阅读说明：本技术 一种电流互感器故障自诊断系统及方法 (Current transformer fault self-diagnosis system and method ) 是由 范建华 姜文 姚兴东 赵传强 赵磊 �田�浩 杨顺 张建 李伟 吴雪梅 卢峰 于 2020-09-07 设计创作，主要内容包括：本发明公开了一种电流互感器故障自诊断系统及方法,包括正弦波发生器、电源模块、控制器模块、测量电阻R_1、分压电阻R_2、供电控制开关VT1和测量控制开关VT2,系统定时检测电流互感器二次出线侧的电感量,通过电感量的变化诊断电流互感器状态是否正常。本发明所述的电流互感器故障诊断系统能够与电流互感器测量电路相结合,不需要增加额外的装置,并且在进行故障自诊断时不会影响电流的实时测量,不会影响测量结果。(The invention discloses a fault self-diagnosis system and method for a current transformer, which comprises a sine wave generator, a power supply module, a controller module and a measuring resistor R 1 A voltage dividing resistor R 2 The power supply control switch VT1 and the measurement control switch VT2, the system detects the inductance value of the secondary outgoing line side of the current transformer at regular time, and the state of the current transformer is diagnosed whether to be normal or not through the change of the inductance value. The current transformer fault diagnosis system can be combined with a current transformer measuring circuit, an additional device is not required to be added, real-time measurement of current is not influenced during fault self-diagnosis, and a measurement result is not influenced.)

1. A fault self-diagnosis system for a current transformer comprises a sine wave generator, a power supply module, a controller module and a measuring resistor R₁A voltage dividing resistor R₂The power supply control switch VT1 and the measurement control switch VT2 are characterized in that: the power supply module is connected with the controller module and is also connected with the source electrode of the power supply control switch VT1, and the drain electrode of the power supply control switch VT1 is connected with the sine wave generatorThe grid of the power supply control switch VT1 is connected with the control pin 1 of the controller module, and the voltage dividing resistor R₂One end of the measuring resistor is connected with the sine wave generator, and the other end of the measuring resistor is connected with the measuring resistor R₁Is connected with the sampling pin of the controller module, and measures the resistance R₁The other end of the voltage-measuring control switch VT2 is grounded, the drain electrode of the voltage-measuring control switch VT2 and the voltage-dividing resistor R₂Is connected to the gate of the measurement control switch VT2, is connected to the control pin 2 of the controller module, and the source of the measurement control switch VT2 is grounded.

2. The fault self-diagnosis system for the current transformer according to claim 1, wherein the sine wave generator is configured to output a sine wave signal U with a fixed voltage amplitude and a frequency f_s，f＝1Hz。

3. The fault self-diagnosis system for the current transformer according to claim 1, wherein the power supply module is used for supplying power to the controller module and supplying power to the sine wave generator through a power supply control switch VT 1.

4. The fault self-diagnosis system for the current transformer according to claim 1, wherein the power supply control switch VT1 is a PMOS transistor, and the power supply control for the sine wave generator is implemented by receiving a control signal from the controller module to turn on and off.

5. The fault self-diagnosis system for current transformer according to claim 1, wherein the measurement control switch VT2 is an NMOS transistor, and the voltage dividing resistor R is turned on and off by receiving a control signal from the controller module₂The ground control of (2).

6. The fault self-diagnosis system for the current transformer according to claim 1, wherein the controller module comprises a control pin 1, a control pin 2 and a sampling pin, and power supply control is controlled through the control pin 1 and the control pin 2 respectivelyThe switch VT1 and the measurement control switch VT2 are turned on and off, and the resistance R is measured through the sampling pin pair₁And a voltage dividing resistor R₂The voltage values in between are sampled.

7. The current transformer fault self-diagnosis system according to claim 1, wherein the measuring resistor R is₁And the two ends of the secondary side of the current transformer are connected for converting the current signal of the secondary side of the current transformer into a voltage signal and providing the voltage signal for the controller module to collect.

8. The fault self-diagnosis system for current transformer according to claim 1, wherein the voltage dividing resistor R is₂With the measuring resistance R when VT2 is closed₁In parallel connection, the current signal of the secondary side of the current transformer is converted into a voltage signal for the controller module to collect, and the voltage signal is connected with the measuring resistor R when the VT2 is switched off₁And the voltage dividing circuit is connected in series, and divides the voltage signal output by the sine wave generator for the acquisition of the controller module.

