An energy-saving customized real-type test load system

Abstract

The present invention belongs to the technical field of distribution network active intervention type arc extinguishing device test system, and in particular, relates to an energy-saving customized real test load system, including an isolated test system and a 10kV power supply, the test system includes a step-down transformer, a step-up transformer and a line with an energy-saving customized load, the 10kV power supply is connected to the step-down transformer and the step-up transformer in sequence, the step-up transformer is connected to the line with the energy-saving customized load; the step-up transformer is connected to the bus; the line with the energy-saving customized load includes a series-connected substation transformer and an energy-saving customized load; the output end of the energy-saving customized load is connected to the low-voltage side of the step-down transformer and the low-voltage side of the step-up transformer. The present invention realizes the arbitrary configuration of the test line load without causing the loss of the same capacity as the test load, improves the load capacity, and realizes the dual simulation of the power load and the power generation load.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution network active intervention type arc extinguishing device test system, and in particular relates to an energy-saving customized true type test load system. Background Art

[0002] The distribution network is the connecting bridge between the power grid and users, and plays a key role in the distribution of power in the power grid. The grounding fault of the distribution network is the most common and most frequent fault type in the operation of the distribution network, and it is also one of the main factors causing power outages due to distribution network faults. At present, my country's distribution network mainly adopts the following three methods: (1) automatic arc suppression coil grounding, which is the main application method of the distribution network; (2) resistance grounding method, which is mainly used in the distribution network of large and medium-sized cities such as Beijing, Shanghai and Guangzhou, which are mainly based on cables; (3) neutral point insulation method, which is mainly used in rural distribution networks dominated by small-scale overhead lines.

[0003] my country's 10kV distribution network generally adopts a low-current grounding form of ungrounded or grounded through an arc suppression coil. Due to the weak steady-state fault current, complex grounding process, unstable arc, etc., the line selection and location of single-phase grounding faults in the distribution network has become a problem that has troubled the site for many years, both at home and abroad. For a long time, the original manual wire pulling method has been used to select the line for the treatment of single-phase grounding faults in the distribution network. This method is inefficient and has poor power supply reliability and economy.

[0004] Chinese invention application CN103021241A discloses a low-voltage power system dynamic simulation system, which includes a generator set, a transmission and distribution transformer, a physical model of the line, a load and a distribution network; the transmission and distribution transformer converts high voltage electricity into low voltage; the physical model of the line calculates the values ​​of resistance, capacitance and inductance according to the equivalent circuit, and uses resistance, capacitance and inductance to build an equivalent circuit of the power line. However, this experimental system occupies a very large area, the topological structure of the test model is not easy to change, it does not have the grounding method simulation of the distribution network, and cannot meet the dual simulation of the electric load and the power generation load.

[0005] Chinese invention application CN110609202A discloses a real-type simulation test device for intermittent arc grounding in a 10kV-66kV distribution network. The application includes an MCU processing unit, a keypad, a switch output unit, and an intermittent arc grounding trigger unit connected between the phase line and the ground in the distribution network; arc generation is controlled by controlling the controlled end of the intermittent arc grounding trigger unit. This test device only performs arc grounding tests in a real 10kV-66kV system, and is subject to many restrictions and cannot achieve dual simulation of electrical load and power generation load. Summary of the invention

[0006] The purpose of the present invention is to provide an energy-saving customized true test load system to address the problems existing in the prior art, to achieve arbitrary configuration of the test line load without causing loss of capacity equivalent to the test load, to increase the load capacity, and to achieve dual simulation of electrical load and power generation load.

[0007] The technical solution of the present invention is:

[0008] An energy-saving customized true test load system comprises an isolated test system and a 10kV power supply, wherein the test system comprises a step-down transformer, a step-up transformer and a circuit with an energy-saving customized load, wherein the 10kV power supply is connected in sequence to the step-down transformer and the step-up transformer, wherein the step-up transformer is connected to the circuit with the energy-saving customized load; wherein the step-up transformer is connected to a busbar; wherein the circuit with the energy-saving customized load comprises a substation transformer and an energy-saving customized load connected in series; wherein the output end of the energy-saving customized load is connected to the low-voltage side of the step-down transformer and the low-voltage side of the step-up transformer.

