Rail potential limiting device based on RC loop and opening control loop thereof

Abstract

The utility model discloses a steel rail potential limiting device based on an RC loop and an opening control loop thereof, the steel rail potential limiting device comprises a first interface, a second interface, a third interface, a fourth interface, a capacitor, a resistor and a diode, the second interface is connected in series with the capacitor and the diode in sequence and then is connected in series with the fourth interface to form a first branch; the first interface is connected with the first branch, and the third interface is connected with the first branch after being connected in series with the resistor; the steel rail potential limiting device is connected to the two ends of a holding resistor of a contactor control loop in parallel to form an RC loop to eliminate the opening sparking phenomenon of the contactor, and the steel rail potential limiting device has the effects of storing energy, filtering and improving the electric energy quality. Meanwhile, the module is further provided with a fusing indication, so that the failure of a loop can be protected, the fusing indication can also be used as an indication for checking the failure of the module on site, and operation and maintenance management is facilitated.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of electrical safety, specifically relates to a rail potential limiting device based on RC loop and opening and closing control loop thereof. BACKGROUND

[0002] The subway direct current traction power supply system adopts DC1500V power supply, and the direct current traction power supply system is designed as a suspension system, the running rail is insulated from the ground through an insulating pad to reduce the leakage of stray current. In order to prevent the potential of the running rail from rising to cause harm to the staff between the station and the vehicle, passengers getting on and off the vehicle and line inspection personnel, a rail potential limiting device (OVPD) is arranged in the station substation, the vehicle depot and the parking lot maintenance warehouse to limit the potential of the running rail to the ground within a predetermined safe range. When the contact voltage between the rail and the ground is greater than or equal to U> or U>> the set value, the DC contactor of the rail potential limiting device will be quickly closed to protect the safety of personnel and equipment. However, it is found in daily maintenance operation that the contactor of the rail potential limiting device frequently appears "firing" in some subway lines in a city. Although the equipment is not damaged, long-term operation will affect the service life of the equipment, and at the same time, there is a certain hidden danger to the safety of the operation and maintenance personnel; the control circuit principle diagram of the contactor of the rail potential limiting device of different manufacturers is compared as shown in the figure. Figure 1

[0003] ​After careful observation and confirmation on site, it is found that the "spark" phenomenon mainly occurs at the contact point of the coil control loop of the rail potential device contactor. The specific causes of the failure of the contactor control loop of the equipment manufacturer (manufacturer 1) are as follows: (1) the contactor is a normally closed contact, the coil is powered off to open the circuit, and the auxiliary contact of the contactor is connected to the main loop of the contactor coil. (2) When the circuit is opened, the K12.5-K12.6 normally open contact is closed, the contactor coil is powered on, and the normally closed contact is opened. Due to the large current in the main loop of the contactor coil, there will be a short discharge when the normally closed contact is opened. Subsequent comparison with the contactor control loop of the rail potential limiting device of other manufacturers shows that manufacturers 2, 3 and 4 all have a "reverse" diode module (also known as "freewheeling diode") connected in parallel with the contactor coil. Its function is to provide a freewheeling circuit for the contactor opening, which not only reduces the overvoltage level but also provides a path for energy consumption, thereby protecting the contactor coil. However, due to the following reasons: first, if a freewheeling diode is connected in parallel with the control loop coil, the closing speed of the equipment contactor will be affected (the design requirement of the contactor of manufacturer 1 is that the action time should be not more than 100 ms). When the rail voltage rises, the contactor closing time is too long, and the frame voltage protection is not matched, which will cause the frame voltage protection to malfunction. Second, due to the impact of continuous high voltage, the freewheeling diode is easily broken down, and the "spark" phenomenon caused by the contactor opening is not fundamentally solved, and it also increases the risk. Third, the historical fault of the equipment shows that the rail potential limiting device with a "reverse" diode module connected in parallel with the contactor coil still has a slight "spark" phenomenon. Therefore, a method is needed to completely solve the "spark" phenomenon caused by the contactor opening of the rail potential limiting device. SUMMARY

[0004] The utility model aims at overcoming the prior art's insufficient, provide a kind of rail potential limiting device based on RC loop and its opening control loop.

[0005] The utility model aims at overcoming the prior art's insufficient, provide a kind of rail potential limiting device based on RC loop and its opening control loop.

[0006] First, the utility model discloses a kind of rail potential limiting device based on RC loop, including first interface, second interface, third interface, fourth interface, capacitor, resistance and diode, the second interface is connected in series with fourth interface after capacitor and diode in turn, and first branch is formed, first interface is connected with first branch, and resistance is connected with first branch after third interface;The rail potential limiting device is connected in parallel at the both ends of the holding resistance of contactor control loop, and RC loop is formed to eliminate the spark phenomenon caused by the contactor opening.

[0007] Based on the first aspect, it further includes a fuse indication, which is not only used for protecting the circuit failure, but also used for indicating the local troubleshooting of the module.

