Intelligent low-voltage switch cabinet

Abstract

The invention relates to the technical field of switch cabinets, in particular to an intelligent low-voltage switch cabinet which comprises a cabinet body. The execution unit comprises a circuit breaker handcart used for disconnecting the current of the load circuit and a plurality of contactors used for switching the load circuit; the detection unit is used for detecting the instantaneous reduction voltage of the load, the current harmonic phase difference of the phase current signal of the main bus, the current harmonic signal proportion and the environment temperature in the cabinet body; the control unit is used for determining a load protection grade according to the instantaneous reduction voltage of the load, and determining the interval duration of starting the circuit breaker handcart and the contactor in the inrush current impact compensation mode according to the load protection grade and the duration of the instantaneous reduction voltage; the asynchronous action starting mode of the contactors is adjusted according to the harmonic wave phase difference, and the access proportion of the reactive load is adjusted according to the harmonic wave signal proportion and the progressive increase node similarity of the environment temperature in the cabinet body in the time sequence. According to the invention, the load stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switch cabinet, and particularly relates to an intelligent low-voltage switch cabinet. BACKGROUND

[0002] In the prior art, the low-voltage switch cabinet is a device of a low-voltage power distribution system, mainly used for power distribution, circuit control, fault protection and monitoring, wherein a molded case circuit breaker trolley is used to deal with short-circuit faults in industrial scenes; a frame circuit breaker trolley is used to realize large-current breaking and support high load demand of a bus system; a cabinet body is made of cold-rolled steel plates, aluminum alloy or composite insulating materials, and electrostatic spraying is used to improve corrosion resistance, so as to meet the demand of harsh environments such as dust and water immersion; and a fan is arranged on the top or side of the cabinet body.

[0003] Chinese Patent Publication No. CN114709716A discloses a low-voltage switch cabinet, comprising: a cabinet body frame; door plates, including a front door plate and a rear door plate, arranged on opposite sides of the cabinet body frame; a plurality of partitions arranged in the cabinet body frame, separating the cabinet body frame into a plurality of chambers; the plurality of chambers include a communication room, an instrument room, a switch room, a cable room, a main bus room and a vertical bus room; the communication room, the instrument room, the switch room and the cable room are arranged on the same side of the cabinet body frame and are sequentially arranged from top to bottom; the main bus room is arranged on the side of the communication room away from the front door plate, and the vertical bus room is arranged on the side of the instrument room and the switch room away from the front door plate; the cable room includes a front cable room and a rear cable room arranged separately, the front door plate and the rear door plate cover the front cable room and the rear cable room respectively, and the front cable room and the rear cable room are respectively provided with outgoing terminals; and a zero-phase and ground bus room is further arranged between the front cable room and the rear cable room. It can be seen that the low-voltage switch cabinet has the problem of reduced operation stability of the switch cabinet due to the fact that the line is damaged by external forces such as strong wind, snow, tree falling and the like, crane, excavator line collision, animal touch and the like, causing phase-to-phase short circuit or single-phase grounding short circuit and then reducing the voltage of the power grid, and the voltage drop caused by the direct start of a large-capacity motor temporarily reduces the bus voltage. SUMMARY

[0004] To this end, the present application provides an intelligent low-voltage switch cabinet to overcome the problem of reduced operation stability of the switch cabinet due to the fact that the line is damaged by external forces such as strong wind, snow, tree falling and the like, crane, excavator line collision, animal touch and the like, causing phase-to-phase short circuit or single-phase grounding short circuit and then reducing the voltage of the power grid, and the voltage drop caused by the direct start of a large-capacity motor temporarily reduces the bus voltage.

