Controllable grounding stray current protection circuit of building

Abstract

The utility model discloses a controllable grounding stray current protection circuit of a building, which is connected in series between the building and an earth screen and comprises a lightning protection circuit and a stray current backflow prevention circuit which are connected in parallel, and the lightning protection circuit comprises a first lightning protection branch and a second lightning protection branch which are connected in parallel. The parallel end of the first ceramic gas discharge tube and the second ceramic gas discharge tube is connected in series with the third ceramic gas discharge tube and then is grounded to a grid, the anti-backflow circuit comprises a first anti-backflow branch and a second anti-backflow branch which are connected in parallel, and the first anti-backflow branch comprises a first resistor and a parallel branch which are connected in series. According to the utility model, the controllable grounding stray current protection of the building is realized, the surge current is effectively drained to the grounding grid, and the stray current is prevented from flowing to the building, so that the problems that the electric equipment of the building is interfered by electromagnetic interference and the steel bar structure is corroded are solved, and the stable operation and safety of each facility in the building are ensured.

Description

Technical Field

[0001] The utility model relates to a controllable grounding stray current protection circuit for a building. Background Art

[0002] In my country's subway system, a DC traction power supply system is generally used. The traction current flows out from the positive pole of the traction station, flows to the train through the traction network and pantograph, and then flows back to the negative pole of the traction station through the running rail. However, due to the long-term operation of the subway, it is impossible to avoid the influence of factors such as moisture and pollution. The running rail cannot be completely insulated from the ground. Therefore, part of the current will leak from the running rail to the ground and surrounding structures. This part of the current is the stray current. Stray current corrosion often occurs in subway tunnels, roadbeds, spikes and other structures, and some corrosion sites are relatively hidden, which will bring hidden dangers to the operation of the subway. Stray current will not only damage the structure of the subway itself, but also invade underground metal pipelines, including pipes, cables, etc. At the same time, it will flow to the concrete structure steel bars near the subway, causing electrochemical corrosion. Once electrochemical corrosion occurs, it will accelerate the corrosion of surrounding metal structures, which will cause serious harm to the safe operation of the subway system. The impact of stray current on buildings around the subway cannot be ignored. In order to prevent surge current from causing damage to electrical equipment and residents when a building is struck by lightning, a ground grid is generally laid under the building so that the surge current can flow from the ground grid to the earth. However, during the operation of the subway system, stray currents will cause serious corrosion to the metal parts in the building, causing damage to the building and accelerating aging. They will also cause electromagnetic interference to surrounding electronic equipment, affecting the operation of electronic equipment in the building. At the same time, some stray currents flow to the ground grid through the drainage network, and then flow to the building, which poses a great threat to the safety of electrical equipment and personnel in the building. Therefore, in order to reduce the damage to the building caused by stray currents and ensure the normal operation of electrical equipment and personnel safety in the building, it is very necessary to adopt controllable grounding stray current protection for the building. Utility Model Content

[0003] The main technical problem solved by the utility model is to provide a controllable grounding stray current protection circuit for a building, which realizes the controllable grounding stray current protection of the building, effectively discharges the surge current to the ground grid, and prevents the stray current from flowing into the building, thereby solving the problems of electromagnetic interference of the building's electrical equipment and corrosion of the steel structure, and ensuring the stable operation and safety of various facilities in the building.

[0004] In order to solve the above technical problems, a technical solution adopted by the utility model is: to provide a controllable grounding stray current protection circuit of a building, which is connected in series between the building and the ground grid, including a lightning protection circuit and a stray current backflow protection circuit connected in parallel, the lightning protection circuit includes a first lightning protection branch and a second lightning protection branch connected in parallel, the first lightning protection branch includes a first varistor and a first ceramic gas discharge tube connected in series, the second lightning protection branch includes a second varistor and a second ceramic gas discharge tube connected in series, the first ceramic gas discharge tube and the second ceramic gas The parallel end of the discharge tube is connected in series with the third ceramic gas discharge tube and then connected to the ground grid. The backflow prevention circuit includes a first backflow prevention branch and a second backflow prevention branch connected in parallel. The first backflow prevention branch includes a first resistor and a parallel branch connected in series. Three parallel branches are provided, including a second resistor and a first diode connected in series, a voltage regulator tube and a capacitor. One end of the parallel branch is connected to the gate of the NMOS tube, and the other end is connected to the source. The drain of the NMOS tube is connected to the ground grid. The second backflow prevention branch includes a third resistor and a second diode connected in series.

[0005] In a preferred embodiment of the present invention, the anode of the voltage regulator tube, the cathode of the first diode and the cathode of the second diode are all connected to the source of the NMOS tube.

