CN203572909U - Single-phase ground fault detection circuit and system - Google Patents

Abstract

The utility model provides a single-phase grounding fault detection circuit, comprising: an alarm circuit, a voltage sensor, a voltage comparison circuit and a timing circuit. Wherein, the voltage sensor collects the voltage value on the connection bar between the transformer and the transition contact. When the voltage value collected by the voltage sensor is greater than the preset voltage value, the first control signal is output to the timing circuit. When the preset time comes , the timing circuit generates a second control signal to control the alarm in the alarm circuit to issue an alarm. Effective early warning of single-phase ground faults ensures the safety of the power supply system.

Description

A single-phase ground fault detection circuit and system

technical field

The utility model relates to the technical field of power fault detection, in particular to a single-phase ground fault detection circuit and system.

Background technique

With the continuous development of social economy and the increasing level of electrification, the consumption of electric energy is also increasing. Usually, my country's distribution network adopts the method of not directly grounding the neutral point to transmit electric energy, which is also called the small current grounding power supply method.

At present, affected by the power supply load of the power grid, the 35kV switch of the main transformer in the 110kV substation (take the three-turn transformation as an example) is often in a hot standby state for a long time, forming a special operation mode in which the 110kV side of the main transformer only supplies 10kV.

The inventors found that under the above operation mode, the connection cable between the medium voltage side bushing of the main transformer and the 35kV transition contact cabinet is prone to breakdown, which in turn leads to the failure of the main transformer differential protection action tripping. Specifically, when the neutral point is not directly grounded for power supply, if a single-phase ground occurs during operation, the operator cannot find it in time. Although the 35kV system is a neutral point ungrounded system, which allows single-phase grounding operation for a period of time, the insulation of the system is very fragile in the single-phase grounding mode. If it is disturbed by some grids or the insulation of the cable itself is poor, it is very likely to develop into two points. The ground fault causes overvoltage in the power supply system, thereby short-circuiting the area near the main transformer, causing power outages, and affecting the safety of the power supply system.

It can be seen that in the above operation mode, it is very important to provide a single-phase ground fault detection device for voltage detection and early warning. It can inform the operator of the working condition of the cable (or busbar) at the first time. For single-phase ground faults, preventive measures can be taken in time to avoid the expansion of accidents and large-scale power outages.

Utility model content

In view of this, the utility model provides a single-phase ground fault detection circuit, which can effectively warn the single-phase ground fault and ensure the safety of the power supply system.

In order to achieve the above object, the utility model provides the following technical solutions:

A single-phase ground fault detection circuit comprising:

An alarm circuit, the alarm circuit at least includes an alarm;

A voltage sensor that collects the voltage value on the connection bar between the transformer and the transition contact;

A voltage comparison circuit that is connected to the voltage sensor and outputs a first control signal when the voltage value collected by the voltage sensor is greater than a preset voltage value;

It is connected with the voltage comparison circuit, receives the first control signal, and generates a second control signal to control the timing circuit of the alarm when the preset time arrives.

Preferably, it also includes:

An indicator light that is set between the voltage comparison circuit and the timing circuit and is turned on when the voltage comparison circuit outputs the first control signal.

Preferably, the voltage sensor includes at least:

A first capacitor connected in series between the signal output terminal of the transformer and the ground.

Preferably, the voltage sensor includes: a piezoresistor, a current limiting resistor, a decoupling capacitor, a first rectifier diode, a second rectifier diode, a voltage regulator tube, a filter capacitor, and a shunt resistor;

The first terminal of the piezoresistor is connected to the first terminal of the current limiting resistor and serves as the input terminal of the voltage sensor, and the second terminal of the current limiting resistor is respectively connected to the first terminal of the decoupling capacitor. , the anode of the first rectifier diode and the cathode of the second rectifier diode are connected, and the cathode of the first rectifier diode is respectively connected to the cathode of the voltage regulator tube, the first end of the filter capacitor and the shunt The first end of the resistor is connected and used as the output end of the voltage sensor, the second end of the piezoresistor, the second end of the decoupling capacitor, the anode of the first rectifier diode, the voltage regulator tube The anode of the filter capacitor, the second end of the filter capacitor and the second end of the shunt resistor are all grounded.

