Voltage transformer secondary side short circuit monitoring and protection system and fault monitoring method

Abstract

The invention provides a voltage transformer secondary side short circuit monitoring and protection system and a fault monitoring method, and relates to the field of voltage transformers, and the system comprises an overcurrent monitoring module, an execution module, a signal output module and a control terminal. The overcurrent monitoring module is used for outputting a control signal when the secondary side current of the voltage transformer is greater than a preset current threshold value; the execution module responds to the control signal, disconnects a secondary circuit of the voltage transformer and outputs an execution action signal; the signal output module responds to the execution action signal and outputs a short circuit monitoring signal; the control terminal is used for acquiring current data acquired by the ampere meter and voltage data acquired by the voltmeter so as to judge whether the secondary side of the voltage transformer has a short-circuit fault or not and acquiring a short-circuit monitoring signal of the signal output module, and the implementation mode solves the problem that the secondary side of the voltage transformer is lack of short-circuit monitoring and protection in the prior art.

Description

Technical Field

[0001] The invention relates to the field of voltage transformers, and in particular to a voltage transformer secondary side short circuit monitoring and protection system and a fault monitoring method. Background Art

[0002] At present, high-voltage PT (voltage transformer) does not have a secondary short-circuit online monitoring and protection system, and has the following defects during operation: when a short circuit occurs on the secondary side of the voltage transformer, if the fuse is not installed or the fuse is not blown, the PT will burn out in 3-5 minutes. The voltage transformer will not burn out during normal operation, but when the external line on the secondary side of the voltage transformer is grounded or there is resonance on the power grid, the voltage transformer will also burn out.

[0003] This is because in normal operation, the secondary load impedance of the PT is very large, which is basically equivalent to the no-load state of the transformer. The PT is a voltage source with extremely small internal resistance. In normal operation, the impedance is very large, which is equivalent to an open circuit. If the secondary of the voltage transformer is suddenly short-circuited, the secondary circuit impedance is almost zero, and the secondary current will be very large.

[0004] When a short circuit occurs on the secondary side, the current on the secondary side is very large, which will burn the secondary winding and then burn the insulation. The high voltage on the primary side will be connected to the secondary side, causing the PT to explode and catch fire, causing the switch cabinet to catch fire, and even causing safety accidents such as casualties. At the same time, the relay protection device loses the sampling voltage, and the distance protection, impedance protection, and composite voltage protection fail. In the event of an accident, the protection malfunctions or refuses to operate, and the circuit breaker trips abnormally. The accident expands, causing the production line to stop and causing serious losses. It is used for measuring circuits, resulting in errors in electric energy measurement. Summary of the invention

[0005] In view of this, the present invention aims to propose a voltage transformer secondary side short-circuit monitoring and protection system and a fault monitoring method to solve the problem of lack of short-circuit monitoring and protection on the secondary side of the voltage transformer in the prior art.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] The first aspect of the present invention provides a voltage transformer secondary side short circuit monitoring and protection system, including an ammeter and a voltmeter; one end of the voltage transformer secondary side terminal is connected to the ammeter input end, the ammeter output end is connected to the voltmeter input end, and the voltmeter output end is connected to the other end of the voltage transformer secondary side terminal, and further includes:

[0008] Overcurrent monitoring module, execution module, signal output module and control terminal;

[0009] The overcurrent monitoring module is used to output a control signal when the current on the secondary side of the voltage transformer is greater than a preset current threshold;

[0010] The execution module disconnects the secondary circuit of the voltage transformer and outputs an execution action signal in response to the control signal;

[0011] The signal output module outputs a short circuit monitoring signal in response to the execution action signal;

[0012] The control terminal is used to obtain the current data collected by the ammeter and the voltage data collected by the voltmeter to determine whether there is a short-circuit fault on the secondary side of the voltage transformer, and to obtain the short-circuit monitoring signal of the signal output module.

