Zero line protection circuit, device and method and unit power supply system

Abstract

The invention discloses a null line protection circuit, device and method and a unit power supply system. The null line protection circuit comprises an input circuit and a protector. The protector comprises at least one normally closed NC passive dry contact. The input circuit and the rear-end circuit form a power supply loop through the protector; and the protector is used for controlling the NC passive dry contact to disconnect the power supply loop based on the fault of the input circuit. The zero line of the power supply system is protected through the protector, and the important effect of protecting the safety of the device is achieved.

Description

Technical Field

[0001] The present invention relates to the field of electric power systems, and in particular to a neutral line protection circuit, device, method and unit power supply system. Background Art

[0002] In the power supply systems of data centers in the prior art, most use 380V industrial three-phase five-wire incoming lines. In low-voltage power supply systems, the disconnection of the distribution network neutral line is a common problem. In this field, the normal load of the neutral line can ensure the stability and symmetry of the three-phase AC voltage. The neutral line or neutral line can ensure that the three-phase load voltage is always equal to the phase voltage of the power supply and is not affected by the nature of the load itself. If any phase of the power line is disconnected, it only affects the voltage load of that phase and will not affect the voltage of the other two phases. However, in the event of a neutral line disconnection, the three-phase voltage is no longer balanced, causing the neutral point to shift, causing the three-phase voltage after the breakpoint to change, resulting in complete asymmetry. The voltage of some phases increases, which will damage electrical equipment, and the voltage of some phases is too low, and the electrical appliances cannot work normally.

[0003] Although neutral line disconnection often occurs, there is still no effective solution. For example, because most electrical equipment and appliances are single-phase load equipment, and the start-up or shutdown of the load is very random, it is difficult to achieve symmetry of the three-phase voltage when the neutral line is disconnected. The current practice is basically: try to distribute the load as evenly as possible in the power distribution link; strengthen the laying quality and connection method of the neutral line itself; specially select the material and cross-sectional area of ​​the neutral line itself; or increase the grounding area of ​​the equipment. However, these practices cannot fundamentally solve the above-mentioned defects, and there are still safety hazards.

[0004] At the same time, if the three-phase power system is connected incorrectly, the phase sequence cannot be consistent, and confusion is likely to occur, causing difficulty in future fault repairs. The power configuration phase sequence is inconsistent, and some equipment requires strict phase sequence requirements, such as shielded motors, air conditioning compressors, etc. It will cause reversal or even damage the equipment.

[0005] How to avoid problems such as overvoltage and phase error in the power supply system and achieve efficient neutral line protection is a problem that needs to be solved. Summary of the invention

[0006] The main purpose of the present invention is to provide a neutral line protection circuit, device, method and unit power supply system, which uses a protector to control the NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit, thereby realizing neutral line protection of the power supply system and achieving the important role of protecting the safety of the protection devices and the back-end circuits.

[0007] To achieve the above object, the present invention provides a neutral line protection circuit, comprising an input circuit and a protector; the protector comprises at least one normally closed NC passive dry contact;

[0008] The input circuit forms a power supply loop with the back-end circuit through the protector;

[0009] The protector is used to control the normally closed NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit.

[0010] Optionally, a power supply inlet terminal is further provided on the protector;

[0011] The live wire of the input circuit is connected to the back-end circuit through the power supply incoming line segment, and the neutral wire of the input circuit is connected to the back-end circuit through the normally closed NC passive dry contact.

[0012] Optionally, the input circuit includes a first transmission line, a second transmission line, a third transmission line and a neutral line;

[0013] The protector comprises a first power supply line terminal, a second power supply line terminal and a third power supply line terminal;

[0014] The first transmission line is connected to the first power supply input terminal, the second transmission line is connected to the second power supply input terminal, and the third transmission line is connected to the third power supply input terminal; the neutral line is connected to one of the normally closed NC passive dry contacts.

[0015] Optionally, a circuit breaker is also included, and the circuit breaker is connected between the normally closed NC passive dry contact and the back-end circuit.

[0016] Optionally, the circuit breaker comprises a synchronizing switch.