[0005] To achieve the above-mentioned purpose, the present application provides an intelligent low-voltage switch cabinet, comprising: a cabinet body; an execution unit arranged in the interior of the cabinet, comprising a circuit breaker trolley for breaking the current of the load circuit and a plurality of contactors for switching the load circuit; a detection unit connected with the cabinet and the execution unit respectively, for detecting the instantaneous reduced voltage of the load, the current harmonic phase difference of the phase current signal of the main bus, the current harmonic signal proportion and the ambient temperature in the cabinet; a control unit connected with the execution unit and the detection unit respectively, for determining the load protection level according to the instantaneous reduced voltage of the load, determining the interval time length of the sequential start of the circuit breaker trolley and the contactors according to the duration of the instantaneous reduced voltage corresponding to the load protection level, adjusting the asynchronous action start mode of a plurality of the contactors according to the harmonic phase difference, and adjusting the access proportion of the reactive load according to the similarity of the increasing nodes in time sequence of the harmonic signal proportion and the ambient temperature in the cabinet.

[0006] Further, the detection unit comprises: a voltage sensor for detecting the instantaneous reduced voltage of the load; a current transformer arranged on the main bus of the load for detecting the harmonic phase difference of the phase current signal of the main bus and the harmonic signal proportion; a temperature sensor arranged on the inner wall of the cabinet for detecting the ambient temperature of the cabinet.

[0007] Further, the control unit is connected with the voltage sensor for obtaining the instantaneous reduced voltage, and if the instantaneous reduced voltage is greater than or equal to a preset first voltage and less than or equal to a preset second voltage, it is determined that the load protection level is first-level protection. If the instantaneous reduced voltage is greater than the preset second voltage and less than or equal to a preset third voltage, it is determined that the load protection level is second-level protection. If the instantaneous reduced voltage is greater than the preset third voltage, it is determined that the load protection level is third-level protection.

[0008] Further, the instantaneous reduced voltage is the difference between the instantaneous voltage detected by the voltage sensor and the instantaneous voltage detected at the last time.

[0009] Further, the control unit is used to determine the inrush current impact compensation mode under the condition that the load protection level is first-level protection, and obtain the duration of the instantaneous reduced voltage, and if the duration is greater than or equal to a preset time length, the interval time length of the sequential start of the circuit breaker trolley and the contactors is increased.

[0010] Further, the inrush current impact compensation mode is that the contactor is controlled to shunt after the first inrush of the circuit breaker trolley and the second inrush of the circuit breaker trolley.

[0011] Further, the control unit is used to acquire the harmonic phase difference and control the asynchronous action start time of the contactor to be adjusted to the time point of starting before the current zero point with an interval of the harmonic phase difference when the load protection level is the secondary protection.

[0012] Further, the control unit is used to acquire the harmonic signal proportion and the cabinet internal environment temperature respectively and calculate the incremental node similarity when the load protection level is the tertiary protection. If the incremental node similarity is greater than or equal to the preset similarity, the access proportion of the reactive load is increased.

[0013] Further, the access proportion of the reactive load is the ratio of the power of the reactive load to the total power of the load circuit.

[0014] Further, the harmonic signal proportion is the ratio of the effective value of the harmonic current component to the effective value of the fundamental current.

[0015] Compared with the prior art, the device has the beneficial effects that the device can cope with voltage fluctuation caused by severe weather or external damage and voltage sag caused by large-capacity motor starting, guarantee the operation stability of the switch cabinet under complex working conditions, monitor the instantaneous voltage change of the load in real time through the voltage sensor, acquire the harmonic current information of the main bus through the current transformer, and perceive the running state through the temperature sensor sensing the internal environment temperature of the cabinet; the control unit can determine the voltage sag level of the load and change the voltage sag at the load end from complete drop to shallow drop by adjusting the start timing of the circuit breaker trolley and the contactor, so as to maintain the voltage level and avoid voltage drop protection shutdown, can leave the load voltage recovery time by adjusting the anti-phase harmonic current of the contactor to offset the original harmonic, avoid the shutdown of the load due to continuous low voltage, and adjust the access proportion of the reactive load, so as to effectively suppress the influence of voltage fluctuation on the stable operation of the switch cabinet and improve the operation stability of the load.

