CN110544925B - Method and system for determining line protection range of fault point of photovoltaic station outgoing line - Google Patents
Method and system for determining line protection range of fault point of photovoltaic station outgoing line Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
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Abstract
The invention discloses a method for determining the line protection range of a line outlet fault point of a photovoltaic station, which comprises the following steps: s1: measurement impedance expression Z for determining power outlet of photovoltaic station M And S2: setting a fault location coefficient threshold value n max Transition resistance threshold Rg max (ii) a S3: acquiring a positive sequence voltage and a positive sequence current fault value at a protection installation position of a photovoltaic substation outgoing line, and equivalent positive sequence impedance values of an outlet and an inlet of the photovoltaic substation; s4: according to Z M Expression, D d Expression, n max 、Rg max Determining the action boundary of a curved polygon; s5: and analyzing the distance protection of the fault point of the sending-out line of the photovoltaic field station according to the action boundary of the curved polygon and the plane where the action boundary is located. The invention effectively ensures that when the photovoltaic sending-out line has a transition resistance grounding fault, the fault in the area is instantaneous or does not malfunction through time delay action, and the fault outside the area does not malfunction, thereby ensuring the stable and reliable operation of the photovoltaic station.
Description
Technical Field
The invention belongs to the technical field of electrical technology and power system protection, and particularly relates to a method and a system for determining a line protection range of a line outgoing fault point of a photovoltaic station.
Background
In recent years, new energy power generation represented by photovoltaic has become an important development field in the power industry, and the installed photovoltaic capacity has increased dramatically. However, the conventional relay protection is affected by a large-capacity photovoltaic access power grid, and the reliable action of the conventional distance protection is more seriously affected by the obvious weak feedback characteristic of the photovoltaic station.
The self-adaptive distance protection method is influenced by the weak feed performance of the new energy station, the traditional distance protection has poor transition resistance, and a self-adaptive distance protection scheme is provided in the prior art, but the stable and reliable operation of the photovoltaic station cannot be guaranteed.
Disclosure of Invention
The present invention is directed to solving, at least in part, one of the technical problems in the related art.
To this end, a first object of the invention is to propose a method for determining the line protection range of a photovoltaic farm outgoing line fault point. When the photovoltaic sending-out line has a transition resistance grounding fault, the fault in the area is instantaneous or does not act by mistake through time delay action, and the stable and reliable operation of the photovoltaic station is ensured.
In order to achieve the above object, a method for determining a line protection range of a line fault point of a photovoltaic farm station, provided in an embodiment of a first aspect of the present invention, includes:
s1: determining a measured impedance expression of the power outlet of the photovoltaic station, wherein the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the distance from the distance protection installation position to the fault point to the total length of the sending line of the photovoltaic station; the Rg is a transition resistance;
z is MN Is the total impedance of the photovoltaic station outgoing line, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively the distribution coefficient of the positive sequence current and the distribution coefficient of the zero sequence current of the power supply of the photovoltaic station, D d In order to obtain a comprehensive coefficient of the image,
in the formula (2), Z SM1 And Z SN1 Respectively representing equivalent positive sequence impedances of an outlet and an inlet of the photovoltaic field station, wherein the equivalent positive sequence impedance of the outlet of the photovoltaic field station is determined by a positive sequence voltage fault value and a positive sequence current fault value of the outlet of the photovoltaic field station, and rho represents the ratio of electromotive force amplitudes of power supplies of the outlet and the inlet of the photovoltaic field station before a sending line of the photovoltaic field station fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the sending-out line of the photovoltaic station;
s2: setting a fault location coefficient threshold value n max Transition resistance threshold Rg max ；
S3: acquiring positive sequence voltage and positive sequence current fault values at the protection installation position of the photovoltaic station outgoing line, and positive sequence impedance values equivalent to the outlet and the inlet of the photovoltaic station;
s4: according to the Z in the S1 M Expression, said n max The institute Rg max The determined values form the action boundary of a curved polygon, and the plane where the action boundary is located is the plane formed by the measured impedance value and the fault position coefficient by the axial coordinate.
S5: and analyzing the line protection range of the fault point of the line which is away from the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon.
According to an embodiment of the present invention, the polygon in the S4 includes:
a curve I, wherein the curve I indicates that when the fault position coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
Curve II, representing the fault location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
Curve III, representing that the fault location factor is from zero to n when the transition resistance Rg is zero max According to said Z M A curve formed by the values of the expression at the plane.
