CN101295874A - Electric power line pilot protection decision method based on fault component positive sequence synthetic impedance - Google Patents

Abstract

The invention discloses a judgment method for the pilot protection of a transmission line based on the synthesized impedance of a positive-sequence fault component. Two protection devices are arranged at the two sides of a protected line segment; a communication channel is arranged between the two protection devices; the voltage phasor Delta U<m1> of the positive-sequence fault component and the current phasor Delta I<m1> of the positive-sequence fault component which are at the side are calculated, and the communication channel is utilized to obtain the voltage phasor Delta U<n1> of the positive-sequence fault component and the current phasor Delta i<n1> of the positive-sequence fault component which are at the same time and at the opposite side. The synthesized impedance of the positive-sequence fault component is calculated (refer to formula (1)), wherein, Delta U<cdl> is shown in formula (2). According to the size relation between the module value and the fixed value of the synthesized impedance of the positive-sequence fault component, whether the line segment has fault is distinguished so as to control the action of the protection devices.

Description

Electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance

Technical field

The present invention relates to the circuit on power system decision method of longitudinal jointing protection of field of relay protection in power, particularly a kind of electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance,

Background technology

Line Current Differential Protection is widely used in the electric power system.But influenced by capacitance current, the sensitivity of differential protection is lower.The method that reduces capacitance current at present generally is to adopt compensation reactor or use the phase amount compensation process; also there is document to propose some new pilot protection principles; as longitudinal differential protection system principle based on the fault component comprehensive impedance; this principle does not need capacitance current is compensated; be not subjected to the influence of transition resistance; can be used for circuit, itself possess the phase of choosing ability with or without compensation reactor.This principle is suitable for high pressure and supertension line, and defective is that the traffic and operand are bigger.

Summary of the invention

Technical problem to be solved by this invention is; a kind of electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance is provided; by calculating the positive sequence fault component comprehensive impedance; on the size discrimination circuit according to positive sequence fault component comprehensive impedance mould value whether fault is arranged; this criterion does not need capacitance current is compensated, and is not subjected to the influence of transition resistance.The traffic and operand are little.

Technical scheme of the present invention is as follows:

A kind of electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance is characterized in that: the both sides in institute protective wire highway section are respectively arranged with protective device, have communication channel between two protective devices,

At first, this side protective device is gathered this side three-phase voltage and current value, calculates this side positive sequence fault component voltage phasor

The positive sequence fault component electric current phasor

And, obtain the positive sequence fault component voltage phasor that circuit offside protective device provides by communication channel

With the positive sequence fault component electric current phasor

Secondly, according to this side and same positive sequence fault component voltage phasor and the positive sequence fault component electric current phasor constantly of offside, calculate fault component positive sequence comprehensive impedance Z _Cd1,

$Z_{\mathrm{cd}1}=\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}},$ Wherein $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1},$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{n1};$

At last, judge, if | Z _Cd1|＜Z _Set, and $\left|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}\right|>I_{\mathrm{set}},$ Then determine in this part of path fault to have taken place the action of this side protective device; The offside protective device is carried out above-mentioned steps equally, then action;

Wherein, I _SetBe current ration, Z _SetBe the impedance definite value.

Z _SetSetting method be: Z _Set=(0.5-0.6) * | Z _C1|, Z _C1It is 2 times all fronts positive sequence capacitive reactance; I _SetSetting method be: I _Set=0.2-0.5I _n, I _nIt is this side of circuit Current Transformer Secondary rated value.

Good effect of the present invention is: positive sequence fault component comprehensive impedance Z among the present invention _Cd1For the positive sequence fault component voltage phasor of part of path both sides and with the positive sequence fault component electric current phasor and ratio.By calculating the positive sequence fault component comprehensive impedance, distinguish according to the size of positive sequence fault component comprehensive impedance mould value whether fault is arranged in the part of path.This method does not need capacitance current is compensated, and is not subjected to the influence of transition resistance on principle, and the traffic is little, and amount of calculation is little.