[0016] Further, the device of the present application realizes the hierarchical response to the voltage sag event by setting the three-level load protection level mechanism, when the instantaneous reduced voltage is in different threshold intervals, the control unit determines the load protection level according to the preset rule, and takes the corresponding inrush current compensation mode, contactor asynchronous action strategy or reactive load adjustment method, through hierarchical control, avoids frequent action under different voltage disturbance intensity, realizes the continuous power supply of key equipment and the improvement of operation stability.

[0017] Further, the device of the present application introduces the inrush current compensation mode, under the first protection level, according to the voltage sag duration, dynamically adjusts the starting interval time of the circuit breaker handcart and the contactor, adopts the step control mode of one-time suction of the circuit breaker handcart, time delay shunt of the contactor and secondary suction of the circuit breaker handcart, uses the inductive inrush current generated in the closing moment of the circuit breaker handcart to inject the system reversely, instantaneously lifts the voltage falling on the bus, reduces the impact current in the closing moment, cuts off the fault current path accompanied by the contactor, and the secondary suction of the contactor realizes the fast and low-impact recovery power supply by using the residual magnetism of the core, prevents the secondary voltage drop and equipment damage caused by the sudden increase of current, thereby improving the safety and reliability of the system.

[0018] Further, the device of the present application adjusts the asynchronous action starting time of the contactor, under the second protection level, according to the current harmonic phase difference, controls the contactor to start before the current zero-crossing point, avoids the electromagnetic interference and mechanical stress impact caused by the non-zero current switching due to harmonics, injects a reverse-phase harmonic current in the circuit through mechanical action to offset the original harmonic, thereby reducing the equipment loss, reducing the disturbance to the system voltage in the switching process, and improving the stability of the load operation.

[0019] Further, the device of the present application calculates the similarity of the harmonic signal proportion and the increasing node of the temperature change in the cabinet body, and then adjusts the access proportion of the reactive load, under the third protection level, when the similarity of the harmonic content and the temperature change trend of the cabinet body is large, it means that the harmonic loss is the main inducement of the abnormal rise of the cabinet body temperature, at this time, the access proportion of the reactive load is increased, the voltage support capacity of the system is improved through reactive compensation, the inductive or capacitive characteristics of the reactive load are used to offset the reactive component in the harmonic current, the transmission loss of the harmonic in the main bus is reduced, the Joule heat generated by the harmonic current flowing through the conductor is reduced, and the further rise of the temperature in the cabinet body is delayed. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the overall structure schematic diagram of the intelligent low-voltage switch cabinet of the embodiment of the present application. Figure 2 It is another angle structure schematic diagram of the intelligent low-voltage switch cabinet of the embodiment of the present application. Figure 3 It is the overall structure block diagram of the intelligent low-voltage switch cabinet of the embodiment of the present application. Figure 4 It is the detection unit structure block diagram of the intelligent low-voltage switch cabinet of the embodiment of the present application. The figure number explanation: 1 - shell, 2 - valve support, 3 - circuit breaker trolley, 4 - contact box, 5 - bus sleeve 5, 6 - instrument room, 7 - pressure relief valve, 8 - current transformer, 9 - grounding switch. DETAILED DESCRIPTION

