Portable residual current detection device

Abstract

A portable residual current detection device belongs to the technical field of power grid monitoring. The invention aims to solve the problem that an existing residual current monitoring device of a low-voltage alternating-current power supply system cannot directly obtain a fault point. Current acquisition calipers are used for acquiring current signals of a neutral point of an alternating current power supply and a feeder line branch, a monitoring controller is used for independently calibrating current transmitted by each current acquisition caliper, and then current synthesis and dual-power-supply common-zero feeder line current synthesis are carried out on a feeder line zero line; the synthesized current received by the man-machine interaction unit is displayed, and a control port monitoring controller for recording the current of the zero feeder branch is provided for receiving a current recording control signal, recording the synthesized current and detecting whether the recording amplitude exceeds a threshold value or not, and if yes, an alarm signal is sent to the man-machine interaction unit; and the man-machine interaction unit is used for displaying the wave recording graph and the alarm signal. The method is mainly used for detecting the residual current of a station AC power supply system.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power grid monitoring. Background Art

[0002] The station AC power supply system is generally composed of a station low-voltage transformer, a 380V low-voltage distribution panel, protection and control, and an AC power supply network. The power supply is generally taken from the station transformer under different busbars in the station or an external backup power supply. When one power supply fails, it automatically switches to another power supply mode to ensure the reliability of power supply. The station power busbar generally adopts the segmented wiring divided by the station transformer, that is, each station transformer has a section of busbar and is equipped with an automatic transfer switch (ATS). When the power supply connected to any busbar is disconnected, the power supply can still be obtained from the adjacent busbar section to maintain the continuity of power supply.

[0003] As an important working power source of the substation, the station AC power supply directly provides working power for the main transformer cooling device, fire protection, DC charger, communication equipment, UPS, heating, moisture control, ventilation, lighting, power distribution and maintenance, and daily electricity. Therefore, the reliability of the station AC power supply directly affects the safe and stable operation of the substation. Due to the complicated AC power wiring at the substation site, inadequate safety measures, or problems such as the quality of power equipment and aging of lines, insulation performance failures may occur, which may not only cause the AC feeder switch to trip and power equipment to lose power, but may even cause fires, AC power loss in the entire station, substation shutdown and other serious accidents.

[0004] In recent years, special research on insulation monitoring technology of station AC power supply system has been carried out at home and abroad, and the residual current monitoring device of station low-voltage AC power supply system has been promoted and applied. It can realize online monitoring of residual current of the whole station and each AC feeder and find the grounding fault branch. However, the specific fault point still needs to be manually disconnected and powered off section by section for search, which consumes a lot of manpower and material resources, is inefficient and has low safety. Summary of the invention

[0005] The present invention aims to solve the problem that the existing residual current monitoring device of the low-voltage AC power supply system cannot directly obtain the fault point, and now provides a portable residual current detection device.

[0006] A portable residual current detection device according to the present invention comprises a plurality of current acquisition clamps, a monitoring controller, a human-computer interaction unit and a data storage device;

[0007] The current acquisition clamp is used to collect the current signal of the neutral point and feeder branch of the AC power supply, and transmit the collected current to the monitoring controller after standardization;

[0008] The monitoring controller calibrates the current transmitted by each current acquisition clamp separately, and then synthesizes the currents of the feeder neutral line and the double-power common-neutral feeder; the synthesized current is sent to the human-machine interaction unit;

[0009] The human-machine interaction unit is used to display the received synthesized current, provide a control port for oscillograph recording of the synthesized current, and send the oscillograph recording control signal to the monitoring controller;

[0010] The monitoring controller receives the current oscillograph recording control signal, performs oscillograph recording on the synthesized current, sends the oscillograph recording diagram to the human-machine interaction unit, and at the same time detects whether the amplitude of the oscillograph recording exceeds the threshold value. If so, an alarm signal is sent to the human-machine interaction unit;

[0011] The human-machine interaction unit displays the received oscillograph recording diagram and alarm signal.

