A signal injection device for TN-S power supply system

Abstract

The present invention discloses a signal injection device for a TN‑S power supply system, and belongs to the field of power monitoring technology. The device comprises: a signal generation and amplification module, a multifunctional tuning module, a data processing and control module, a communication module, and a working power supply module. The multifunctional tuning module comprises: a coupling capacitor, a signal output transformer, a power supply transformer, and a reactor; the present invention adopts an open triangle line signal injection method, and considers the signal amplifier, coupling capacitor, signal transformer, power supply transformer, and reactor as a whole, and designs them into an L‑C‑R series resonance mode, which is a technical innovation method for creating a basic signal for online real-time monitoring of insulation resistance in a TN‑S system under the condition of symmetrical line-to-ground impedance, and provides an important means for the safe and reliable operation of the power supply system.

Description

Technical Field

[0001] The present invention relates to the technical field of power monitoring, and more particularly to a signal injection device for a TN-S power supply system. Background Art

[0002] At present, for power supply systems (IT systems) where the neutral point of the transformer is grounded through an arc suppression coil, the signal injection method where the signal injection device is connected between the neutral point of the transformer and the earth is more common. Because the ground wire current of the neutral point of the transformer grounded through the arc suppression coil is very small, and the current flowing through the injection device is also very small, so the injection device can easily inject signal current into the power supply system.

[0003] However, the TN-S system, also known as the three-phase five-wire power supply system, is a low-voltage power distribution system. This system consists of a distribution substation, a high-voltage distribution line (i.e., a voltage above 1 kV), a power supply transformer, a low-voltage distribution line (a voltage below 1 kV), and corresponding control and protection equipment. In the TN-S system, the transformer neutral point grounding line current is very large in the case of a ground fault, especially a metallic ground fault, and the grounding current is as high as several thousand amperes. At this time, the signal injection device connected between the transformer neutral point and the earth is a load of the power supply system, and the injection device will bear a large fault short-circuit current from the power supply system. In addition, for the three-phase TN-S system, since the load current and the ground leakage current cannot be separated, the insulation resistance of the line is an important electrical parameter that is not clear and cannot be understood but is distributed. Real-time online monitoring of the insulation resistance of the power supply system is a very difficult problem at present. It can be seen that in the prior art, such a large current cannot be injected into the source device, and the insulation resistance monitoring of the TN-S system under the condition of symmetrical line-to-ground impedance cannot be realized.

[0004] Therefore, how to provide a signal injection device for a TN-S power supply system that can solve the above-mentioned problems is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0005] In view of this, the present invention provides a signal injection device for a TN-S power supply system, which can provide a safe and reliable injection signal in real time during online insulation resistance monitoring.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A signal injection device for a TN-S power supply system, comprising:

[0008] Signal generation and amplification module, multifunctional tuning module, data processing and control module, communication module and working power supply module;

[0009] Among them, the signal generation and amplification module generates a sinusoidal AC signal of the target injection frequency, and amplifies and outputs the sinusoidal AC signal; the multifunctional tuning module processes the sinusoidal AC signal and injects it into the TN-S power supply system by electromagnetic induction; the signal voltage establishment module is used to establish the signal voltage and limit the single-phase grounding current; the data processing and control module detects the working status and controls the rapid protection action in the event of a fault; the communication module uploads the status information detected by the data processing and control module to the host computer; the working power supply module provides working power for each module.

[0010] Preferably, the multifunctional tuning module comprises: a coupling capacitor, a signal output transformer, a power supply transformer and a reactor;

[0011] Among them, the connection between the power amplifier output voltage and the signal output transformer is realized through the coupling capacitor, and the coupling capacitor, the signal output transformer, the power supply transformer and the reactor form an LCR series resonance mode, so that the signal transmission channel is a circuit in the form of LRC series resonance, which is used for signal coupling and self-protection.

[0012] Preferably, the reactor in the multifunctional tuning module is arranged between the neutral point on the low-voltage side of the power supply transformer and the ground grid to play a role in establishing the signal voltage.

