Transformer closing excitation inrush current suppression device

Abstract

The invention relates to a transformer closing excitation inrush current suppression device of a power supply and distribution circuit system. Wherein the branch switch is arranged on a branch led out of a low-voltage side bus of a power grid system and serves as a main switch of the branch. The boosting transformer and the branch switch are located on the same branch, and the high-voltage winding side of the boosting transformer is connected to the wire outlet side of the branch switch. The closing inrush current suppression device and the branch switch are located on the same branch, and the outgoing line side of the closing inrush current suppression device is connected to the low-voltage winding side of the boosting transformer. Through the branch circuit formed by the branch switch, the boosting transformer, the closing inrush current suppression device and the power generation equipment, the original direct closing of the main transformer and the generation of the excitation inrush current are converted into the excitation inrush current generated when the branch circuit completes the closing and opening operation. Therefore, the magnitude of the impulse current formed on the low-voltage winding side of the main transformer depends on the maximum allowable working condition of the power generation equipment side, and the rated current of the power generation equipment is far smaller than the rated current of the low-voltage winding side of the main transformer, so that the peak value of the excitation surge current is clamped.

Description

Technical Field

[0001] The invention relates to a circuit system for power supply and distribution, and in particular to a transformer closing excitation surge current suppression device. Background Art

[0002] In the power supply network system and distribution network system, when the main transformer of a newly built substation is put into operation or the transformer is put into operation after maintenance, a large excitation surge current will appear when the unloaded transformer is closed, which will have an impact on the power grid system.

[0003] For example, the excitation surge current generated by the closing of the transformer will cause the transformer winding to shift in the oil tank, which may put the connection between the coils and the connection between the coils and the terminals at risk of being damaged, ultimately leading to an open circuit in the winding.

[0004] For another example, the magnetizing inrush current generated when the transformer is switched on contains harmonics that cause the power grid system to resonate at a certain frequency, thereby adversely affecting the power supply quality of the power grid system.

[0005] In addition, the DC component of the magnetizing inrush current generated when the transformer is switched on will produce an oscillatory mechanical torque on the motor, thereby increasing the motor's oscillations and causing a reduction in the motor's life.

[0006] Therefore, controlling the transformer closing excitation inrush current is an important task in the industry. At present, the traditional strategies for controlling the transformer closing excitation inrush current are as follows:

[0007] 1. Pre-insertion resistance method. That is, a resistor is connected in series with the neutral point of the transformer, and the resistor is inserted in the process of closing the transformer to limit the closing current, and the resistor is removed after the power supply is completed. However, this method itself has certain limitations, such as: due to the heating and loss of the resistor, it is not suitable for occasions where it is frequently switched on and off; and the power supply reliability is reduced due to the need to maintain the resistor in the later stage of operation.

[0008] Second, demagnetization method. That is, AC or DC demagnetization method is used on site to eliminate the residual magnetic flux of the transformer. However, there is no standard operation process for this method, and the demagnetization effect is judged only by experience, so when the transformer is closed, a large excitation inrush current will still appear.

[0009] 3. Simple phase control method. That is, the circuit breaker selects different points on the voltage waveform to perform closing and opening actions, so as to achieve selective closing and opening operations. However, this method cannot accurately calculate the closing time due to the error in residual magnetism measurement. Secondly, the operating mechanism of the circuit breaker is mostly a spring mechanism or a hydraulic mechanism, which has a large dispersion in operation and is not conducive to accurate closing. In this way, large excitation inrush current events will still occur in actual applications. Summary of the invention

[0010] In order to solve the negative problems in the above background technology when using the pre-insertion resistance method, demagnetization method and simple phase control method to control the transformer closing excitation inrush current, the present invention provides a technical solution for a transformer closing excitation inrush current suppression device, which includes:

[0011] The main transformer is a transformer to be put into operation in the power system for receiving and distributing electricity.

[0012] Main switch: The low-voltage winding side of the main transformer is connected to the low-voltage busbar of the power system through the main switch.

[0013] The branch switch is installed on the branch connected to the low-voltage side bus of the power system and serves as the main switch of the branch.

[0014] The step-up transformer is on the same branch line as the branch switch, and its high-voltage winding side is connected to the outgoing line side of the branch switch.

[0015] The closing inrush current suppression device is on the same branch line as the branch switch and is connected to the low-voltage winding side of the step-up transformer.