[0013] Preferably, the system comprises an analog-to-digital converter, and an analog quantity input terminal of the analog-to-digital converter is respectively connected to a voltmeter data output terminal and an ammeter data output terminal.

[0014] Preferably, the overcurrent monitoring module comprises an overcurrent relay;

[0015] One end of the coil of the overcurrent relay is connected to one end of the secondary wiring terminal of the voltage transformer, and the other end is connected to the input end of the ammeter.

[0016] Preferably, the operating current of the overcurrent relay is less than or equal to 2A and greater than or equal to 0.5A, and the operating time is less than or equal to 0.5 seconds.

[0017] Preferably, the system further comprises a first power supply; the execution module comprises an execution relay;

[0018] The first end of the first power supply is connected to one end of the normally open contact of the overcurrent relay, and the other end of the normally open contact of the overcurrent relay is connected to one end of the coil of the execution relay; the other end of the coil of the execution relay is connected to the second end of the first power supply;

[0019] One end of the normally closed contact of the execution relay is connected to one end of the secondary wiring terminal of the voltage transformer, and the other end is connected to one end of the coil of the overcurrent relay.

[0020] Preferably, the system further comprises a second power supply; the signal output module comprises a signal relay;

[0021] The first end of the second power supply is connected to one end of the normally open contact of the execution relay, the other end of the normally open contact of the execution relay is connected to one end of the coil of the signal relay, and the other end of the coil of the signal relay is connected to the second end of the second power supply.

[0022] Preferably, the system further comprises a communication management machine and a third power source;

[0023] The first end of the third power supply is connected to one end of the normally open contact of the signal relay, and the other end of the normally open contact of the signal relay is connected to the digital input end of the communication management machine; the common end of the communication management machine is connected to the second end of the third power supply;

[0024] The data receiving end of the communication management machine is also connected to the digital quantity output end of the analog-to-digital converter.

[0025] Preferably, the control terminal is connected to the network communication terminal of the communication management machine, and is used to obtain the current data of the ammeter and the voltage data of the voltmeter.

[0026] A second aspect of the present invention provides a method for monitoring a short-circuit fault on the secondary side of a voltage transformer applied to a control terminal as described in the first aspect, comprising:

[0027] The voltmeter voltage data U and the ammeter current data I are obtained through the control terminal. According to the formula Z=U / I, the impedance Z is calculated and an impedance change curve is generated. When it is judged that the impedance is less than the preset impedance threshold, a short circuit fault exists.

[0028] Preferably, when it is determined through the control terminal that a short circuit fault exists, an alarm signal is output.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] In the present invention, the current on the secondary side of the voltage transformer is monitored online in real time through the overcurrent monitoring module, and when a short circuit occurs on the secondary side of the voltage transformer, a control signal is output when the current is greater than a preset threshold value; the secondary circuit is disconnected by the execution module when a short circuit occurs on the secondary side of the voltage transformer, thereby avoiding equipment loss and casualties caused by the explosion of the voltage transformer. The signal output module outputs a short circuit monitoring signal when a short circuit occurs on the secondary side of the voltage transformer, and the control terminal can determine whether a short circuit fault occurs in the transformer based on the short circuit monitoring signal. The control terminal identifies whether a short circuit fault occurs on the secondary side of the voltage transformer, and implements an early warning or alarm of a short circuit fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 It is a wiring circuit diagram of a three-phase voltage transformer of the present invention;

[0033] Figure 2 It is a wiring circuit diagram of a two-phase voltage transformer of the present invention;

[0034] Figure 3 A phase voltage connection voltage transformer wiring circuit diagram of the present invention;

[0035] Figure 4 The whole of the present invention and the voltage transformer wiring circuit diagram;

[0036] Figure 5 A circuit diagram of a voltage transformer secondary side short circuit monitoring and protection system of the present invention;

[0037] Figure 6 The present invention is a flow chart of a method for monitoring a short-circuit fault on the secondary side of a voltage transformer. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "back", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0040] In addition, in the description of the present invention, unless otherwise clearly defined, the terms "installed", "connected", "connected", and "connector" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

[0041] The following will refer to the attached Figures 1 to 6 The present invention is described in detail with reference to embodiments.