Curve IV indicating that the transition resistance is Rg max When the fault location coefficient is from zero to n max According to said Z M The values of the expression in the plane constitute a curve.
According to an embodiment of the present invention, the polygon in S4 further includes:
a curve V, wherein the curve V shows that when the fault position coefficient is 0.8, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
And a curve VI which shows that when the tail end of the adjacent line outside the fault point of the photovoltaic station outgoing line fails, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
According to an embodiment of the present invention, the analyzing, in S5, a distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary of the curved polygon and the plane includes:
and the plane enclosed by the curve V, the curve IV and the curve VI is the maximum line range of the line protection range of the outgoing line of the photovoltaic station, wherein the line fault falls into the line protection range of the outgoing line of the photovoltaic station.
According to an embodiment of the present invention, the analyzing, in S5, a distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary of the curved polygon and the plane, further includes:
and a plane enclosed by the curve II, the curve III, the curve IV, the curve V and the curve VI and the coordinate curve is a delay action line range of the protection range of the photovoltaic station outgoing line.
The system for determining the line protection range of the line fault point sent out from the photovoltaic station provided by the embodiment of the second aspect of the invention comprises:
a modeling unit for determining a measured impedance expression of the power outlet of the photovoltaic station, the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the total length of a sending line of the photovoltaic field station, wherein the distance from the distance protection installation position to the fault point is the percentage; the Rg is a transition resistance;
z is MN Is the total impedance of the photovoltaic station outgoing line, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively a positive sequence current distribution coefficient and a zero sequence current distribution coefficient of the power supply of the photovoltaic field station, D d In order to obtain a comprehensive coefficient of the image,
in the formula (2), Z SM1 And Z SN1 Respectively representing the equivalent positive sequence impedance of the outlet and the inlet of the photovoltaic station, wherein the equivalent positive sequence impedance of the outlet of the photovoltaic station is represented by the positive sequence voltage fault value and the positive sequence voltage fault value of the outlet of the photovoltaic stationDetermining a sequence current fault value, wherein rho represents the ratio of the electromotive force amplitudes of the outlet and inlet power supplies of the photovoltaic field station before the outlet line of the photovoltaic field station fails; and delta represents the phase difference of the electromotive force of the outlet and inlet power supplies of the photovoltaic station before the failure of the outlet line of the photovoltaic station.
A setting unit for setting a fault location coefficient threshold value n max Transition resistance threshold Rg max 。
And the acquisition unit is used for acquiring the positive sequence voltage and the positive sequence current fault value of the protection installation position of the photovoltaic substation outgoing line and the equivalent positive sequence impedance values of the photovoltaic substation outlet and the photovoltaic substation inlet.
A calculation unit for calculating the Z value according to the Z value in the modeling unit M Expression, said n in said setting unit max The institute Rg max The determined values form the action boundary of a curved polygon, and the plane where the action boundary is located is the plane formed by the measured impedance value and the fault position coefficient by the axial coordinate.
And the analysis unit is used for analyzing the line protection range of the fault point of the sending line away from the photovoltaic station according to the action boundary and the plane of the curved polygon.
According to an embodiment of the invention, the calculation unit comprises:
a first calculating unit, configured to calculate that when the fault location coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M Values at the plane are expressed.
A second calculation unit for calculating the failure location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M Values at the plane are expressed.
A third calculating unit, for calculating the fault location coefficient from zero to n when the transition resistance Rg is zero max According to said Z M Values at the plane are expressed.
A fourth calculation unit for calculating the transition resistance Rg max When said fault occursPosition coefficient from zero to n max According to said Z M Values at the plane are expressed.
According to an embodiment of the invention, the computing unit further comprises: a fifth calculating unit, configured to calculate that, when the fault location coefficient is 0.8, a value of the transition resistor Rg is from zero to Rg max According to said Z M Values at the plane are expressed.
A sixth calculating unit, configured to calculate that, when the end of the adjacent line outside the failure point of the outgoing line of the photovoltaic plant fails, the value of the transition resistance Rg ranges from zero to Rg max According to said Z M Values at the plane are expressed.