Preferably, it also includes:

a photocoupler arranged between the voltage comparison circuit and the timing circuit;

The input terminal of the photoelectric coupler is connected in series between the output terminal of the voltage comparison circuit and the ground, and the output terminal of the photoelectric coupler is connected with the input terminal of the timing circuit.

Preferably, the timing circuit includes: a power supply resistor, a delay capacitor, a first voltage dividing resistor, a second voltage dividing resistor, a first Zener diode and an operational amplifier;

The first end of the power supply resistor is respectively connected to the first end of the first voltage dividing resistor and the cathode of the first Zener diode and serves as the first output end of the timing circuit, and the first end of the power supply resistor The two ends are connected to the first output end of the photocoupler, and the second end of the first voltage dividing resistor is respectively connected to the inverting input end of the operational amplifier and the first end of the second voltage dividing resistor , the second output end of the photocoupler is respectively connected to the first end of the delay capacitor and the non-inverting input end of the operational amplifier, the second end of the delay capacitor, the second voltage dividing resistor Both the second terminal of the voltage regulator tube and the cathode of the first regulator tube are grounded and serve as the second output terminal of the timing circuit, and the output terminal of the operational amplifier is used as the signal output terminal of the timing circuit.

Preferably, the alarm circuit includes: a relay, a switch tube and an alarm;

The control terminal of the switching tube is connected to the signal output terminal of the timing circuit, the coil of the relay is connected in series between the input terminal of the switching tube and the first output terminal of the timing module, and the switching tube The output end of the relay is grounded, and the normally open switch of the relay is connected with the alarm.

Preferably, the preset voltage value is 1.2 times the rated phase voltage on the connection bar, and the preset time is two minutes.

Preferably, it also includes:

A GSM transceiver module that is connected to the signal output end of the timing circuit and sends alarm information after receiving the second control signal.

A single-phase ground fault detection system is characterized in that it includes a remote monitoring platform and any single-phase ground fault detection circuit as described above.

It can be seen from the above technical solutions that, compared with the prior art, the utility model provides a single-phase ground fault detection circuit, including: an alarm circuit, a voltage sensor, a voltage comparison circuit and a timing circuit. Wherein, the voltage sensor collects the voltage value on the connection bar between the transformer and the transition contact. When the voltage value collected by the voltage sensor is greater than the preset voltage value, the first control signal is output to the timing circuit. When the preset time comes , the timing circuit generates a second control signal to control the alarm in the alarm circuit to issue an alarm. Effective early warning of single-phase ground faults ensures the safety of the power supply system.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description It is only an embodiment of the utility model, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is a functional block diagram of a single-phase ground fault detection circuit provided by the utility model;

Fig. 2 is a schematic diagram of the principle of a single-phase ground fault detection circuit provided by the utility model;

Fig. 3 is a schematic diagram of the principle of another single-phase ground fault detection circuit provided by the utility model;

Fig. 4 is a specific circuit diagram of a single-phase ground fault detection circuit provided by the utility model.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. example. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Please refer to Fig. 1, which is a functional block diagram of a single-phase ground fault detection circuit provided by the present invention. The single-phase ground fault detection circuit includes: a voltage sensor 101, a voltage comparison circuit 102, a timing circuit 103 and an alarm circuit 104, Wherein, the alarm circuit 104 includes an alarm 1041 .

Wherein, the voltage sensor 101 is used to collect the voltage value on the connection bar between the transformer and the transition contact. The voltage comparison circuit is connected to the voltage sensor, receives the voltage value collected by the voltage sensor, and compares the received voltage value with the preset voltage value, and outputs the first control when the collected voltage value is greater than the preset voltage value signal to the timing circuit. When the preset time arrives, the timing circuit generates a second control signal to control the alarm in the alarm circuit to generate an alarm.

It can be seen that the utility model provides a single-phase ground fault detection circuit, which can effectively warn the single-phase ground fault and ensure the safety of the power supply system.

