CN106199481B

CN106199481B - Current transformer working state monitoring system and control method thereof

Info

Publication number: CN106199481B
Application number: CN201610611824.1A
Authority: CN
Inventors: 卢庆港; 乐晓蓉
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-07-30
Filing date: 2016-07-30
Publication date: 2023-03-03
Anticipated expiration: 2036-07-30
Also published as: CN106199481A

Abstract

The invention provides a current transformer working state monitoring system and a control method thereof, the current transformer working state monitoring system is provided with a double-iron core and a double-winding structure, the two groups of iron cores have different magnetic conduction characteristics, a monitoring winding is wound on the monitoring iron core, the monitoring winding and the monitoring iron core are arranged on the inner side of a CT winding, when a CT is unsaturated, the output voltage of a monitoring coil is very low, when a CT secondary circuit is opened and saturated, the induction voltage of the monitoring winding is increased, the CT working state is monitored according to the characteristics of the output voltage of the monitoring winding, when the CT is opened and saturated, a signal is sent to application equipment such as a relay protection device and the like, the signal is used as a protection action criterion, and the reliability and the accuracy of the relay protection action are improved. In addition, the over-voltage protection function of the open circuit of the CT can be realized, when the open circuit of the CT is monitored, the contacts of the over-voltage protection circuit connected in parallel with the two ends of the CT winding are driven to be closed, the secondary current output end of the CT is short-circuited, the fault and the damage of electrical equipment caused by the over-voltage of the open circuit of the CT are avoided, meanwhile, an alarm signal is sent out, a manager is informed to take treatment measures as soon as possible, and the normal operation is recovered.

Description

Current transformer working state monitoring system and control method thereof

Technical Field

The invention belongs to the technical field of power system automation, and particularly relates to a current transformer working state monitoring system and a control method thereof.

Background

In an electric power system, a special protection level current transformer (abbreviated as CT) is installed on important elements such as a generator, a transformer, a motor and the like, and a common model is 5P30, and is used for providing a secondary current for a relay protection device, so that the relay protection device can monitor a fault, trip and isolate the fault in time, and protect the safe operation of the electric power system. In addition, an open circuit occurs in a CT secondary circuit in operation due to various reasons, after the CT secondary circuit is opened, an iron core can enter a saturation region under the action of smaller primary current due to no demagnetization of secondary current, and high peak voltage is induced on a CT secondary winding along with fluctuation of the primary current, so that equipment such as terminal breakdown burning, fire starting, relay protection, measuring instruments and the like on the secondary circuit are easily damaged. When the iron core is saturated, the vibration force of the silicon steel sheet is increased due to the increase of the magnetic flux density and the non-sine property of the magnetic flux, so that larger noise is generated, the iron loss of the iron core is increased, the iron core is overheated, the temperature of the CT is increased, the insulation performance is reduced after the internal insulation is heated, and peculiar smell, even smoke and burnout can be generated.

The CT saturation not only causes the failure of the relay protection device, but also causes the misoperation, and the analysis on the cause of the misoperation of the differential protection of the motor (electrical application J, 9 th 2014, luqinggang and the like) indicates that the transient characteristics of the current transformer change due to the impedance difference of a differential CT secondary circuit, the current transformer at the tail end of the motor is subjected to transient saturation, the secondary current is subjected to distortion, the differential misoperation is caused, and the actual recorded wave waveform and the actual case analysis of the CT saturation are provided.

The CT is used as a key element for converting primary current into secondary current in a power system, the working characteristics of the CT influence the reliability and accuracy of the action of a relay protection device, the correctness of the protection action is improved in order to avoid the relay protection judgment error caused by CT saturation, at present, relay protection equipment manufacturers carry out a lot of research and attempts on CT saturation identification, but because the CT belongs to primary equipment and the relay protection device belongs to secondary equipment, the CT saturation identification technology at present mostly utilizes the characteristics of distorted CT secondary current for identification, the accuracy is still to be improved, and if the CT product can output signals in the abnormal working state, the reliability and accuracy of the relay protection action can be improved.

Disclosure of Invention

The invention provides a current transformer working state monitoring system and a control method thereof, wherein the monitoring system comprises a current transformer with a double-iron-core and double-winding structure and a monitoring module, the two groups of iron cores in the current transformer are made of different silicon steel sheets, the magnetic permeability of a CT iron core is high, the magnetic permeability of the monitoring iron core is low, a monitoring winding is wound on the monitoring iron core, the monitoring module monitors and identifies the CT working state according to the characteristics of the output voltage of the monitoring winding, and a signal is sent out when the iron core is saturated.