[0016] The power generating equipment is on the same branch line as the branch switch, and its output side is connected to the low voltage winding side of the step-up transformer through a closing inrush current suppression device.

[0017] Furthermore, the main transformer is a three-winding transformer or a two-winding transformer. If the main transformer is a three-winding transformer, its high-voltage winding side is connected to the high-voltage bus of the power system, its medium-voltage winding side is connected to the medium-voltage bus of the power system, and its low-voltage winding side is connected to the low-voltage bus of the power system. If the main transformer is a two-winding transformer, its high-voltage winding side is connected to the high-voltage bus of the power system, and its low-voltage winding side is connected to the low-voltage bus of the power system.

[0018] Furthermore, the branch circuit composed of the main switch, branch switch, step-up transformer, closing inrush current suppression device and power generation equipment is used to pre-magnetize the main transformer before it is put into operation so that it can smoothly enter a steady state, thereby clamping the peak value of the excitation inrush current generated when the main transformer is put into operation.

[0019] Furthermore, the step-up transformer is a double-winding transformer, the high-voltage winding side of which is connected to the low-voltage busbar of the power system, and the low-voltage winding side of which is connected to the closing inrush current suppression device.

[0020] Furthermore, the high voltage winding side of the step-up transformer and the low voltage winding side of the main transformer have the same nominal voltage.

[0021] Furthermore, the nominal voltage on the low voltage winding side of the step-up transformer is not higher than 10KV.

[0022] Furthermore, the closing inrush current suppression device comprises:

[0023] The phase-controlled switching main circuit is composed of a phase-controlled circuit breaker and a bypass switch in series, and is used to complete the switching of power generation equipment.

[0024] The inrush current suppression unit is connected in parallel with the bypass switch and in series with the phase-controlled circuit breaker to suppress the excitation inrush current of the circuit.

[0025] The voltage limiting protection unit is connected in series to the phase-controlled circuit breaker, and the phase-controlled circuit breaker is grounded through the voltage limiting protection unit to suppress overvoltage.

[0026] The inrush current control unit includes a transformer for collecting bus side voltage signals and a transformer for collecting load side voltage signals, a sensor for collecting load side current signals, and a phase control controller for performing data processing and phase control switching command processing.

[0027] Furthermore, the phase-controlled circuit breaker is a three-phase circuit breaker using an eddy current drive method.

[0028] Furthermore, the branch switch is a three-phase circuit breaker using an eddy current drive mode, and it can be used in place of a phase-controlled circuit breaker at its original circuit position, thereby removing the phase-controlled circuit breaker.

[0029] Furthermore, the inrush current suppression unit is a silicon stack.

[0030] Furthermore, the voltage limiting protection unit is a nonlinear varistor.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention uses a branch circuit composed of a branch switch, a step-up transformer, a closing inrush current suppression device and a power generation equipment to transform the original direct closing of the main transformer and the generation of the excitation inrush current into the generation of the excitation inrush current when the branch circuit completes the closing and opening operations. That is, the excitation inrush current is generated in the circuit on the low-voltage winding side of the step-up transformer. In this way, the magnitude of the impact current formed on the low-voltage winding side of the main transformer depends on the maximum allowable operating condition on the power generation equipment side, and the rated current of the power generation equipment is much smaller than the rated current on the low-voltage winding side of the main transformer, so that the peak value of the excitation inrush current can be clamped.

[0033] 2. The present invention uses a branch composed of a branch switch, a step-up transformer, a closing inrush current suppression device and a power generation equipment to transform the original direct closing of the main transformer and the generation of the excitation inrush current into the generation of the excitation inrush current when the branch completes the closing and opening operations. That is, the excitation inrush current is generated in the circuit on the low-voltage winding side of the step-up transformer. In this way, compared with directly managing the excitation inrush current on the low-voltage winding side of the main transformer, the present invention chooses to manage it on the side of the power generation equipment with a smaller excitation inrush current peak, which reduces the difficulty of management, and the closing inrush current suppression device can be used to further suppress the excitation inrush current of the branch.

[0034] 3. The present invention uses the closing and opening current suppression operation of the closing inrush current suppression device to enable the present invention to frequently perform switching operations. Since the present invention abandons the method of connecting a resistor in series at the neutral point of the transformer, the negative effects brought about by this method are avoided.