[0009] Specifically, the energy-saving customized load is based on a parallel type of multiple load modules, with the load-side circuit breaker connected to the substation transformer, and the energy-feeding-side circuit breaker connected to the low-voltage side of the step-down transformer; a single load module adopts a back-to-back AC-DC converter structure.

[0010] Specifically, the protection logic of the energy-saving customized load includes external protection and internal protection of the device; the external protection includes input / output side current overcurrent protection, short circuit protection, voltage out-of-bounds protection, phase loss protection and power-off protection; the internal protection includes device short circuit protection, bus overvoltage / undervoltage protection, positive and negative voltage imbalance protection when using a multi-level structure, and circulating current protection during modular parallel connection.

[0011] Specifically, the overcurrent protection requires relay parameter setting, and the relay parameter setting includes the following steps: setting four parameters, including two time constant parameters (t set1ij , t set2ij ) and two current constant parameters (I set1ij , I set2ij ) The time setting parameters are determined by the fault current characteristics and the time required for removal; the time setting parameters are selected as t set1ij =1ms and t set2ij =2ms; the minimum fault current I fminij and maximum operating current I opmaxij With the appropriate current I selected set1ij For comparison; if I opmaxij Less than I fminij , then set I set1ij =I fminij ;if Iopmaxij Greater than I fminij , then set I set1ij =I opmaxij ; When I is defined set2ij When protecting R ij It can be used as a backup protection for the lower level protection; at the same time, if I opmaxij If the current is not within the range defined by the backup protection zone, it is also necessary to define I set2ij .

[0012] Specifically, the overcurrent protection comprises the following steps:

[0013] S1, Processing P = 1, K ij =0 and K ji =0;

[0014] S2. Determine whether S is satisfied ijk =1 and I fijk Greater than I opmaxij When processing d=1, K ij =K ij +1 and go to step S3; if S is not satisfied ijk =1 and I fijk Greater than I opmaxij When d=0, proceed to step S3;

[0015] S3. Determine whether S is satisfied jik =1 and I fjik Greater than I opmaxji When processing K ji =K ji +1, go to step S4; if S is not satisfied jik =1 and I fjik Greater than I opmaxji When it is determined that d=0 is satisfied, differential protection is used in the line section; if d=0 is not satisfied, the process goes to step S4;

[0016] S4, when it is determined that P=n is satisfied, go to step S5; if P=n is not satisfied, set P=P+1 and go to step S2;

[0017] S5. Determine whether K is satisfied ij =n, go to step S6; if K is not satisfied ij =n, go to step S7;

[0018] S6. Determine whether K is satisfied ji =n, R ij or R ji Put into operation; if K is not met ji =n, R ij Put into operation;

[0019] S7. Determine whether K is satisfiedji =n, R ji Put into operation; if K is not met ji =n,R ij and R ji Put into operation;

[0020] Where n is the number of nodes, n≥i≥1, n≥j≥1; n-1≥P≥1, P is the number of different structures that the line can form; R ij For installation in line L ij Overcurrent protection at the head end; R ji For installation in line L ij Overcurrent protection at the end; I opmaxij To protect R ij The maximum operating current reflected; K ij ≥0, K ji ≥0, K ij and K ji R ij and R ji The number of different structures formed by the protected lines; S ijk =1 means protection R ij Identified the Kth th The fault current of the line structure, that is, the fault current I fijk Greater than I opmaxij ; d = 1 means that the fault can be controlled by protection R ij Identification; d = 0 means that the fault cannot be protected by R ij Identify; Protect R ij Able to identify line L ij When all possible faults within K ij =n; if protection R ij Unable to identify line L ij When all possible faults are within the ij and R ji Need to be put into operation at the same time.

