Dragging cable electric leakage detection circuit

Abstract

The utility model relates to an electric leakage detection circuit for a dragged cable. The electric leakage detection circuit comprises a leakage current detection module and a controller, the leakage current detection module is provided with a mutual inductor, a resistor R1, an electric control switch K1 and a signal processing circuit, the mutual inductor is used for detecting the current of the power main loop, the resistor R1 is connected to the two ends of the mutual inductor in parallel, the electric control switch K1 is connected with the resistor R1 in parallel, and the signal processing circuit is used for obtaining voltage signals at the two ends of the resistor R1, carrying out differential amplification and then inputting the voltage signals into an AD sampling channel of the controller; the controller is electrically connected with the controlled end of the electric control switch K1 to control on-off.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the security protection equipment in the power electronics field, concretely relates to a dragging cable electric leakage detection circuit. BACKGROUND

[0002] The secondary side output of the zero sequence current transformer is AC current, which cannot be directly converted by the AD conversion chip, and the current signal must be converted into a voltage signal by using a resistor first, and then the voltage signal is processed (amplified, filtered, clamped, etc.) to be input into the AD conversion chip for conversion, and then the converted digital quantity is sent to the MCU. Figure One As shown in the figure.

[0003] In the dragging cable electric leakage monitor, the transformer is configured as 1000:5, the resistor R1 is configured as 5Ω / 5W, and the electric leakage current alarm value allowed to be set by the monitor is 0.5A-12.5A. For the convenience of description, it is assumed that the electric leakage current alarm value set by the monitor is 12.5A, and the actual electric leakage current value is 10A. Because the actual electric leakage current value is less than the set alarm value, the monitor will not alarm, and will not control the main circuit to be disconnected. However, at this time, there is always a current of 0.05A on the resistor R1, and the power consumption is 0.0125W. Due to long-time work, the resistor will have a certain temperature rise. Because the power of the resistor is 5W, which is much larger than the actual power, although there is a temperature rise, it is still within the bearing range of the resistor.

[0004] If the electric leakage current is 1000A, the monitor will also report a fault immediately, but the main circuit switch cannot be disconnected due to some reasons (damage of the actuator, short circuit or disconnection of the control circuit, etc.). The 5A current on the secondary side will be applied to the resistor R1 for a long time after the 1000A electric leakage current is induced by the transformer. At this time, the power P borne by the resistor R1 is P=I 2 ×R=5 2 ×5=125W, which is much larger than the bearing power 5W of the resistor. At this time, if the main circuit switch cannot be disconnected in time, the resistor will be quickly burned out, causing the open circuit of the secondary side of the transformer. The open circuit of the secondary side of the transformer will output high voltage on the secondary side, causing great safety hazards. CONTENT OF THE UTILITY MODEL

[0005] The utility model aims at improving the reliability of the electric leakage monitoring equipment, preventing the damage or damage of the resistor, and eliminating the open circuit of the transformer.

[0006] To this end, a drag cable leakage detection circuit is provided, comprising a leakage current detection module and a controller.

[0007] As an improved scheme, a contactor control circuit is further included, and a power loop switch KJ1 for controlling the on-off of the main loop is connected in series in the power main loop, and the controller controls the on-off of the power loop switch KJ1 via the contactor control circuit.

[0008] As an improved scheme, the electric control switch K1 is configured as a relay contact. Further, the relay contact is configured as a normally closed contact.

[0009] As an improved scheme, an operation panel is further included, and the operation panel is electrically connected with the controller.

[0010] Compared with the prior art, the utility model has the advantages of:

[0011] 1. By connecting the relay switch in parallel with the sampling resistor of the transformer, the damage of the resistor due to long-term over-power operation is effectively solved, and the transformer is also prevented from working in an open circuit state.

[0012] 2. The safety performance of the leakage monitoring device is further improved, and the device is more secure and safe to use. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A conventional monitor leakage detection topology diagram is shown;

[0014] Figure 2 A leakage monitoring device system integration block diagram of the utility model is shown;

[0015] Figure 3 A leakage current detection module topology diagram of the utility model is shown. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model.