The utility model provides a current transformer operating condition monitored control system, including having two iron cores, the current transformer and the monitoring module of duplex winding structure, specifically include the CT iron core, the monitoring iron core, the CT winding, the monitoring module, the monitoring winding is connected with the monitoring module, the winding of monitoring winding is on the monitoring iron core, the monitoring iron core behind CT iron core and the winding monitoring winding is parallelly placed, the winding of CT winding is unshakable in one's determination at the CT, the outside unshakable in one's determination is monitored to the monitoring winding and the monitoring, the monitoring winding is unshakable in one's determination in the inboard of CT winding with the monitoring.

Preferably, the CT winding is connected with a monitoring module, and the secondary current of the CT winding flows through the monitoring module and is sampled.

Preferably, the two groups of iron cores in the current transformer are made of different silicon steel sheets, the magnetic permeability characteristics are different, the magnetic permeability of the CT iron core is high, the magnetic permeability of the monitoring iron core is low, and the monitoring winding is wound on the monitoring iron core.

A control method of a current transformer working state monitoring system is characterized in that when CT is not saturated, magnetic flux forms a minor magnetic hysteresis loop in two groups of iron cores, the magnetic flux mainly passes through the CT iron core with higher magnetic permeability, the magnetic flux passing through the corresponding monitoring iron core is less, and the output voltage of a monitoring coil is very low; when the CT secondary circuit is open-circuited and saturated, the magnetic permeability of the CT iron core is reduced due to saturation, magnetic flux is dispersed to the outside of the CT iron core to form a loop, part of the magnetic flux enters the monitoring iron core, the induction voltage of the monitoring winding is increased at the moment, and the monitoring module is responsible for identifying the working state of the CT and sending a signal.

Preferably, the monitoring module adopts passive scheme to realize, through the two-way TVS pipe of rational configuration divider resistance and adoption specific breakdown voltage, realize the settlement of breakdown voltage threshold value, two-way TVS pipe does not puncture when the voltage of monitoring winding is lower, when the voltage of monitoring winding is higher, punctures two-way TVS pipe, and the electric current drive signal relay action that flows through, relay output contact shifts and sends out the signal.

Preferably, the monitoring module is implemented by adopting an active scheme, the output voltage of the monitoring winding is connected into the digital module, the digital module collects the output voltage of the monitoring winding, and the contact signal or the communication message is driven to be output after the working state of the CT is identified.

Preferably, the monitoring module is realized by adopting an active scheme, the output voltage of the monitoring winding and the output current of the CT winding are connected into a digital module, the digital module continuously acquires the output voltage of the monitoring winding and the output current of the CT winding, the digital module compares and judges whether the iron core is saturated according to a set voltage threshold value, meanwhile, the digital module identifies and judges whether a CT open circuit exists by synthesizing secondary current, then the digital module respectively drives corresponding contact signals or communication message codes to be output, and when the CT open circuit exists, the digital module drives the overvoltage protection loop contacts connected in parallel at two ends of the CT winding to be closed, so that the secondary current output end of the CT is short-circuited.

Preferably, the monitoring module is realized by adopting an active scheme, the output voltage of the monitoring winding is connected into a digital module, the CT iron core saturation and the CT secondary circuit open circuit are distinguished according to the waveform characteristics of the output voltage of the monitoring winding, then the digital module respectively drives corresponding contact signals or communication message codes to be output so as to be convenient for other devices to use, and when the CT open circuit exists, the digital module drives the overvoltage protection circuit contacts connected in parallel at two ends of the CT winding to be closed, so that the secondary current output end of the CT is short-circuited.

Preferably, overvoltage protection circuit contacts at two ends of the CT winding can be integrated inside the monitoring module, and can also be installed in a CT body, a switch cabinet, a control cabinet and other places as independent modules, and are connected with the CT winding and the monitoring module through cables.

Preferably, the monitoring module can be used as a part of the CT and integrated on the CT, or can be used as an independent module and installed in an external switch cabinet, a control cabinet and other places, or can be used as a module to integrate partial functions or all functions on a relay protection device and other electric power automation equipment.

Preferably, the monitoring iron core can adopt a mode of opening an air gap, so that the magnetic permeability is reduced, and the rapid saturation is avoided.

Preferably, the monitoring module has an interface for outputting signals to the outside, and the interface can be implemented by a mechanical contact or a communication interface.