Preferably, the utility model also provides a schematic diagram of the principle of a single-phase fault detection circuit, as shown in Figure 2, the detection circuit includes: a voltage sensor 101, a voltage comparison circuit 102, a timing circuit 103 and an alarm circuit 104, wherein, The alarm circuit 104 includes an alarm. It is not difficult to find out from the figure that the alarm circuit 104 includes: a relay 1042, a switching tube and an alarm.

Among them, the connection relationship of each device is: the control terminal of the switch tube is connected to the signal output terminal of the timing circuit, the coil of the relay is connected in series between the input terminal of the switch tube and the first output terminal of the timing module, and the output terminal of the switch tube Grounded, the normally open switch of the relay is connected to the alarm.

Combined with the specific structure of the alarm circuit, the working principle of the single-phase fault detection circuit provided by this embodiment is:

The voltage sensor 101 is used to collect the voltage value on the connection bar between the transformer and the transition contact. The voltage comparison circuit 102 is connected with the voltage sensor 101, receives the voltage value collected by the voltage sensor 101, and compares the received voltage value with the preset voltage value, and outputs when the collected voltage value is greater than the preset voltage value The first control signal is sent to the timing circuit 103 . When the preset time arrives, the timing circuit generates a second control signal to the switch tube to control the switch tube to turn on. At this time, the relay 1042 is energized to act, that is, the normally open switch is closed, and the alarm is energized to generate an alarm.

The utility model provides a single-phase grounding fault detection circuit, which can effectively warn the single-phase grounding fault and ensure the safety of the power supply system.

Preferably, in combination with the actual situation, this embodiment also provides the optimal solution for the preset voltage value and preset time, such as defining the preset voltage value as 1.2 times the rated phase voltage on the connection bar, and the preset time is two Minutes wait. It should be noted that the limitation here is only for illustration, and does not limit the protection scope of the present application thereto. The preset time and preset voltage here can be realized by modifying the voltage comparison circuit 102 and the timing circuit 103 .

For better early warning, as shown in FIG. 3 , an indicator light 105 is provided between the voltage comparison circuit 102 and the timing circuit 103 in this embodiment. The indicator light 105 lights up when the voltage comparison circuit 102 outputs the first control signal. That is, when the detected voltage is higher than 1.2 times of single-phase rated voltage, the indicator light is on. In addition, in this embodiment, a photocoupler 106 is provided between the voltage comparison circuit 102 and the timing circuit 103 . The input end of the photoelectric coupler is connected in series between the output end of the voltage comparison circuit and the ground, and the output end is connected with the input end of the timing circuit.

Specifically, this embodiment also provides a specific realization circuit of a single-phase ground fault detection circuit, as shown in FIG. 4 , wherein the detection circuit includes: a voltage sensor, a voltage comparison circuit, a timing circuit and an alarm circuit.

Wherein, the voltage sensor includes at least a first capacitor connected in series between the signal output terminal of the transformer and the ground. The voltage is kept and collected through the capacitor. Specifically, the voltage sensor includes: a piezoresistor, a current limiting resistor, a decoupling capacitor, a first rectifier diode, a second rectifier diode, a voltage regulator tube, a filter capacitor and a shunt resistor.

Its connection relationship is:

The first terminal of the piezoresistor is connected to the first terminal of the current limiting resistor and serves as the input terminal of the voltage sensor, and the second terminal of the current limiting resistor is respectively connected to the first terminal of the decoupling capacitor, the anode of the first rectifier diode and the second terminal of the second rectifier diode. The cathodes of the rectifying diodes are connected, the cathodes of the first rectifying diodes are respectively connected to the cathode of the voltage regulator tube, the first end of the filter capacitor and the first end of the shunt resistor and used as the output end of the voltage sensor, the second end of the piezoresistor, The second terminal of the decoupling capacitor, the anode of the first rectifier diode, the anode of the voltage regulator tube, the second terminal of the filter capacitor and the second terminal of the shunt resistor are all grounded.

