(3\right)$

Safety factor K wherein _K1≈ 1.1～1.2.

Utilize the current transformer of installing on the little reactor of shunt reactor and neutral point (TA) to obtain when breaking down Be used for calculating the amplitude ratio $\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|.$

Therefore, Dui Ying criterion is

$\left|{\stackrel{\·}{I}}_{\mathrm{nax}}\right|/\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|{\≤K}_{\mathrm{DZ}1}---\left(4\right)$

Formula (4) is set up and just is judged to transient fault, the reclosing action; Otherwise, being judged to permanent fault, reclosing does not overlap.

2, the method for discrimination of spill current

The spill current method of discrimination has compensated the line distribution capacitance influence, not only can be used for short-term road, also can be used for long transmission line.When circuit generation single phase ground fault, no matter transient fault or permanent fault take place, all be reference model, at the little reactor current of known side (N side) neutral point with the transient fault

With perfect phase voltage

Situation under ask for shunt reactor fault phase current

Find the solution by A phase π model equivalent circuit shown in Figure 2

Promptly

${\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}}={\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}1}+{\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}2}+{\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}3}+{\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}4}=k_1[({\stackrel{\·}{U}}_{\mathrm{mb}}+{\stackrel{\·}{U}}_{\mathrm{mc}})/2]+k_2[({\stackrel{\·}{U}}_{\mathrm{nb}}+{\stackrel{\·}{U}}_{\mathrm{nc}})/2]-k_3{\stackrel{\·}{U}}_{\mathrm{xl}}-k_4{\stackrel{\·}{U}}_{n0}---\left(5\right)$

Wherein,

Be A phase all fronts road inductive drop,

Be N side shunt reactor neutral point equivalent voltage source voltage, k ₁, k ₂, k ₃, k ₄Corresponding equivalent admittance value for the A equal value.Offside (M side) perfects phase terminal voltage

Obtain indirectly by N end electric parameters.

Analyze as can be known, during transient fault, fault model is consistent with reference model, and this moment, the shunt reactor fault was asked for electric current mutually Should with the actual measurement electric current

Equate, promptly ${\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}}-{\stackrel{\·}{I}}_{\mathrm{nax}}=0.$ And during permanent fault, fault model and reference model are inconsistent, and this moment, the shunt reactor fault was asked for electric current mutually

Should with the actual measurement electric current

Unequal, promptly ${\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}}-{\stackrel{\·}{I}}_{\mathrm{nax}}\≠0.$ Therefore can certificate

Distinguish transient fault and permanent fault.

For eliminating the influence of factors such as model simplification, the error of calculation, improve the reliability of this method, setting value is pressed following formula and is determined

$K_{\mathrm{DZ}2}=K_{k2}\left|{\stackrel{\·}{I}}_{\mathrm{no}}\right|,---\left(6\right)$

Wherein, safety factor K _K2=0.5～0.1.

Therefore, can provide the criterion of following form:

$|{\widehat{\stackrel{\·}{I}}}_{\mathrm{nax}}-{\stackrel{\·}{I}}_{\mathrm{nax}}|{\≤K}_{\mathrm{DZ}2}---\left(7\right)$

When formula (7) is set up, promptly be judged to transient fault, reclosing carries out feed motion; Formula (7) is judged to permanent fault when being false, and reclosing is failure to actuate.

Transmission line for two ends band shunt reactor, aforementioned method of discrimination is suitable equally, the differentiation thinking of current amplitude ratio method and an end band shunt reactor transmission line are in full accord, and for the spill current method of discrimination mainly is to ask for the algorithm that disconnects the reactor current that is in parallel need at one end change slightly on the basis with shunt reactor circuit algorithm.

Figure 3 shows that current amplitude ratio method of the present invention carries out the flow process that single-phase fault character is differentiated:

1, determines the single-phase fault phase by phase selection element;

2, at first protective device collects the fault reactor current amount i that is in parallel _Npx, the little reactor i of neutral point _N0Change into the phasor form

Obtain corresponding amplitude

Calculate the current amplitude ratio

3, with setting value K _DZ1Compare, satisfy formula (4) establishment and just be judged to transient fault; Otherwise, be judged to permanent fault; If be judged to be transient fault, then to send out and overlap order, circuit breaker overlaps; If the permanent fault of being judged to, then reclosing is failure to actuate, and circuit breaker keeps off-state.