[0035] 4. The present invention can control the phase-controlled circuit breaker and the bypass switch to perform corresponding closing and opening actions within a preset closing and opening phase angle range through the inrush current control unit, without relying on calculating the residual magnetic flux of the transformer, thus avoiding the negative impact brought about by the empirical judgment method of the demagnetization method.

[0036] 5. The present invention can control the phase-controlled circuit breaker and bypass switch to perform corresponding closing and opening actions within the preset closing and opening phase angle range through the inrush current control unit, so that the inrush current and overvoltage at the closing and opening moment are relatively small, and then the inrush current suppression unit and the voltage limiting protection unit are used to further suppress the inrush current generated at this moment, thereby overcoming the problem that the simple phase control method cannot well suppress the inrush current due to the closing error. In addition, the phase-controlled circuit breaker of the present invention adopts an eddy current drive mode, which can realize rapid closing and opening actions, which is conducive to improving the closing accuracy.

[0037] 6. The present invention uses a branch circuit composed of a branch switch, a step-up transformer, a closing inrush current suppression device and a power generation device, and can use the power generation device to pre-magnetize the low-voltage winding side of the main transformer to make the main transformer magnetically enter a steady state. In this way, a steady-state magnetic flux is established inside the iron core of the main transformer before it is put into operation, so that a large closing excitation inrush current will not be generated when the switch is closed and put into operation.

[0038] 7. The present invention achieves the purpose of controlling the closing excitation inrush current of the main transformer by controlling the inrush current of the branch circuit composed of the branch switch, the step-up transformer, the closing inrush current suppression device and the power generation equipment, thereby reducing the impact of the inrush current on the power system, ensuring the operating stability and power supply reliability of the power system, and being conducive to improving the power supply quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the logic diagram of excitation and inrush current suppression of the present invention;

[0040] Figure 2 It is a wiring diagram of a closing inrush current suppression device of a phase-controlled circuit breaker of the present invention located at the incoming line side of a bypass switch;

[0041] Figure 3 It is a wiring diagram of a closing inrush current suppression device of a phase-controlled circuit breaker of the present invention located at the outgoing line side of a bypass switch;

[0042] Figure 4 It is a working logic diagram of the closing inrush current control unit of the present invention;

[0043] Figure 5This is an example diagram of the application of the present invention in a 220KV transformer substation;

[0044] Figure 6 This is an example diagram of the application of the present invention in a 110KV transformer substation. DETAILED DESCRIPTION

[0045] The preferred specific embodiments for implementing the present invention are described in detail below, and a clear and complete description is made in conjunction with the accompanying drawings.

[0046] See also Figure 1-Figure 4 The present invention provides a transformer closing excitation inrush current suppression device, which is suitable for scenarios where main transformers of newly built substations at all levels are put into use, and is also suitable for scenarios where transformers are put into use after maintenance. Figure 2 and Figure 3 In the figure, ZK represents the inrush current control unit, K2 represents the phase-controlled switch, K1 represents the bypass switch, TL represents the inrush current suppression unit, and ZCD-B represents the voltage limiting protection unit. Figure 4 In the figure, Ua, Ub and Uc represent the three-phase lines A, B and C connected to the phase-controlled circuit breaker respectively, TV represents the mutual inductance for collecting the voltage signal on the bus side, and TA represents the current sensor for collecting the current signal on the load side.

[0047] The transformer closing excitation inrush current suppression device provided by the present invention comprises a main transformer, a main switch, a branch switch, a closing inrush current suppression device and a power generation device. Among them, when the main transformer and the main switch are already present in the power system, the construction of the present invention only requires a branch circuit consisting of a branch switch, a step-up transformer, a closing inrush current suppression device and a power generation device to be connected to the low-voltage side bus of the power system. The branch circuit can reduce the difficulty of inrush current and overvoltage control and improve the control effect. That is, there is no need to change the working magnetic flux of the main transformer, nor the performance and working mode of the circuit breaker in the main switch, and there is no need to change the operating mechanism of power receiving and distribution of the original power system.

[0048] Specifically:

[0049] The main transformer is used as the main transformer to be put into operation in the power system for receiving and distributing electricity. For example, in the application of the distribution network system, the main transformer in the power grid system of the substation can be selected as the main transformer; or a new transformer can be added to the power grid system of the substation to replace the original transformer, and the new transformer can be used as the main transformer; or a new transformer can be added to the power grid system of the substation and the new transformer can be used as the main transformer.