[0021] Specifically, the R ij and R ji The commissioning consists of two stages: setting the protection R ij The main protection area covers the line L ij All and feeder lines, protect R ij The reserve protection area includes line L i+1，j+1 ; Line L i+1，j+1 The main protection is R i+1，j+1 ;

[0022] The first stage: at time t set1ij In case of a fault, the protection R ij Identify the fault; when the protection Rij The detected fault current is greater than I fminij When the protection triggers the tripping coil;

[0023] The second stage: When i <j、I fmin(i+1，j+1) <I<I fminij or <i、I fmin(i-1，j-1) <I<I fminij When the forward fault current is within the above two conditions, the protection R ij At time t set2ij Running in backup protection function; t set1ij and t set2ij The step difference is set to 0.5s to ensure the selectivity of system protection.

[0024] With the mature application of microcomputer technology, more single-phase grounding fault line selection and positioning methods based on microcomputers have been applied, but the line selection and positioning devices in field operation are not ideal. There are many reasons for this. One important factor is that although there are many line selection products for single-phase grounding faults in small current grounding systems on the market, the quality is uneven, and many products have not been systematically tested and verified. Although simulation based on simulation and test platforms has the advantages of comprehensive simulation results and good visibility, it cannot fully reflect the nature of field faults in distribution networks. It is feasible to discover problems through field applications, but its efficiency is too low, as follows:

[0025] (1) It may take a long time to encounter a fault on site;

[0026] (2) The fault scenarios and operating conditions experienced by the field devices are limited, making it difficult to fully examine their performance;

[0027] (3) The on-site fault data record is not comprehensive, which is not conducive to problem analysis, and thus the fault cannot be effectively recorded and restored, which is not conducive to timely discovery of defects and subsequent product improvement.

[0028] As the distribution network directly connects users and the power transmission network, the above-mentioned technical problems faced by it in handling single-phase grounding faults are becoming increasingly prominent.

[0029] The positive and beneficial effects of the present invention are as follows: the energy-saving customized load has energy-saving characteristics, and the large load current passing through the line load side can be injected into the power supply end through the energy feeding side, thereby reducing the test loss and playing an energy-saving role; at the same time, the energy-saving customized load has customized characteristics, and can work in the power generation or power consumption state according to the test needs, and realize the simulation of typical test loads such as wind power, photovoltaics, steel rolling, elevators, etc. through the controller.

[0030] The test system provided by the present invention is isolated from the power supply system, which effectively ensures the safety of the test; by adopting an energy-saving customized load topology structure based on a modular parallel type, it is convenient to increase the load capacity and mass produce the load units; a single load module adopts a back-to-back AC-DC converter structure, has four-quadrant operation capability, and can realize dual simulation of power load and power generation load. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a topological diagram of an energy-saving customized real test load system provided in Example 1;

[0032] Figure 2 This is a schematic diagram of an energy-saving customized load structure based on a modular parallel type provided in Example 1;

[0033] Figure 3 is a topological diagram of a single-stage energy storage device provided in Example 2;

[0034] Figure 4 It is a flow chart based on overcurrent protection steps provided in Example 2;

[0035] Figure 5 is a schematic diagram of the characteristics of the overcurrent protection relay provided in Example 2;

[0036] Figure 6 This is a schematic diagram of the overcurrent protection relay parameter setting process provided in Example 2. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0038] Example 1

[0039] like Figure 1 Shown is a topological diagram of an energy-saving customized true test load system provided by the present embodiment, which includes an isolated test system and a 10kV power supply. The test system includes a step-down transformer, a step-up transformer and a line with an energy-saving customized load. The 10kV power supply is connected to the step-down transformer and the step-up transformer in sequence, and the step-up transformer is connected to the line with the energy-saving customized load; the step-up transformer is connected to the busbar; the line with the energy-saving customized load includes a substation transformer and an energy-saving customized load connected in series; the output end of the energy-saving customized load is connected to the low-voltage side of the step-down transformer and the low-voltage side of the step-up transformer.

[0040] The energy-saving customized load is based on a parallel type of multiple load modules, with the load-side circuit breaker connected to the substation transformer, and the energy-feeding-side circuit breaker connected to the low-voltage side of the step-down transformer; a single load module adopts a back-to-back AC-DC converter structure.