9. A fault self-diagnosis method for a current transformer is characterized by comprising the following steps:

step 1) after the system is installed on site, the system enters a fault diagnosis mode to obtain u_b(1)；

Step 2) entering a normal measurement mode, starting a fault diagnosis mode at regular time, entering step 3) when the set time is reached, and otherwise, repeating the step 2);

step 3) entering a fault diagnosis mode to obtain u_b(n)；

Step 4) utilizing a digital wave trap to enable sine wave component U with frequency f in sampling data U of a sampling pin of a controller module_bAfter filtering, calculating the primary side line current I_S1Wherein, the filtering function of the digital wave trap is realized by the software of the controller module; step 5) R ═ u_b(n)/u_b(1) If R is less than or equal to R_SETReporting the fault of the current transformer, and then turning to the step (2); if R is>R_SETThen, thenDirectly proceeding to step (2), wherein R is u obtained in the failure diagnosis mode_b(n) and u_b(1) Ratio of (A) to (B), R_SETIs a default value set by the system.

10. The method for fault self-diagnosis of the current transformer according to claim 9, wherein the specific working flow of the fault diagnosis mode is as follows: the controller module control pin 2 controls the measurement control switch VT2 to be switched off, the controller module control pin 1 controls the power supply control switch VT1 to be switched on, and the sine wave generator outputs a sine wave signal U with fixed voltage amplitude and frequency of 1Hz_sThe controller module samples a pin to collect voltage data U with a sampling period of 1/f, and performs DFT analysis on U to obtain a sine wave vector U with a frequency of f_bAmplitude of u_bAnd (n) is the number of times of calculation.

11. The method for self-diagnosing the fault of the current transformer according to claim 9, wherein a specific working flow of a normal measurement mode is as follows: the control pin 1 of the controller module controls the power supply control switch VT1 to be switched off, the control pin 2 of the controller module controls the measurement control switch VT2 to be switched on, the sampling pin of the controller module collects voltage data U', and primary side line current I is calculated_S1。

Technical Field

The invention relates to the field of current transformers, in particular to a fault self-diagnosis system and method for a current transformer.

Background

The current transformer is an instrument for converting a large primary side current into a small secondary side current according to an electromagnetic induction principle to measure, and is widely applied to power systems such as transformer substations and power distribution networks.

The current transformer is connected in series or clamped on a power line, when line alternating current flows through a primary side coil of the transformer, an alternating magnetic field is generated in an iron core, the alternating magnetic field enables a secondary side coil wound on the iron core to generate induced potential so as to generate secondary current, the calculation of the actual current of the line is realized by measuring the size of the secondary current, the current transformer is mainly used for electric energy metering, fault diagnosis and state monitoring, and is key equipment of an intelligent power grid.

In the actual use process of the existing current transformer, short-circuit wires are easily added on the primary side or the secondary side of the current transformer or a short-circuit ring is added on a through hole of the through transformer for electricity stealing, so that economic loss is brought to power supply enterprises.

The current open type current transformer is in the in-service use process, the opening part of the current open type current transformer is easily influenced by severe weather, moist air invades the interior, and the iron core can be corroded and damaged, so that the measurement precision of the current transformer is reduced, and the measurement data is inaccurate.

At present, an auxiliary winding is generally added on an iron core of a current transformer, a self-checking signal is applied through the auxiliary winding, and the fault of the transformer is judged according to the signal fed back by a measuring winding. Such a design is not only complex but also affects the real-time measurement of the current.

Disclosure of Invention

The invention aims to provide a current transformer fault self-diagnosis system and a current transformer fault self-diagnosis method aiming at the defects or shortcomings of the existing current transformer, the system is combined with a current transformer measuring circuit, no additional device is needed to be added, the real-time measurement of current is not influenced, the inductance value of the secondary outgoing line side of the current transformer can be detected at regular time, and whether the state of the current transformer is normal or not can be diagnosed through the change of the inductance value.

In order to achieve the aim, the invention provides a fault self-diagnosis system of a current transformer, which comprises a sine wave generator, a power supply module, a controller module and a measuring resistor R₁A voltage dividing resistor R₂A power supply control switch VT1 and a measurement control switch VT 2.