[0021] In order to make the purpose and advantages of the present application more clear and understandable, the present application will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0022] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0023] It should be noted that in the description of the present application, the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the direction or positional relationship terms based on the direction or positional relationship shown in the drawings, which are only for the convenience of description and do not indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0024] In addition, it should also be noted that in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0025] Please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , which are respectively the overall structure schematic diagram, another angle structure schematic diagram, overall structure block diagram and detection unit structure block diagram of the intelligent low-voltage switch cabinet of the embodiment of the present application. The present application is an intelligent low-voltage switch cabinet, comprising: a cabinet body; an execution unit, which is arranged inside the cabinet body, comprising a circuit breaker trolley 3 for breaking the load current and a plurality of contactors for shunting the load circuit; a detection unit connected with the cabinet and the execution unit respectively, used to detect the instantaneous reduced voltage of the load, the current harmonic phase difference of the phase current signal of the main bus, the current harmonic signal proportion and the temperature of the environment in the cabinet; a control unit connected with the execution unit and the detection unit respectively, used to determine the load protection level according to the instantaneous reduced voltage of the load, to determine the interval time length of the start of the circuit breaker handcart 3 and the contactor according to the surge impact compensation mode according to the duration of the instantaneous reduced voltage according to the load protection level, to adjust the asynchronous action start mode of a plurality of contactors according to the harmonic phase difference, to adjust the access proportion of the reactive load according to the similarity of the increasing nodes in time sequence of the harmonic signal proportion and the temperature of the environment in the cabinet.

[0026] Specifically, as Figure 1 The overall structure diagram of the intelligent low-voltage switch cabinet of the embodiment of the application and Figure 2 As shown in the structure diagram of another angle of the intelligent low-voltage switch cabinet of the embodiment of the application, the cabinet includes: a shell 1; a pressure relief valve 7 arranged on the upper surface of the shell 1, used to release the gas in the shell 1; a contact box 4 connected with the circuit breaker handcart 3, used to insulate the contacts in the circuit breaker handcart 3; a valve support 2 connected with the contact box 4, used to open and close the contact box 4; a bus sleeve connected with the contact box 4, used to fix the bus of the load; an instrument room 6 connected with the shell 1, used to install the display screen of the voltage sensor, the current transformer 8 and the temperature sensor; a grounding switch 9 connected with the shell 1, used to release the surface charge of the shell 1.

[0027] Specifically, the control unit is a microprocessor or a PLC controller.

[0028] Specifically, the harmonic phase difference is obtained by performing Fourier transform analysis on the amplitude of the third harmonic of the bus of the load.

[0029] In the implementation, the device described in the application can deal with voltage fluctuation caused by severe weather or external force damage, and voltage sag caused by large-capacity motor starting, guarantee the operation stability of the switch cabinet under complex working conditions, and realize real-time monitoring of instantaneous voltage change of the load through the voltage sensor, obtain harmonic current information of the main bus through the current transformer 8, and realize operation state sensing through the temperature sensor sensing the internal environment temperature of the cabinet. The control unit can determine the voltage sag level of the load, adjust the starting time sequence of the circuit breaker handcart 3 and the contactor, change the voltage sag at the load end from complete drop to shallow drop, maintain the voltage level, avoid voltage drop protection shutdown, adjust the anti-phase harmonic current of the contactor to offset the original harmonic current, leave the load voltage recovery time, avoid load shutdown due to continuous low voltage, adjust the proportion of reactive load access, effectively suppress the influence of voltage fluctuation on stable operation of the switch cabinet, and improve the operation stability of the load.

[0030] Specifically, the detection unit comprises: a voltage sensor for detecting instantaneous reduced voltage of the load; a current transformer 8 arranged on the main bus of the load for detecting harmonic phase difference of the phase current signal of the main bus and harmonic signal proportion; a temperature sensor arranged on the inner wall of the cabinet for detecting the environment temperature of the cabinet.

[0031] Specifically, the control unit is connected with the voltage sensor to obtain the instantaneous reduced voltage. If the instantaneous reduced voltage is greater than or equal to a preset first voltage and less than or equal to a preset second voltage, it is determined that the load protection level is first protection. If the instantaneous reduced voltage is greater than the preset second voltage and less than or equal to a preset third voltage, it is determined that the load protection level is second protection. If the instantaneous reduced voltage is greater than the preset third voltage, it is determined that the load protection level is third protection.

[0032] Specifically, the instantaneous reduced voltage is the difference between the instantaneous voltage detected by the voltage sensor and the instantaneous voltage detected at the last time.

[0033] Specifically, the voltage sensor detection frequency interval is 5 ms.