According to one embodiment of the invention, the analysis unit comprises: and the first analysis unit is used for analyzing the maximum line range of the line protection range of the outgoing line of the photovoltaic station according to the fourth calculation unit, the fifth calculation unit and the sixth calculation unit, wherein the outgoing line fault of the photovoltaic station falls into the maximum line range of the line protection range of the outgoing line of the photovoltaic station.
According to an embodiment of the invention, the analysis unit further comprises: and the second analysis unit is used for analyzing the delay action line range of the protection range of the line sent out from the photovoltaic station according to the second calculation unit, the third calculation unit, the fourth calculation unit, the fifth calculation unit and the sixth calculation unit.
The invention achieves the technical effects that: firstly, the method effectively solves the problem of influence of the weak feed of the photovoltaic power supply on distance protection; secondly, a self-adaptive distance polygon is obtained by measuring an impedance expression, and the self-adaptive distance polygon has better adaptability to high-resistance ground faults; and thirdly, by dividing action areas with different time limits, the correct action of the fault in the protection area is ensured, the fault outside the protection area is not mistakenly operated, and the stable and reliable operation of the photovoltaic station is guaranteed.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a schematic diagram of a single-phase ground short circuit of a two-terminal system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of action zone division disclosed according to an embodiment of the invention;
FIG. 3 is a schematic diagram of a disclosed simulation system according to an embodiment of the invention;
fig. 4 is a flowchart of a method for determining a line protection range of a line fault point sent out by a photovoltaic field station according to an embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, the present invention shall be described in detail with reference to specific embodiments.
The first embodiment is as follows:
in recent years, new energy power generation represented by photovoltaic has become an important development field in the power industry, and the installed photovoltaic capacity has increased dramatically. However, a large-capacity photovoltaic access power grid affects traditional relay protection, wherein the reliable action of traditional distance protection is affected more seriously by the obvious weak feed characteristic of a photovoltaic station. Influenced by the weak feed of new energy station, the traditional distance protection has poor anti-transition resistance capability, and the self-adaptive distance protection scheme is provided for the existing scholars:
taking a single-phase ground fault as an example, a dual-power-supply system including a photovoltaic device is short-circuited through a transition resistor in a single-phase ground manner as shown in fig. 1, and a measurement impedance expression at the photovoltaic device M side is as follows:
in formula (1), n is a fault location coefficient, and the value is the percentage of the total length of the line from the protective installation to the fault point, Δ Z is the additional measured impedance, and Z is MN Is the total impedance of the line, Z Σ Is the sum of the impedances of the sequences. Dd is defined as the overall coefficient, and is expressed as:
z in the formula (2) SM1 And Z SN1 Respectively representing equivalent positive sequence impedance of an M-side system and an N-side system, and formula (3) is an equivalent positive sequence impedance expression of a photovoltaic side, wherein delta U M1 And Δ I M1 Respectively, positive sequence voltage and current fault components of the photovoltaic power outlet. Rho represents the ratio of the electromotive force amplitudes of the two ends of the power supply before the fault, and delta represents the electromotive force phase difference of the two ends of the power supply before the fault.
The formula (4) is a relation proportional expression of two-end power supply electromotive force before M side and N side faults, and C in the formula (5) M1 And C M0 Respectively positive sequence current distribution coefficient and zero sequence current distribution coefficient, which represent the ratio of each sequence fault current to each sequence current at fault point,
To protect the fault component of the fault phase positive sequence current at the installation,
to protect zero sequence current at the installation site.
And
respectively a fault point positive sequence current and a fault point zero sequence current.
Because the M-side system is a photovoltaic station, the photovoltaic station generally adopts a negative sequence current suppression control strategy, and therefore the photovoltaic side can equivalently have no negative sequence current output after the fault, and therefore has no negative sequence current distribution coefficient.
From the measured impedance expressions, it can be found that the magnitude of the additional impedances is equal to n, rg, ρ, δ and Z SM1 The size of the isoparameter is relevant. Where ρ, δ and Z SM1 Can be determined by the system operation mode. In addition, according to the actual engineering requirements, the range of the protected line and the tolerable transition resistance value are predetermined, so that the ranges of n and Rg can be determined to form an action area of a curved quadrilateral, as shown in fig. 2, the action area is defined by curves i to iv, and the meanings of the four curves are as follows:
a curve I: n =0, rg ranges from 0 to R gmax ；
And a curve II: n = n max Rg ranges from 0 to R gmax ；
Curve iii: rg =0,n ranges from 0 to n max ；
Curve iv: rg = R gmax N ranges from 0 to n max . Wherein R is gmax Maximum transition resistance value n endured by the present impedance relay max Is the ratio of the maximum protected length of the line to the total length of the line, usually n max And taking 1 to represent the total length of the protection circuit.