A control method of a current transformer working state monitoring system comprises the following steps:

the first step is as follows: the monitoring module samples the induction voltage of the monitoring winding;

the second step is that: the monitoring module identifies the working state of the CT according to the induction voltage;

the third step: and outputting corresponding signals and taking corresponding control measures according to the identification result.

Preferably, in the second step, the monitoring module uses the current of the CT winding as a criterion to distinguish between steady state saturation and CT open circuit.

Advantageous effects

The invention provides a current transformer working state monitoring system and a control method thereof, which have the functions of iron core working state monitoring and alarm output, have a double-iron-core and double-winding structure, send out alarm signals in time when a CT is opened and saturated, send the alarm signals to application equipment such as a relay protection device and the like, and use the alarm signals as a protection action criterion, thereby improving the reliability and accuracy of the relay protection action, and being capable of short-circuiting a secondary current output end of the CT when the CT is opened and protecting the equipment and personal safety.

Drawings

Fig. 1 shows hysteresis loops in unsaturated and saturated states of a current transformer core.

Fig. 2 is a schematic diagram of a composition structure of a current transformer working state monitoring system.

Fig. 3 is a magnetization curve of two cores inside the current transformer.

Fig. 4 shows the induced voltage change of the CT core during the unsaturated-transient saturated-steady state saturated change.

Fig. 5 shows the induced voltage variation during transient saturation of the CT core caused by inrush current.

Fig. 6 is an engineering application schematic diagram of a current transformer working state monitoring system.

Detailed Description

The following provides a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings.

When the CT works normally, due to the demagnetization effect of the secondary current, the synthetic residual magnetic flux in the CT iron core is very low, when the conditions of overlarge primary current, overlarge impedance of a CT secondary circuit, open circuit of the CT secondary circuit and the like occur, the magnetic flux in the CT iron core is increased, the iron core enters a saturated state, the magnetic conductivity of the saturated iron core is reduced rapidly, the secondary current cannot reflect the actual change of the primary current, the distortion of the secondary current is caused, in addition, the high peak induced voltage after the open circuit of the CT secondary circuit not only influences the reliable operation of equipment, but also causes personal safety accidents.

The CT core is made of ferromagnetic material, and according to the characteristics of magnetic domains, the operating state of the CT core can be divided into two states of saturation and unsaturation, wherein the saturation can be divided into transient saturation and steady saturation, when the CT core is in the unsaturated state during normal operation, the hysteresis loop of the CT core is as shown in 101 in fig. 1, and the hysteresis loop loops within a small range and does not enter the saturation region. When the iron core is saturated in a steady state due to the reasons of overlarge primary current, overlarge impedance of the secondary CT circuit, open circuit of the secondary CT circuit and the like, a hysteresis loop of the magnetic core is shown as 102 in fig. 1, the hysteresis loop enters a saturation region, the hysteresis loop loops in the first quadrant and the third quadrant and presents symmetry, wherein the open circuit of the CT is a special condition of steady state saturation. When transient saturation is caused by reasons of residual magnetism of the CT iron core, non-periodic components contained in primary current and the like, such as magnetizing inrush current, a magnetic hysteresis loop of the iron core returns in a region which is deviated to one side quadrant and does not present symmetry any more, and along with attenuation of non-periodic shunt and gradual demagnetization of residual magnetism, the magnetic hysteresis loop of the iron core slowly exits from a saturated region, and the iron core is recovered to an unsaturated state.

A current transformer working state monitoring system has the working principle that when CT is not saturated, magnetic flux forms a minor hysteresis loop in two groups of iron cores, the magnetic flux mainly passes through the CT iron core with higher magnetic permeability, the passing magnetic flux in the corresponding monitoring iron core is little, and the output voltage of a monitoring coil is low; when the CT secondary circuit is open-circuited and saturated, the magnetic permeability of the CT iron core is reduced due to saturation, the magnetic flux is dispersed to the outside of the CT iron core to form a loop, part of the magnetic flux enters the monitoring iron core, and the induced voltage of the monitoring winding is increased accordingly.