[0012] Further, in the present invention, there are 4 current acquisition clamps.

[0013] Further, in the present invention, the current acquisition clamp adopts a clamp-type current sensor.

[0014] Further, in the present invention, the measurement range of the current acquisition clamp is: 0.0 - 10000.0 mA.

[0015] Further, in the present invention, the method for synthesizing the zero current of the feeder branch and the zero current of the double-power common-neutral feeder branch is to add and subtract the three-phase currents and subtract the zero line current value to obtain the synthesized current.

[0016] The present invention investigates the wiring forms of the substation AC power supply system, and forms a technical system for sensing and measuring the residual current of the AC power supply under different grounding methods for different application scenarios such as single-loop, phase-zero separated loop, and double-power common-neutral loop, so as to realize accurate identification of the insulation fault of the AC power supply system, and quickly obtain the location of the fault point of the low-voltage AC power supply system according to the direction and magnitude of the current. Description of the Drawings

[0017] Figure 1 is the principle block diagram of the portable residual current detection device described in the present invention;

[0018] Figure 2 is the schematic diagram of the residual current monitoring of the station AC power supply system;

[0019] Figure 3(a) is a schematic diagram of direct measurement of the residual current of a single loop with an independent protective ground wire in the loop;

[0020] Figure 3(b) is a schematic diagram of direct measurement of the residual current of a single loop without an independent protective ground wire in the loop;

[0021] Figure 4(a) is a schematic diagram of the combined measurement of phase and zero residual current in a single circuit with an independent protective ground wire;

[0022] Figure 4(b) is a schematic diagram of the combined measurement of phase and zero residual current in a single circuit without an independent protective ground wire;

[0023] Figure 5 is a schematic diagram of the combined measurement of the residual current in a double - power common - zero circuit with an independent protective ground wire;

[0024] Figure 6 is a schematic diagram of the combined measurement of the residual current in a double - power common - zero circuit without an independent protective ground wire. Specific implementation mode

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0026] Specific implementation mode one: Refer to Figure 1 Specifically illustrate this implementation mode. A portable residual current detection device described in this implementation mode includes a plurality of current acquisition clamps 1, a monitoring controller 2, a human - machine interaction unit 3, and a data memory 4;

[0027] The current acquisition clamp 1 is used to collect the current signals of the neutral point of the AC power supply and the feeder branch, and after standardizing the collected current, it transmits the current to the monitoring controller 2;

[0028] The monitoring controller 2 calibrates the current transmitted by each current acquisition clamp 1 separately, and then performs current synthesis for the feeder zero line and current synthesis for the double - power common - zero feeder; and sends the synthesized current to the human - machine interaction unit 3;

[0029] The human - machine interaction unit 3 is used to display the received synthesized current, and provides a control port for recording the wave of the synthesized current, and sends the recording control signal to the monitoring controller 2;

[0030] The monitoring controller 2 receives the current recording control signal, records the wave of the synthesized current, sends the recorded wave diagram to the human - machine interaction unit 3, and at the same time detects whether the amplitude of the recorded wave exceeds the threshold. If so, it sends an alarm signal to the human - machine interaction unit 3;

[0031] The human - machine interaction unit 3 displays the received recorded wave diagram and the alarm signal.

[0032] Further, in the present invention, there are 4 current acquisition clamps 1.

[0033] Further, in the present invention, the current acquisition clamp 1 adopts a clamp - type current sensor.

[0034] Further, in the present invention, the measurement range of the current acquisition clamp 1 is: 0.0 - 10000.0 mA.

[0035] Further, in the present invention, the method for synthesizing zero - current of the feeder branch and synthesizing current of the double - power - supply common - zero feeder branch is to add and subtract the three - phase currents and subtract the neutral - line current value to obtain the synthesized current.