The action condition when the single-phase earth fault outside the protection inspection area is considered. When a point outside the zone is grounded through different transition resistors, the measured impedance trace may be as shown by a curve v in fig. 2, where a part of the measured impedance value (as shown by a dashed box) falls within the protected action zone, which may cause a malfunction.
Aiming at the problem, the invention technically improves the existing self-adaptive curved quadrilateral characteristic distance protection. The invention provides a self-adaptive distance protection scheme for dividing different time limit action areas, aiming at the problems that the reliable action of the traditional distance protection is seriously influenced by the obvious weak feed characteristic of a photovoltaic station and the fault misoperation exists outside the area due to the existing self-adaptive distance quadrilateral characteristic. The method can effectively distinguish the zone internal fault and the zone external fault of the photovoltaic sending-out line, realize the instantaneous action of the zone internal fault, and avoid the misoperation of the zone external fault through time delay. Meanwhile, the maximum tolerable transition resistance value can be changed according to the actual engineering requirements, and the transition resistance tolerance capability is strong. The related parameters are obtained only by using photovoltaic side electric quantity of the outgoing line, and related electric quantity of a system on the opposite side of the line is not needed.
The specific analysis process of the method is as follows:
taking a single-phase earth fault as an example, firstly, three-phase positive sequence voltage and positive sequence current fault components at a protection installation position are obtained, photovoltaic equivalent positive sequence impedance is calculated in real time, and then four action boundaries of a curved quadrilateral are determined by a photovoltaic side measurement impedance formula. As shown in figure 2 of the drawings, in which,
curve i: n =0, rg ranges from 0 to R gmax ；
And a curve II: n = n max Rg ranges from 0 to R gmax ；
Curve iii: rg =0,n ranges from 0 to n max ；
Curve iv: rg = R gmax N ranges from 0 to n max 。
Secondly, in order to distinguish the end fault of the line from the outlet fault of the adjacent line, a curve V is determined, wherein the position of 80% of the total length of the protected line has the transition resistance from 0 to R gmax 。
Then, in order to solve the problem of protection misoperation caused by the fact that the out-of-area fault falls into the action area, a curve VI is determined, wherein the adjacent line tail end fault is caused, and the transition resistance is from 0 to R gmax . The curve IV, the curve V and the curve VI enclose a red curve shaded area, and the maximum area of the out-of-zone fault falling into the protection range of the line is obtained.
The instantaneous action region of the adaptive distance protection is shown in fig. 2 and is composed of a curve I, a curve II, a curve III, a curve IV, a curve V, and a curve VI; the hatched area portion of the graph formed by the curve II, the curve III, the curve IV, the curve V, and the curve VI serves as a delay action area. When the measured impedance falls into the instantaneous action area, the adaptive distance protection performs instantaneous action, when the measured impedance falls into the delay action area, the adaptive distance protection judges whether the measured impedance is still in the action area after a period of delay, and the action is performed if the criterion is established.
The invention achieves the technical effects that: through the division of different delay action areas, the part which possibly falls into the action area during the external fault and the end part of the line are divided into the delay action areas, so that the adjacent line protection jumps first under the external fault condition, and then the fault is removed, and the line protection cannot be mistakenly operated. Therefore, the scheme can effectively ensure that when the photovoltaic sending-out line has a transition resistance ground fault, the fault in the area is instantaneous or does not malfunction through time delay action, and the fault outside the area can not malfunction, thereby ensuring the stable and reliable operation of the photovoltaic station.
The second embodiment:
a model of a dual-power-supply system with a photovoltaic station is characterized in that a model topological structure is shown in FIG. 3, corresponding simulation models are established in PSCAD simulation software, the system voltage level is 110kV, the photovoltaic station capacity is 1.5MW, the lengths of two lines L1 and L2 are 80km and 50km respectively, line parameters are Z1=0.105+ j1.258 Ω/km, and Z0=0.315+ j3.774 Ω/km respectively. And researching the action condition of the protection 1, wherein the fault is set to be a fault at the point K1 of the line and faults at the points K2 and K3 of the adjacent lines.