[0050] Preferably, the main transformer is a three-winding transformer or a two-winding transformer. If the main transformer is a three-winding transformer, its high-voltage winding side is connected to the high-voltage bus of the power system, its medium-voltage winding side is connected to the medium-voltage bus of the power system, and its low-voltage winding side is connected to the low-voltage bus of the power system; if the main transformer is a two-winding transformer, its high-voltage winding side is connected to the high-voltage bus of the power system, and its low-voltage winding side is connected to the low-voltage bus of the power system.

[0051] The main switch is installed in the main switch cabinet in the wiring line between the low-voltage winding side of the main transformer and the low-voltage busbar of the connected power system. The low-voltage winding side of the main transformer is connected to the low-voltage busbar of the power system through the main switch. By controlling the closing and opening operations of the main switch, the circuit state between the main transformer and the low-voltage busbar of the power system can be controlled.

[0052] The branch switch is installed in the branch switch cabinet in the branch connected to the low-voltage busbar of the power system. As the main switch of the branch, the branch switch can control the circuit state between the low-voltage busbar of the power system and the branch by controlling the closing and opening operations of the branch switch.

[0053] Preferably, the branch switch is a three-phase circuit breaker using an eddy current drive mode, and the switches on the three-phase lines A, B and C can perform closing and opening actions respectively. When the closing and opening actions of the switches on each phase in the branch switch are controlled by the closing and opening commands issued by the surge control unit, it is equivalent to transferring the role of the phase-controlled circuit breaker to the branch switch. Therefore, it is equivalent to replacing the phase-controlled circuit breaker with the branch switch without changing the circuit position of the branch switch, so that the phase-controlled circuit breaker can be removed from the closing surge suppression device. In this way, since the closing surge suppression device is no longer equipped with a phase-controlled circuit breaker, the cost of the closing surge suppression device is reduced, thereby reducing the purchase cost of the purchaser.

[0054] The step-up transformer is on the same branch line as the branch switch, and its high-voltage winding side is connected to the outgoing line side of the branch switch. Through the step-up transformer, the voltage output by the power generation equipment can be increased and supplied to the low-voltage winding side of the main transformer, realizing the pre-magnetization of the low-voltage winding side of the main transformer.

[0055] Preferably, the step-up transformer is a double-winding transformer. Its high-voltage winding side is connected to the low-voltage busbar of the power system, and its low-voltage winding side is connected to the closing inrush current suppression device. The high-voltage winding side of the step-up transformer and the low-voltage winding side of the main transformer have the same nominal voltage.

[0056] More preferably, the nominal voltage on the low-voltage winding side of the step-up transformer is not higher than 10KV. Since the closing inrush current suppression device is on the low-voltage winding side of the step-up transformer, the closing inrush current suppression device controls the inrush current and overvoltage here, and the lower the nominal voltage on the low-voltage winding side of the step-up transformer, the correspondingly limited inrush current peak value, the lower the difficulty of inrush current control, and the more conducive it is for the closing inrush current suppression device to control the inrush current. In addition, under the condition that the low-voltage winding side of the main transformer is not higher than 10KV, in order to save construction costs, the step-up transformer can be omitted, and the power generation equipment can be connected to the branch switch through the closing inrush current suppression device.

[0057] The closing inrush current suppression device is located on the same branch line as the branch switch, and its incoming line side is connected to the low-voltage winding side of the step-up transformer, while its outgoing line side is connected to the power generation equipment. The closing inrush current suppression device includes a phase-controlled switching main line, an inrush current suppression unit, a voltage limiting protection unit and an inrush current control unit. Among them, the phase-controlled switching main line is composed of a phase-controlled circuit breaker and a bypass switch in series, and the switching of the power generation equipment can be controlled by the closing and opening coordination between the phase-controlled circuit breaker and the bypass switch; the inrush current suppression unit is connected in parallel to the bypass switch and in series with the phase-controlled circuit breaker, and cooperates with the closing and opening actions of the phase-controlled circuit breaker to suppress the excitation inrush current of the circuit; the voltage limiting protection unit is connected in series to the phase-controlled circuit breaker, and the phase-controlled circuit breaker is grounded through the voltage limiting protection unit, and the overvoltage of the circuit is suppressed by the voltage limiting protection unit; the inrush current control unit includes a transformer for collecting bus side voltage signals and a transformer for collecting load side voltage signals, a sensor for collecting load side current signals, and a phase-controlled controller for data processing and phase-controlled switching command processing.