[0013] Preferably, the signal output transformer includes: receiving the signal of the coupling capacitor, connecting the strong current with the weak current, and superimposing the weak current injection signal on the TN-S power supply system, forming an open triangle through the signal output transformer, and injecting the signal from the open triangle end, and the induced voltage is injected from the secondary ABC output end of the main transformer into the power supply line of the TN-S power supply system.

[0014] Preferably, the data processing control module includes: a detection circuit and a single chip microcomputer;

[0015] Wherein, the detection circuit is used to detect the output voltage and current of the injection source;

[0016] The single chip microcomputer is used to receive and process the detection signal, determine the current working state, and output corresponding control instructions.

[0017] Preferably, the communication module includes: a 485 chip and an isolation circuit, which uploads the status information detected by the data processing control module to the host computer

[0018] It can be seen from the above technical scheme that compared with the prior art, the present invention discloses a signal injection device for a TN-S power supply system, which adopts an open triangle line signal injection, and considers the signal amplifier, coupling capacitor, signal transformer, power supply transformer, and reactor as a whole, and designs them into an LCR series resonance mode. This is a technical innovation method for creating a basic signal for online real-time monitoring of insulation resistance in a TN-S system under the condition of symmetrical line-to-ground impedance, so as to achieve real-time and accurate detection of line insulation performance and ensure power safety and fire safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0021] Figure 2 It is a wiring diagram of the injection device of the present invention and the TN-S power supply system;

[0022] Figure 3 This is the circuit schematic diagram of the multifunctional tuning module;

[0023] Figure 4 is the equivalent circuit diagram of the injection device and the power supply system;

[0024] Figure 5 It is a simplified equivalent circuit diagram of the injection device and the power supply system;

[0025] Figure 6 is the equivalent circuit diagram for a single-phase transformer;

[0026] Figure 7 The schematic diagram of the power amplifier output connected to the signal transformer through a resistor or inductor;

[0027] Figure 8 This is the schematic diagram of the power amplifier output directly connected to the signal transformer;

[0028] Fig. 9 The schematic diagram of single-phase grounding in the power supply system;

[0029] Fig.10 This is the schematic diagram of a non-metallic ground fault. DETAILED DESCRIPTION

[0030] 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.

[0031] See also Figure 1 As shown, an embodiment of the present invention discloses a signal injection device for a TN-S power supply system, comprising:

[0032] Signal generation and amplification module, multifunctional tuning module, data processing and control module, communication module and working power supply module;

[0033] In a specific embodiment, see Figure 3 As shown, the multifunctional tuning module includes a coupling capacitor C, a signal output transformer T2, a power supply transformer T1 and a reactor L, which together form an LCR series resonance mode design, realize the coupling of the front and rear stages of the signal voltage, the isolation of the DC component, the stabilization of the electronic circuit working point, the avoidance of the DC component flowing into the signal output transformer, the improvement of the power amplifier efficiency, and the power amplifier self-protection function when single-phase grounding occurs in the power supply system.

[0034] In a specific embodiment, the installation position of the signal voltage establishment module is shown in Figure 2 The L in the signal voltage establishment module is mainly composed of a high-power reactor. The inductor of the reactor has different inductance with different signal frequencies. The injected signal frequency is 6 times the industrial frequency, and the inductance is also 6 times, which can reduce the power of the injected signal source.

[0035] In a specific embodiment, the data processing control module mainly includes: a detection circuit and a single chip microcomputer, which mainly performs rapid detection on the output voltage and current of the injection source, determines the current working state, and performs rapid control.

[0036] In a specific embodiment, the communication module includes: a 485 chip and an isolation circuit, which uploads the status information detected by the data processing control module to the host computer.

