Graded protection configuration method for power distribution network with fast magnetic control switch

Abstract

The invention discloses a grading protection configuration method for a power distribution network with a fast magnetic control switch, and the method comprises the steps: installing the fast magnetic control switch at a preset position below an outlet switch of a transformer substation, and enabling the fast magnetic control switch to replace the I-section protection function of the transformer substation, and to protect the I-section protection function in a near region range; exiting the overcurrent I-section protection of the outlet switch of the transformer substation, and setting the action time of the overcurrent II-section protection of the outlet switch of the transformer substation to be 0.6 s; setting the overcurrent I-section protection action time of the rapid magnetic control switch to be 0.02 s; setting the overcurrent II section protection action time of the rapid magnetic control switch to be 0.5 s; a section switch is arranged in a distribution network line, and the overcurrent I section protection action time of the section switch is set to be 0 s; and the over-current II section protection action time of the section switch is set to be 0.3 s. On the basis of power distribution network line model data, a power distribution network protection grading configuration mode containing the rapid magnetic control switch is calculated, the fault duration time is greatly shortened, and the voltage sag problem is effectively relieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power distribution, and particularly relates to a power distribution network hierarchical protection configuration method containing a fast magnetic control switch. BACKGROUND

[0002] Voltage sag is an inherent phenomenon of power grid when encountering disturbance. When the power grid is subjected to lightning, flood and external damage, or large motor, capacitor and other equipment are put into operation, voltage will drop for different degrees and different durations, causing the under-voltage protection action of voltage sensitive equipment such as frequency converter and servo driver in enterprises, resulting in equipment shutdown, and further causing the interruption of enterprise production. The voltage sag shutdown event is one of the core problems of power quality management of the power distribution network.

[0003] The equipment shutdown caused by voltage sag contains two essential factors: the duration of voltage sag and the depth of voltage sag. The depth of voltage sag is related to system impedance, fault type and fault location, which is an uncontrollable factor and is difficult to optimize by technical means. The duration of voltage sag is mainly determined by the fault clearance time, but the traditional hierarchical protection of power distribution network has limited prevention and control. SUMMARY

[0004] The application provides a power distribution network hierarchical protection configuration method containing a fast magnetic control switch, which is used for quickly removing faults and effectively reducing the shutdown risk of sensitive equipment, and is a powerful technical measure for voltage sag prevention and control of the power distribution network.

[0005] The application provides a power distribution network hierarchical protection configuration method containing a fast magnetic control switch, which comprises:

[0006] A fast magnetic control switch is installed at a preset position below the outlet switch of the substation, and the fast magnetic control switch is used to replace the I-section protection function of the substation and protect the range outside the near area;

[0007] The overcurrent I-section protection of the outlet switch of the substation is exited, and the overcurrent II-section protection action time of the outlet switch of the substation is set to 0.6s, wherein the current setting value of the overcurrent II-section of the outlet switch of the substation is set according to the maximum load current of the line;

[0008] The overcurrent I-section protection action time of the fast magnetic control switch is set to 0.02s, wherein the current setting value of the overcurrent I-section of the fast magnetic control switch is set according to the minimum fault current value at the end of the near area range;

[0009] The overcurrent II-section protection action time of the fast magnetic control switch is set to 0.5s, wherein the current setting value of the overcurrent II-section of the fast magnetic control switch is set according to the maximum load current of the line;

[0010] The sectionalizing switch is arranged outside the critical distance, and the overcurrent I section protection action time of the sectionalizing switch is set to 0s, wherein the current setting value of the overcurrent I section of the sectionalizing switch is set according to the minimum fault current value at the end of the line;

[0011] The overcurrent II section protection action time of the sectionalizing switch is set to 0.3s, wherein the current setting value of the overcurrent II section of the sectionalizing switch is differentially matched with the overcurrent II section protection of the outlet switch of the transformer substation.