[0017] The present invention also provides a neutral line protection device, comprising the above-mentioned neutral line protection circuit. The neutral line protection circuit comprises an input circuit and a protector; the protector comprises at least one normally closed NC passive dry contact; the input circuit forms a power supply circuit with a back-end circuit through the protector; the protector is used to control the NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit.

[0018] The present invention also provides a unit power supply system, comprising a power supply, a back-end circuit and the above-mentioned neutral line protection device;

[0019] The neutral line protection device is connected to the power supply and the back-end circuit respectively.

[0020] The present invention also provides a neutral line protection method, which is applied to the above-mentioned neutral line protection circuit, and the method comprises:

[0021] Collecting electrical parameters of the input circuit;

[0022] Determining whether the input circuit is faulty based on the electrical parameter;

[0023] Based on the input circuit failure, the NC passive dry contact is controlled to disconnect the power supply circuit.

[0024] Optionally, based on the input circuit fault, controlling the normally closed NC passive dry contact to disconnect the power supply circuit includes:

[0025] Based on the input circuit fault, determining a fault type of the input circuit;

[0026] Based on the fact that the fault type is an overvoltage fault or a phase error fault, the normally closed NC passive dry contact is controlled to disconnect the power supply circuit.

[0027] In the technical solution of the present invention, a neutral line protection circuit, device, method and unit power supply system are provided, wherein the neutral line protection circuit includes an input circuit and a protector; the protector includes at least one normally closed NC passive dry contact; the input circuit forms a power supply circuit with the back-end circuit through the protector; the protector is used to control the normally closed NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit. The protector protects the neutral line of the power supply system, thereby achieving the important role of protecting the safety of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0030] Figure 1 It is a schematic diagram of a power supply architecture in the prior art;

[0031] Figure 2 A schematic diagram of a fault power supply architecture in the prior art;

[0032] Figure 3 A schematic diagram of a neutral line protection circuit provided in an embodiment of the present application;

[0033] Figure 4A schematic diagram of a zero line protection circuit fault provided in an embodiment of the present application;

[0034] Figure 5 A schematic diagram of a neutral line protection method flow chart provided in an embodiment of the present application;

[0035] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0038] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] The existing commonly used indirect evaporative cooling power supply architecture in data centers mostly uses 380V industrial three-phase five-wire incoming lines. At this time, each device that needs 220V strong power supply at the back end takes power from any one of the three phases A / B / C and N to control the power supply of the control system and switching power supply. When the input is overvoltage or the input fault of the live and neutral lines is wrong, a voltage of 380V or a voltage greater than the rated range of the device will be input between the three phases A / B / C and the N line, exceeding the pressure-bearing capacity of the control system and some devices, and damaging the subsequent devices.

[0042] Figure 1 Schematic diagram of power supply architecture in the prior art, such as Figure 1 As shown, the components that need 220V strong power supply at the back end take power from any one of the three phases A / B / C and N, which is used to control the power supply of the control system and the switching power supply. The circuit breaker is connected between the input circuit and the back end circuit.

[0043] Figure 2 This is a schematic diagram of a fault power supply architecture in the prior art. If a power supply voltage overvoltage or a live and neutral line phase mismatch input fault occurs, such as Figure 2 As shown, a voltage of 380V will be input into the A / B / C three-phase and N line, exceeding the pressure-bearing capacity of the control system and some components, and damaging the subsequent components.

[0044] According to the relevant national standards and industry regulations, the protector generally has functions such as residual current protection, short circuit protection, overload protection, zero / phase loss protection, overvoltage / undervoltage protection, etc. The embodiment of the present application proposes a neutral line protection circuit, which uses the passive dry contact of the three-phase protector to protect the neutral line of the power supply system, thereby achieving the important role of protecting the safety of control system components and subsequent components.

[0045] Figure 3 The neutral line protection circuit provided in an embodiment of the present application is shown, including an input circuit and a protector; the protector includes at least one normally closed NC passive dry contact; the input circuit forms a power supply loop with the back-end circuit through the protector.

[0046] The protector is used to control the NC passive dry contact to disconnect the power supply circuit based on the failure of the input circuit. The protector is a commonly used device for power supply system architecture detection. It can detect faults such as phase mismatch, phase loss, undervoltage, overvoltage, etc. of the input power supply, and output a normally open / normally closed signal through a passive / active dry contact. The products produced by different manufacturers have different appearances, but the principles are basically the same.