[0041] Connect energy-saving customized loads under the substation of a 10kV line to isolate the test system from the power system to ensure the safety of the test. It can realize any configuration of the test line load without causing loss of the same capacity as the test load. When conducting a large-load real-type test, only the converter itself is lost, which is usually less than 5% of the load capacity. Figure 2 The figure shows a schematic diagram of the energy-saving customized load structure based on the modular parallel type provided in this embodiment. The test system includes an energy feedback side and a load simulation. The load simulation is connected to the bus to be tested through a transformer to simulate different loads. The energy feedback side is connected to the energy feedback bus to feed energy back to the power grid. The electronic load mainly consists of a cabinet, which has been equipped with distribution equipment, 6-8 AC to DC power electronic equipment, including 1 unit with a power of 50kW, 2 units with a power of 100kW, 3 units with a power of 150kW, 4 units with a power of 200kW, 5 units with a power of 250kW, and 10 units with a power of 500kW. There is also a human-machine interface, which is installed on the cabinet door. It has high grid friendliness, can simulate a variety of load characteristics, has simple adjustment, modular design, and convenient maintenance, with an efficiency of up to 95%, comprehensive protection functions, and is safe and reliable. By adopting a modular parallel type energy-saving customized load topology structure, it is convenient to increase the load capacity and mass produce the load unit; a single load module adopts a back-to-back AC-DC converter structure, has a four-quadrant operation capability, and can realize dual simulation of power load and power generation load. It can effectively carry out fault reproduction, product testing, teaching and training, and has the actual measurement and verification function of the fault line selection device.

[0042] Example 2

[0043] The difference between this embodiment and embodiment 1 is that the protection logic of the energy-saving customized load is provided, including external protection and internal protection of the device; wherein the external protection includes input and output side current overcurrent protection, short circuit protection, voltage out-of-bounds protection, phase loss protection and power-off protection, etc.; the internal protection includes device short circuit protection, bus overvoltage / undervoltage protection, positive and negative voltage imbalance protection when a multi-level structure is adopted, and circulating current protection when modular parallel connection is used. The energy-saving customized load can customize the size, phase, rate of change, power factor and action timing of the load according to the actual load type and true test requirements. Figure 3The figure shows the topology of a single-stage energy storage device. The test system includes a modular single-stage energy storage device, which is mainly composed of a cabinet (distribution equipment has been configured in the cabinet), 1-10 AC-DC power electronic devices (50kW / 1 unit, 100kW / 2 units, 150kW / 3 units, 200kW / 4 units, 250kW / 5 units, 500kW / 10 units), 1 STS static transfer switch (optional), 1 isolation transformer (optional), 1 human-machine interface (installed on the cabinet door), mainly composed of one or more AC-DC power electronic devices, and the cabinet is also equipped with lightning arresters, AC / DC circuit breakers and other distribution units and STS units (on-grid and off-grid switching devices).

[0044] like Figure 4 As shown, the specific steps of the overcurrent protection are as follows:

[0045] S1, Processing P = 1, K ij =0 and K ji =0;

[0046] S2. Determine whether S is satisfied ijk =1 and I fijk Greater than I opmaxij When processing d = 1, K ij =K ij +1 and go to step S3; if S is not satisfied ijk =1 and I fijk Greater than I opmaxij When d=0, proceed to step S3;

[0047] S3. Determine whether S is satisfied jik =1 and I fjik Greater than I opmaxji When processing K ji =K ji +1, go to step S4; if S is not satisfied jik =1 and I fjik Greater than I opmaxji When it is determined that d=0 is satisfied, differential protection is used in the line section; if d=0 is not satisfied, the process goes to step S4;

[0048] S4, when it is determined that P=n is satisfied, go to step S5; if P=n is not satisfied, set P=P+1 and go to step S2;

[0049] S5. Determine whether K is satisfied ij =n, go to step S6; if K is not satisfied ij =n, go to step S7;

