Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a line protection method based on transition resistance calculation, which comprehensively utilizes the information of the electrical quantity of two ends of a line and the parameter information of the line to calculate the transition resistance of the line, uses the transition resistance as the fault quantity to judge whether a fault occurs in a line area, and has strong resistance to the transition resistance. After the invention is adopted, the transition resistance capability of line protection can be effectively improved, and high-resistance grounding faults can be reliably cut off.
The invention specifically adopts the following technical scheme:
a line protection method based on transition resistance calculation, the method comprising the steps of:
step 1: setting a first setting transition resistance R according to the voltage grade of the acquisition lineset1And a second setting transition resistance Rset2;
Step 2: acquiring voltage quantity and current quantity information of two sides of a line and related parameters of the line;
and step 3: calculating to obtain a line transition resistance R according to the line related parameters and the voltage amount and current amount information on two sides of the lineg;
And 4, step 4: based on the first setting transition resistance R set in the step 1set1Second setting transition resistance Rset2And the line transition resistance R in step 3gRespectively calculating the line transition resistance RgAnd a first setting transition resistance Rset1The difference of (A) is used as the first impedance difference X and the line transition resistance RgAnd a second setting transition resistance Rset2The difference of (a) is taken as a second impedance difference Y;
and 5: calculating the phase angle difference between the first impedance difference X and the second impedance difference Y according to the calculation result of the
step 4
Step 6: judging whether the calculation result of the step 5 is in a preset range, and if so, judging that a fault occurs in the line area; otherwise, no fault occurs in the line area;
and 7: and 6, removing the fault according to the judgment result of the step 6.
The invention further adopts the following preferred technical scheme:
in step 1, a first set transition resistance R is set by the following formulaset1:
Rset1=KK×Rmax
In the formula, KKFor a reliability factor, RmaxThe maximum transition resistance present on the line.
The transition resistance reliability coefficient KKThe value range is between 1.1 and 2.
In step 1, when metallic earth fault needs to be reflected, a second setting transition resistance Rset2Is a negative real number, and the value range is between-50 omega and-1 omega;
second setting transition resistance R when metallic earth fault does not need to be reflectedset2Is a positive real number not greater than the first setting transition resistance.
In the step 2, in the step of processing,
the voltage quantity and current quantity information on the two sides of the line comprises fundamental voltage, fundamental current and fundamental zero-sequence current information on the two sides of the line;
the line related parameters comprise line positive sequence impedance and line zero sequence compensation coefficients.
In the step 3, the line transition resistance is calculated by the following formula:
wherein i ═ A, B, C represents a phase a, a phase B and a phase C, respectively, and R represents
giIn order to calculate the resulting transition resistance,
and
are respectively the fundamental wave voltage at the two sides of the line,
and
are respectively the fundamental wave current at the two sides of the line,
and
respectively the fundamental zero-sequence current, Z, of both sides of the line
LThe positive sequence impedance of the line and K is the zero sequence compensation coefficient of the line.
The calculated line transition resistance RgiIs a plurality of numbers.
In step 4, the first impedance difference X and the second impedance difference Y are both complex numbers.
In a
step 6, the process is carried out,
and if not, determining that no fault occurs in the line area.
In step 7, when the judgment result in the step 6 is that a fault occurs in the line area, the fault is removed by a protection action;
and when the judgment result is that no fault occurs in the line area, the protection does not act.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a line protection method based on transition resistance calculation, which is characterized in that line transition resistance is calculated by comprehensively utilizing line double-end electrical quantity information and line parameter information, the phase angle difference of the impedance difference between the line transition resistance and a set transition resistance value is calculated, and whether a fault occurs in a line area is judged according to whether the phase angle difference exceeds a preset value range. The invention takes the transition resistance as the fault quantity, has extremely strong transition resistance capability, is little influenced by the change of the system operation mode, is simple and convenient to set, can effectively identify the high-resistance grounding fault of the line and realizes the quick and reliable removal of the fault in the line area.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only some embodiments, not all embodiments, and the scope of protection of the present application is not limited thereto. All other embodiments obtained by a person skilled in the art without making any inventive step on the basis of the spirit of the present invention are within the scope of protection of the present invention.
As shown in fig. 1, the line protection method based on transition resistance calculation specifically includes the following steps:
step 1: setting a first setting transition resistance R according to the voltage grade of the acquisition lineset1And a second setting transition resistance Rset2. Specifically, the first set transition resistance R is calculated according to the following formulaset1:
Rset1=KK×Rmax
In the formula, Rset1Is a first setting of the transition resistance, KKFor a reliability factor, RmaxThe maximum transition resistance that may occur on the line. Preferably, for a 220kV line, RmaxTaking the value as 100 omega; for 500kV lines, RmaxTaken as 300 omega.
Preferably, the transition resistance reliability factor KKShould be greater than 1, a value range between 1.1 and 2 is suggested.
Second setting transition resistance Rset2Is selected according to requirements, if metallic earth fault needs to be reflected, the second setting transition resistance Rset2Should be a negative real number, preferably between-50 Ω and-1 Ω; if metallic ground fault does not need to be reflected, a second setting transition resistance Rset2Should be a positive real number and should not be greater than the first setting transition resistance Rset1。
Step 2: and collecting the voltage quantity, the current quantity and the related parameters of the line at two ends of the line with the fault.