The timing circuit includes: a power supply resistor, a delay capacitor, a first voltage dividing resistor, a second voltage dividing resistor, a first voltage stabilizing diode and an operational amplifier;

The first end of the power supply resistor is respectively connected to the first end of the first voltage dividing resistor and the cathode of the first Zener diode as the first output end of the timing circuit, and the second end of the power supply resistor is connected to the first output of the photocoupler The second end of the first voltage dividing resistor is connected with the inverting input end of the operational amplifier and the first end of the second voltage dividing resistor respectively, and the second output end of the photocoupler is respectively connected with the first end of the delay capacitor and the same-phase input terminal of the operational amplifier, the second terminal of the delay capacitor, the second terminal of the second voltage dividing resistor and the cathode of the first voltage regulator tube are all grounded and used as the second output terminal of the timing circuit, the output of the operational amplifier The terminal is used as the signal output terminal of the timing circuit.

Combined with the specific connection relationship above, the working principle of the single-phase ground fault detection circuit is as follows:

The varistor f1 and the Zener diode DW1 are used for overvoltage protection, and the decoupling capacitor C1 is charged through the current limiting resistor R1, that is, the process of collecting voltage. In this circuit, the rectifier diodes D1 and D2 are added to make the current smooth. The filter capacitor C4 is used to filter the collected voltage, and the resistor R4 is used to adjust the value of the starter valve. Thereafter, the collected voltage signal is input to the input terminal of the comparator U1, and when the input voltage of the comparator U1 is greater than a preset value, a first control signal is output to turn on the light emitting diode LED1 and the photocoupler U4.

Then the output signal of the photocoupler U4 charges the delay capacitor C7 through the resistor R10. It should be noted here that the delay time can be determined by setting the capacity of different capacitors. When the capacitor C7 is charged with enough electricity, this When the voltage of the non-inverting input terminal of the comparator is higher than the voltage of the inverting input terminal, the comparator outputs a second control signal to the switch tube Q1, Q1 conducts to make the relay act, and the alarm sends out an alarm.

Combining the above circuit connection relationship, it is not difficult to find that the single-phase ground fault detection device provided by this embodiment adopts the transmission of switching signals, which can effectively avoid the existing voltage or current transmission compared with the direct transmission of voltage or current. Malformation and distortion phenomenon, high transmission efficiency.

Preferably, a short message sending and receiving module can also be set to send an alarm message to the operator's mobile phone or remote console after receiving the second control signal, so that the operator can deal with the on-site failure in a timely manner.

It should be noted that the single-phase ground fault detection device provided in this embodiment also includes a charging display device, which has the same structure and function as the charging display device on the panel of the switch cabinet in the prior art. In the normal operation state of the main transformer, the single-phase grounding of the bus is detected and alarmed by the bus voltage transformer, and the single-phase grounding fault detection device does not work. When the main transformer switch is disconnected, the busbar between the main transformer and the main transformer switch is single-phase grounded. At this time, the single-phase ground fault detection device works to effectively warn the single-phase ground fault and ensure the safety of the power supply system. .

In addition to the above embodiments, the utility model also provides a single-phase ground fault detection system, including a remote monitoring platform and a single-phase ground fault detection circuit as described above. For the working principle and structure of the detection circuit, please refer to the above-mentioned embodiments, and will not be described in detail again.

To sum up, the utility model provides a single-phase ground fault detection circuit, including: an alarm circuit, a voltage sensor, a voltage comparison circuit and a timing circuit. Wherein, the voltage sensor collects the voltage value on the connection bar between the transformer and the transition contact. When the voltage value collected by the voltage sensor is greater than the preset voltage value, the first control signal is output to the timing circuit. When the preset time comes , the timing circuit generates a second control signal to control the alarm in the alarm circuit to issue an alarm. Effective early warning of single-phase ground faults ensures the safety of the power supply system.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the device provided in the embodiment, since it corresponds to the method provided in the embodiment, the description is relatively simple, and for the relevant details, please refer to the description of the method part.

The above description of the provided embodiments enables those skilled in the art to realize or use the utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features provided herein.

