CN210894645U - Fault alarm device - Google Patents

Abstract

The utility model discloses a fault alarm device of a power distribution terminal, which comprises a sampling resistor and a detection circuit, wherein the sampling resistor detects the fault current in the circuit; a transistor connected to the sampling resistor, and turned on or off according to a voltage drop of the sampling resistor; and the alarm part is connected to the transistor and used for waking up and sending an alarm signal outwards when the on or off of the transistor is detected. According to the technical scheme of the utility model, MCU's calculation process and calculated amount have been simplified, the consumption can be effectively reduced.

Description

Fault alarm device

technical field

The utility model relates to a fault alarm device, in particular to a fault alarm device used in power distribution terminal equipment for fault alarm.

Background technique

The 10kV distribution line at the end of the grid in power transmission enables an efficient connection between the transmission network and end users. A main function of intelligent power distribution terminal equipment is fault alarm and remote transmission. Because of the immediacy requirements of alarm information, as long as a fault is detected, the information must be immediately transmitted to the master station through some communication method.

Existing wake-up mechanisms for smart power distribution terminals mainly rely on MCU programming. In the low-power working mode of the MCU, the device always opens the metering data cache, and performs various mathematical calculations to obtain the actual value. At the moment of the fault, the MCU program design detects the sudden change of the instantaneous current of the distribution line fault, calculates the real value, and compares it with the criterion for fault judgment to determine whether the distribution line is faulty. If the judgment result is yes, wake up the MCU immediately, make the device enter the normal operation mode from the sleep mode, and transmit the fault alarm information remotely through the wireless communication function.

The disadvantage of the above processing method is that in order to ensure the accurate judgment of fault information, the software must maintain high-speed and high-efficiency work during the calculation process, and the data cache speed and calculation speed are high. This will increase the power consumption of the MCU, which can reach 1.5 to 2.0 times the usual power consumption. The increase in power consumption shortens the service life of the device. If the current of the distribution line is small, the increase in power consumption will directly affect the normal use of the equipment.

Under normal conditions (without fault conditions), when the current of the distribution line is above 20A, the distribution terminal equipment can run at full function and at full speed. However, when the current of the distribution line is below 20A, the intelligent power distribution terminal needs to operate with low power consumption. Save backup power usage. The traditional method can only rely on MCU to reduce power consumption as much as possible, but due to the limitation of function and data calculation processing, the power consumption is limited.

Utility model content

In view of this, the present invention proposes a novel fault alarm device. According to one aspect of the present invention, a fault alarm device is provided, comprising: a sampling resistor, which detects the fault current in the circuit; a transistor, which is connected to the sampling resistor and turns on or off according to the voltage drop of the sampling resistor; an alarm component , connected to the transistor, used to wake up and send out an alarm signal when the on or off of the transistor is detected

According to the technical solution of the utility model, a large amount of time and codes for fault judgment and calculation can be saved, and the requirements of low power consumption and immediacy of alarm can also be achieved.

Description of drawings

FIG. 1 shows a simplified circuit block diagram according to the working principle of the present invention.

FIG. 2 shows a schematic connection diagram of a fault alarm device according to an embodiment of the present invention.

FIG. 3 shows a schematic connection diagram in the case of using an N-channel MOS transistor.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model more clearly understood, the present utility model will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

According to the technical scheme of the utility model, the transient current characteristic when the circuit fails is utilized. The working principle of the present invention is described below by taking the power distribution equipment as an example: in the power distribution equipment with non-disposable backup power supply, the backup power supply needs to be charged and managed. During the charging process of the backup power supply, for the protection of the backup power supply, the charging current of the backup power supply is strictly controlled. The technical scheme of the utility model can make use of the characteristic that the charging current of the backup power supply will suddenly increase when the current on the power distribution line suddenly increases, and cooperates with the general detection of the switch circuit and the MCU to achieve the purpose of waking up the device and giving an alarm.

Figure 1 shows a simplified circuit block diagram of the above working principle. The transistor, the sampling resistor and the MCU constitute the fault alarm device according to the present invention. Among them, the transistor is selectively turned on/off according to the voltage drop of the sampling resistor, and the MCU is an alarm component, which is connected to the transistor and is used to wake up and send out an alarm signal when the on/off of the transistor is detected.