[0012] Further, the fast magnetic control switch adopts a direct-acting transmission structure, and the sum of the protection action time and the opening action time of the fast magnetic control switch is controlled to be less than 25ms.

[0013] Further, the calculation of the near-zone range is based on a voltage divider circuit model, the critical distance is determined through the line impedance and the system impedance between the fault point and the outlet point of the transformer substation, and then the size of the near-zone range is determined, wherein the expression for calculating the critical distance is:

[0014]

[0015] In the formula, l crit is the critical distance, Z s is the system impedance between the outlet point of the transformer substation and the power supply, Z is the unit length line impedance, and U is the critical voltage.

[0016] Further, a fast fuse is arranged at the front end of the preset abnormal branch line, the overcurrent I section protection action time of the fast fuse is set to 0s, and the overcurrent II section protection current time of the upper-level switch is greater than the full opening time of the fuse under the same size short-circuit current.

[0017] The power distribution network grading protection configuration method with the fast magnetic control switch provided by the application is based on the model data of the power distribution network, calculates the grading protection configuration mode of the power distribution network with the fast magnetic control switch, greatly reduces the fault duration time, and effectively alleviates the occurrence of voltage sag problems. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The sectionalizing switch of the application is provided with a schematic diagram of the sectionalizing switch of the application.

[0020] Figure 2A voltage divider model schematic diagram of voltage sag for an embodiment of the present application is provided. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] By installing a fast magnetic control switch, the I-section protection function of the substation is replaced by the fast magnetic control switch, and the magnetic control switch is required to be protected to the near zone range outside, and the fault in the range is quickly removed, so as to effectively avoid the voltage sag phenomenon, and the main principle is as follows:

[0023] The schematic diagram of the grading protection setting of the distribution network containing the magnetic control switch is shown in Figure 1 On the one hand, the magnetic control switch can remove the fault within 25 ms, and almost all pole-mounted sectional switches need to be tripped within 150 ms after the fault occurs; on the other hand, the voltage sag phenomenon brings huge economic losses to sensitive enterprises, and needs to reduce the sag depth and sag time, which can be achieved by quickly removing the fault by the magnetic control switch to make the sensitive equipment pass through the sag. Therefore, the magnetic control switch is installed at the 01# pole below the outlet switch of the substation, and the fast magnetic control switch needs to be protected to the near zone range, and the fault in the range is quickly removed to reduce the voltage sag depth and duration.

[0024] Under the existing technical conditions, almost all pole-mounted sectional switches can be tripped within 150 ms after the fault occurs, so the grading time difference of the distribution network line switch should be at least not less than 0.2 s, so as to effectively cooperate with the time. In addition, considering the influence of the magnetizing inrush current during power transmission of the distribution network, the last section time setting value of each level of protection should be not less than 0.3 s, so as to effectively avoid the magnetizing inrush current misoperation. The outlet switch of the distribution network line containing the fast magnetic control switch exits the I-section protection, and the II-section protection action time is 0.6 s; the magnetic control switch is divided into two sections: 0.02 s and 0.5 s, and the I-section protection range is within the near zone range of the substation; the sectional switch: 0 s and 0.3 s.

[0025] A grading protection configuration method of a distribution network containing a fast magnetic control switch, specifically comprising:

[0026] Step 1, installing a fast magnetic control switch at a preset position below the outlet switch of the substation, the fast magnetic control switch is used to replace the I-section protection function of the substation, and is protected to the near zone range inside.

[0027] In particular, the radial system in the power grid, available Figure 2 The voltage divider circuit schematic diagram is shown. Assuming the power supply voltage E = 1, the substation outlet voltage sag residual voltage U dip is:

[0028]

[0029] In the formula, Z F is the line impedance between the fault point and the substation outlet; Z S is the system impedance between the PCC point and the power supply.