[0047] In a possible implementation, a power supply input terminal and an NC passive dry contact are provided on the protector; the live wire of the input circuit is connected to the back-end circuit through the power supply input segment, and the neutral wire of the input circuit is connected to the back-end circuit through the NC passive dry contact.

[0048] In a possible implementation, the input circuit includes a first transmission line L1, a second transmission line L2, a third transmission line L3 and a neutral line N; the protector includes a first power supply input terminal R, a second power supply input terminal S and a third power supply input terminal T.

[0049] The first transmission line L1 is connected to the first power supply input terminal R, the second transmission line L2 is connected to the second power supply input terminal S, and the third transmission line L3 is connected to the third power supply input terminal T; the neutral line N is connected to one of the NC passive dry contacts.

[0050] In a possible implementation manner, a circuit breaker is further included, and the circuit breaker is connected between the NC passive dry contact and the back-end circuit.

[0051] In a possible implementation manner, the circuit breaker includes a synchronous switch.

[0052] During the operation of the neutral line protection circuit, the electrical parameters of the input circuit are collected in real time, and the electrical parameters include current and voltage. Further, based on the electrical parameters, it is determined whether the input circuit is faulty; based on the input circuit fault, the NC passive dry contact is controlled to disconnect the power supply circuit. Specifically, based on the input circuit fault, the fault type of the input circuit is determined; based on the fault type being an overvoltage fault or a phase mismatch fault, the NC passive dry contact is controlled to disconnect the power supply circuit.

[0053] In the technical solution of the present invention, the neutral line protection circuit includes an input circuit and a protector; the protector includes at least one normally closed NC passive dry contact; the input circuit forms a power supply circuit with the back-end circuit through the protector; the protector is used to control the NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit. The protector protects the neutral line of the power supply system, thereby achieving the important role of protecting the safety of the device. By making full use of this characteristic of the three-phase protector, the three-phase protector is innovatively used as a line protection device in the protection of the control line, which can protect the controller and recover losses when a sudden power input failure occurs.

[0054] Figure 4 The schematic diagram of the neutral line protection circuit provided by the embodiment of the present application in the event of a fault is shown, wherein the neutral line protection circuit includes at least one NC passive dry contact (also known as passive dry node) protector and a related configuration line group. The input circuit forms a power supply loop with the back-end circuit through the protector; the input circuit includes three-phase transmission lines L1, L2, L3, a neutral line N, and a ground line PE.

[0055] Passive dry contacts are when the signal sender only needs to provide a pair of passive contacts. The signal receiver forms a current loop inside itself, and the dry contacts of the signal sender only need to play the role of "disconnecting" and "connecting" this loop. The signal sender does not need to know the signal voltage, current and polarity required by the signal receiver. It only needs to "turn on" or "turn off" the contacts of the signal receiver to transmit the switch signal to the receiver.

[0056] The protector can be a three-phase protector. R in the protector refers to the power supply line of the three-phase inverter; S refers to the power supply line of the three-phase servo drive; T refers to the power supply line of the three-phase servo spindle drive. It can display the three-phase power supply voltage in real time, and can provide users with alarm output and contact control signals of protection circuit action output in the form of relay output when the power supply has overvoltage protection, undervoltage protection, phase loss protection, unbalance protection, phase error protection and other faults, so as to play an alarm and protection role.

[0057] The phase sequence of the three-phase power supply is that the phase of the phase quantity is arranged in front, and the phase of the phase of the quantity is arranged in the back. The three phases are 120 degrees apart, the second phase lags the first phase by 120 degrees, and the last phase lags the first phase by 240 degrees. Since the phase difference of 360 degrees is equivalent to the same phase, the last phase is equivalent to leading the first phase by 120 degrees. The order of phases is the order in which the instantaneous value of the alternating current changes from negative to positive through zero. There are three conductors in the AC power system, which are divided into three phases. Under normal circumstances, the three-phase voltage and current are symmetrical, and the phase difference is 120. However, when a system failure occurs, the three phases are no longer symmetrical, and it is judged as a wrong item.

