CN104967104A - Transient energy protection method of transmission line with unified power flow controller - Google Patents

Abstract

The invention relates to a transient energy protection method of a transmission line with a unified power flow controller, which belongs to the technical field of power system relay protection. When the transmission line with the unified power flow controller fails, according to current and voltage values measured by transformers on both ends of the line, transient energy values on both ends of the line are calculated. Through symbols of the transient energy values on both ends of the line, in region and out region failures are judged and distinguished. If the symbols of the transient energy on both ends of the line are respectively positive and negative, out region failures are judged. If the symbols of the transient energy values on both ends of the line are negative, in region failures are judged. According to the invention, instantaneous power transient energy polarity acquired through integrating can be determined; unconstant change of instantaneous power positive and negative polarity after a failure can be avoided; and the judgment reliability is improved.

Description

A kind of method for protecting transient state energy of the transmission line with THE UPFC

Technical field

The present invention relates to a kind of method for protecting transient state energy of the transmission line with THE UPFC, belong to Relay Protection Technology in Power System field.

Technical background

THE UPFC (UPFC) is the flexible AC transmission equipment of new generation that a kind of function is the most powerful, characteristic is superior, also be the FACTS device that versatility is best up to now, the power of transmission line can be controlled as required neatly, the parameters such as the voltage on a transmission line, electric current can also be changed, there is the control effects of highly significant.Because existing relaying protection depends on, power-frequency voltage, power current and calculating gained respective impedance value are carried out in district, external area error judges, therefore the access of UPFC can cause traditional relay protection to occur erroneous judgement situation.

Containing UPFC transmission line malfunction, just wink not to be able to do in time action due to control system, and when between fault occurs in observation station and UPFC drops into some, the variation tendency of fault transient amount does not change; And after UPFC during fault, due to the effect of UPFC part in series leakage reactance, make its high fdrequency component deep fades, be difficult to fault high-frequency transient amount be detected at measuring end, but in short window, the change direction of (2 τ) fault component does not change, and power frequency and low frequency component still can pass through UPFC.Therefore, a kind of transient state energy protection with THE UPFC transmission line is needed.

Summary of the invention

The object of the invention is the method for protecting transient state energy proposing a kind of transmission line with THE UPFC, in order to solve the problem.

Technical scheme of the present invention is: when the transmission line containing THE UPFC breaks down, according to electric current, magnitude of voltage that circuit amount two ends instrument transformer is surveyed, calculate the transient state energy value at circuit two ends, distinguish in district and external area error by the symbol decision of circuit two ends transient state energy value.If the transient state energy symbol at circuit two ends be one positive one negative time be judged to external area error, if be judged to troubles inside the sample space when the transient state energy value symbol at circuit two ends is all negative.

Concrete steps are:

The first step, when being with the transmission line of THE UPFC to break down, utilizing transmission line measuring end to obtain voltage u (t), current i (t), being multiplied and obtaining instantaneous power,

p(t)＝u _a(t)×i _a(t)+u _b(t)×i _b(t)+u _c(t)×i _c(t) (1)

In formula: p (t) is measuring end three phase power: u _a(t), u _b(t), u _ct () measures terminal voltage value for a, b, c phase; i _a(t), i _b(t), i _ct () is a, b, c phase measuring end current value.

Second step, to instantaneous power in certain hour section upper integral, obtain transient state energy

$E\left(t\right)={\∫}_0^{t}p\left(\mathrm{\τ}\right)d\mathrm{\τ}---\left(2\right)$

In t a certain moment after representing fault in formula, 0 represents fault moment, and E (t) is the energy exchanging between line bus two side system and transmit, i.e. transient state energy.

3rd step, failure judgement direction; Rated current positive direction is the direction that bus points to circuit, and when for positive direction fault, measuring end transient state energy is negative, and when for reverse direction failure, measuring end transient state energy is just.

Accordingly, for the directional relay of measuring end, criterion is proposed:

If E (t) < 0, then it is positive direction fault (3)

If E (t) >=0, then it is reverse direction failure (4)

4th step, relay respond; When the relay at circuit two ends is all judged as positive direction fault, will breaker actuation be acted on, when only having one end to be judged as positive direction fault, when the other end is judged as reverse direction failure, then can locking circuit breaker, be failure to actuate.

The invention has the beneficial effects as follows: due to the power of transient state energy direction component and energy information perseverance be present in fault just wink, between fault transient and fault steady state period; thus failure process can be considered that row wave power and energy regain the process of balance under new boundary condition by the catadioptric repeatedly of row ripple, and the transient state energy directional pilot protection proposed on this basis will have the advantage of reliability and quick-action concurrently.Carry out to instantaneous power the transient state energy Polarity comparision that integration tries to achieve to determine, avoid instantaneous power after a failure positive-negative polarity change inconstant situation, improve the reliability of judgement.