FIG. 2 shows a schematic circuit connection diagram of the fault alarm device. Among them, the sampling resistor and the transistor are shown as the sampling resistor R1 and the NPN transistor Q2 respectively, and only the MCU port (MCU IO) of the MCU is shown, so as to simplify the illustration. As shown in the figure, the resistor R1 is connected to the backup power supply, and is connected in parallel between the base and the emitter of the NPN transistor, and the collector of the transistor Q2 is connected to the port (MCU IO) of the alarm part MCU.

Referring to Figure 1 and Figure 2, the sampling resistor R1 is used to capture the transient current characteristics in the circuit when the circuit fails. Specifically, when the circuit fails, the charging current of the backup power supply will suddenly increase, and then fall down. The voltage drop across the sampling resistor R1 will increase so that the transistor can switch on/off states in response.

MMBT5088 can be selected for the triode, and its turn-on voltage is 0.7V. When the distribution line is running normally, due to the charging management and protection function of the rechargeable backup power supply, it can ensure that the charging current does not change abruptly and runs stably below 200mA in the steady state. In the shutdown state, the MCU detects the high level all the time.

When the distribution line fails, the current suddenly changes. Due to the influence of the transient characteristics, the charging current of the rechargeable backup power supply will surge instantaneously, and the duration is 50ms-90ms. Because the charging current of the rechargeable power supply surges (the sudden value of the primary side current is above 150A), the charging circuit current of the backup power supply will increase to 250mA or even higher due to the influence of the line fault current. The voltage drop of the sampling resistor will suddenly increase, resulting in the transient conduction of the triode. The MCU detects the instantaneous low level and the duration, so as to wake up the device, and send out fault alarm remote transmission information according to the detected short-term level change.

In the event of a fault, the MCU detects a low level instead of a high level, depending on how the transistors are connected. As shown in Figure 2, the connection mode of the triode is open-collector connection, so in this design, the triode is low level when it is turned on. R2 in Figure 2 is a pull-up resistor, and its main function is to connect the pull-up resistor in the open-collector connection method to output a high level to the MCU (during steady-state operation). The present invention is not limited here. The above is a description of the specific implementation of the present invention in the case of a failure. However, in other cases, it basically works in a steady state. According to the charge and discharge management of the backup power supply, it can be ensured that during this steady state, the transistors in the device are in an off state. In the off state, that is, the MCU can detect the high level of the device. During this period, the wake-up mechanism of the device mainly depends on the timing wake-up in the program design.

The resistance of the resistor can be designed according to the current value that the circuit usually reaches when the fault occurs and the turn-on voltage of the triode. In the above case, the charging loop current of the backup power supply will increase to 250mA or even higher due to the influence of the line fault current, so that the voltage on the sampling resistor reaches the transistor turn-on voltage of 0.7V. So the resistor can take a value of 3Ω.

According to the technical scheme of the present invention, when the power distribution line is in normal steady state operation, the triode is in the off state, and the MCU detects the high level all the time. When the distribution line fails, the current suddenly changes. Due to the influence of transient characteristics, the charging current of the backup power supply surges, and the voltage drop of the sampling resistor will suddenly increase, resulting in the instantaneous conduction of the triode. The MCU detects an instantaneous low level, through which it can determine whether there is a fault, so as to quickly wake up the device and issue a fault alarm and remote transmission information in time. The technical scheme of the utility model simplifies the calculation process and calculation amount of the MCU, and can effectively reduce the power consumption. In addition, the hardware detection circuit of the solution of the present invention is in the power supply circuit of the equipment, so that the circuit design is simple and efficient.

It should be understood that the transistor shown in FIG. 2 as a triode is only for example, and the present invention is not limited herein. Other transistors such as N-channel MOS transistors can also be used. FIG. 3 shows a schematic connection diagram in the case of using an N-channel MOS transistor.