Description of drawings

Fig. 1 is this side, offside line protective devices connection layout.

Short circuit additivity figure when Fig. 2 is mn section line-internal fault.

Short circuit additivity figure when Fig. 3 is mn section circuit external fault.

Fig. 4 is a logic determines block diagram of the present invention, “ ﹠amp among the figure; " representative " with ", "+" representative " or ", only when satisfying logical condition shown in the logic diagram, be judged as line fault, send trip command.

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

With reference to Fig. 1,, be respectively arranged with line protective devices m, n in its m side and n side for protective wire highway section mn.The protective device of circuit has data processing function and communication function, and three-phase voltage of this side of can sampling and electric current are controlled the actuator of this side.Protective device m, the n of circuit are by optical fiber communication.With line protective devices m is example; part of path m side is this side; part of path n side is offside; line protective devices m the sample three-phase voltage and the electric current of this side; calculate the positive sequence voltage and the electric current of this side; obtain together the positive sequence voltage and the forward-order current of offside constantly by fiber channel simultaneously, carry out the actuator that data processing is controlled this side then.Line protective devices n protection philosophy and control are with line protective devices m.

Short circuit additivity figure when Fig. 2 is mn section line-internal fault, the fault additivity figure when being bilateral power supply power supply model F point breaking down on the line, circuit employing ∏ type Type Equivalent Circuit Model.Among the figure, Z _M1, Z _N1Be circuit both sides positive sequence source impedance, Z _Lm1, Z _Lm1Be respectively the circuit positive sequence impedance at two ends, fault point, Z _C1Be the circuit positive sequence capacitive reactance of twice,

The fault component positive sequence electromotive force of ordering for F,

For flowing through the forward-order current of fault branch, R _FBe transition resistance,

With

Be respectively the positive sequence fault component voltage and current at circuit m, n place, the positive sequence fault component comprehensive impedance is: $Z_{\mathrm{cd}1}=\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}},$ Wherein $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1},$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{n1}.$

When breaking down in the mn section circuit, with respect to the positive sequence fault component differential current, the electric current that flows through in the circuit positive sequence electric capacity is very little, therefore, in the following surface analysis, has ignored the influence of electric capacity.The impedance of failure definition point both sides is respectively Z ₁=Z _M1+ Z _Lm1, Z ₂=Z _N1+ Z _Ln1, then:

${\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_{F1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{F1}/(R_F+Z_1//Z_2),$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{F1}\&times;\frac{Z_2}{Z_1+Z_2}\&times;Z_{m1}$

$\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{F1}\&times;\frac{Z_1}{Z_1+Z_2}\&times;Z_{n1},$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{n1}=-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{F1}$

Can draw the fault component comprehensive impedance $Z_{\mathrm{cd}1}=\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1}}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}}=-\frac{Z_2\&times;Z_{m1}+Z_1\&times;Z_{n1}}{Z_1+Z_2}$

In high-pressure system, the impedance angle of source impedance and line impedance all near 90 °, is established Z ₁, Z ₂, Z _M1, Z _N1The impedance angle approximately equal, and because of Z _M1＜ _Z1, Z _N1＜Z ₂, as with the Z in the following formula _M1Value is Z ₁, Z _N1Value is Z ₂, can obtain Z _Cd1The upper limit, promptly

Z _cd1＜2Z ₁Z ₂/(Z ₁+Z ₂)，Z _cd1＜2×(Z ₁//Z ₂)，Z _cd1＜min{2Z ₁，2Z ₂}

Promptly when inside, protection zone (in the mn section circuit) fault takes place on the circuit, the Z of corresponding positive sequence fault component comprehensive impedance _Cd1Reflected positive sequence source impedance and positive sequence line impedance, its mould value is less, and the size of it and transition resistance is irrelevant.