[0006] In a preferred embodiment of the utility model, when the building is not struck by lightning, the first ceramic gas discharge tube, the second ceramic gas discharge tube and the third ceramic gas discharge tube act as switching elements, and the first ceramic gas discharge tube, the second ceramic gas discharge tube and the third ceramic gas discharge tube are disconnected, which is equivalent to an open circuit. At this time, the external voltage is less than the conduction voltage of the first varistor and the second varistor, and the first varistor and the second varistor are in a high-resistance state, which is similar to an open circuit. The current cannot flow from the building to the ground grid through the lightning protection circuit, and because the circuit is equivalent to an open circuit state, stray current cannot flow into the building through the circuit.

[0007] In a preferred embodiment of the utility model, when a building is struck by lightning, there is a surge current, and the first ceramic gas discharge tube, the second ceramic gas discharge tube and the third ceramic gas discharge tube are turned on, which is equivalent to a short circuit, and a large current can pass through. At this time, the externally applied voltage is greater than the turn-on voltage of the first varistor and the second varistor, and the first varistor and the second varistor are broken down and are in a low-resistance state. The surge current can be successfully discharged from the building to the ground grid until the external voltage is less than the turn-on voltage of the first varistor and the second varistor, and the first varistor and the second varistor can return to a high-resistance state.

[0008] In a preferred embodiment of the utility model, when the building presents a forward potential to the ground grid, the body diode of the NMOS tube is turned on, and a small current flows from the building through the third resistor and the second diode and then through the body diode to the ground grid.

[0009] In a preferred embodiment of the present invention, when the gate-source voltage of the NMOS tube is greater than the turn-on voltage of the NMOS tube, the NMOS tube is turned on, and the body diode is short-circuited, and the line forms a loop through the NMOS tube. At this time, the voltage regulator tube plays a role in preventing the voltage from being too large and the NMOS tube from being broken down, and the capacitor C plays a role in soft start, so that the gate voltage of the NMOS tube is gradually established.

[0010] In a preferred embodiment of the present invention, when the building is at a negative potential with respect to the ground grid, the NMOS tube is not turned on and the body diode is reversely connected, so stray current cannot flow to the building through the circuit.

[0011] The beneficial effects of the utility model are as follows: the utility model points out a controllable grounding stray current protection circuit for a building, which realizes the controllable grounding stray current protection of the building, effectively discharges the surge current to the ground grid, and prevents the stray current from flowing into the building, thereby solving the problem of electromagnetic interference to the building's electrical equipment and corrosion of the steel structure, and ensuring the stable operation and safety of various facilities in the building. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0013] Figure 1 It is a circuit diagram of a preferred embodiment of a controllable grounding stray current protection circuit for a building of the utility model;

[0014] Figure 2 The utility model is a schematic diagram of an application of a preferred embodiment of a controllable grounding stray current protection circuit for a building. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0016] See also Figure 1 Combination Figure 2 As shown, the embodiment of the utility model includes:

[0017] A controllable grounding stray current protection circuit for a building is connected in series between the building and the ground grid, and comprises a lightning protection circuit and a stray current backflow prevention circuit connected in parallel.

[0018] Wherein, the lightning protection circuit includes a first lightning protection branch and a second lightning protection branch connected in parallel, the first lightning protection branch includes a first varistor RV1 and a first ceramic gas discharge tube G1 connected in series, the second lightning protection branch includes a second varistor RV2 and a second ceramic gas discharge tube G2 connected in series, and the parallel end of the first ceramic gas discharge tube G1 and the second ceramic gas discharge tube G2 is connected in series with the third ceramic gas discharge tube G3 and then connected to the ground grid.

[0019] The current carrying capacity of the first ceramic gas discharge tube G1, the second ceramic gas discharge tube G2 and the third ceramic gas discharge tube G3 needs to be selected according to the actual required current carrying capacity. When selecting the first varistor RV1 and the second varistor RV2, it is necessary to select varistors that can withstand the line peak voltage and maximum current carrying capacity according to actual conditions.

[0020] The working process of lightning protection circuit is:

[0021] When the building is not struck by lightning, the first ceramic gas discharge tube G1, the second ceramic gas discharge tube G2 and the third ceramic gas discharge tube G3 act as switching elements, and the first ceramic gas discharge tube G1, the second ceramic gas discharge tube G2 and the third ceramic gas discharge tube G3 are disconnected, which is equivalent to an open circuit. At this time, the external voltage is less than the turn-on voltage of the first varistor RV1 and the second varistor RV2, and the first varistor RV1 and the second varistor RV2 are in a high-resistance state, which is similar to an open circuit. The current cannot flow from the building to the ground grid through the lightning protection circuit, and since the circuit is equivalent to an open circuit state, stray current cannot flow into the building through the circuit.