A current transformer working state monitoring system specifically comprises a current transformer and a monitoring module 201, wherein the current transformer is composed of a CT iron core 206, a monitoring iron core 202, a CT winding 205 and a monitoring winding 203, the monitoring winding 203 is connected with the monitoring module 201, the monitoring winding 203 is wound on the monitoring iron core 202, the CT iron core 206 and the monitoring iron core 202 wound with the monitoring winding 203 are placed in parallel, the CT winding 205 is wound on the outer sides of the CT iron core 206, the monitoring winding 203 and the monitoring iron core 202 are arranged on the inner side of the CT winding 205, a primary current 204 penetrates through the monitoring iron core and the middle of the CT iron core, the CT winding 205 is connected with the monitoring module 201, and a secondary current of the CT winding 205 flows through the monitoring module 201 and is sampled. The monitoring module 201 identifies the operating state of the iron core according to the induced voltage and the secondary current, provides a contact signal or a network message signal, and can take control measures when the open circuit of the CT is monitored, so as to avoid overvoltage caused by the open circuit of the CT. .

The magnetic permeability of the two cores in the current transformer is different, and the magnetization curves of the monitoring core 202 and the CT core 206 are shown in fig. 3, where a curve 301 is the magnetization curve of the CT core 206, and a curve 302 is the magnetization curve of the monitoring core 202, in practical applications, due to the diversity of CT products, the curve 301 is only one common curve among many available magnetization curves of the CT core 206, and in practical manufacturing, the monitoring core 202 can change the magnetic permeability of the cores and the shapes of the magnetization curves by opening an air gap or selecting different magnetic permeable materials.

The number of turns of the monitor winding 203 and the CT winding 205 in fig. 2 are only schematic for illustrating the principles of the present invention, and the actual number of turns is related to factors such as the primary current, the material used for the core, and the design of the monitoring module.

Fig. 4 shows the variation process of the induced voltage during the unsaturated-transient saturated-steady state saturated variation process of the iron core, in which a curve 401 in fig. 4 (a) is the primary current converted by the CT transformation ratio, a curve 402 corresponds to the secondary loop current, and in fig. 4 (b) a curve 403 is the induced voltage of the monitoring winding, and it can be seen from the curve 403 that as the primary current increases, the CT firstly appears transient saturation and then enters steady state saturation.

Fig. 5 shows the variation of induced voltage during transient saturation caused by inrush current, a curve 501 in fig. 5 (a) is a primary inrush current waveform converted by CT transformation ratio, a curve 502 corresponds to a secondary loop current, and a curve 503 in fig. 5 (b) is the induced voltage of a monitoring winding, and it can be seen from the curve 503 that, in an inrush current state, a CT core works in transient saturation, and the CT core gradually drops out of the transient saturation along with the gradual attenuation of the inrush current.

According to the current transformer working state monitoring system, the CT transformation ratio and the used iron core materials are different, the change of the induction voltage of the monitoring winding is different, in order to correctly identify the working state of the CT iron core, the threshold value of voltage identification is reasonably set, when the iron core is saturated, the induction voltage waveform in the figures 4 and 5 is obviously discontinuous at the part lower than the threshold value, the waveform is discontinuous, and the size of the discontinuous part is measured through the discontinuity angle.

When the monitoring module 201 only collects the induced voltage of the monitoring winding 203, the core state identification is performed according to the following principle by combining the waveform characteristics of the induced voltage shown in fig. 4 and 5:

1. unsaturation: the induction voltage is smaller than the threshold value;

2. transient saturation: the induction voltage is higher than the threshold value, the discontinuous angle is larger, the induction voltage is deviated to one side of a coordinate axis, and the amplitude difference of two sides of the coordinate axis is larger;

3. steady state saturation: the induced voltage is higher than a threshold value, the break angle of the induced voltage is smaller, the induced voltage is distributed on two sides of a coordinate axis, and the positive and negative amplitudes of the two sides of the coordinate axis are close;

analyzing the above recognition principle, it can be found that when using the single criterion of monitoring the induced voltage of winding 203 for recognition, CT open circuit is a special case of steady state saturation, and similar to steady state saturation, it is difficult to recognize based on the amplitude and waveform characteristics of the induced voltage.

When the monitoring module 201 collects the induced voltage of the monitoring winding 203 and the current of the CT winding 205, the core state is identified according to the following principle:

1. unsaturated reaction: the induction voltage is smaller than the threshold value, and the secondary reflux current is very small or zero;

2. saturation: the induced voltage is higher than a threshold value, and the secondary loop current is not zero;

2. transient saturation: the induced voltage is higher than a threshold value, the secondary loop current is not zero, the discontinuous angle is larger, the induced voltage is deviated to one side of a coordinate axis, and the amplitude difference of two sides of the coordinate axis is larger;

3. steady state saturation: the induced voltage is higher than a threshold value, the secondary loop current is not zero, the break angle of the induced voltage is small, the induced voltage is distributed on two sides of a coordinate axis, and the positive and negative amplitudes of the two sides of the coordinate axis are close;

4. CT open circuit: the induced voltage is higher than the threshold value, and the secondary loop current is zero.

By analyzing the above recognition principle, it can be found that when the two criteria of monitoring the induced voltage of the winding 203 and the current of the CT winding 205 are used for comprehensive recognition, the open CT circuit can be effectively distinguished from the large domain of core saturation.