[0037] Specifically, the signal generation and amplification module generates a sinusoidal AC signal of the target injection frequency, and amplifies it to a voltage signal with a set power for signal generation and amplification; the multifunctional tuning module receives the AC signal through a coupling capacitor; the signal output transformer in the multifunctional tuning module is used to achieve safe connection between strong and weak electricity after receiving the signal of the coupling capacitor, and safely superimpose the weak current injection signal on the strong power supply system, and the primary of the three-phase transformer is formed into an open triangle through the signal output transformer in the multifunctional tuning module, and the signal is injected from the open triangle end, and the induced voltage is injected from the secondary output ABC end of the main transformer into the power supply line respectively; the inductor is used to establish the signal voltage and limit the single-phase grounding current; the data processing and control module is used to monitor the working status of the injection device and protect it in the event of a fault; the communication module is used to upload the relevant signals of the injection device to the upper-level department, or accept the instructions of the upper-level department to act; the working power supply module is used to provide stable working power to each unit of the injection device.

[0038] In a specific embodiment, the device of the present invention is installed in a TN-S power supply system. Figure 2 M: T1: power supply transformer; UA, UB, UC grid voltage; Ua, Ub, Uc transformer secondary voltage; L: grounding reactor; CT1: residual current transformer; M: injection device; ia, ib, ic, in power supply line A, B, C, N line current; iaf, ibf, icf power supply line A, B, C phase load current; iad, ibd, icd power supply line A, B, C phase residual current; Ca, Cb, Cc power supply line A, B, C relative to ground leakage capacitance; Ra, Rb, Rc power supply line A, B, C relative to ground insulation resistance; Zfa, Zfb, Zfc power supply line A, B, C phase load; K1: grounding relay; Rb: grounding resistance;

[0039] Specifically, in the injection device: Ao: power amplifier; CT2: current transformer; T2: signal output transformer; Sx: signal source; C: coupling capacitor; K2: power amplifier protection relay.

[0040] In a specific embodiment, Figure 4-6 , which is an equivalent circuit schematic diagram after the injection device of the present invention is connected to the TN-S power supply system.

[0041] Figure 4 In order to facilitate analysis, the parameters of the power supply system grid power S and power supply transformer T1, signal output transformer T2, and reactor XL are all converted to the open triangle side of the signal transformer T2. The grid power potential conversion value is S', and its internal resistance conversion value is Rs'; the transformation ratio of the system transformer T1 is k1 = U 高 / U 低, the primary winding leakage reactance is converted to X1', the primary winding resistance is converted to R1', the secondary winding leakage reactance is converted to X2', the secondary winding resistance is converted to R2', and the excitation impedance is converted to Zm'; the transformation ratio of the signal output transformer T2 is k2 = U Y / U ▲ , the primary winding leakage reactance is converted to x1', the primary winding resistance is converted to r1', the secondary winding leakage reactance is x2, the secondary winding resistance is r2, and the excitation impedance is Zmx; the reactor reactance is converted to XL'; Zj' is the parallel connection of Zja', Zjb', and Zjc' after the insulation impedance of each phase of the line is converted; the capacitive reactance of the resonant coupling capacitor is Xc.

[0042] The line parameters are transformed as follows:

[0043] Rs'=Rs / (k1*k2)2, R1'=R1 / (k1*k2)2, X1'=X1 / (k1*k2)2, R2'=R2 / k22, X2'=X2 / k22,

[0044] Zm'=Zm / k22, XL'=XL / k22, Zj'=(Zja / / Zjb / / Zjc) / k22, r1'=r1 / k22, x1'=x1 / k22;

[0045] Assume: Z1'=R1'+jX1', Z2'=R2'+jX2', Z1'=r1'+jx1', z2'=r2'+jx2', Z1"=Z1'+Z2'

[0046] z1”=z1'+z2'

[0047] From the above conversion, we can know that: because the capacity of the power grid can be regarded as infinite, then Rs'→0; Zm'>>Z1'; Zmx>>(Z1'+Z2'+z1'), for the signal injection device, the power grid equipment becomes the load of the injection device. Figure 4 The circuit can be simplified to Figure 5 :

[0048] Wherein: Z1” is the converted value of the internal impedance of transformer T1, z1” is the converted value of the internal impedance of signal output transformer T2, XL’ is the converted value of the grounding reactor, Zj’ is the converted value of the insulation impedance of the power supply line to the ground, and Zj’=(Zja / / Zjb / / Zjc) / k22.