[0034] Specifically, under the condition of a single-phase switching power supply low-voltage switch cabinet and a power grid rated voltage of 220V, the preset first voltage generally has a value range of [20V, 45V], the preset second voltage generally has a value range of [50V, 75V], the preset third voltage generally has a value range of [80V, 115V], the preferred embodiment of the preset first voltage is 22V, the preferred embodiment of the preset second voltage is 55V, and the preferred embodiment of the preset third voltage is 110V.

[0035] Those skilled in the art can understand that the optional range and preferred embodiment of the preset first voltage, the preset second voltage and the preset third voltage provided in the embodiment are the best values selected under the condition of a single-phase switching power supply low-voltage switch cabinet and a power grid rated voltage of 220V for the effect of solving the technical problems of the technical scheme of the application. In actual application or experiment, those skilled in the art can adaptively adjust the preset first voltage, the preset second voltage and the preset third voltage according to the actual application environment and application scenario.

[0036] In implementation, the device described in the application realizes graded response to voltage sag events by setting a three-level load protection level mechanism. When the instantaneous reduced voltage is in different threshold intervals, the control unit determines the load protection level according to the preset rule and adopts the corresponding inrush current impact compensation mode, contactor asynchronous action strategy or reactive load adjustment method. Through graded control, frequent action is avoided under different voltage disturbance intensities, and the continuous power supply of key equipment and the improvement of operation stability are realized.

[0037] Specifically, the control unit is configured to determine an inrush current impact compensation mode when the load protection level is a first protection level, and obtain a duration of the instantaneous reduced voltage. If the duration is greater than or equal to a preset duration, the interval duration between the start of the circuit breaker handcart and the start of the contactor is increased.

[0038] Specifically, the inrush current impact compensation mode is that the contactor is controlled to shunt after the interval duration after the first suction of the circuit breaker handcart.

[0039] Specifically, under the condition of a single-phase switching power supply low-voltage switch cabinet and a power grid rated voltage of 220V, the preset duration generally has a value range of [5ms, 15ms], and the preferred embodiment of the preset duration is 10ms.

[0040] Those skilled in the art can understand that the optional range of the preset time length and the preferred embodiment provided in the embodiment are the best values selected for the effect of the technical problem solved by the technical solution of the application under the condition of a low-voltage switch cabinet for a single-phase switching power supply and a power grid rated voltage of 220V, and in actual application or experiments, those skilled in the art can adaptively adjust the preset time length according to the actual application environment and application scenarios.

[0041] In implementation, the maximum value of the interval time length of the subsequent start of the circuit breaker trolley 3 and the contactor is 5 ms, and the interval time length of the subsequent start of the circuit breaker trolley 3 and the contactor increases by 0.2 ms for each 1 ms increase in the difference between the duration time and the preset time length, and the initial value of the interval time length is 3 ms, for example, when the difference between the duration time and the preset time length is 13 ms, the interval time length is determined as 3 ms + 0.2*3 = 3.6 ms.

[0042] In implementation, the device of the application dynamically adjusts the interval time length of the start of the circuit breaker trolley 3 and the contactor according to the voltage sag duration time under the first protection level by introducing a surge impact compensation mode, adopts a step control mode of one-time attraction of the circuit breaker trolley 3, time-delay shunt of the contactor, and two-time attraction of the circuit breaker trolley 3, uses the inductive surge generated at the moment of the closure of the circuit breaker trolley 3 to reversely inject the system, instantaneously lifts the voltage that is falling on the bus, reduces the impact current at the moment of closing, cuts off the fault current path accompanied by the contactor, and realizes fast and low-impact power supply recovery by the two-time attraction of the contactor using the residual magnetism of the core, thereby preventing secondary voltage drop and equipment damage caused by sudden current increase, and improving the safety and reliability of the system.

[0043] Specifically, the control unit is configured to, under the condition that the load protection level is the second protection level, acquire the harmonic phase difference, and control the asynchronous action start time of the plurality of contactors to be adjusted to a time point that is separated from the current zero-crossing point by the harmonic phase difference.