The method that Figure 4 shows that spill current of the present invention is carried out the flow process that single-phase fault character is differentiated:

1, determines the single-phase fault phase by phase selection element;

2, protective device is collected two non-fault phase voltage amount u _N1, u _N2, magnitude of current i _L1, i _L2, disconnect the reactor current i that is in parallel _Npx, the little reactor current i of neutral point _N0Change into the phasor form; It is calculated that model is asked for disconnects the reactor current that is in parallel

Calculate spill current

And setting value

3, will

With setting value K _DZ2Compare, satisfy formula (7) establishment and just be judged to transient fault; Otherwise, be judged to permanent fault; If be judged to be transient fault, then to send out and overlap order, circuit breaker overlaps; If the permanent fault of being judged to, then reclosing is failure to actuate, and circuit breaker keeps off-state.

Above-mentioned the analysis showed that, method of discrimination of the present invention has adopted the discrimination principles based on the magnitude of current, and at single-phase fault under transient fault and permanent fault situation, both fault loop and corresponding equivalent model have distinct difference, corresponding current amplitude ratio and spill current have tangible difference, and the single-phase fault that just can distinguish the circuit generation according to these characteristics reliably, effectively is transient fault or permanent fault.

The distance relay that makes up according to this method is hardware block diagram of the present invention referring to Fig. 5 in the frame of broken lines, is made of data acquisition system, microcomputer main system, output system three parts, and method of discrimination of the present invention is realized in the microcomputer main system by programming.Now the circuit with an end band shunt reactor is that example describes, and for the transmission line of two ends band shunt reactor, it is identical to analyze thinking.

With N side protective device among Fig. 5 is example; input variable is for perfecting voltage, the magnitude of current and the shunt reactor magnitude of current; wherein perfecting phase voltage is obtained by line side voltage transformer TV; perfect phase current and obtained by line side current transformer TA, shunt reactor A, B, C three-phase current are obtained by the current transformer TA of reactor protection.Perfect phase voltage, the magnitude of current and A, B, C parallel three phase reactor current analog quantity through low-pass filtering, sampling keep and the A/D conversion after, obtain corresponding digital quantity, adopt the corresponding digital filter to calculate the phasor of input electric parameters by the microcomputer main system; The current amplitude that is adopted by discriminating element calculates current amplitude ratio and spill current amplitude respectively than algorithm and spill current algorithm then, it is calculated that the single-phase fault that the result judges that circuit takes place is transient fault or permanent fault.

Claims (3)

1, a kind of permanent failure judgement method for power transmission line with shunt reactor comprises the steps: successively

1) after single-phase fault takes place, determines the fault phase by the protective device phase selection element;

2) only utilize the magnitude of current of shunt reactor and the little reactor current amount of neutral point to construct criterion, calculate operating value;

3) operating value that calculates then is judged to transient fault, reclosing multiple action during less than setting value; The operating value that calculates then is judged to permanent fault during greater than setting value, and reclosing does not overlap.

2, a kind of permanent failure judgement method for power transmission line as claimed in claim 1 with shunt reactor; it is characterized in that: described step 2); criterion is that current amplitude compares method of discrimination; this method is that shunt reactor A, B, C three-phase current sampled value are obtained in protection according to this side; and then reactor current phasor and the little reactive current phasor of neutral point of being in parallel that must be out of order, and obtain its amplitude ratio.

3, a kind of permanent failure judgement method for power transmission line as claimed in claim 1 with shunt reactor, it is characterized in that: described step 2), criterion is the spill current method of discrimination, this method is to be computation model with the transient fault model behind the arc extinction, ask for the fault reactor current that is in parallel according to single-end electrical quantity, and calculate the reactor current of asking and the difference of measured current and the ratio of the little reactive current amount of neutral point.

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