As shown in Figure 3, the sampling resistor R8 is 8Ω, and the value is determined according to the turn-on voltage of the MOS tube and the sudden change of the fault circuit current. The transistor selects the N-channel MOS tube Q4 of IRF110, and the turn-on voltage is 2V. A pull-up resistor R6 is connected to the drain of the transistor. When the distribution line is in normal operation, due to the charging management and protection functions of the rechargeable backup power supply, it can ensure that the charging current does not change abruptly and runs stably below 200mA in a steady state, the transistor IRF110 is in the off state, and the MCU detects high level. When the distribution line fails, the current suddenly changes. Due to the influence of the transient characteristics, the charging current of the rechargeable backup power supply will have an instantaneous surge, which lasts for 50ms-90ms, because the charging current of the rechargeable power supply surges to 250mA. Above, the voltage drop of the sampling resistor will suddenly increase, causing the IRF110 to be turned on instantaneously. The MCU detects the instantaneous low level and the duration, and wakes up the device. According to the detected short-term level change, a fault alarm remote transmission is issued. information.

The transistors that can be used in the present invention are not limited to the examples listed above. As long as a transient feature occurs in the case of a circuit failure, the selected transistor and the sampling resistor cooperate with each other, so that the transistor can be turned on or off under the transient feature. It is enough that the level of the input MCU changes.

The above-mentioned alarm component MCU may further include a time calculation circuit for calculating the duration of conduction of the transistor. The point of calculating the duration is to prevent false positives. If the duration is too short, it may just be that there is a switch on the line, and if the time is too long, the load may be added to the line.

The technical solution of the present invention is described above by taking power distribution equipment as an example. Those skilled in the art should understand that the solution of the present invention can also be applied to other situations, as long as the purpose of waking up an alarm can be realized by the combination of the sampling resistor and the transistor, that is, Can.

Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary, and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples; under the spirit of the present invention, the above embodiments Alternatively, the technical features in the different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Additionally, to simplify illustration and discussion, and in order not to obscure the present invention, well-known power/ground connections to integrated circuit (IC) chips and other components may or may not be shown in the figures provided in the figures provided. connect. Furthermore, devices may be shown in block diagram form in order to avoid obscuring the invention, and this also takes into account the fact that the details regarding the implementation of these block diagram devices are highly dependent on the platform on which the invention will be implemented (ie, these details should be well within the understanding of those skilled in the art). Where specific details (eg, circuits) are set forth to describe exemplary embodiments of the present invention, it will be apparent to those skilled in the art that these specific details may be made without or with changes In this case, the utility model is implemented. Accordingly, these descriptions are to be considered illustrative rather than restrictive.

Although the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations to these embodiments will be apparent to those of ordinary skill in the art from the foregoing description.

Embodiments of the present invention are intended to cover all such alternatives, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims (7)

1. A fault warning device, comprising:

a sampling resistor that detects a fault current in the circuit;

a transistor connected to the sampling resistor, turned on or off according to a voltage drop of the sampling resistor;

and the alarm component is connected to the transistor and used for waking up and sending an alarm signal outwards when the on or off of the transistor is detected.

2. The fault warning device according to claim 1, wherein the transistor is a triode, the sampling resistor is connected in parallel between a base and an emitter of the triode, and a collector of the triode is connected to the warning part.

3. The fault warning device according to claim 2, wherein a pull-up resistor is connected to the collector of the transistor to provide a high level to the warning element during steady state operation;

the sampling resistor is valued such that, in the event of a fault, the product of the fault current and the resistance of the sampling resistor satisfies the turn-on voltage of the transistor, thereby providing a low level to the alarm component during the fault.

4. The fault warning device according to claim 3, wherein the sampling resistor has a value of 3 ohms.

5. The fault warning device according to claim 1, wherein the transistor is an N-channel MOS transistor, the sampling resistor is connected in parallel between a source and a gate of the MOS transistor, and a drain of the MOS transistor is connected to the warning element.

6. The fault warning device according to claim 1, wherein the warning element further comprises a time calculation circuit for calculating a duration of time the transistor is turned on.

7. The fault warning device of any one of claims 1-6, connected in a power distribution terminal equipment, and the sampling resistor is connected to a backup power source of the power distribution equipment.

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