[0049] Specifically, if the power supply transformer T1: Sn = 2000kA, U1n = 10kV, U2n = 400V, short-circuit voltage Ud% = 5%, then k1 = 10000 / 400 = 25, I1n = 2000000 / (400*sqr3) = 2887AZ1n = 400 / 2887 = 0.14Ω, transformer internal resistance: Z1d = Z1n*Ud% = 0.14*5% = 0.007Ω;

[0050] If the signal transformer T2: Snx = 500VA, U1nx = 220V, U2nx = 100V, the short-circuit voltage Udx% = 10%;

[0051] Then k2=220 / 100=2.2, I1nx=500 / (100*sqr3)=2.88A; Z1nx=100 / 2.88=34 ohms, internal resistance of signal transformer: Z1xd=Z1nx*Udx%=34*10%=3.4Ω.

[0052] Convert the short-circuit impedance of the power supply transformer T1 and the short-circuit impedance of the signal transformer T2 to one side of the delta winding of the signal transformer, then: Z1" = Z1d / k22 = 0.007 / 2.22 = 0.0014Ω; z1" = Z1xd = 3.4Ω.

[0053] It can be seen from this that the internal impedance of the power supply transformer T1 can be completely ignored. The equivalent circuit diagram is shown in Figure 5 .

[0054] Figure 6 This is the equivalent circuit diagram for a single-phase transformer, U2=U1-Ix*z1”; for a three-phase transformer, since U1 is added to the three-phase open delta winding, the voltage distributed to each winding is U1'=U1 / 3, U2'=U1 / 3-Ix*z1”.

[0055] Depend on Figure 6 It can be seen that the signal transmission channel is designed as an LRC series resonance circuit, and the connection between the power amplifier output voltage and the signal transformer is achieved through the coupling capacitor C, rather than the direct connection between the power amplifier output voltage and the signal transformer or the connection through a resistor or a reactance.

[0056] Depend on Figure 6It can be seen that the signal transmission circuit is designed as an LRC circuit (∵Zj'>>XL), the base frequency (f1=50Hz) inductance of the reactor is XL1=5Ω, the signal frequency (f6=300Hz) inductance of the reactor is XL6=30Ω; the base frequency internal resistance of the signal transformer T2 is z=3.4Ω. Assuming that the copper resistance and leakage reactance are equally distributed, XL1=3.4*0.707=2.4Ω, r1=2.4Ω; XL6=6*XL1=2.4*6=14.4Ω. XL'=30 / 2.22=6.2Ω.

[0057] Since the power amplifier output voltage U1 is added to the open delta winding of the signal transformer, the voltage is equally divided by the three windings and then induced and output to each phase of the ABC power supply system. U1 is not directly connected to a certain winding of the open delta and then induced and output, so there is a connection coefficient J = 3. Then the actual power supply line injection signal Uz = k2*U1 / J.

[0058] The total inductance of the injected signal loop ΣXL=XL'+XL1'=6.2+14.4=20.6Ω, and the coupling capacitance C at resonance is: C=1000000 / (2*π*300*20.6)=25.6(uF).

[0059] In order to make the injected signal have good stability, the coupling capacitor is C = 10uF, Xc6 = 53Ω, Ix = Uo / (Xc-(XL'+z1'))≈30 / (53-20.6) = 0.925A (ignore r1) U1 = Ix*(XL'+z1') = 19.1V; Uc = Ix*Xc = 49V

[0060] The signal Uz actually injected into the power supply line is: Uz=k2*U1 / J=13.97V; J: connection coefficient of open triangle: Uo=Uc-U1=49-19.1=30V.