[0058] Preferably, the phase-controlled circuit breaker is a three-phase circuit breaker using an eddy current drive mode, and the switches on the three-phase lines A, B and C can respectively make closing and opening actions. That is, the switches on the three-phase lines A, B and C in the phase-controlled circuit breaker can respectively complete the corresponding closing and opening actions within the respective preset closing and opening phase angle ranges. In practical applications, the phase-controlled circuit breaker can be selectively set on the incoming line side or the outgoing line side of the bypass switch, and the phase-controlled switching of the power generation equipment is realized by performing phase-by-phase operation on the switches on the three-phase lines A, B and C of the phase-controlled circuit breaker, thereby achieving the purpose of suppressing inrush current and overvoltage. Among them, if the phase-controlled circuit breaker is connected to the incoming line side of the bypass switch, the bypass switch is connected to the low-voltage winding side of the step-up transformer through the phase-controlled circuit breaker, and the phase-controlled circuit breaker is connected to the power generation equipment through the bypass switch; if the phase-controlled circuit breaker is connected to the outgoing line side of the bypass switch, the bypass switch is connected to the power generation equipment through the phase-controlled circuit breaker, and the phase-controlled circuit breaker is connected to the low-voltage winding side of the step-up transformer through the bypass switch.

[0059] Preferably, the closing and opening operations of the bypass switch are used to control the switching of the inrush current suppression unit. During the commissioning of the power generation equipment, the bypass switch is closed later than the phase-controlled switch; during the withdrawal of the power generation equipment, the bypass switch is opened earlier than the phase-controlled switch.

[0060] Preferably, the surge current suppression unit is a silicon stack. That is, the surge current suppression unit is composed of a number of diodes connected in series in the same direction, and the cathode of the diode is in the same direction as the outgoing line side of the closing surge current suppression device. When the bypass switch is in the open state, the surge current suppression unit can cooperate with the phase-controlled closing of the phase-controlled circuit breaker to clamp the surge current for a second time. The so-called secondary clamping means that the surge current is clamped once by the phase-controlled closing of the phase-controlled circuit breaker, and the surge current after the phase-controlled clamping is clamped again by the surge current suppression unit.

[0061] Preferably, the voltage limiting protection unit is a nonlinear varistor. After the charge on the negative electrode side of the inrush current suppression unit accumulates and reaches the turn-on voltage of the voltage limiting protection unit, the voltage limiting protection unit is turned on, the current is shunted to the voltage limiting protection unit, and the voltage limiting protection unit converts the current flowing through it into heat, thereby consuming the charge to suppress overvoltage.

[0062] The power generation equipment is located on the same branch line as the branch switch, and its output side is connected to the outgoing line side of the closing inrush current suppression device. The nominal voltage output by the power generation equipment is the same as the nominal voltage on the low-voltage winding side of the step-up transformer. After the power generation equipment is started, power is supplied to the low-voltage winding side of the step-up transformer through the closing inrush current suppression device.

[0063] In the application of the present invention:

[0064] Before the main transformer is put into operation, the main transformer is first magnetized through the branch composed of the main switch, branch switch, step-up transformer, closing inrush current suppression device and power generation equipment, so that the main transformer enters steady-state operation before it is put into operation, thereby avoiding the situation where the surge current in the power system increases due to the transient magnetic flux change caused by the direct operation of the main transformer. Since the main transformer is excited by the branch composed of the main switch, branch switch, step-up transformer, closing inrush current suppression device and power generation equipment before entering the steady state, it is equivalent to transferring the excitation inrush current generated by directly closing the main transformer to the low-voltage winding side circuit of the step-up transformer in the branch for treatment. That is, the closing inrush current suppression device clamps the inrush current appearing in the low-voltage winding side circuit of the step-up transformer and suppresses its peak value.

[0065] Switch status before commissioning: Before commissioning the main transformer, the main switch and branch switches are in the closed state, and the phase-controlled circuit breaker and bypass switch are in the open state.

[0066] Preparation work before commissioning: Turn on the power generation equipment for preheating so that the power generation equipment can transmit electricity to the step-up transformer in the subsequent process.