[0036] The basic detection principle of the residual current on - line monitoring device for the station - used AC power supply system of the present invention is as Figure 2 shown. In the figure, I A , I B , I C are phase currents, I N is the neutral - line current, I d is the residual current of the phase line to the ground at point a, and S is any closed surface. According to Kirchhoff's law, the sum of the effective - value phasors of the currents flowing into any closed surface S is equal to zero. Then there is I A +I B +I C -I N -I d = 0. After arrangement, we get I A +I B +I C -I N = I d . Under normal circumstances, the vector sum of the three - phase currents is equal in magnitude and opposite in direction to the current flowing through the N line, and they cancel each other out. If the insulation of the line deteriorates or other reasons cause a ground current to be generated at point a on the A - phase line, then a current proportional to the residual current I d will be induced in the coil of the current transformer at S in the figure, and its numerical value reflects the leakage situation of the current in the distribution line and electrical equipment.

[0037] The on - site AC power supply wiring in the substation is intricate and complex, with various wiring forms and grounding methods. The research on the insulation deterioration mechanism and fault evolution process of the AC power supply is insufficient, and there are also certain differences in the relevant national standards and industry standards, resulting in the complexity and difficulty of monitoring the station - used AC insulation.

[0038] The device described in the present invention can be used alone or combined freely to achieve single-channel acquisition of residual current or multi-channel software vector synthesis; the residual current clamp adopts an open-type clamp structure for easy on-site application. Any one residual current clamp can be used to detect the residual current of a single circuit. Two residual current clamps are used to separately detect the phase line and neutral line of a single circuit and then perform vector synthesis, and 2 to 4 residual current clamps are used to achieve synthetic detection of the residual current of a common neutral circuit.

[0039] First, for the insulation fault monitoring technology of the station AC power supply system described in the present invention, for different application scenarios such as single circuits, phase-neutral separated circuits, and dual-power common neutral circuits, the residual current monitoring technology can be divided into the following types:

[0040] (1) Single-circuit residual current direct measurement technology

[0041] During on-site measurement, a single clamp-on current sensor is used to clamp the four wires A, B, C, and N of the circuit to be measured directly to obtain the residual current value of the measured circuit. The measurement method of the current clamp meter is as shown in Figure 3(a) and 3(b) shown:

[0042] (2) Single-circuit phase and neutral residual current synthetic measurement technology

[0043] For the scenario where the phase line and neutral line of the AC feeder branch circuit are arranged separately, when it is restricted by the on-site wiring conditions and it is impossible to use a single clamp-on current sensor for measurement, two clamp-on current sensors can be used to clamp the A, B, and C phases and the N line of the circuit respectively, and then the residual current value of the measured circuit can be obtained by vector synthesis of the monitoring host software of the finder. The measurement method of the current clamp meter is as shown in Figure 4(a) and 4(b) shown:

[0044] (3) Dual-power common neutral circuit current synthetic measurement technology

[0045] For the dual-power common neutral circuit, 2 to 4 clamp-on current sensors are used to clamp the two power supply circuits respectively, and then the residual current value of the measured circuit can be obtained by vector synthesis of the monitoring host software of the finder. The measurement method of the clamp-on current sensor is as shown in Figure 5 Figure 6 shown:

[0046] For the special application scenario of a dual - power common - neutral circuit, the residual current monitoring is basically divided into two categories: the hardware synthesis method of residual current sensors and the software vector synthesis method. The hardware synthesis means that the secondary outputs of the residual current sensors are directly paralleled for acquisition or they simultaneously pass through a current transformer to collect its secondary output. The software vector synthesis method is to separately collect two channels synchronously and then perform software vector synthesis. The advantage of the hardware synthesis method is that data processing is simple, but the disadvantage is that the two residual current sensors need to have exactly the same performance, otherwise it will have a greater impact on the results. The synthesis method described in the present invention has relatively low requirements for sensors. It can be calibrated separately first and then perform software vector synthesis. Therefore, the monitoring host described in the present invention can monitor the residual current of the neutral point of the station - used AC power supply system and the faulty feeder branch through a residual current clamp, collect 1 - 4 channels of AC residual current values in real - time, and calibrate the current of each channel separately; it can realize the synthesis of phase - neutral current of the loop and the synthesis of current in the dual - power common - neutral circuit, and arbitrarily synthesize 2 - 4 channels of residual current vectorially; it can manually start wave recording and automatically start wave recording after over - limit, and automatically alarm when over - limit; it can view historical data records, and the data can be exported to a U disk; the device uses a rechargeable lithium - battery, and it can be used for 8 - 10 hours after being fully charged. The current clamp uses an open - type, high - precision current sensor, with a clamp - type structure. There are a total of 4 clamps, which are used to collect the residual current signals of the neutral point of the AC power supply and each feeder branch. After standardizing the collected signals, they are uploaded to the monitoring host, and it has relatively high requirements for both accuracy and measurement range. The human - machine interaction unit has a friendly interface. It transfers the relevant parameter data of the whole process of AC insulation fault detection and monitoring to a U disk, can view the residual current value and alarm status of each branch, click on the wave - recording icon corresponding to the branch to view its wave - recording data, and can generate a detection report and print it out for convenient analysis.

[0047] Carry out functional verification on the portable residual current finder. According to the different grounding forms of the substation AC power supply system and the characteristics of the portable residual current finder itself, and considering comprehensively the practicability and economy, the present invention proposes a test and verification scheme combining a prototype test and a fault signal generator. Use the prototype test method to simulate different grounding methods and wiring forms of the substation AC power supply system for AC power insulation faults, and detect the functions of the device described in the present invention. Simulate the loop residual current and unbalanced current through the signal generator to calibrate the sampling accuracy of the device described in the present invention.

[0048] 1) Current clamp measurement range: 0.0 - 10000.0 mA;

[0049] 2) Current clamp measurement accuracy: 0.2 level;

[0050] 3) Monitoring host measurement accuracy: ≤ ±0.5%;

[0051] 4) Number of current sensors connected: 4;

[0052] 5) Number of data stored: 200 groups.

[0053] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Accordingly, it should be understood that numerous modifications may be made to the exemplary embodiments, and other arrangements may be designed, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a particular embodiment may be used in other described embodiments.

Claims

1. A portable residual current detection device, characterized in that: It comprises a plurality of current acquisition clamps (1), a monitoring controller (2), a human-computer interaction unit (3) and a data storage device (4); The current acquisition clamp (1) is used to collect current signals of the neutral point and feeder branch of the AC power supply, and standardize the collected current before transmitting it to the monitoring controller (2); The monitoring controller (2) calibrates the current transmitted by each current acquisition clamp (1) individually, and then performs current synthesis on the feeder zero line and dual power supply common zero feeder current synthesis; and sends the synthesized current to the human-computer interaction unit (3); The human-machine interaction unit (3) is used to display the received synthetic current, and provide a control port for recording the synthetic current, and send a recording control signal to the monitoring controller (2); The monitoring controller (2) receives the current recording control signal, records the synthetic current, sends the recording graph to the human-machine interaction unit (3), and detects whether the amplitude of the recording exceeds a threshold value. If so, an alarm signal is sent to the human-machine interaction unit (3); The human-computer interaction unit (3) displays the received waveform diagram and alarm signal.

2. A portable residual current detection device according to claim 1, characterized in that: There are four current collection clamps (1).

3. A portable residual current detection device according to claim 1, characterized in that: The current collection clamp (1) adopts a clamp-type current sensor.

4. A portable residual current detection device according to claim 1, characterized in that: The measuring range of the current acquisition caliper (1) is 0.0 to 10000.0 mA.

5. A portable residual current detection device according to claim 1, characterized in that: The method for synthesizing the zero current of the feeder branch and the current of the dual power supply common zero feeder branch is to add the three-phase current and subtract the neutral line current value to obtain the synthesized current.

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