[0042] Example 1

[0043] In general, the current wiring diagrams of three-phase voltage and two-phase voltage transformers are as follows: Figure 1 And as shown in 2.

[0044] Taking the three-phase voltage transformer system as an example, the A-phase power supply is connected to the PT (voltage transformer) and the wiring is as follows: Figure 3 When a short circuit occurs at point X, the secondary resistance is almost zero, which will generate a very large short circuit current, burn out the PT within 3-5 minutes, and even cause an explosion or fire.

[0045] Based on this, the present invention proposes the following technical solutions:

[0046] like Figure 4As shown, the present invention discloses a voltage transformer secondary side short circuit monitoring and protection system, the system input end is connected to the voltage transformer secondary side wiring terminals da and dn, and the output end is connected to the secondary side voltmeters or needs to introduce a voltage quantity loop.

[0047] like Figure 5 As shown, the system includes: an ammeter and a voltmeter.

[0048] One end da of the secondary side terminal of the voltage transformer is connected to the input end of the ammeter, the output end of the ammeter is connected to the input end of the voltmeter, and the output end of the voltmeter is connected to the other end dn of the secondary side terminal of the voltage transformer; among them, the ammeter and voltmeter are used to monitor the voltage and current of the secondary side circuit of the voltage transformer, which is an important basis for judging whether there is a short circuit fault on the secondary side of the transformer.

[0049] The system also includes: an overcurrent monitoring module, an execution module, a signal output module and a control terminal.

[0050] The overcurrent monitoring module is used to output a control signal when the secondary side current of the voltage transformer is greater than a preset current threshold.

[0051] The execution module disconnects the secondary circuit of the voltage transformer and outputs an execution action signal in response to a control signal of the execution module.

[0052] The signal output module outputs a short-circuit monitoring signal in response to the execution action signal output by the execution module.

[0053] The control terminal is used to obtain the current data collected by the ammeter and the voltage data collected by the voltmeter to determine whether there is a short-circuit fault on the secondary side of the voltage transformer, and to obtain the short-circuit monitoring signal of the signal output module.

[0054] The present invention monitors the current on the secondary side of the voltage transformer in real time online through an overcurrent monitoring module, and outputs a control signal when a short circuit occurs on the secondary side of the voltage transformer and the current is greater than a preset threshold value; the execution module disconnects the secondary circuit when a short circuit occurs on the secondary side of the voltage transformer, thereby avoiding equipment loss and casualties caused by an explosion of the voltage transformer. The signal output module outputs a short circuit monitoring signal when a short circuit occurs on the secondary side of the voltage transformer, and the control terminal can determine whether a short circuit fault occurs in the transformer based on the short circuit monitoring signal. The control terminal identifies whether a short circuit fault occurs on the secondary side of the voltage transformer, thereby realizing an early warning or alarm of a short circuit fault.

[0055] In a possible implementation, the system includes an analog-to-digital converter, and an analog quantity input terminal of the analog-to-digital converter is respectively connected to a voltage meter data output terminal and an ammeter data output terminal.

[0056] The analog-to-digital converter is used to convert the analog data of the voltmeter and the ammeter into digital data that can be recognized by the communication management machine.

[0057] In a possible implementation, the overcurrent monitoring module includes an overcurrent relay KA.

[0058] One end of the coil of the overcurrent relay KA is connected to one end of the secondary terminal of the voltage transformer, and the other end is connected to the input end of the ammeter.

[0059] When a short circuit fault occurs on the secondary side of the voltage transformer, the current in the coil of the overcurrent relay KA is greater than the preset threshold, the overcurrent relay KA operates, and its normally open contacts close.