[0061] In a specific embodiment, the signal injection channel is designed in LCR series mode, and the following features are achieved:

[0062] (1) By Figure 5 It can be seen that the injection loop has the minimum impedance and the signal injection current has the maximum value, which is convenient for the weak current signal current to be coupled and superimposed on the strong power supply system. When C = 10uF, Ix ≈ 0.925A, the power amplifier output voltage Uo = 30V, and the line signal voltage Uz = 13.97V;

[0063] (2) If the amplifier output is not coupled through a coupling capacitor but is directly connected to the signal transformer through a resistor or inductor (such as Figure 7), R will heat up a lot during normal operation; the inductor will affect the output power of the power amplifier, resulting in reduced efficiency of the power amplifier injection signal, increased power consumption of the power amplifier, unstable working point and other disadvantages; the DC component injected into the signal transformer will cause the transformer to be magnetized and saturated, the waveform will be distorted, the excitation current will increase, and the transformer will overheat.

[0064] (3) Capacitor coupling, isolating DC and conducting AC. The DC shunt of the power amplifier cannot enter the transformer winding, thus avoiding the deviation of the transformer hysteresis loop and the deviation of the power amplifier working point.

[0065] (4) By properly adjusting the coupling capacitor C, the injected signal of the power supply line can obtain a voltage value higher than the output of the power amplifier;

[0066] (5) When a single-phase ground fault occurs in the power supply system, the power amplifier is close to being short-circuited. At this time, the reactance Xc6 generated by the designed coupling capacitor C has a strong current limiting effect. At this time, the signal fault current is: Idx≈Uo / Xc6=30V / 53=0.38A, and the coupling capacitor effectively protects the power amplifier;

[0067] Specifically, if the amplifier output is not connected through a coupling capacitor but directly to the signal transformer (see Figure 8 ), at this time the power amplifier current is very large, causing great harm to the power amplifier.

[0068] (6) When a single-phase ground fault occurs in the power supply system, the open delta winding of the signal transformer will have a fundamental voltage of 100V, which is applied to the power amplifier circuit. At this time, the power amplifier becomes the load of the power supply system. At this time, the designed coupling capacitor C generates a reactance of Xc1=6*Xc1=53*6=318Ω. The current backflow to the power amplifier is: Idg=100V / Xc1=0.314A, Xc1>>Xc6, and the coupling capacitor has a strong current limiting effect, which protects the power amplifier; see Fig. 9 .

[0069] (7) When the power grid has a third harmonic voltage, the open delta winding will generate a third harmonic voltage. The coupling capacitor reactance Xc3 = 106Ω. Assuming the third harmonic voltage U3 = 100V, the third harmonic backflow current I3 = 100V / 109 = 0.92A, the third harmonic backflow power: P3 = 100*0.92 = 92W, which is less than the rated power of the power amplifier 500W, indicating that the coupling capacitor effectively plays a current limiting role and protects the power amplifier; secondly, since the internal resistance of the power amplifier is very small, the heat generated is very small. In fact, the third harmonic voltage is not at the level of 100V.

[0070] (8) The injection device is designed with overcurrent protection, overvoltage protection, power-off protection, etc. When the injection device fails to work normally for any reason, the injection device will quickly disconnect from the power supply system to ensure the safe operation of the power supply system and the safety of the power amplifier.

[0071] In a specific embodiment, the principle of the above technical solution is described as follows:

[0072] When a non-metallic grounding fault (live wire grounded) occurs in the line, refer to Fig.10 , the voltage Upe of the PE line will not increase due to the addition of the signal injection source. Before the injection device is added, the short-circuit current Id of non-metallic single-phase grounding is Id = U / (Ra + Rb + Zd), where U is the phase voltage, Ra is the grounding resistance of the transformer, Rb is the grounding resistance of the grounding point, and Zd is the short-circuit impedance of the transformer; when the injection device is added, the short-circuit current Id' of non-metallic single-phase grounding is Id' = U / (Ra + Rb + Zd + XL1), where XL1 is the fundamental wave reactance generated by the injection device on the neutral reactor of the transformer. Id' < Id, and Upe = Id * Ra, Upe' = Id' * Ra, so Upe' < Upe. Therefore, the potential of Upe' decreases, ensuring personal safety.