[0008] The second aspect, the utility model discloses a kind of contactor control loop, for the rail potential limiting device based on RC loop described above, it is characterized by comprising: contactor A2, resistance and normally closed contact A1, the normally closed contact of the rail potential limiting device is connected with normally closed contact A1, the second interface and the fourth interface of rail potential limiting device are connected in parallel at the two ends of contactor A2, normally closed contact A1 is connected with the second interface after resistance is connected in series.

[0009] The utility model has the advantages of:

[0010] 1) the rail potential limiting device of the utility model is installed at the two ends of the holding resistance of contactor control loop, forms RC loop, eliminates the fault phenomenon of rail potential limiting device contactor opening " firing ", and has the effects of energy storage, filtering and improving power quality; At the same time, the device is also provided with a fuse indication, which can not only protect the circuit fault, but also serve as an indication for on-site troubleshooting module failure, facilitating operation and maintenance management. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 For comparison of contactor control circuit principle diagram of rail potential limiting device of different manufacturers;

[0012] Figure 2 For internal diagram of the rail potential limiting device of the utility model;

[0013] Figure 3 For the schematic diagram of optimization of the utility model on the contactor control circuit of manufacturer 1;

[0014] Figure 4 For the equivalent circuit schematic diagram of existing control circuit;

[0015] Figure 5 For the equivalent circuit schematic diagram of control circuit optimized by the utility model;

[0016] Figure 6 For the voltage waveform diagram of the two ends of existing holding resistance and coil;

[0017] Figure 7 For the voltage waveform diagram of the two ends of holding resistance and coil optimized by the utility model; DETAILED DESCRIPTION

[0018] The technical solutions of the utility model will be described clearly and completely in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the utility model.

[0019] Refer to Figures 1-7 The utility model discloses a rail potential limiting device based on RC loop, is installed in the control loop's holding resistance two ends of contactor, forms RC loop, is used for eliminating the failure phenomenon of rail potential limiting device contactor break " strike the fire ", rail potential limiting device, including first interface, second interface, third interface, fourth interface, electric capacity, resistance and diode, second interface is connected with fourth interface in series after electric capacity and diode are connected in series in proper order and forms first branch, and first interface is connected with first branch, and third interface is connected with first branch after resistance is connected in series, rail potential limiting device is connected in parallel in the holding resistance two ends of contactor control loop, forms RC loop and eliminates contactor break strike fire phenomenon.

[0020] Specifically, it also includes a fuse indication, which is not only used for protecting the circuit from failure, but also used for indicating the on-site troubleshooting of the module failure, thereby facilitating operation and maintenance management.

[0021] The utility model discloses a break control loop, including: contactor A2, resistance and normally closed contact A1, the normally closed contact of rail potential limiting device is connected with normally closed contact A1, and the second interface and fourth interface of rail potential limiting device are connected in parallel at the two ends of contactor A2, and normally closed contact A1 is connected with the second interface after resistance is connected in series.

[0022] Exemplarily, the equivalent circuit of the existing control loop includes a contactor , normally closed contact; control circuit switch K1, normally open contact; holding resistance R, the resistance value is ; coil resistance , the resistance value is about ; 220V DC control power supply; the inductance voltage, the capacitor voltage; L is inductance, the current flowing to inductance L, I2 is the current flowing to contactor ; the positive pole of the DC control power supply U S is connected in series with control circuit switch K1, the control circuit switch K1 is connected in series with contactor , the protection resistance R is connected in parallel with the contactor , the contactor is connected in series with coil resistance and inductance L in proper order, and the inductance L is connected in series with the negative pole of the DC control power supply . When the coil loses power, the contactor is closed, and the control circuit switch K1 is disconnected. When the coil is powered, the control circuit switch K1 is closed, and because the current As the current gradually increases from 0A, a certain magnetic flux is required to engage the contactor armature. Therefore, the contactor... It is still in the closed state, at which time the coil voltage is... This is equivalent to applying a full 220V voltage across the terminals, while the current flowing into the inductor L... When the voltage increases, a reverse electromotive force is generated in the coil and flows through the contactor. The current I2 (current in the contactor circuit) = the current flowing through the inductor L Its value will accumulate and increase. When the magnetic flux of the coil reaches a certain value, the contactor... Disconnect, flow through contactor The current I2 will drop to 0A instantly, and the energy will be released in the form of a spark, thus producing the "arcing" phenomenon.

[0023] Compared to the equivalent circuit of the existing control loop, this invention adds a capacitor C, which is connected in parallel with the protective resistor R. The parameters of the capacitor C are as follows: After capacitor C is connected in parallel with the protective resistor R, in the contactor The two ends form an RC circuit, contactor When disconnected, the voltage across capacitor C does not change abruptly. contactor The high voltage across the terminals will charge the capacitor C, and the current flowing into the inductor L will... A portion flows to the capacitor C branch and then to the contactor. The current I2 is small, making the contactor The two ends will not spark.