Fig. 3 is the short circuit additivity figure when mn section circuit external fault takes place, among the figure

Be respectively the fault component electric current that flows through circuit two ends positive sequence electric capacity.

The fault component differential current is: $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{n1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{mc}}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{nc}}=\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}}{Z_{c1}}+\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1}}{Z_{c1}}$

The fault component comprehensive impedance is: $Z_{\mathrm{cd}1}=(\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1})/\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=Z_{c1}$

When being outside, protection zone (mn section circuit outside) fault, Z _Cd1And Z _C1Equate that with respect to system power supply impedance and line impedance, it is a bigger numerical value.

From the above analysis, in when, on the circuit protection zone external fault taking place when, | Z _Cd1| equal in theory | Z _C1|.When the protection zone internal fault takes place, corresponding | Z _Cd1| reflection system power supply positive sequence impedance and circuit positive sequence impedance, much smaller than | Z _C1|.Therefore, according to | Z _Cd1| size can distinguish inside, route protection district, external fault, and on principle, be not subjected to the influence of transition resistance, do not need capacitance current is compensated.

In sum, criterion of the present invention is: Z _SetBe impedance definite value, I _SetBe current ration.According to former theoretical analysis, when not having fault on the protected circuit section, corresponding positive sequence fault component comprehensive impedance is the positive sequence condensance of circuit, and numerical value is bigger; And when breaking down on the circuit, corresponding positive sequence fault component comprehensive impedance and system's positive sequence impedance and circuit positive sequence impedance are in the same order of magnitude, and with respect to the capacitive reactance of circuit positive sequence, its numerical value is less.When with Z _SetSetting range be taken as (0.5-0.6) * | Z _C1| the time, when not having fault on the protected circuit, this criterion can malfunction, and when on the protected circuit fault being arranged, this criterion can action message.Therefore, the impedance definite value Z among the present invention _SetThe principle of adjusting can be defined as: Z _Set=(0.5-0.6) * | Z _C1|.

Be the positive sequence fault component differential current, when normally moving in system,

Be zero in theory, I _SetBe current ration.General I _SetDesirable 0.2I _n-0.5I _n, I _nIt is line current instrument transformer secondary rated value.

With reference to Fig. 4, if

Illustrate there is fault on the circuit protection tripping operation.

Data deduct the method for the preceding data of fault after the calculating employing fault of fault component, with the fault component data that obtain, use complete all fourier algorithms, calculate the fault component phasor.

Claims (2)

1, a kind of electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance is characterized in that: the both sides in institute protective wire highway section are respectively arranged with protective device, have communication channel between two protective devices,

At first, this side protective device is gathered this side three-phase voltage and current value, calculates this side positive sequence fault component voltage phasor

The positive sequence fault component electric current phasor

And, obtain the positive sequence fault component voltage phasor that circuit offside protective device provides by communication channel

With the positive sequence fault component electric current phasor

Secondly, according to this side and same positive sequence fault component voltage phasor and the positive sequence fault component electric current phasor constantly of offside, calculate fault component positive sequence comprehensive impedance Z _Cd1,

$Z_{\mathrm{cd}1}=\frac{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}}{\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}},$ Wherein $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_{n1},$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{m1}+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{n1};$

At last, judge, if | Z _Cd1|＜Z _Set, and $\left|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}1}\right|>I_{\mathrm{set}},$ Then determine in this part of path fault to have taken place the action of this side protective device; The offside protective device is carried out above-mentioned steps equally, then action;

Wherein, I _SetBe current ration, Z _SetBe the impedance definite value.

2, the electric power line longitudinal coupling protection decision method based on fault component positive sequence comprehensive impedance according to claim 1 is characterized in that: Z _SetSetting method be: Z _Set=(0.5-0.6) * | Z _C1|, Z _C1It is 2 times all fronts positive sequence capacitive reactance; I _SetSetting method be: I _Set=0.2-0.5 I _n, I _nIt is this side of circuit Current Transformer Secondary rated value.

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