Firstly, three-phase positive sequence voltage and positive sequence current fault components at a protection installation position and three-phase measured voltage current and zero sequence current are obtained, photovoltaic equivalent positive sequence impedance is calculated in real time, and then six action boundaries of a curved polygon are determined by a photovoltaic side measured impedance formula. The maximum transition resistance is 100 omega, the whole length of the circuit is protected, and the circuit can rapidly move within 80 percent of the range. The action area is divided according to figure 2,
and curve I, line L1 head end fault, rg from 0 to 100.
And a curve II: when the tail end of the line L1 is in fault, the value range of Rg is 0 to 100;
and Rg is 0, and the fault location is from the head end to the tail end of the line L1.
Rg is 100 and the fault location is from the head end to the tail end of the line L1.
Curve V, rg from 0 to 100 at 80% of line L1.
Curve V I line L2 end fault, rg from 0 to 100. The white area acts instantaneously and the shadow area acts with delay.
Taking a single-phase ground short circuit as an example, when a point K1 in a region has a fault (fault position n =0.5, transition resistance is 80 Ω), the measured impedance (123.06 + j33.03 Ω) falls in a transient action region, so that protection can be performed in a transient action.
When a K2 point outside the region is in fault (fault position n =1.6, transition resistance is 15 Ω), the measured impedance (161.64 + j47.81 Ω) falls in the delay action region, the outside line protection action of the region is waited, the measured impedance becomes 28.165+ j163.54 Ω and falls outside the protection range, and the line protection does not act after the delay.
And (3) a fault at a K3 point outside the region (the fault position is n =1.2 (K3), the transition resistance is 10 omega), the measured impedance (47.06 + j111.71 omega) falls outside the delay action region, and the protection does not act.
The technical effect that this application reached does: firstly, the method effectively solves the problem of the influence of the weak feed of the photovoltaic power supply on the distance protection; secondly, a self-adaptive distance polygon is obtained by measuring an impedance expression, and the self-adaptive distance polygon has better adaptability to high-resistance ground faults; and thirdly, by dividing action areas with different time limits, the correct action of the fault in the protection area is ensured, the fault outside the protection area is not mistakenly operated, and the stable and reliable operation of the photovoltaic station is guaranteed.
Example three:
the method for determining the line protection range of the outgoing line fault point of the photovoltaic station, as shown in fig. 4, includes:
s1: determining a measured impedance expression of the power outlet of the photovoltaic station, wherein the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the distance from the distance protection installation position to the fault point to the total length of the sending line of the photovoltaic station; the Rg is a transition resistance;
z is MN Total impedance of the line for the photovoltaic station, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively a positive sequence current distribution coefficient and a zero sequence current distribution coefficient of the power supply of the photovoltaic field station, D d In order to obtain a comprehensive coefficient of the image,
in the formula (2), Z SM1 And Z SN1 Respectively representing equivalent positive sequence impedances of an outlet and an inlet of the photovoltaic field station, wherein the equivalent positive sequence impedance of the outlet of the photovoltaic field station is determined by a positive sequence voltage fault value and a positive sequence current fault value of the outlet of the photovoltaic field station, and rho represents the ratio of the electromotive force amplitudes of the outlet and the inlet of the photovoltaic field station before the outlet line of the photovoltaic field station fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the outlet line of the photovoltaic station;
s2: setting a fault location coefficient threshold value n max Transition resistance threshold Rg max ；
S3: acquiring positive sequence voltage and positive sequence current fault values at the protection installation position of the photovoltaic station outgoing line, and positive sequence impedance values equivalent to the outlet and the inlet of the photovoltaic station;
s4: according to the Z in the S1 M Expression, said D d Expression, said n max The institute Rg max And determining the action boundary of the curved polygon, wherein the plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient which are axial coordinates.
S5: and analyzing the line protection range from the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon.
According to an embodiment of the present invention, the polygon in the S4 includes:
a curve I, wherein the curve I indicates that when the fault position coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
Curve II, representing the fault location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
Curve III, representing that the fault location factor is from zero to n when the transition resistance Rg is zero max According to said Z M The values of the expression in the plane form a curve.
Curve IV, the curve IV representing the transition resistance Rg max When the fault location coefficient is from zero to n max According to said Z M The values of the expression in the plane constitute a curve.