[0067] Action 1: The phase-controlled split-phase closing method is adopted so that after the phase-controlled circuit breaker receives the closing command, the switches on the A, B and C three-phase lines complete the corresponding closing action within the preset closing phase angle range. Since the phase-controlled circuit breaker is controlled to close the circuit in phase, the size of the inrush current can be suppressed during the closing process, so that the peak value of the inrush current can be reduced. Among them, the eddy current drive method of the phase-controlled circuit breaker makes its closing and opening speed better than that of the traditional mechanical circuit breaker, thereby improving the closing accuracy. In addition, after the phase-controlled circuit breaker completes the closing, the current of the power generation equipment flows to the low-voltage winding side of the step-up transformer through the phase-controlled circuit breaker and the inrush current suppression unit. During this period, the inrush current is suppressed again by the inrush current suppression unit, which improves the effect of inrush current suppression and overcomes the problem that the simple phase control method cannot suppress the inrush current well due to the closing error. It can even limit the inrush current to less than one times the rated current of the transformer, thereby achieving the purpose of eliminating the false operation of the differential protection and improving the power quality.

[0068] Operation 2: After the inrush current generated by the closing of the phase-controlled circuit breaker is suppressed, the current in the circuit is stable, and the bypass switch can be closed to exit the inrush current suppression unit. At this time, the current of the power generation equipment flows to the low-voltage winding side of the step-up transformer through the phase-controlled circuit breaker and the bypass switch. After being stepped up, it flows to the low-voltage winding side of the main transformer through the main switch and the branch switch, realizing the stable magnetization of the main transformer.

[0069] In the first and second switching actions, if the voltage on the negative side of the inrush current suppression unit exceeds the threshold of the voltage limiting protection unit, the resistance of the voltage limiting protection unit decreases rapidly and turns on, causing a large amount of current to flow into the voltage limiting protection unit, and the voltage limiting protection unit converts the inrush current into heat, thereby consuming the inrush current. That is, the voltage limiting protection unit can both shunt and suppress overvoltage.

[0070] When it is necessary to cut off the power generation equipment, after the phase-controlled controller receives the opening command, it sends an opening command to the phase-controlled circuit breaker and the bypass switch, and opens the bypass first. The phase switches of the phase-controlled circuit breaker then complete their respective opening actions within their respective preset opening phase angle ranges, and finally open the branch switch.

[0071] Embodiment 1

[0072] See also Figure 5 In this embodiment, the three windings of the main transformer are 220KV, 110KV and 35KV respectively, and an application example of the present invention in 220KV transformer is given.

[0073] The low-voltage winding side of the main transformer is 35KV, which is connected to the 35KV bus through the main switch cabinet on the 35KV side. The bus is connected to a branch through the 35KV side branch switch cabinet, and a 10KV to 35KV step-up transformer, a closing inrush current suppression device and a generator car are arranged in this branch in sequence.

[0074] Among them, the high-voltage winding side of the step-up transformer is connected to the outgoing side of the 35KV side branch switch cabinet, the low-voltage winding side of the step-up transformer is connected to the incoming side of the closing inrush current suppression device, and the output side of the power generation vehicle is connected to the outgoing side of the closing inrush current suppression device.

[0075] Embodiment 2

[0076] See also Figure 6 In this embodiment, the three windings of the main transformer are 110KV, 35KV and 10KV respectively, and an application example of the present invention in 110KV transformer is given.

[0077] The low-voltage winding side of the main transformer is 10KV, which is connected to the 10KV bus through the main switch cabinet on the 10KV side. The bus is connected to a branch through the 10KV side branch switch cabinet, and a 10KV to 6.3KV step-up transformer, a closing inrush current suppression device and a generator car are arranged in this branch in sequence.

[0078] Among them, the high-voltage winding side of the step-up transformer is connected to the outgoing side of the 10KV side branch switch cabinet, the low-voltage winding side of the step-up transformer is connected to the incoming side of the closing inrush current suppression device, and the output side of the power generation vehicle is connected to the outgoing side of the closing inrush current suppression device.

[0079] In addition, in order to further save the cost of constructing the project of the present invention, the step-up transformer can be directly removed so that the output side of the power generation vehicle can be directly connected to the 10KV side branch switch cabinet.

[0080] Embodiment 3

[0081] Based on the first or second embodiment, this embodiment provides a case where the main transformer is a double-winding transformer, that is, the three-winding transformer in the first or second embodiment is replaced by a double-winding transformer.