[0073] When a metallic grounding fault (live wire connected to the PE line) occurs in the line, before the injection device is added, the short-circuit current Id = U / (Ra + Zd); when the injection device is added, Id' = U / (Ra + Zd + XL); the short-circuit current of the metallic grounding fault is reduced to avoid the impact of the short-circuit current on the transformer, and the fault current is clamped within the range of Id' = U / (Ra + Zd + XL).

[0074] When it is detected that the ground wire current Id of the transformer is greater than the threshold, the injection device controls the normally open contact relay K1 to close within 20 ms. The action time limit of the ground protection is 0.4S, which will not affect the sensitivity of the existing protection.

[0075] In a specific embodiment, the signal generation and amplification module M1 realizes the following functions:

[0076] (1) Generate a sine wave signal.

[0077] (2) For the selection of the signal source frequency, the following aspects are considered:

[0078] This frequency is beneficial to establishing a signal voltage in the power supply system. As Figure 5 shows, the signal voltage U2 of the power supply system is U2 = Ix * (XL' / / Zj'), where: Ix: signal injection current; XL': conversion value of the grounding reactor on the low-voltage side of the transformer, XL' = (2 * π * f * L) / k22; Zj': conversion value of the impedance of the power supply line to the ground, Zj' = Rj / k22 - j1 / (2 * π * f * C) / k22, C is the leakage capacitance to the ground; thus, the higher the frequency f, the more beneficial it is to establish the injected signal, but the higher the frequency, the smaller the capacitive reactance of the line to the ground and the larger the capacitive current, which is more unfavorable for the test of the insulation resistance of the power supply line. Therefore, it needs to be selected appropriately.

[0079] The harmonic components containing the injected frequency in the power grid should be small in order to obtain a relatively stable measurement signal.

[0080] In the signal injection channel, the LRC is convenient for generating resonance to obtain higher power amplifier efficiency.

[0081] It is related to the AD sampling rate. The higher the injection signal frequency, the higher the AD sampling rate is required.

[0082] Taking the above factors into consideration and analyzing the normal power grid data, the sixth harmonic component of the power grid is relatively small. Therefore, 300Hz is the most suitable frequency for the injection signal.

[0083] In a specific embodiment, the following functions are implemented for the power amplifier:

[0084] (1) Amplify the small voltage signal of the signal source to a voltage signal with a set power, and the power amplifier has a sufficiently large power supply.

[0085] (2) The power supply voltage of the power amplifier is greater than the voltage component applied in reverse to the power amplifier itself when the power supply system is single-phase grounded.

[0086] (3) The voltage amplitude of the injected signal meets the requirements of the line insulation resistance measurement equipment.

[0087] (4) The output signal voltage of the power amplifier is set to 30V, the power supply voltage of the power amplifier is greater than 2*30*1.414=85V, and the negative power supply is taken as positive and negative 50.

[0088] Data processing control module, communication module and working power supply module;

[0089] In a specific embodiment, the signal output transformer implements the following functions:

[0090] In order to safely inject a single-phase weak current signal into a strong current power supply system, the present invention innovatively designs a three-phase signal transformer as an injection bridge between the power supply system (strong current) and the injected signal system (weak current).

[0091] Specifically, the signal injection bridge uses a three-phase signal transformer, the grid side uses a star connection method, the neutral point is grounded, and a signal loop is formed; the power amplifier side uses an open triangle connection method to connect with weak current signals. The transformation ratio is 220V / 100V. The three-phase signal transformer is easy to manufacture to meet the requirements of ground insulation. Its advantages are as follows:

[0092] (1) The voltage output by the open delta winding at 50Hz mains voltage is very small. When the three-phase circuit is completely symmetrical, the open delta voltage is zero. The open delta winding is very conducive to the access of the injection signal.