[0044] Specifically, the frequency interval of the asynchronous action of the plurality of contactors is an integer multiple of the half cycle of the current.

[0045] In implementation, the device of the application adjusts the asynchronous action start time of the contactor, controls the contactor to start before the current zero-crossing point under the second protection level according to the current harmonic phase difference, avoids electromagnetic interference and mechanical stress impact caused by non-zero current switching due to harmonics, injects a reverse-phase harmonic current in the circuit through mechanical action to offset the original harmonic, thereby reducing equipment loss, reducing disturbance to the system voltage in the switching process, and improving the stability of load operation.

[0046] Specifically, the control unit is configured to acquire the harmonic signal proportion and the cabinet internal environment temperature respectively under the condition that the load protection level is the third protection level, and calculate the incremental node similarity, If the incremental node similarity is greater than or equal to the preset similarity, the access proportion of the reactive load is increased.

[0047] Specifically, the access proportion of the reactive load is adjusted by the reactive compensation device, and the reactive load is one or more groups of power capacitor banks connected in parallel to the bus, each power capacitor bank is connected to a switching switch, and the switching switch controls the access of the power capacitor bank to the bus or the disconnection.

[0048] Specifically, the access proportion of the reactive load is the ratio of the power of the reactive load to the total power of the load circuit.

[0049] Specifically, the harmonic signal proportion is the ratio of the effective value of the harmonic current component to the effective value of the fundamental current.

[0050] Specifically, the calculation process of the incremental node similarity is as follows: a minute is taken as a period, a plurality of nodes are continuously collected to obtain a harmonic proportion sequence H=[H1, H2,..., H10] and a cabinet temperature sequence T=[T1, T2,..., T10]; the difference between adjacent data of each sequence is calculated to obtain a harmonic change trend: ΔH=[H2-H1, H3-H2,..., H10-H9] and a cabinet temperature change trend: ΔT=[T2-T1, T3-T2,..., T10-T9]; and the direction consistency of the two trends, i.e., the similarity, is calculated using the cosine similarity.

[0051] Specifically, under the condition that the single-phase switching power supply low-voltage switch cabinet and the grid rated voltage are 220V, the preset similarity generally takes a value in the range of [0.65, 0.72], and the preferred embodiment of the preset similarity is 0.7.

[0052] Those skilled in the art can understand that the optional range and preferred embodiment of the preset similarity provided in the embodiment are the best values selected under the condition that the single-phase switching power supply low-voltage switch cabinet and the grid rated voltage are 220V, and the effect of solving the technical problem of the technical solution of the present application is the best, in actual application or experiment, those skilled in the art can adaptively adjust the preset similarity according to the actual application environment and application scene.

[0053] In implementation, for example, when the detection unit collects the harmonic signal proportion sequence H = [0.12%, 0.15%, 0.18%, 0.21%, 0.25%, 0.28%, 0.32%, 0.35%, 0.38%, 0.41%] with a cycle of one minute, the cabinet temperature sequence T = [35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃], ΔH = [0.03%, 0.03%, 0.03%, 0.04%, 0.03%, 0.04%, 0.03%, 0.03%, 0.03%], ΔT = [1℃, 1℃, 1℃, 1℃, 1℃, 1℃, 1℃, 1℃, 1℃], the cosine similarity calculation shows that the direction consistency is about 0.98, which is greater than the preset similarity, the control unit determines that the harmonic signal proportion is highly correlated with the increasing trend of the cabinet temperature, which indicates that the harmonic current increase causes the cabinet body to continuously heat up due to the increase of harmonic loss, the control unit sends an instruction to the reactive power compensation device to increase the access proportion of the reactive load, controls the switching of the switch to close, and puts in two groups of parallel power capacitor banks, each group of which has a capacity of 50kVar, and the access proportion of the reactive load is increased from the initial 15% to 25%.