[0060] In one possible implementation, the operating current of the overcurrent relay KA is less than or equal to 2A and greater than or equal to 0.5A, and the operating time is less than or equal to 0.5 seconds. Generally, the value of the secondary current of the voltage transformer is 0.5A, so in order to achieve a fast response of the overcurrent relay KA, its operating current needs to be between 0.5 seconds and 2 seconds, and the operating time is not less than 0.5 seconds.

[0061] In a possible implementation, the system further includes a first power supply; and the execution module includes an execution relay KM1.

[0062] The first end L1 of the first power supply is connected to one end of the normally open contact of the overcurrent relay KA, and the other end of the normally open contact of the overcurrent relay KA is connected to one end of the coil of the execution relay KM1; the other end of the coil of the execution relay KM1 is connected to the second end N1 of the first power supply; when the overcurrent relay KA is actuated, the normally open contact of the overcurrent relay KA is closed, and its output control signal drives the execution relay KM1 to act.

[0063] One end of the normally closed contact of the execution relay KM1 is connected to one end of the secondary terminal of the voltage transformer, and the other end is connected to one end of the coil of the overcurrent relay KA; after the execution relay KM1 is actuated, the normally closed contact of the execution relay KM1 is disconnected to disconnect the secondary circuit of the voltage transformer, thereby preventing the voltage transformer from burning due to secondary short circuit.

[0064] In a possible implementation, the system further includes a second power supply; and the signal output module includes a signal relay KS1.

[0065] The first end L2 of the second power supply is connected to one end of the normally open contact of the execution relay KM1, the other end of the normally open contact of the execution relay KM1 is connected to one end of the coil of the signal relay KS1, and the other end of the coil of the signal relay KS1 is connected to the second end N2 of the second power supply. After the execution relay KM1 is actuated, the normally open contact of the execution relay KM1 is closed, at which time the execution action signal is output and the signal relay KS1 is driven to actuate, the normally open contact of the signal relay KS1 is closed, at which time the signal relay KS1 outputs the short circuit monitoring signal to the communication management machine, the communication management machine sends the signal to the control terminal, and issues an alarm through the control terminal.

[0066] In one possible implementation, the system also includes a communication management machine and a third power source.

[0067] The first end L3 of the third power supply is connected to one end of the normally open contact of the signal relay KS1, and the other end of the normally open contact is connected to the digital input end of the communication management machine; the common end M of the communication management machine is connected to the second end N3 of the third power supply.

[0068] The data receiving end of the communication management machine is also connected to the digital output end of the analog-to-digital converter.

[0069] The control terminal is connected to the network communication terminal of the communication management machine and is used to obtain the current data of the ammeter and the voltage data of the voltmeter.

[0070] Example 2

[0071] like Figure 6 As shown, this embodiment provides a voltage transformer secondary side short circuit fault monitoring method applied to the control terminal as in Embodiment 1, comprising:

[0072] Step S1, obtaining voltage data U of a voltmeter and current data I of an ammeter through a control terminal.

[0073] Step S2: According to the formula Z=U / I, the impedance Z is calculated and an impedance change curve is generated; by tracking the trend of the curve.

[0074] Step S3: When it is determined that the impedance is less than the preset impedance threshold, a short circuit fault exists; at this time, the preset impedance threshold is a number close to 0 (eg, 0.1Ω for example).

[0075] When the control terminal determines that there is a short-circuit fault or a short-circuit fault, an alarm signal is output, such as a pop-up window alarm, and the operation and maintenance personnel are notified to perform maintenance and troubleshoot the fault point.

[0076] In this embodiment, the control terminal obtains the current data of the ammeter and generates a current change curve diagram, and can determine whether a short circuit fault exists according to the size of the obtained current value.

[0077] The control terminal is also used to obtain voltage data from the voltmeter, generate a voltage change curve, and determine whether a short circuit fault exists based on the size of the obtained voltage value.