[0050] S6. Determine whether K is satisfied ji =n, R ij or R jiPut into operation; if K is not met ji =n, R ij Put into operation;

[0051] S7. Determine whether K is satisfied ji =n, R ji Put into operation; if K is not met ji =n,R ij and R ji Put into operation;

[0052] Where n is the number of nodes, n≥i≥1, n≥j≥1; n-1≥P≥1, P is the number of different structures that the line can form; R ij For installation in line L ij Overcurrent protection at the head end; R ji For installation in line L ij Overcurrent protection at the end; I opmaxij To protect R ij The maximum operating current reflected; K ij ≥0, K ji ≥0, K ij and K ji R ij and R ji The number of different structures formed by the protected lines; S ijk =1 means protection R ij Identified the Kth th The fault current of the line structure, that is, the fault current I fijk Greater than I opmaxij ; d = 1 means that the fault can be controlled by protection R ij Identification; d = 0 means that the fault cannot be protected by R ij Identify; Protect R ij Able to identify line L ij All possible faults within K ij =n; if protection R ij Unable to identify line L ij When all possible faults are within the ij and R ji They must be put into operation at the same time. ij When any fault occurs in the circuit, it can be ij Overcurrent protection R ij Or the overcurrent protection R ji Protect, protect R ij and R ji The positive direction is when it points into the line.

[0053] like Figure 5 As shown, the R ij and Rji The commissioning consists of two stages: setting the protection R ij The main protection area covers the line L ij All and feeder lines, protect R ij The reserve protection area includes line L i+1，j+1 ; Line L i+1，j+1 The main protection is R i+1，j+1 ;

[0054] The first stage: at time t set1ij In case of a fault, the protection R ij Identify the fault; in order to identify all possible faults, the minimum value of the fault current I fminij need to be taken into account; when protecting R ij The detected fault current is greater than I fminij When the protection triggers the tripping coil;

[0055] The second stage: When i <j、I fmin(i+1，j+1) <I<I fminij or <i、I fmin(i-1，j-1) <I<I fminij When the forward fault current is within the above two conditions, the protection R ij At time t set2ij Running in backup protection function; t set1ij and t set2ij The step difference is set to 0.5s to ensure the selectivity of system protection.

[0056] like Figure 6 As shown, the overcurrent protection relay parameter setting includes the following steps: setting four parameters, including two time setting parameters (t set1ij , t set2ij ) and two current constant parameters (I set1ij , I set2ij ) The time setting parameters are determined by the fault current characteristics and the time required for removal; considering the high transient and large amplitude of the fault current in the system, the time setting parameters are selected as t set1ij =1ms and t set2ij =2ms; the current setting parameters are determined by the diagram, and the minimum fault current I fminij and maximum operating current I opmaxij With the appropriate current I selected set1ij For comparison; if I opmaxij Less than I fminij , then set I set1ij =I fminij ;if I opmaxij Greater than I fminij , then set I set1ij =I opmaxij ; When I is definedset2ij When protecting R ij It can be used as a backup protection for the lower level protection; at the same time, if I opmaxij If the current is not within the range defined by the backup protection zone, it is also necessary to define I set2ij .