[0054] In implementation, the device calculates the increasing node similarity of the harmonic signal proportion and the temperature change of the cabinet body, and then adjusts the access proportion of the reactive load. When the harmonic content and the cabinet temperature change trend similarity are large under the three-level protection level, it indicates that the harmonic loss is the main inducement for the abnormal rise of the cabinet temperature. At this time, the access proportion of the reactive load is increased, the voltage support capability of the system is improved by reactive compensation, the inductive or capacitive characteristics of the reactive load are used to offset the reactive component in the harmonic current, the transmission loss of the harmonic in the main bus is reduced, the Joule heat generated by the harmonic current flowing through the conductor is reduced, and the further rise of the temperature in the cabinet body is delayed.

[0055] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after the changes or replacements will fall within the protection scope of the present application.

Claims

1. An intelligent low voltage switchgear, characterized in that, The application relates to a power distribution cabinet. The cabinet body comprises an execution unit arranged in the cabinet body, a detection unit connected with the cabinet body and the execution unit, and a control unit connected with the execution unit and the detection unit. The execution unit comprises a circuit breaker trolley for breaking the current of a load circuit and a plurality of contactors for switching the load circuit. The detection unit detects the instantaneous voltage drop of the load, the current harmonic phase difference of the phase current signal of the main bus, the current harmonic signal proportion, and the temperature of the cabinet. The control unit determines the load protection level according to the instantaneous voltage drop of the load, adjusts the interval time of the asynchronous action start mode of the plurality of contactors according to the harmonic phase difference, and adjusts the access proportion of the reactive load according to the increasing node similarity of the harmonic signal proportion and the temperature of the cabinet.

2. The intelligent low voltage switchgear of claim 1, wherein, The detection unit comprises a voltage sensor for detecting the instantaneous voltage drop of the load, a current transformer arranged on the main bus of the load for detecting the harmonic phase difference of the phase current signal of the main bus and the harmonic signal proportion, and a temperature sensor arranged on the inner wall of the cabinet for detecting the temperature of the cabinet. The control unit is connected with the voltage sensor to obtain the instantaneous voltage drop. If the instantaneous voltage drop is greater than or equal to a preset first voltage and less than or equal to a preset second voltage, the load protection level is determined to be first-level protection. If the instantaneous voltage drop is greater than the preset second voltage and less than or equal to a preset third voltage, the load protection level is determined to be second-level protection.

3. The intelligent low voltage switchgear of claim 2, wherein, If the instantaneous voltage drop is greater than the preset third voltage, the load protection level is determined to be third-level protection. The instantaneous voltage drop is the difference between the instantaneous voltage detected by the voltage sensor and the instantaneous voltage detected at the last time. If the duration of the instantaneous voltage drop is greater than or equal to a preset time, the interval time of the asynchronous action start mode of the plurality of contactors is increased.

4. The intelligent low voltage switchgear of claim 3, wherein, The control unit adjusts the asynchronous action start time of the plurality of contactors to be the time point of the interval harmonic phase difference before the current zero-crossing point.

5. The intelligent low voltage switchgear of claim 4, wherein, The control unit respectively obtains the harmonic signal proportion and the temperature of the cabinet, and calculates the increasing node similarity.

6. The intelligent low voltage switchgear of claim 5, wherein, If the increasing node similarity is greater than or equal to a preset similarity, the access proportion of the reactive load is increased.

7. The intelligent low voltage switchgear of claim 4, wherein, The access proportion of the reactive load is the ratio of the power of the reactive load to the total power of the load circuit.

8. The intelligent low voltage switchgear of claim 4, wherein, ​ ​ 9. The intelligent low voltage switchgear of claim 8, wherein, ​ 10. The intelligent low voltage switchgear of claim 9, wherein, The harmonic signal proportion is a ratio of an effective value of a harmonic current component to an effective value of a fundamental current. The harmonic signal proportion is a ratio of an effective value of a harmonic current component to an effective value of a fundamental current.

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