[0078] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Voltage transformer secondary side short circuit monitoring and protection system, including ammeter and voltmeter; One end of the secondary side terminal of the voltage transformer is connected to the input end of the ammeter, the output end of the ammeter is connected to the input end of the voltmeter, and the output end of the voltmeter is connected to the other end of the secondary side terminal of the voltage transformer, characterized in that: Also includes: Overcurrent monitoring module, execution module, signal output module and control terminal; The overcurrent monitoring module is used to output a control signal when the current on the secondary side of the voltage transformer is greater than a preset current threshold; The execution module disconnects the secondary circuit of the voltage transformer and outputs an execution action signal in response to the control signal; The signal output module outputs a short circuit monitoring signal in response to the execution action signal; The control terminal is used to obtain the current data collected by the ammeter and the voltage data collected by the voltmeter to determine whether there is a short-circuit fault on the secondary side of the voltage transformer, and to obtain the short-circuit monitoring signal of the signal output module.

2. The voltage transformer secondary side short circuit monitoring and protection system according to claim 1, characterized in that: The system comprises an analog-to-digital converter, wherein an analog quantity input terminal of the analog-to-digital converter is respectively connected to a voltage meter data output terminal and an ammeter data output terminal.

3. The voltage transformer secondary side short circuit monitoring and protection system according to claim 2, characterized in that: The overcurrent monitoring module includes an overcurrent relay; One end of the coil of the overcurrent relay is connected to one end of the secondary wiring terminal of the voltage transformer, and the other end is connected to the input end of the ammeter.

4. The voltage transformer secondary side short circuit monitoring and protection system according to claim 3, characterized in that: The operating current of the overcurrent relay is less than or equal to 2A and greater than or equal to 0.5A, and the operating time is less than or equal to 0.5 seconds.

5. The voltage transformer secondary side short circuit monitoring and protection system according to claim 3, characterized in that: The system further comprises a first power supply; the execution module comprises an execution relay; The first end of the first power supply is connected to one end of the normally open contact of the overcurrent relay, and the other end of the normally open contact of the overcurrent relay is connected to one end of the coil of the execution relay; the other end of the coil of the execution relay is connected to the second end of the first power supply; One end of the normally closed contact of the execution relay is connected to one end of the secondary wiring terminal of the voltage transformer, and the other end is connected to one end of the coil of the overcurrent relay.

6. The voltage transformer secondary side short circuit monitoring and protection system according to claim 5, characterized in that: The system further comprises a second power supply; the signal output module comprises a signal relay; The first end of the second power supply is connected to one end of the normally open contact of the execution relay, the other end of the normally open contact of the execution relay is connected to one end of the coil of the signal relay, and the other end of the coil of the signal relay is connected to the second end of the second power supply.

7. The voltage transformer secondary side short circuit monitoring and protection system according to claim 6, characterized in that: The system also includes a communication management machine and a third power supply; The first end of the third power supply is connected to one end of the normally open contact of the signal relay, and the other end of the normally open contact of the signal relay is connected to the digital input end of the communication management machine; the common end of the communication management machine is connected to the second end of the third power supply; The data receiving end of the communication management machine is also connected to the digital quantity output end of the analog-to-digital converter.

8. The voltage transformer secondary side short circuit monitoring and protection system according to claim 7, characterized in that: The control terminal is connected to the network communication terminal of the communication management machine and is used to obtain the current data of the ammeter and the voltage data of the voltmeter.

9. A method for monitoring short-circuit faults on the secondary side of a voltage transformer applied to a control terminal as claimed in any one of claims 1 to 8, characterized in that: include: The voltage data U of the voltmeter and the current data I of the ammeter are obtained through the control terminal. According to the formula Z=U / I, the impedance Z is calculated to generate an impedance change curve. When it is judged that the impedance is less than the preset impedance threshold, a short circuit fault exists.

10. The method for monitoring a short-circuit fault on the secondary side of a voltage transformer according to claim 9, characterized in that: When a short circuit fault is determined to exist through the control terminal, an alarm signal is output.

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