Accompanying drawing explanation

Fig. 1 is for containing UPFC model of power transmission system;

Fig. 2 is that spacing M that in embodiment, M side and UPFC drop into point on circuit MN holds 60km that the electric current of measuring end under AG fault occurs;

Fig. 3 is that spacing M that in embodiment, M side and UPFC drop into point on circuit MN holds 60km that the voltage of measuring end under AG fault occurs;

Fig. 4 is F on circuit MN ₁₁the change curve of both-end transient state energy during fault;

Fig. 5 is F on circuit PM ₂the change curve of both-end transient state energy during fault.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Embodiment 1: containing UPFC vertical line line system simulation model as shown in Figure 1, UPFC is arranged on circuit mid point (apart from M75km), and circuit MN total length is 150km.Fault initial angle is 90 °, and sample rate is 20kHz, time window long be 3ms.There is AG fault F in the 60km place, spacing M side that order M side and UPFC on circuit MN drop into point ₁₁

1, transmission line measuring end is utilized to obtain the impact of UPFC input on fault current, voltage, as shown in Figure 2 and Figure 3.Instantaneous power is calculated according to the formula (1) in specification.

2, according to the formula (2) in specification, integration is carried out to instantaneous power and obtain corresponding transient state energy, as shown in Figure 4.

3, according to the formula (3) in specification, (4), transient state energy is carried out to the judgement of symbol, by sign (E in Fig. 4 _m) < 0 and sign (E _n) < 0 knows this fault point (F ₁₁) relay R is held for M ₁for positive direction fault, relay R is held for N ₂for positive direction fault.

4th step, relay respond; The relay at circuit two ends is all judged as forward fault, breaker protection action.

Embodiment 2: containing UPFC vertical line line system simulation model as shown in Figure 1, UPFC is arranged on circuit mid point (apart from M75km), and circuit MN total length is 150km.Fault initial angle is 90 °, and sample rate is 20kHz, time window long be 3ms.AG fault F is there is apart from 40km place, M side in order on circuit PM ₂.

1, utilize transmission line measuring end to obtain the impact of UPFC input on fault current, voltage, and calculate instantaneous power according to the formula (1) in specification.

2, according to the formula (2) in specification, integration is carried out to instantaneous power and obtain corresponding transient state energy, as shown in Figure 5.

3, according to the formula (3) in specification, (4), transient state energy is carried out to the judgement of symbol, by sign (E in Fig. 4 _m) > 0 and sign (E _n) < 0 knows this fault point (F ₂) relay R is held for M ₁for reverse direction failure, relay R is held for N ₂for positive direction fault.

4th step, relay respond; The relay at circuit two ends is all judged as a forward fault, a reverse fault, locking R ₁-R ₂.

Below by reference to the accompanying drawings the specific embodiment of the present invention is explained in detail, but the present invention is not limited to above-mentioned execution mode, in the ken that those of ordinary skill in the art possess, various change can also be made under the prerequisite not departing from present inventive concept.

Claims (1)

1. a method for protecting transient state energy for the transmission line with THE UPFC, is characterized in that concrete steps are:

The first step, when being with the transmission line of THE UPFC to break down, utilizing transmission line measuring end to obtain voltage u (t), current i (t), being multiplied and obtaining instantaneous power:

p(t)＝u _a(t)×i _a(t)+u _b(t)×i _b(t)+u _c(t)×i _c(t) (1)

In formula: p (t) is measuring end three phase power: u _a(t), u _b(t), u _ct () measures terminal voltage value for a, b, c phase; i _a(t), i _b(t), i _ct () is a, b, c phase measuring end current value;

Second step, to instantaneous power in certain hour section upper integral, obtain transient state energy:

$E\left(t\right)={\&Integral;}_0^{t}p\left(\mathrm{\&tau;}\right)d\mathrm{\&tau;}---\left(2\right)$

In t a certain moment after representing fault in formula, 0 represents fault moment, and E (t) is the energy exchanging between line bus two side system and transmit, i.e. transient state energy;

3rd step, failure judgement direction: rated current positive direction is the direction that bus points to circuit, and when for positive direction fault, measuring end transient state energy is negative, and when for reverse direction failure, measuring end transient state energy is just;

Accordingly, for the directional relay of measuring end, criterion is proposed:

If E (t) < 0, then it is positive direction fault (3)

If E (t) >=0, then it is reverse direction failure (4)

4th step, relay respond: when the relay at circuit two ends is all judged as positive direction fault, will act on breaker actuation, when only having one end to be judged as positive direction fault, when the other end is judged as reverse direction failure, then can locking circuit breaker, and be failure to actuate.