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention. Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be equivalently substituted without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. An energy-saving customized real-type test load system, characterized in that: It includes an isolated test system and a 10kV power supply, wherein the test system includes a step-down transformer, a step-up transformer and a line with an energy-saving customized load; The 10kV power supply is connected to the step-down transformer and the step-up transformer in sequence, and the step-up transformer is connected to the line with the energy-saving customized load; The step-up transformer is connected to the busbar; The line with energy-saving customized load includes a station area transformer and an energy-saving customized load connected in series; The output end of the energy-saving customized load is connected to the low-voltage side of the step-down transformer and the low-voltage side of the step-up transformer; The protection logic of the energy-saving customized load includes external protection and internal protection of the device; the external protection includes input / output side current overcurrent protection, short circuit protection, voltage over-limit protection, phase loss protection and power-off protection; the internal protection includes device short circuit protection, busbar overvoltage / undervoltage protection, positive and negative voltage imbalance protection when using a multi-level structure, and circulating current protection when modular parallel connection; The overcurrent protection described above requires relay parameter setting, which includes the following steps: setting four parameters, including two time setting parameters (t set1ij , t set2ij ) and two current constant parameters (I set1ij , I set2ij ) The time setting parameters are determined by the fault current characteristics and the time required for removal; the time setting parameters are selected as t set1ij =1ms and t set2ij =2ms; the minimum fault current I fminij and maximum operating current I opmaxij With the appropriate current I selected set1ij For comparison; if I opmaxij Less than I fminij , then set I set1ij =I fminij ;if I opmaxij Greater than I fminij , then set I set1ij =I opmaxij ; When I is defined set2ij When protecting R ij It can be used as a backup protection for the lower level protection; at the same time, if I opmaxij If the current is not within the range defined by the backup protection zone, it is also necessary to define I set2ij ; The overcurrent protection comprises the following steps: S1, Processing P = 1, K ij =0 and K ji =0; S2. Determine whether S is satisfied ijk =1 and I fijk Greater than I opmaxij When processing d=1, K ij =K ij +1 and go to step S3; if S is not satisfied ijk =1 and I fijk Greater than I opmaxij When d=0, proceed to step S3; S3. Determine whether S is satisfied jik =1 and I fjik Greater than I opmaxji When processing K ji =K ji +1, go to step S4; if S is not satisfied jik =1 and I fjik Greater than I opmaxji When it is determined that d=0 is satisfied, differential protection is used in the line section; if d=0 is not satisfied, the process goes to step S4; S4, when it is determined that P=n is satisfied, go to step S5; if P=n is not satisfied, set P=P+1 and go to step S2; S5. Determine whether K is satisfied ij =n, go to step S6; if K is not satisfied ij =n, go to step S7; S6. Determine whether K is satisfied ji =n, R ij or R ji Put into operation; if K is not met ji =n, R ij Put into operation; S7. Determine whether K is satisfied ji =n, R ji Put into operation; if K is not met ji =n, R ij and R ji Put into operation; Where n is the number of nodes, n≥i≥1, n≥j≥1; n-1≥P≥1, P is the number of different structures that the line can form; R ij For installation in line L ij Overcurrent protection at the head end; R ji For installation in line L ij Overcurrent protection at the end; I opmaxij To protect R ij The maximum operating current reflected; K ij ≥0, K ji ≥0, K ij and K ji R ij and R ji The number of different structures formed by the protected lines; S ijk =1 means protection R ij Identified the Kth th The fault current of the line structure, that is, the fault current I fijk Greater than I opmaxij ; d = 1 means that the fault can be controlled by protection R ij Identification; d = 0 means that the fault cannot be protected by R ij Identify; Protect R ij Able to identify line L ij All possible faults within K ij =n; if protection R ij Unable to identify line L ij When all possible faults are within the ij and R ji Need to be put into operation at the same time.

2. The energy-saving customized real-type test load system according to claim 1 is characterized in that: The energy-saving customized load is based on a parallel type of multiple load modules, with the load-side circuit breaker connected to the substation transformer, and the energy-feeding-side circuit breaker connected to the low-voltage side of the step-down transformer; a single load module adopts a back-to-back AC-DC converter structure.

3. According to claim 1, the energy-saving customized real-type test load system is characterized in that: The R ij and R ji The commissioning consists of two stages: setting the protection R ij The main protection area covers the line L ij All and feeder lines, protect R ij The reserve protection area includes line L i+1，j+1 ; Line L i+1，j+1 The main protection is R i+1，j+1 ; The first stage: at time t set1ij In case of a fault, the protection R ij Identify the fault; when the protection R ij The detected fault current is greater than I fminij When the protection triggers the tripping coil; The second stage: When i <j、I fmin(i+1，j+1) <I<I fminij or <i、I fmin(i-1，j-1) <I<I fminij When the forward fault current is within the above two conditions, the protection R ij At time t set2ij Running in backup protection function; t set1ij and t set2ij The step difference is set to 0.5s to ensure the selectivity of system protection.

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