According to an embodiment of the present invention, the polygon in S4 further includes:
a curve V, wherein the curve V shows that when the fault position coefficient is 0.8, the value of the transition resistor Rg is from zero to Rg max According to said Z M Is expressed inThe values of the planes constitute a curve.
And a curve VI which shows that when the tail end of the adjacent line outside the fault point of the photovoltaic station outgoing line fails, the value of the transition resistor Rg is from zero to Rg max According to said Z M The values of the expression in the plane form a curve.
According to an embodiment of the present invention, the analyzing, in S5, a distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary of the curved polygon and the plane includes:
and a plane enclosed by the curve V, the curve IV and the curve VI is the maximum line range of the line protection range of the outgoing line of the photovoltaic field station, wherein the outgoing line fault of the photovoltaic field station falls into the maximum line protection range of the outgoing line of the photovoltaic field station.
According to an embodiment of the present invention, the analyzing, in S5, a distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary of the curved polygon and the plane, further includes:
and a plane enclosed by the curve II, the curve III, the curve IV, the curve V and the curve VI and the coordinate curve is a delay action line range of the protection range of the photovoltaic station outgoing line. Namely, the area enclosed by the curve II, the curve III, the curve IV, the curve V, the curve VI, the coordinate curve and the coordinate curve is the delay action line range of the protection range of the photovoltaic field station outgoing line, which is shown by filling with horizontal lines in fig. 2, and the remaining blank part is the non-delay action line range of the protection range of the photovoltaic field station outgoing line.
The system for determining the line protection range of the line fault point sent out from the photovoltaic station provided by the embodiment of the second aspect of the invention comprises:
a modeling unit for determining a measured impedance expression of the power outlet of the photovoltaic station, the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the distance from the distance protection installation position to the fault point to the total length of the sending line of the photovoltaic station; the Rg is a transition resistance;
z is MN Is the total impedance of the photovoltaic station outgoing line, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively the distribution coefficient of the positive sequence current and the distribution coefficient of the zero sequence current of the power supply of the photovoltaic station, D d In order to obtain a comprehensive coefficient of the image,
in the formula (2), Z SM1 And Z SN1 Respectively representing equivalent positive sequence impedances of an outlet and an inlet of the photovoltaic field station, wherein the equivalent positive sequence impedance of the outlet of the photovoltaic field station is determined by a positive sequence voltage fault value and a positive sequence current fault value of the outlet of the photovoltaic field station, and rho represents the ratio of the electromotive force amplitudes of the outlet and the inlet of the photovoltaic field station before the outlet line of the photovoltaic field station fails; and delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the sending-out line of the photovoltaic station occurs.
A setting unit for setting a fault location coefficient threshold value n max Transition resistance threshold Rg max 。
And the acquisition unit is used for acquiring the positive sequence voltage and the positive sequence current fault value of the protection installation position of the photovoltaic substation outgoing line and the equivalent positive sequence impedance values of the photovoltaic substation outlet and the photovoltaic substation inlet.
A calculation unit for calculating a Z value according to the Z in the modeling unit M Expression, said D d Expression, said n in said setting unit max And Rg of the institute max And determining the action boundary of the curved polygon, wherein the plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient which are axial coordinates.
And the analysis unit is used for analyzing the line protection range from the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon.
According to an embodiment of the invention, the calculation unit comprises:
a first calculating unit, configured to calculate that when the fault location coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M Values at the plane are expressed.
A second calculation unit for calculating the failure location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M Values at the plane are expressed.
A third calculating unit, for calculating the fault location coefficient from zero to n when the transition resistance Rg is zero max According to said Z M Values at the plane are expressed.
A fourth calculation unit for calculating the transition resistance Rg max When the fault location coefficient is from zero to n max According to said Z M Values at the plane are expressed.
According to an embodiment of the invention, the computing unit further comprises: a fifth calculating unit, configured to calculate that, when the fault location coefficient is 0.8, the value of the transition resistance Rg is from zero to Rg max According to said Z M Values at the plane are expressed.
A sixth calculating unit, configured to calculate that, when an adjacent line outside the failure point of the outgoing line of the photovoltaic plant fails, a value of the transition resistance Rg ranges from zero to Rg max According to said Z M Values at the plane are expressed.