[0024] For example, the contactor control circuit employs overvoltage suppression measures, and a capacitor module is connected in parallel across the holding resistor instead of a freewheeling diode. There are four main reasons for this: First, if a freewheeling diode is connected in parallel with the control circuit coil, the contactor's closing speed will be affected (the contactor's design requires an operating time of no more than 100ms). When the rail voltage rises, if the contactor's closing time is too long and there is a misalignment with the timing of the frame voltage protection, it will lead to malfunction of the frame voltage protection. Second, due to the impact of continuous high voltage, the freewheeling diode is easily damaged, the contactor's opening discharge phenomenon is not fundamentally resolved, and the risk is increased. Third, the capacitor has the functions of energy storage, filtering, and improving power quality. Fourth, a review of historical equipment faults revealed that the rail potential limiting device with a freewheeling diode module connected in parallel with the contactor coil still exhibits a slight discharge phenomenon. The selection of capacitor parameters is also important. This invention is equivalent to forming an RC circuit across the contactor of the rail potential limiting device. As the basic principle of an RC circuit shows, the value of the capacitor C affects the charging and discharging time; a larger C value results in a longer charging and discharging time, and a smaller C value results in a shorter charging and discharging time. Based on research and experience with similar circuit designs, the following parameters were selected: The capacitor.

[0025] For example, to verify the technical effectiveness of this solution, a pilot site with severe arcing during contactor tripping of the rail potential limiting device was selected as a test site. The capacitor module proposed in this solution was installed. Simultaneously, the voltage across the holding resistor and coil of the control circuit before and after adding the capacitor module was tested to observe voltage changes. A RIGOL oscilloscope was used for testing. This instrument can test the waveform of different signals (voltage, current, frequency, etc.) amplitude changes over time. It has a very rapid response to pulse signals, and the waveform is clearly visible, which is helpful for qualitative and quantitative analysis. Test terminals were added to the holding resistor (A, B) and coil (B, C) of the rail potential limiting device.

[0026] Specifically, the voltage waveforms across the existing holding resistor and the coil are as follows: Figure 6 As shown, the solid line represents the voltage across the coil, and the line marked with an × represents the voltage across the holding resistor; the optimized voltage waveforms across the holding resistor and the coil of this invention are shown below. Figure 7 As shown, the voltage across the coil is represented by the dashed line, and the voltage across the holding resistor is represented by the dashed line. Figure 6 and Figure 7 The horizontal axis represents the magnitude and direction of voltage, with each small division representing 100V. The vertical axis represents time, with each small division representing 50ms. Before optimization, the voltage surge across the holding resistor reached a maximum of 660V, and the reverse voltage across the coil reached a maximum of 440V. The contactor tripped with "sparking," and the voltage waveform was jagged, indicating voltage instability and low power quality. After optimization, the voltage surge across the holding resistor reached a maximum of 490V, a decrease of 170V compared to before optimization. The reverse voltage surge across the coil reached a maximum of 250V, a decrease of 190V compared to before optimization. The contactor tripping "sparking" phenomenon disappeared, and the voltage waveform was smoother, the voltage was stable, and the power quality was significantly improved. Tests on the voltage waveforms across the holding resistor and coil in the control circuit before and after optimization showed that the voltage across the holding resistor and coil was significantly reduced after optimization, and voltage stability was improved, resulting in a significant improvement in power quality. During the experiment, it was found that this solution completely solved the "sparking" phenomenon of the contactor tripping in the rail potential limiting device.

[0027] Specifically, the utility model installs the capacitor module in the steel rail potential limiting device of the transformer substation of all stations of the second and third phases of a subway line before January 2023, and after more than one year of operation, the phenomenon of the contactor of the original steel rail potential limiting device breaking "igniting" has been completely solved, and the effectiveness of the scheme is verified again. In the future, the optimization of circuits with the same structure design will be completed according to the needs of other lines, and can be popularized and applied in the whole line network to further protect the safety of personnel and equipment, prolong the service life of equipment, and ensure the safe operation of urban rail transit.

[0028] The above is only the preferred embodiment of the utility model, and it should be understood that the utility model is not limited to the form disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein by the above teaching or related technical or knowledge. The modification and change made by the person skilled in the art without departing from the spirit and scope of the utility model shall be within the protection scope of the claims attached to the utility model.

Claims

1. An RC circuit based rail potential limiting device, characterized in that, It includes first interface, second interface, third interface, fourth interface, capacitor, resistance and diode, the second interface is connected with the fourth interface in series after the capacitor and diode are connected in series, the first interface is connected with the first branch, and the third interface is connected with the first branch after the resistance is connected in series;The rail potential limiting device is connected in parallel between the holding resistance of the contactor control loop, forming an RC circuit to eliminate the contactor opening fire phenomenon.

2. A rail potential limiting device based on an RC circuit according to claim 1, characterized in that: It also includes a fuse indication, which is not only used for protecting the circuit fault, but also for indicating the local troubleshooting module fault.

3. A closing control circuit for an RC circuit based rail potential limiting device according to any one of claims 1-2, characterized in that, It includes: The normally closed contact of the contactor A2, resistance and normally closed contact A1, the normally closed contact of the rail potential limiting device is connected with the normally closed contact A1, the second interface and the fourth interface of the rail potential limiting device are connected in parallel between the contactor A2, and the normally closed contact A1 is connected with the second interface after the resistance is connected in series.

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