Preferably, the voltage amount and current amount information of the two sides of the line to be acquired includes fundamental voltage, fundamental current and fundamental zero-sequence current information of the two sides of the line, and the line-related parameters to be acquired include line positive-sequence impedance and line zero-sequence compensation coefficient.
Fig. 2 is a schematic diagram of a power transmission line structure according to an embodiment of the present invention, that is, a general model of a power transmission line in a power grid, where the model includes an M-side system power supply 1, an M-side system 2, an M-side bus 3, an M-side line protection 4, an N-side system power supply 8, an N-side system impedance 7, an N-side bus 6, and an N-side line protection 5. Fig. 3 is a schematic diagram of a power transmission line structure with a ground fault in an embodiment of the present invention. As shown in fig. 2 to 3, in one embodiment of the present invention, when a ground fault occurs on a line, information on the amount of voltage and the amount of current on both sides of the line and line-related parameters may be acquired. The method comprises the steps of obtaining fundamental voltage, fundamental current and fundamental zero-sequence current information of an M side end and an N side end respectively, and obtaining relevant line parameters including line positive-sequence impedance and line zero-sequence compensation coefficients.
And step 3: and (3) calculating to obtain the line transition resistance according to the line related parameters acquired in the step (2) and the voltage amount and current amount information on the two sides of the line.
Preferably, the formula for calculating the line transition resistance is:
wherein i ═ A, B, C represents a phase a, a phase B and a phase C, respectively, and R represents
giIn order to calculate the resulting transition resistance,
and
are respectively the fundamental wave voltage at the two sides of the line,
and
are respectively the fundamental wave current at the two sides of the line,
and
respectively the fundamental zero-sequence current, Z, of both sides of the line
LThe positive sequence impedance of the line and K is the zero sequence compensation coefficient of the line. And the calculated line transition resistance R
giIs a plurality of numbers. According to the above formula, A, B, C three-phase transition resistances can be calculated respectively.
And 4, step 4: based on the first setting transition resistance R set in the step 1set1Second setting transition resistance Rset2And the line transition resistance R in step 3gRespectively calculating the line transition resistance RgAnd a first setting transition resistance Rset1Differential, line transition resistance RgAnd a second setting transition resistance Rset2The difference of (a). That is to say that the first and second electrodes,
X=Rgi-Rset1
Y=Rgi-Rset2
wherein X is a line transition resistance RgAnd a first setting transition resistance Rset1The difference of (a) is recorded as a first impedance difference; y is line transition resistance RgAnd a second setting transition resistance Rset2The difference of (d) is recorded as a second impedance difference. And, the first impedance difference and the second impedance difference are both complex.
And 5: calculating the phase angle difference between the first impedance X and the second impedance Y according to the calculation result of the
step 4
Step 6: judging whether the calculation result of the step 5 is in a preset range, and if so, judging that a fault occurs in the line area; otherwise, no fault occurs in the line area.
In particular, when
And if not, determining that no fault occurs in the line area.
Fig. 4 is a schematic diagram of the discrimination of the intra-area fault according to the present invention. The transition resistance is used as the fault amount, whether the fault occurs in the line area is judged by using the transition resistance obtained by calculation, and the method has the advantage of strong transition resistance. The size of the transition resistance is irrelevant to the system operation mode, so the transition resistance protection method provided by the invention is less influenced by the change of the system operation mode.
When the system normally operates and a fault occurs outside a line area, the calculated line transition resistance theoretically should be infinite and does not meet the criterion. When the fault occurs in the line area, the calculated transition resistance is theoretically between 0 and RmaxIn between, the above criteria are met. As shown in FIG. 4, when the calculated transition resistance of each phase satisfies the above criterion, the transition resistance falls within the impedance circle in FIG. 4, and it is determined that the phase has occurredA line zone internal fault.
And 7: based on the judgment result of the step 6, if the fault in the line area is judged to occur, the fault is removed by protection action; and if the fault does not occur in the route area, the protection does not act.
Compared with the prior art, the line protection method based on the transition resistance calculation has the advantages that the line transition resistance is obtained through calculation by comprehensively utilizing the electrical quantity information of the two ends of the line and the parameter information of the line, whether a fault occurs in a line area is judged by comparing the calculated line transition resistance with the set transition resistance, and the transition resistance resisting capability is strong. The size of the transition resistance is irrelevant to the system operation mode, so the transition resistance protection method provided by the invention is less influenced by the change of the system operation mode. The invention takes the transition resistance as the fault quantity, has extremely strong transition resistance capability, is little influenced by the change of the system operation mode, is simple and convenient to set, can effectively identify the high-resistance grounding fault of the line and realizes the quick and reliable removal of the fault in the line area.
While the best mode for carrying out the invention has been described in detail and illustrated in the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the invention should be determined by the appended claims and any changes or modifications which fall within the true spirit and scope of the invention should be construed as broadly described herein.