[0058] The protector is provided with a power supply inlet terminal and an NC passive dry contact; the live wire of the input circuit is connected to the back-end circuit through the power supply inlet segment, and the neutral wire of the input circuit is connected to the back-end circuit through the NC passive dry contact. L1 is connected to the power supply inlet terminal R of the frequency converter, L2 is connected to the power supply inlet terminal S of the servo drive, and L3 is connected to the power supply inlet terminal T of the servo spindle drive; the neutral wire N is connected to one of the NC passive dry contacts.

[0059] Connect the neutral line of the system to the NC passive dry contact of the three-phase protector, that is, use the NC node to control the on and off of the line, and the neutral line protection device will take effect. Due to the difference in performance of components from different manufacturers, the upper limit of the power that a single dry contact can withstand is different.

[0060] A circuit breaker is also provided between the NC passive dry contact and the back-end circuit, and the circuit breaker includes a synchronous switch.

[0061] During operation, the circuit collects electrical parameters of the input circuit in real time, including current and voltage. Further, based on the electrical parameters, it is determined whether the input circuit is faulty; further, if the input circuit is faulty, the NC passive dry contact is controlled to disconnect the power supply circuit.

[0062] In the process of determining whether the input circuit is faulty, specifically, the following methods are included but not limited to: based on the input circuit fault, determining the fault type of the input circuit; based on the fault type being an overvoltage fault or a phase error fault, controlling the NC passive dry contact to disconnect the power supply circuit.

[0063] The fault type includes but is not limited to an overvoltage fault or a phase error fault.

[0064] In short, when the input circuit is normal, the passive NC dry contact is closed, and the control neutral line is normally formed through the NC passive dry contact of the protector to supply power to the devices in the back-end circuit. When the input circuit fails, the protector detects the power failure and the passive NC dry contact is disconnected. At this time, although the voltage at the front stage of the circuit breaker rises suddenly, the circuit cannot be formed because the neutral line is broken, and the back-end devices are automatically powered off, achieving the effect of protecting the back-end load.

[0065] The three-phase protector provided in the embodiment of the present application adopts non-volatile storage technology to record faults when overvoltage, undervoltage, phase loss, imbalance, and phase sequence faults occur. Even if the power is completely cut off, the fault information can be memorized to facilitate fault query.

[0066] The dry contacts involved in the embodiments of the present application are equivalent to passive switches, and have two states: closed and open. There is no polarity between the two contacts, and they can be interchanged. The embodiments of the present application use normally closed passive dry contacts.

[0067] Common dry contact signals include: 1. Various switches such as limit switches, travel switches, foot switches, rotary switches, temperature switches, liquid level switches, etc. 2. Various buttons. 3. Outputs of various sensors, such as sensors in environmental power monitoring: water immersion sensors, fire alarm sensors, glass breakage, vibration, smoke and condensation sensors. 4. Outputs of relays and reed switches.

[0068] In a preferred embodiment of the present invention, a neutral line protection device is also provided, comprising the above-mentioned neutral line protection circuit.

[0069] The neutral line protection circuit includes an input circuit and a protector; the protector is provided with a power supply inlet terminal and an NC passive dry contact; the live wire of the input circuit is connected to the back-end circuit through the power supply inlet segment, and the neutral wire of the input circuit is connected to the back-end circuit through the NC passive dry contact. The input circuit forms a power supply loop with the back-end circuit through the protector; the protector is used to control the NC passive dry contact to disconnect the power supply loop when a fault occurs in the input circuit.

[0070] The input circuit includes a first transmission line, a second transmission line, a third transmission line and a neutral line; the protector includes a first power supply input terminal, a second power supply input terminal and a third power supply input terminal;

[0071] The first transmission line is connected to the first power supply incoming terminal, the second transmission line is connected to the second power supply incoming terminal, and the third transmission line is connected to the third power supply incoming terminal; the neutral line is connected to an NC passive dry contact.

[0072] The invention also comprises a circuit breaker connected between the NC passive dry contact and the back-end circuit. The circuit breaker comprises a synchronous switch.

[0073] The protector is used to protect the neutral line of the power supply system, thus achieving the important function of protecting the safety of the device. By making full use of this feature of the three-phase protector, the three-phase protector is innovatively used as a line protection device to protect the control line, which can protect the controller and recover the loss in the event of a sudden power input failure.