[0030] Let Z F = zl, l is the distance between the fault point and the substation outlet, and z is the unit length line impedance. It can be obtained that:

[0031]

[0032] When the substation outlet voltage decreases to equal the critical voltage U, the distance between the fault point and the substation outlet is defined as the critical distance. Assuming that the X / R value of the line impedance and the system impedance is equal, the critical distance is:

[0033]

[0034] In the formula, l crit is the critical distance, Z s is the system impedance between the substation outlet and the power supply, z is the unit length line impedance, and U is the critical voltage.

[0035] The related fault occurring within the critical distance l crit will cause the sensitive load at the substation outlet to be abnormally operated. By referring to the Electrical Handbook, the unit length resistance reactance values of various conductors can be obtained. When the critical voltage U is set to 70%, the substation near-zone distance under different conductor conditions is shown in Table 1.

[0036] Table 1 Substation near-zone distance under different conductor conditions

[0037]

[0038] Step 2, exit the overcurrent I section protection of the substation outlet switch, and set the overcurrent II section protection action time of the substation outlet switch to 0.6s, wherein the current setting value of the overcurrent II section of the substation outlet switch is set according to the maximum load current.

[0039] In particular, the substation outlet switch protection setting value is set as follows:

[0040] (1) Overcurrent I section setting

[0041] To avoid the same jump phenomenon with the fast magnetic control switch, exit substation outlet overcurrent I section protection.

[0042] (2) Overcurrent II section setting

[0043] The overcurrent II section time setting is 0.6s, and the current setting is set according to the maximum load current of the line:

[0044] I c2 ≥K k *I fhmax

[0045] In the formula, I c2 is the overcurrent II section current setting of the substation outlet switch, K k is the reliability coefficient, which is 1.1; I fhmax is the maximum load current of the line in the annual operation mode, which can be queried according to historical records.

[0046] Step 3, the overcurrent I section protection action time of the fast magnetic control switch is set to 0.02s, wherein the overcurrent I section current setting of the fast magnetic control switch is set according to the minimum fault current at the end of the near area range.

[0047] Step 4, the overcurrent II section protection action time of the fast magnetic control switch is set to 0.5s, wherein the overcurrent II section current setting of the fast magnetic control switch is set according to the maximum load current of the line.

[0048] Specifically, the fast magnetic control switch protection setting is:

[0049] (1) Overcurrent I section setting

[0050] The fast magnetic control switch is installed on the overhead line 01# tower of the sensitive enterprise bus which often fails, the overcurrent I section time setting is 0.02s, which ensures that the overcurrent I section quickly removes the fault and reduces the temporary drop time, and the delay is 20ms to facilitate cooperation with the branch line fast fuse. Before the fuse is completely fused, the magnetic control switch does not act. The overcurrent I section current setting is set according to the minimum fault current at the end of the near area range, that is:

[0051]

[0052] In the formula: I k1 is the overcurrent I section current setting of the magnetic control switch; is the two-phase short-circuit fault current at the end of the near area range under the minimum operation mode, that is, at the setting position of the sectional switch.

[0053] (2) Overcurrent II section setting

[0054] The overcurrent II section time setting is 0.5s, and the current setting is set according to the maximum load current of the line:

[0055] I k2 ≥K k *I fhmax ,

[0056] I k2 is the current setting value of the over-current I section of the magnetic control switch.

[0057] Step 5, set a sectional switch in the distribution network line, and set the over-current I section protection action time of the sectional switch to 0 s, wherein the current setting value of the over-current I section of the sectional switch is set according to the minimum fault current value at the end of the line.

[0058] Step 6, set the over-current II section protection action time of the sectional switch to 0.3 s, wherein the current setting value of the over-current II section of the sectional switch is differentially matched with the over-current II section protection of the outlet switch of the substation.

[0059] Specifically, the sectional switch protection setting value is set as

[0060] (1) Over-current I section setting

[0061] The over-current I section time setting value of the sectional switch is set to 0 s, and the I section current setting value of the sectional switch is set to I d1 according to the minimum fault current value at the end of the line:

[0062]

[0063] wherein, is the two-phase short-circuit current at the end of the line in the minimum operation mode.