According to one embodiment of the invention, the analysis unit comprises: and the first analysis unit is used for analyzing the maximum line range of the line protection range of the outgoing line of the photovoltaic station according to the fourth calculation unit, the fifth calculation unit and the sixth calculation unit, wherein the outgoing line fault of the photovoltaic station falls into the maximum line range of the line protection range of the outgoing line of the photovoltaic station.
According to an embodiment of the invention, the analysis unit further comprises: and the second analysis unit is used for analyzing the delay action line range of the protection range of the line sent out from the photovoltaic station according to the second calculation unit, the third calculation unit, the fourth calculation unit, the fifth calculation unit and the sixth calculation unit.
The invention achieves the technical effects that: firstly, the method effectively solves the problem of the influence of the weak feed of the photovoltaic power supply on the distance protection; secondly, a self-adaptive distance polygon is obtained by measuring an impedance expression, and the self-adaptive distance polygon has better adaptability to high-resistance ground faults; and thirdly, by dividing action areas with different time limits, the correct action of the fault in the protection area is ensured, the fault outside the protection area is not mistakenly operated, and the stable and reliable operation of the photovoltaic station is guaranteed.
The above-mentioned serial numbers of the embodiments of the present application are merely for description, and do not represent the advantages and disadvantages of the embodiments.
In the above embodiments of the present application, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units or modules is only one logical division, and there may be other divisions when the actual implementation is performed, for example, a plurality of units or modules or components may be combined or integrated into another system, or some features may be omitted or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of modules or units through some interfaces, and may be in an electrical or other form.
The units or modules described as separate parts may or may not be physically separate, and parts displayed as units or modules may or may not be physical units or modules, may be located in one place, or may be distributed on a plurality of network units or modules. Some or all of the units or modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units or modules in the embodiments of the present application may be integrated into one processing unit or module, or each unit or module may exist alone physically, or two or more units or modules are integrated into one unit or module. The integrated unit or module may be implemented in the form of hardware, or may be implemented in the form of a software functional unit or module.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present application and it should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.
Claims (6)
1. The method for determining the line protection range of the fault point of the photovoltaic station outgoing line is characterized by comprising the following steps:
s1: determining a measured impedance expression of the power outlet of the photovoltaic station, wherein the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the total length of a sending line of the photovoltaic station, wherein the distance from a protective installation position to the fault point is the percentage; the Rg is a transition resistance;
z is MN Is the total impedance of the photovoltaic station outgoing line, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively the distribution coefficient of the positive sequence current and the distribution coefficient of the zero sequence current of the power supply of the photovoltaic station, D d In order to obtain the comprehensive coefficient of the image,
in the formula (2), Z SM1 And Z SN1 Respectively representing equivalent positive sequence impedances of an outlet and an inlet of the photovoltaic field station, wherein the equivalent positive sequence impedance of the outlet of the photovoltaic field station is determined by a positive sequence voltage fault value and a positive sequence current fault value of the outlet of the photovoltaic field station, and rho represents the ratio of electromotive force amplitudes of power supplies of the outlet and the inlet of the photovoltaic field station before a sending line of the photovoltaic field station fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the outlet line of the photovoltaic station;
s2: setting a fault location coefficient threshold value n max Maximum value of transition resistance Rg max ；
S3: acquiring positive sequence voltage and positive sequence current fault values at the protection installation position of the photovoltaic station outgoing line, and positive sequence impedance values equivalent to the outlet and the inlet of the photovoltaic station;
s4: according to the Z in the S1 M Expression, said n max The Rg max The determined values form an action boundary of a curved polygon, and a plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient which are axial coordinates;
s5: analyzing the line protection range of the fault point away from the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon;
in S4, the polygon includes:
a curve I, wherein the curve I indicates that when the fault position coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by values of the expression in the plane;
curve II, representing the fault location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M A curve formed by values of the expression in the plane;
curve III, representing that the fault location factor is from zero to n when the transition resistance Rg is zero max According to said Z M A curve formed by values of the expression in the plane;
curve IV indicating that the transition resistance is Rg max When the fault location coefficient is from zero to n max According to said Z M The values of the expression in the plane form a curve;
the polygon in S4 further includes:
a curve V, wherein the curve V shows that when the fault position coefficient is 0.8, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by values of the expression in the plane;
and a curve VI which shows that when the tail end of the adjacent line outside the fault point of the photovoltaic station outgoing line fails, the value of the transition resistor Rg is from zero to Rg max According to said Z M A curve formed by the values of the expression at the plane.