[0082] Embodiment 4

[0083] Based on any one of the above embodiments 1 to 3, this embodiment provides a method for further saving the cost of constructing the project of the present invention. That is, the branch switch in the branch switch cabinet adopts a three-phase circuit breaker driven by eddy current, and the switches on the three-phase lines A, B and C can respectively make closing and opening actions, and the branch switch replaces the phase-controlled circuit breaker in the closing inrush current suppression device, so that the phase-controlled circuit breaker can be removed.

[0084] Based on the above content and the accompanying drawings, those skilled in the art can understand and implement the present invention. In addition, any non-creative modifications made to the present invention by those skilled in the art without creative work still fall within the protection scope of the present invention.

Claims

1. A transformer closing excitation inrush current suppression device, comprising a transformer to be put into operation for receiving and distributing power in a power system, namely, a main transformer, characterized in that: The device also includes: Main switch: The low-voltage winding side of the main transformer is connected to the low-voltage busbar of the power system through the main switch; The branch switch is installed on the branch connected to the low-voltage busbar of the power system and serves as the main switch of the branch; The step-up transformer is on the same branch line as the branch switch, and its high-voltage winding side is connected to the outgoing line side of the branch switch; The closing inrush current suppression device is located on the same branch line as the branch switch and is connected to the low-voltage winding side of the step-up transformer; The power generating equipment is on the same branch line as the branch switch, and its output side is connected to the low voltage winding side of the step-up transformer through a closing inrush current suppression device.

2. The transformer closing excitation inrush current suppression device according to claim 1, characterized in that: The main transformer is a three-winding transformer or a two-winding transformer; If the main transformer is a three-winding transformer, its high-voltage winding side is connected to the high-voltage bus of the power system, its medium-voltage winding side is connected to the medium-voltage bus of the power system, and its low-voltage winding side is connected to the low-voltage bus of the power system; If the main transformer is a double-winding transformer, its high-voltage winding side is connected to the high-voltage side bus of the power system, and its low-voltage winding side is connected to the low-voltage side bus of the power system.

3. The transformer closing excitation inrush current suppression device according to claim 1, characterized in that: The circuit composed of the main switch, branch switch, step-up transformer, closing inrush current suppression device and power generation equipment is used to pre-magnetize the main transformer before it is put into operation so that it can smoothly enter the steady state, so as to clamp the peak value of the excitation inrush current generated when the main transformer is put into operation.

4. The transformer closing excitation inrush current suppression device according to claim 1 or 3, characterized in that: The step-up transformer is a double-winding transformer, with its high-voltage winding side connected to the low-voltage busbar of the power system, and its low-voltage winding side connected to the closing inrush current suppression device; The high voltage winding side of the step-up transformer and the low voltage winding side of the main transformer have the same nominal voltage.

5. The transformer closing excitation inrush current suppression device according to claim 4, characterized in that: The nominal voltage on the low voltage winding side of the step-up transformer is not higher than 10KV.

6. The transformer closing excitation inrush current suppression device according to claim 1 or 3, characterized in that: The closing inrush current suppression device includes: The phase-controlled switching main circuit is composed of a phase-controlled circuit breaker and a bypass switch in series, and is used to complete the switching of power generation equipment; The inrush current suppression unit is connected in parallel with the bypass switch and in series with the phase-controlled circuit breaker to suppress the excitation inrush current of the circuit; A voltage limiting protection unit is connected in series to the phase-controlled circuit breaker, and the phase-controlled circuit breaker is grounded through the voltage limiting protection unit, for suppressing overvoltage; The inrush current control unit includes a transformer for collecting bus side voltage signals and a transformer for collecting load side voltage signals, a sensor for collecting load side current signals, and a phase control controller for performing data processing and phase control switching command processing.

7. The transformer closing excitation inrush current suppression device according to claim 6, characterized in that: The phase-controlled circuit breaker is a three-phase circuit breaker that adopts eddy current drive.

8. The transformer closing excitation inrush current suppression device according to claim 7, characterized in that: The branch switch is a three-phase circuit breaker using an eddy current drive mode, and it can replace the phase-controlled circuit breaker at its original circuit position and remove the phase-controlled circuit breaker.

9. The transformer closing excitation inrush current suppression device according to claim 6, characterized in that: The inrush current suppression unit is a silicon stack.

10. The transformer closing excitation inrush current suppression device according to claim 6, characterized in that: The voltage limiting protection unit is a nonlinear varistor.

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