[0064] (2) Over-current II section setting

[0065] The over-current II section time setting value of the sectional switch is set to 0.3 s, and the over-current II section current setting value of the sectional switch is set to I d2 differentially matched with the over-current II section protection of the outlet switch of the substation, and the setting method is as follows:

[0066] I d2 ≤K p *I c2 ,

[0067] wherein, K p is a matching coefficient, and is 0.9; I c2 is the over-current II section setting value of the outlet switch of the substation.

[0068] In one specific embodiment, for the fault hidden point, the history frequent trip or the branch line connected with the sensitive enterprise, the fast fuse can be installed at the front end, the protection time setting value is 0s, and the current time of the upper end protection is greater than the full opening time of the fuse under the same size short-circuit current. Cooperate with the upper end setting value, that is, before the upper switch acts under the end setting value in the fault, the fuse has been fused.

[0069] The fuse can be selected according to the time-current curve: 1) the rated current of the rear load; 2) not fused under the closing excitation inrush current; 3) the current time of the upper end protection is greater than the full opening time of the fuse under the same size short-circuit current.

[0070] In summary, the method of the application is based on the distribution network line model data, calculates the protection grading configuration mode of the distribution network containing the fast magnetic control switch, greatly reduces the fault duration time, and effectively alleviates the occurrence of voltage sag problem.

[0071] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A power distribution network hierarchical protection configuration method containing fast magnetic control switch, characterized in that, The application relates to a power distribution network protection method and device. A quick magnetic control switch is installed at a preset position below a substation outlet switch, the quick magnetic control switch is used to replace the I-section protection function of the substation, and the quick magnetic control switch is used to protect the range outside the near area; The overcurrent I-section protection of the substation outlet switch is exited, and the overcurrent II-section protection action time of the substation outlet switch is set as 0.6s, wherein the current fixed value of the overcurrent II-section of the substation outlet switch is set according to the maximum load current of the line; The overcurrent I-section protection action time of the quick magnetic control switch is set as 0.02s, wherein the current fixed value of the overcurrent I-section of the quick magnetic control switch is set according to the minimum fault current of the end of the near area range; The overcurrent II-section protection action time of the quick magnetic control switch is set as 0.5s, wherein the current fixed value of the overcurrent II-section of the quick magnetic control switch is set according to the maximum load current of the line; A section switch is arranged in the distribution network line, the section switch is arranged outside the critical distance, the overcurrent I-section protection action time of the section switch is set as 0s, wherein the current fixed value of the overcurrent I-section of the section switch is set according to the minimum fault current of the end of the line; The overcurrent II-section protection action time of the section switch is set as 0.3s, wherein the current fixed value of the overcurrent II-section of the section switch is differentially matched with the overcurrent II-section protection of the substation outlet switch.

2. The power distribution network hierarchical protection configuration method with fast magnetic control switch according to claim 1, characterized in that, The quick magnetic control switch adopts a direct-acting transmission structure, and the sum of the protection action time and the opening action time of the quick magnetic control switch is controlled within 25ms.

3. The power distribution network hierarchical protection configuration method with fast magnetic control switch according to claim 1, characterized in that, The near area range is calculated based on a voltage distributor circuit model, the critical distance is determined through the line impedance and the system impedance between a fault point and the substation outlet, and then the size of the near area range is determined, wherein the expression for calculating the critical distance is: where l crit is the critical distance, Z s is the system impedance between the substation outlet and the power source, z is the line impedance per unit length, and U is the critical voltage.

4. The power distribution network hierarchical protection configuration method with fast magnetic control switch according to claim 1, characterized in that, A quick fuse is arranged at the front end of a preset abnormal branch line, the overcurrent I-section protection action time of the quick fuse is set as 0s, and the overcurrent II-section protection current time of the upper switch is greater than the full opening time of the fuse under the same size short-circuit current.

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