2. The method of claim 1, wherein analyzing the distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon in the S5 comprises:
and a plane defined by the curve V, the curve IV and the curve VI is the maximum line range of the protection range of the line of the outgoing line of the photovoltaic field station, wherein the line of the outgoing line of the photovoltaic field station is out of line.
3. The method according to claim 1, wherein the step S5 of analyzing the distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon further comprises:
and a plane defined by the curve II, the curve III, the curve IV, the curve V and the curve VI and the coordinate curve is a delay action line range of the protection range of the photovoltaic station outgoing line.
4. A system for determining line protection limits for a point of failure of a photovoltaic farm outgoing line, the system comprising:
a modeling unit for determining a measured impedance expression of the power outlet of the photovoltaic station, the measured impedance expression Z M Comprises the following steps:
in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the total length of a sending line of the photovoltaic field station, wherein the distance from a protective installation position to the fault point is the percentage; the Rg is a transition resistance;
z is MN Is the total impedance of the photovoltaic station outgoing line, Z Σ Is the sum of the impedances of the photovoltaic stations, C M1 And C M0 Respectively the distribution coefficient of the positive sequence current and the distribution coefficient of the zero sequence current of the power supply of the photovoltaic station, D d In order to obtain a comprehensive coefficient of the image,
in formula (2), Z SM1 And Z SN1 Respectively representing the equivalent positive sequence impedance of the outlet and the inlet of the photovoltaic field station, wherein the photovoltaic fieldThe station outlet equivalent positive sequence impedance is determined by a positive sequence voltage fault value and a positive sequence current fault value of the outlet of the photovoltaic station, and rho represents the ratio of the electromotive force amplitudes of the outlet and the inlet of the photovoltaic station before the outlet line of the photovoltaic station fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the outlet line of the photovoltaic station;
a setting unit for setting a fault location coefficient threshold value n max Maximum value of transition resistance Rg max ；
The acquisition unit is used for acquiring a positive sequence voltage and a positive sequence current fault value at a protection installation position of the photovoltaic station outgoing line and equivalent positive sequence impedance values of an outlet and an inlet of the photovoltaic station;
a calculation unit for calculating a Z value according to the Z in the modeling unit M Expression, said n in said setting unit max The Rg max The determined values form the action boundary of a curved polygon, and the plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient by axial coordinates;
the analysis unit is used for analyzing the line protection range from the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon;
a computing unit comprising:
a first calculating unit, configured to calculate that when the fault location coefficient n is zero, the value of the transition resistor Rg is from zero to Rg max According to said Z M Expressing the values of the expression in the plane;
a second calculation unit for calculating the failure location coefficient as n max When the transition resistance Rg takes a value from zero to Rg max According to said Z M Expressing values at said plane;
a third calculating unit, configured to calculate that the fault location coefficient is from zero to n when the transition resistance Rg is zero max According to said Z M Expressing values at said plane;
a fourth calculation unit for calculating the transition resistance Rg max When the fault location coefficient is from zero to n max According to said Z M Expressing values at said plane;
the computing unit further comprises:
a fifth calculating unit, configured to calculate, when the fault location coefficient is 0.8, a value of the transition resistor Rg from zero to Rgmax according to the Z M Expressing values at said plane;
a sixth calculating unit, configured to calculate that, when the end of the adjacent line outside the failure point of the outgoing line of the photovoltaic plant fails, the value of the transition resistance Rg ranges from zero to Rg max According to said Z M Values at the plane are expressed.
5. The system of claim 4, wherein the analysis unit comprises:
and the first analysis unit is used for analyzing the maximum line range of the line protection range of the outgoing line of the photovoltaic station according to the fourth calculation unit, the fifth calculation unit and the sixth calculation unit, wherein the outgoing line fault of the photovoltaic station falls into the maximum line range of the line protection range of the outgoing line of the photovoltaic station.
6. The system of claim 4, wherein the analysis unit further comprises:
and the second analysis unit is used for analyzing the delay action line range of the protection range of the line sent out from the photovoltaic station according to the second calculation unit, the third calculation unit, the fourth calculation unit, the fifth calculation unit and the sixth calculation unit.
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