[0093] (2) Smoothly realize the safe coupling and signal superposition of three-phase strong electricity and single-phase signal weak electricity.

[0094] The output signal voltage of the power amplifier is coupled to the signal transformer through an open delta winding. The signal transformer injects almost equal-value and same-phase measurement signals into each phase of the power supply system, providing a good measurement signal for the line insulation online monitoring equipment.

[0095] (3) Three-phase signal transformer: For the power supply system, the star side bears the strong voltage of 380V / 220V; the open triangle side only bears the weak signal voltage.

[0096] (4) After adding the signal injection device, the original insulation level of the power supply system is maintained.

[0097] (5) The capacity of the three-phase signal transformer is designed to be 500W.

[0098] In summary, due to the single-phase ground short circuit in the TN-S system, the short-circuit current flowing through the neutral point grounding short circuit on the low-voltage side of the transformer is very large, especially for metallic ground faults, the short-circuit current is as high as several thousand amperes. If a signal injection device is connected in series between the neutral point N on the low-voltage side of the transformer and the ground grid P, the fault short-circuit current will flow through the injection source device, which is not allowed. To solve this problem, this device adopts the line signal injection method of the open triangle, and considers the signal amplifier, coupling capacitor, signal transformer, power supply transformer, and reactor as a whole, and designs it into an LCR series resonance mode, which is a technical innovation method for creating basic signals for the TN-S system to realize online real-time monitoring of insulation resistance under the condition of symmetrical line-to-ground impedance, and provides an important means for the safe and reliable operation of the power supply system.

[0099] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0100] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A signal injection device for a TN-S power supply system, characterized in that: include: Signal generation and amplification module, multifunctional tuning module, data processing and control module, communication module and working power supply module; Among them, the signal generation and amplification module generates a sinusoidal AC signal of the target injection frequency, and amplifies and outputs the sinusoidal AC signal; the multifunctional tuning module couples and receives the sinusoidal AC signal and injects it into the TN-S power supply system in the form of electromagnetic induction; the reactor in the multifunctional tuning module is used to establish the signal voltage and limit the single-phase grounding current; the data processing and control module detects the working state and controls the rapid protection action in the event of a fault; the communication module uploads the state information detected by the data processing and control module to the host computer; the working power supply module provides working power for each module; Wherein, the multifunctional tuning module comprises: a coupling capacitor, a signal output transformer, a power supply transformer and a reactor; The coupling capacitor is used to connect the power amplifier output voltage to the signal output transformer. The coupling capacitor, the signal output transformer, the power supply transformer and the reactor form an LCR series resonance mode, so that the signal transmission channel is a circuit in the form of LRC series resonance, which is used for signal coupling and self-protection. The reactor in the multifunctional tuning module is arranged between the neutral point on the low voltage side of the power supply transformer and the ground grid to play a role in establishing the signal voltage; The signal output transformer receives the coupling capacitor signal of the multifunctional tuning module, connects the strong current with the weak current, and superimposes the weak current injection signal on the TN-S power supply system. An open triangle is formed through the signal output transformer once, and the signal is injected from the open triangle end. The induced voltage is respectively injected from the secondary ABC output ends of the signal output transformer into the power supply line of the TN-S power supply system.

2. A signal injection device for a TN-S power supply system according to claim 1, characterized in that: The data processing control module includes: a detection circuit and a single chip microcomputer; Wherein, the detection circuit is used to detect the output voltage and current of the injection source; The single chip microcomputer is used to receive and process the detection signal, determine the current working state, and output corresponding control instructions.

3. The signal injection device of a TN-S power supply system according to claim 1, characterized in that: The communication module includes: a 485 chip and an isolation circuit, which uploads the status information detected by the data processing control module to the host computer.

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