[0017] The utility model discloses a leakage monitoring device and system, which can effectively solve the problems of the prior art. Figure 2As shown in the figure, the leakage detection circuit of the towing cable, referred to as the monitor, is composed of a leakage current detection module 4, a contactor control circuit 6, a controller 3 and an operation panel 7 for human-computer interaction. The leakage current detection module 4 detects the output current of the power main loop current sensor in real time, and sends the processed current to the controller 3 for calculation and decomposition. A power loop switch KJ1 for controlling the on-off of the main loop is connected in series in the power main loop, and the controller 3 controls the on-off of the power loop switch KJ1 through the contactor control circuit 6. When the controller 3 judges that the sensor and the corresponding circuit are abnormal according to the decomposed current data, the contactor control circuit 6 is immediately controlled to turn off the power loop switch KJ1, thereby cutting off the power supply of the towing cable and the electrical equipment.

[0018] The leakage current detection module 4 has the structure as shown in the figure Figure 3 The leakage current detection module 4 has the structure as shown in the figure

[0019] After the leakage detection circuit of the towing cable is started, if a trip command is issued and the leakage detection module 4 continuously detects a large leakage current, the controller 3 controls the relay K1 in the leakage detection module 4 to be closed through the wire, so as to ensure the safety of the leakage detection circuit and make the transformer short-circuit.

[0020] The control switch K1 is preferably set as a relay contact to achieve reliable on-off of a large current. The relay contact can be a normally closed contact or a normally open contact. Preferably, the normally closed contact is selected to automatically short-circuit the secondary side of the transformer for protection when the controller 3 abnormally loses normal judgment or control ability. If it is a normally closed contact, the K1 relay coil is powered on after the monitor is powered on, and the K1 contact is opened. Once a large current is detected, the K1 relay coil is de-energized, and the contact returns to the normally closed state.

[0021] In the above circuit topology, a relay switch is connected in parallel on the sampling resistor R1, and the relay is controlled by the control center. When the leakage current is greater than 12.5A set by the monitor, the control center will report a fault and issue a main loop trip command. If the leakage current does not decrease or disappear after 1 second of the command, the control center controls the K1 relay to be attracted, and the secondary side of the transformer is short-circuited. At this time, the current passes through the K1 relay contact, and there is no current on the resistor R1, and the resistor power is 0W.

[0022] The leakage detection circuit topology of the towing cable of the utility model not only ensures the safety of the resistor, but also eliminates the open circuit of the transformer.

[0023] The utility model has the advantages that:

[0024] 1. By connecting a relay switch in parallel with the sampling resistor of the transformer, the damage of the resistor due to long-term over-power operation is effectively solved, and the transformer is also prevented from working in an open circuit state.

[0025] 2. The safety performance of the electric leakage monitoring device is further improved, so that the device is safer and more reliable to use.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A drag cable leakage detection circuit, characterized in that: comprising a leakage current detection module and a controller; The leakage current detection module is provided with a mutual inductor, a resistor R1, an electrically controlled switch K1 and a signal processing circuit, the mutual inductor is used to detect the current of the power main loop, the resistor R1 is connected in parallel across the mutual inductor, the electrically controlled switch K1 is connected in parallel with the resistor R1, the signal processing circuit is used to obtain the voltage signal across the resistor R1, and the voltage signal is input to the AD sampling channel of the controller after differential amplification, and the controller is electrically connected with the controlled end of the electrically controlled switch K1 to control the on-off. Further comprising a contactor control circuit, a power loop switch KJ1 for controlling the on-off of the main loop is connected in series in the power main loop, and the controller controls the on-off of the power loop switch KJ1 through the contactor control circuit.

2. The drag cable leakage detection circuit of claim 1, wherein: The electrically controlled switch K1 is configured as a relay contact.

3. The drag cable leakage detection circuit of claim 1, wherein: The relay contact is configured as a normally closed contact.

4. The drag cable leakage detection circuit of claim 3, wherein: Further comprising an operation panel, and the operation panel is electrically connected with the controller.

5. The drag cable leakage detection circuit of claim 1, wherein: ​

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