[0022] When a building is struck by lightning, there is a surge current. The first ceramic gas discharge tube G1, the second ceramic gas discharge tube G2 and the third ceramic gas discharge tube G3 are turned on, which is equivalent to a short circuit, and a large current can pass through. At this time, the external voltage is greater than the conduction voltage of the first varistor RV1 and the second varistor RV2. The first varistor RV1 and the second varistor RV2 are broken down and are in a low-resistance state. The surge current can be successfully discharged from the building to the ground grid until the external voltage is less than the conduction voltage of the first varistor RV1 and the second varistor RV2. The first varistor RV1 and the second varistor RV2 can restore the high-resistance state. Therefore, when a building is struck by lightning, through the action of the ceramic gas discharge tube and the varistor, the surge current can be successfully discharged from the building to the ground grid, so that the line voltage of the building is controlled within a safe range, thereby protecting the building.

[0023] The anti-backflow circuit includes a first anti-backflow branch and a second anti-backflow branch connected in parallel, the first anti-backflow branch includes a first resistor R1 and a parallel branch connected in series, the parallel branch is provided with three branches, including a second resistor R2 and a first diode D2 connected in series, a voltage regulator D1 and a capacitor C, one end of the parallel branch is connected to the gate of the NMOS tube Q, and the other end is connected to the source, the drain of the NMOS tube Q is connected to the ground grid, and the second anti-backflow branch includes a third resistor R3 and a second diode D3 connected in series. The anode of the voltage regulator D1, the cathode of the first diode D2 and the cathode of the second diode D3 are all connected to the source of the NMOS tube Q.

[0024] The working process of the stray current backflow prevention circuit is:

[0025] When the building is at a forward potential to the ground grid, the body diode of the NMOS tube Q is turned on, and a small current flows from the building through the third resistor R3 and the second diode D3 to the ground grid via the body diode.

[0026] A suitable first resistor R1 and a second resistor R2 are set. When the gate-source voltage of the NMOS tube Q is greater than the turn-on voltage of the NMOS tube Q, the NMOS tube Q is turned on. At this time, the body diode is short-circuited, and the line forms a loop through the NMOS tube Q. At this time, the voltage regulator D1 prevents the voltage from being too large and the NMOS tube Q from being broken down, and the capacitor CC plays a role of soft start, so that the gate voltage of the NMOS tube Q is gradually established.

[0027] When the building is at a negative potential with respect to the ground grid, the NMOS tube Q is not conducting and the body diode is reversely connected, so stray current cannot flow to the building through the circuit.

[0028] In summary, through varistors, ceramic gas discharge tubes, and several cables, surge current is discharged to the ground grid when there is a lightning strike. When there is no lightning strike, the circuit is close to an open circuit state, preventing stray current from flowing into the building. Through resistors, NMOS tubes, voltage regulators, diodes, capacitors, and several connecting cables, small currents can flow from buildings to the ground grid, while stray currents cannot flow into buildings through the ground grid.

[0029] To sum up, the utility model points out a controllable grounding stray current protection circuit for a building, which realizes the controllable grounding stray current protection of the building, effectively discharges the surge current to the ground grid, and prevents the stray current from flowing into the building, thereby solving the problem of electromagnetic interference of the building's electrical equipment and corrosion of the steel structure, and ensuring the stable operation and safety of various facilities in the building.

[0030] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A controllable grounding stray current protection circuit for a building, connected in series between the building and the ground grid, characterized in that: The invention comprises a lightning protection circuit and a stray current backflow prevention circuit connected in parallel, wherein the lightning protection circuit comprises a first lightning protection branch and a second lightning protection branch connected in parallel, wherein the first lightning protection branch comprises a first varistor and a first ceramic gas discharge tube connected in series, wherein the second lightning protection branch comprises a second varistor and a second ceramic gas discharge tube connected in series, wherein the parallel end of the first ceramic gas discharge tube and the second ceramic gas discharge tube is connected in series with a third ceramic gas discharge tube and then connected to a grounding grid, wherein the backflow prevention circuit comprises a first backflow prevention branch and a second backflow prevention branch connected in parallel, wherein the first backflow prevention branch comprises a first resistor and a parallel branch connected in series, wherein three parallel branches are provided, including a second resistor and a first diode connected in series, a voltage regulator tube and a capacitor, wherein one end of the parallel branch is connected to a gate of an NMOS tube, and the other end is connected to a source, wherein a drain of the NMOS tube is connected to a grounding grid, and wherein the second backflow prevention branch comprises a third resistor and a second diode connected in series.

2. The controllable grounding stray current protection circuit for a building according to claim 1, characterized in that: The anode of the voltage regulator tube, the cathode of the first diode and the cathode of the second diode are all connected to the source of the NMOS tube.

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