Claims (10)

1. A single-phase ground fault detection circuit, characterized in that, comprising: An alarm circuit, the alarm circuit at least includes an alarm; A voltage sensor that collects the voltage value on the connection bar between the transformer and the transition contact; A voltage comparison circuit that is connected to the voltage sensor and outputs a first control signal when the voltage value collected by the voltage sensor is greater than a preset voltage value; It is connected with the voltage comparison circuit, receives the first control signal, and generates a second control signal to control the timing circuit of the alarm when the preset time arrives. 2. The single-phase ground fault detection circuit according to claim 1, further comprising: An indicator light that is set between the voltage comparison circuit and the timing circuit and is turned on when the voltage comparison circuit outputs the first control signal. 3. The single-phase ground fault detection circuit according to claim 1, wherein the voltage sensor comprises at least: A first capacitor connected in series between the signal output terminal of the transformer and the ground. 4. The single-phase ground fault detection circuit according to claim 1, wherein the voltage sensor comprises: a piezoresistor, a current limiting resistor, a decoupling capacitor, a first rectifier diode, a second rectifier diode, a voltage regulator tube, filter capacitor and shunt resistor; The first terminal of the piezoresistor is connected to the first terminal of the current limiting resistor and serves as the input terminal of the voltage sensor, and the second terminal of the current limiting resistor is respectively connected to the first terminal of the decoupling capacitor. , the anode of the first rectifier diode and the cathode of the second rectifier diode are connected, and the cathode of the first rectifier diode is respectively connected to the cathode of the voltage regulator tube, the first end of the filter capacitor and the shunt The first end of the resistor is connected and used as the output end of the voltage sensor, the second end of the piezoresistor, the second end of the decoupling capacitor, the anode of the first rectifier diode, the voltage regulator tube The anode of the filter capacitor, the second end of the filter capacitor and the second end of the shunt resistor are all grounded. 5. The single-phase ground fault detection circuit according to claim 1, further comprising: a photocoupler arranged between the voltage comparison circuit and the timing circuit; The input terminal of the photoelectric coupler is connected in series between the output terminal of the voltage comparison circuit and the ground, and the output terminal of the photoelectric coupler is connected with the input terminal of the timing circuit. 6. The single-phase ground fault detection circuit according to claim 5, wherein the timing circuit comprises: a power supply resistor, a delay capacitor, a first voltage divider resistor, a second voltage divider resistor, a first Zener diode and operational amplifiers; The first end of the power supply resistor is respectively connected to the first end of the first voltage dividing resistor and the cathode of the first Zener diode and serves as the first output end of the timing circuit, and the first end of the power supply resistor The two ends are connected to the first output end of the photocoupler, and the second end of the first voltage dividing resistor is respectively connected to the inverting input end of the operational amplifier and the first end of the second voltage dividing resistor , the second output end of the photocoupler is respectively connected to the first end of the delay capacitor and the non-inverting input end of the operational amplifier, the second end of the delay capacitor, the second voltage dividing resistor Both the second terminal of the voltage regulator tube and the cathode of the first regulator tube are grounded and serve as the second output terminal of the timing circuit, and the output terminal of the operational amplifier is used as the signal output terminal of the timing circuit. 7. The single-phase ground fault detection circuit according to claim 5, wherein the alarm circuit comprises: a relay, a switching tube and an alarm; The control terminal of the switching tube is connected to the signal output terminal of the timing circuit, the coil of the relay is connected in series between the input terminal of the switching tube and the first output terminal of the timing module, and the switching tube The output end of the relay is grounded, and the normally open switch of the relay is connected with the alarm. 8 . The single-phase ground fault detection circuit according to claim 1 , wherein the preset voltage value is 1.2 times the rated phase voltage on the connection bar, and the preset time is two minutes. 9. The single-phase ground fault detection circuit according to claim 1, further comprising: A GSM transceiver module that is connected to the signal output end of the timing circuit and sends alarm information after receiving the second control signal. 10. A single-phase ground fault detection system, characterized by comprising a remote monitoring platform and the single-phase ground fault detection circuit according to any one of claims 1-9.

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