In order to avoid overvoltage caused by CT open circuit, the monitoring module can realize the function of CT open circuit overvoltage protection, when the open circuit of the CT is monitored, the contacts of overvoltage protection loops connected in parallel at two ends of a CT winding are driven to be closed, a secondary current output end of the CT is short-circuited, the fault and damage of electrical equipment caused by the overvoltage of the CT open circuit are avoided, meanwhile, an alarm signal is sent out, and a manager is informed to take treatment measures as soon as possible to recover normal operation.

In a particular engineering application, four exemplary embodiments of the monitoring system are as follows:

embodiment of the monitoring system 1:

the monitoring module 201 is realized by adopting a passive scheme, the breakdown voltage threshold is set by reasonably configuring a voltage dividing resistor and adopting a bidirectional TVS (transient voltage suppressor) with specific breakdown voltage, when the voltage of the monitoring winding is lower, the bidirectional TVS is not broken down, no current flows through the monitoring winding, and the precision of CT (current transformer) is not influenced. When the voltage of the monitoring winding is higher, the bidirectional TVS tube is broken down, the flowing current drives the signal relay to act, the output contact of the relay shifts to send out a signal, and the method can realize the alarm output of the abnormal working state of the CT without an additional working power supply.

Embodiment of the monitoring system 2:

the monitoring module is realized by adopting an active scheme, the output voltage of the monitoring winding is connected into a digital module, the digital module continuously collects the output voltage of the monitoring winding, the digital module performs comparison and judgment according to a set voltage threshold value and then drives a contact signal or communication message to output, because the monitoring winding is in voltage output, the monitoring module 201 adopts a sampling circuit with high-impedance input to sample a voltage signal, the current is very weak, the influence on CT precision can be ignored, and a working power supply needs to be provided for the digital module during engineering application.

Embodiment of the monitoring system 3:

the monitoring module is realized by adopting an active scheme, the output voltage of a monitoring winding and the output current of a CT winding are connected into a digital module, the digital module continuously collects the output voltage of the monitoring winding and the output current of the CT winding, the digital module compares the output voltage of the monitoring winding and the output current of the CT winding according to a set voltage threshold to judge whether an iron core is saturated or not, and simultaneously synthesizes secondary current to identify and judge whether a CT open circuit exists or not, so that the secondary loop current is zero, the CT secondary loop is judged to be open circuit, when the secondary loop current is not zero, the CT iron core is judged to be saturated, then the digital module respectively drives corresponding contact signals or communication message coding output, when the CT open circuit is found, overvoltage protection loop contacts connected in parallel at two ends of the CT winding are driven to be closed, the secondary current output end of the CT is short circuit, a voltage sampling circuit of the monitoring module 201 is high-impedance input, meanwhile, a low-resistance sampling resistor is connected in series in the CT secondary loop or a Hall device is adopted to sample the secondary current, the sampling of the sampling resistor or the Hall device, the sampling device can ignore the influence of the CT precision, and a working power supply needs to be provided for the digital module in engineering application.

Embodiment of the monitoring system 4:

the monitoring module is realized by adopting an active scheme, the output voltage of the monitoring winding is connected into a digital module, the saturation of a CT iron core and the open circuit of a CT secondary circuit are distinguished according to the waveform characteristics of the output voltage of the monitoring winding, the output current of the CT winding is not needed, then the digital module respectively drives corresponding contact signals or communication message codes to be output so as to be convenient for other devices to use, and when the open circuit of the CT is found, the contacts of an overvoltage protection circuit connected in parallel at the two ends of the CT winding are driven to be closed, so that the secondary current output end of the CT is short-circuited.