[0074] In a preferred embodiment of the present invention, a unit power supply system is also provided, including a power supply, a back-end circuit and a neutral line protection device; the neutral line protection device is respectively connected to the power supply and the back-end circuit to protect the neutral line through the protector, thereby achieving the important role of protecting the safety of the device and the back-end circuit.

[0075] The structure of the present invention can be applied not only to the power supply system of the unit, but also to any power supply system.

[0076] In a preferred embodiment of the present invention, a neutral line protection method is also provided, which is applied to the above-mentioned neutral line protection circuit. Figure 5 As shown, the method includes:

[0077] Step 501: Collecting electrical parameters of the input circuit;

[0078] Step 502: Determine whether the input circuit is faulty based on the electrical parameters;

[0079] Step 503: Based on the input circuit failure, control the NC passive dry contact to disconnect the power supply circuit.

[0080] In a possible implementation manner, in step 503, based on the input circuit fault, controlling the NC passive dry contact to disconnect the power supply circuit includes:

[0081] Based on the input circuit fault, determine the fault type of the input circuit; based on the fault type being an overvoltage fault or a phase error fault, control the NC passive dry contact to disconnect the power supply circuit.

[0082] When the input circuit is normal, the protector controls the passive NC dry contact to close, controls the neutral line to form a loop through the protector's NC passive dry contact, and supplies power to the devices in the back-end circuit. When the input circuit fails, the protector detects the power failure and controls the passive NC dry contact to disconnect. At this time, although the voltage at the front stage of the circuit breaker rises suddenly, the circuit cannot be formed because the neutral line is broken, and the back-end devices are automatically powered off, achieving the effect of protecting the back-end load.

[0083] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

[0084] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0085] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0086] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0087] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some implementation methods", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A neutral line protection circuit, characterized in that: It includes an input circuit and a protector; the protector includes at least one normally closed NC passive dry contact; The input circuit forms a power supply loop with the back-end circuit through the protector; The protector is used to control the normally closed NC passive dry contact to disconnect the power supply circuit based on a fault in the input circuit.

2. The neutral line protection circuit according to claim 1, characterized in that: The protector is further provided with a power supply inlet terminal; The live wire of the input circuit is connected to the back-end circuit through the power supply incoming line segment, and the neutral wire of the input circuit is connected to the back-end circuit through the normally closed NC passive dry contact.

3. The neutral line protection circuit according to claim 1, characterized in that: The input circuit includes a first power transmission line, a second power transmission line, a third power transmission line and a neutral line; the protector includes a first power supply input terminal, a second power supply input terminal and a third power supply input terminal.

4. The neutral line protection circuit according to claim 3, characterized in that: The first transmission line is connected to the first power supply input terminal, the second transmission line is connected to the second power supply input terminal, and the third transmission line is connected to the third power supply input terminal; the neutral line is connected to one of the normally closed NC passive dry contacts.

5. The neutral line protection circuit according to any one of claims 1 to 4, characterized in that: It also includes a circuit breaker connected between the normally closed NC passive dry contact and the back-end circuit.

6. The neutral line protection circuit according to claim 5, characterized in that: The circuit breaker includes a synchronizing switch.

7. A neutral line protection device, characterized in that: The invention comprises the neutral line protection circuit as described in any one of claims 1 to 6.

8. A unit power supply system, characterized in that: It comprises a power supply, a back-end circuit and the neutral line protection device according to claim 7; The neutral line protection device is connected to the power supply and the back-end circuit respectively.

9. A neutral line protection method, applied to the neutral line protection circuit according to any one of claims 1 to 6, characterized in that: The method comprises: Collecting electrical parameters of the input circuit; Determining whether the input circuit is faulty based on the electrical parameter; Based on the input circuit failure, the normally closed NC passive dry contact is controlled to disconnect the power supply circuit.

10. The neutral line protection method according to claim 9, characterized in that: The controlling the normally closed NC passive dry contact to disconnect the power supply circuit based on the input circuit fault comprises: Based on the input circuit fault, determining a fault type of the input circuit; Based on the fact that the fault type is an overvoltage fault or a phase error fault, the normally closed NC passive dry contact is controlled to disconnect the power supply circuit.

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