In the above embodiment 1, since the monitoring module is passive, only whether the core is saturated or not can be identified, and the open circuit of the CT cannot be effectively identified, when the relay protection device receives the output alarm signal of the monitoring module 201, it performs comprehensive judgment according to the secondary current of the current CT loop, so that when the secondary loop current is zero, it can be judged that the secondary loop of the CT is open, and when the secondary loop current is not zero, it can be judged that the core of the CT is saturated, and then the relay protection device determines whether to send out the open circuit alarm signal of the CT, the trip signal of the CT protection or the trip of the latch protection according to the set algorithm, or takes a control measure, closes the contacts of the overvoltage protection loop connected in parallel to the two ends of the CT winding, and short-circuits the secondary current output end of the CT.

The overvoltage protection circuit contacts at the two ends of the CT winding can be integrated inside the monitoring module 201, or can be installed in a switch cabinet or a control cabinet or other places as an independent module, and are connected with the CT winding and the monitoring module through cables.

The monitoring module 201 can be used as a part of the CT and integrated on the CT, or can be used as an independent module and installed on site, or installed in a switch cabinet or a control cabinet or other places by adopting an installation mode similar to that of a CT secondary circuit overvoltage protector, and connected with a CT winding and a monitoring winding through a secondary cable.

The monitoring module is provided with an interface for outputting signals externally, and can be realized through a mechanical contact or a communication interface. The output alarm signal of the monitoring module 201 can send out a signal through the displacement of the contacts of an electromagnetic relay, a solid-state relay and other relays, for example, when the iron core is not saturated in normal operation, the contacts are normally open, when the iron core is saturated and the CT is open, the contacts are closed, the signal can be sent to a monitoring system to report that the CT iron core works in an abnormal state, and can also be sent to application equipment such as a relay protection device and the like to be used as a protection action criterion; in addition, the output alarm signal of the monitoring module 201 can also be realized by sending a data message signal through an optical fiber, an RS485 and other communication network interfaces.

Fig. 6 is a schematic diagram of an engineering application of a current transformer working state monitoring system, in which a monitoring module outputs a signal to a relay protection device for auxiliary judgment.

The implementation process is described only for the single-phase CT, and the implementation scheme is repeated for the CT in the multi-phase power network, the current transformer parts are independent from each other, and the monitoring module parts can be combined together to implement the implementation.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention.

The above description is only a preferred embodiment of the present invention and should not be construed as limiting the present invention, and various modifications and changes can be made by those skilled in the art, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a current transformer operating condition monitored control system, including having two unshakable in one's determination, the current transformer and the monitoring module of duplex winding structure, specifically include the CT iron core, the monitoring iron core, the CT winding, the monitoring module, the monitoring winding is connected with the monitoring module, the winding is on the monitoring iron core in the monitoring winding, the monitoring iron core behind CT iron core and the winding monitoring winding is unshakable in one's determination and is placed in parallel, the winding of CT is unshakable in one's determination, the outside unshakable in one's determination of monitoring winding and monitoring, the monitoring winding is unshakable in one's determination with the monitoring, two sets of unshakable in one's determination magnetic characteristic difference, the monitoring module is according to induced voltage and the operating condition of secondary current discernment unshakable in one's determination, and send out the signal.

2. The system for monitoring the working state of the current transformer as claimed in claim 1, wherein the monitoring module is implemented by a passive scheme, the setting of the breakdown voltage threshold is implemented by reasonably configuring a voltage dividing resistor and adopting a bidirectional TVS tube with a specific breakdown voltage, when the voltage of the monitoring winding is low, the bidirectional TVS tube is not broken down, when the voltage of the monitoring winding is high, the bidirectional TVS tube is broken down, the flowing current drives the signal relay to act, and the output contact of the relay shifts to send out a signal.

3. The system for monitoring the working condition of the current transformer according to claim 1, wherein the output voltage of the monitoring winding is connected to a digital module, the digital module collects the output voltage of the monitoring winding, and the digital module drives the output of the contact signal or the communication message after identifying the working condition of the CT.

4. The system for monitoring the working state of the current transformer according to claim 1, wherein the output voltage of the monitoring winding and the output current of the CT winding are connected into a digital module, the digital module collects the output voltage of the monitoring winding and the output current of the CT winding, and drives a contact signal or a communication message to be output after the working state of the CT is identified.

5. The system for monitoring the working state of the current transformer as claimed in claim 1, wherein when the monitoring module monitors the open circuit of the CT, the digital module drives the contacts of the overvoltage protection circuit connected in parallel to the two ends of the winding of the CT to close, so as to short-circuit the secondary current output terminal of the CT.

6. A control method of a current transformer working state monitoring system is characterized by comprising the following steps:

the second step is that: the monitoring module identifies the working state of the iron core according to the induced voltage and the secondary current;