The power supply module is connected with the controller module and is also connected with the source electrode of the power supply control switch VT1, the drain electrode of the power supply control switch VT1 is connected with the sine wave generator, the grid electrode of the power supply control switch VT1 is connected with a control pin 1 of the controller module, and the voltage dividing resistor R₂One end of the voltage divider is connected with a sine wave generator, and a voltage dividing resistor R₂The other end and a measuring resistor R₁Is connected with the sampling pin of the controller module, and measures the resistance R₁And the other end of the same is grounded. Drain electrode and voltage dividing resistor R of measurement control switch VT2₂Is connected to the gate of the measurement control switch VT2, is connected to the control pin 2 of the controller module, and the source of the measurement control switch VT2 is grounded.

Sine wave signal U with fixed output voltage amplitude and frequency f of sine wave generator_s，f＝1Hz。

The power module supplies power to the controller module and to the sine wave generator through a power control switch VT 1.

The power supply control switch VT1 is a PMOS tube, and receives the control signal of the controller module to close and close, so as to realize the power supply control of the sine wave generator.

The measurement control switch VT2 is an NMOS tube, and receives the control signal of the controller module to close and close, so as to realize the voltage dividing resistance R₂The ground control of (2).

The controller module comprises a control pin 1, a control pin 2 and a sampling pin, wherein the control pin 1 and the control pin 2 are used for respectively controlling the power supply control switch VT1 and the measurement control switch VT2 to be switched on and off, and the sampling pin is used for measuring the resistance R₁And a voltage dividing resistor R₂The voltage values in between are sampled.

Measuring resistance R₁And the two ends of the secondary side of the current transformer are connected for converting the current signal of the secondary side of the current transformer into a voltage signal for the controller module to collect.

Voltage dividing resistor R₂With the measuring resistance R when the measuring control switch VT2 is closed₁In parallel connection, a current signal at the secondary side of the current transformer is converted into a voltage signal for being collected by the controller module; when the measurement control switch VT2 is turned off, the resistance R is measured₁And the voltage dividing circuit is connected in series, and divides the voltage signal output by the sine wave generator for the acquisition of the controller module.

The invention relates to a fault self-diagnosis method for a current transformer, which comprises the following steps of:

step 1) after the system is installed on site, the system enters a fault diagnosis mode to obtain u_b(1)；

And 2) entering a normal measurement mode. Starting a fault diagnosis mode at regular time, entering the step (3) when the set time is reached, and otherwise, repeating the step (2);

step 3) entering a fault diagnosis mode to obtainu_b(n)；

Step 4) utilizing a digital wave trap to enable sine wave component U with frequency f in sampling data U of a sampling pin of a controller module_bAfter filtering, calculating the primary side line current I_S1The filtering function of the digital wave trap is realized by software of the controller module;

step 5) R ═ u_b(n)/u_b(1) If R is less than or equal to R_SETReporting the fault of the current transformer, and then turning to the step (2); if R is>R_SETThen go directly to step 2), where R is u obtained in the failure diagnosis mode_b(n) and u_b(1) Ratio of (A) to (B), R_SETIs a default value set by the system.

The fault diagnosis mode comprises the following steps: the controller module control pin 2 controls the measurement control switch VT2 to be switched off, the controller module control pin 1 controls the power supply control switch VT1 to be switched on, and the sine wave generator outputs a sine wave signal U with fixed voltage amplitude and frequency of 1Hz_sThe sampling pin of the controller module collects voltage data as U, the sampling period is 1/f, DFT analysis is carried out on U, and sine wave vector U with frequency of f is obtained_bAmplitude of u_bAnd (n) is the number of times of calculation.

The normal measurement mode includes the steps of: the control pin 1 of the controller module controls the power supply control switch VT1 to be switched off, the control pin 2 of the controller module controls the measurement control switch VT2 to be switched on, the sampling pin of the controller module collects voltage data U', and primary side line current I is calculated_S1。

The invention has the following beneficial effects:

1. the current transformer fault self-diagnosis system can diagnose whether the current transformer has faults or not at regular time and report fault information.

2. The current transformer fault self-diagnosis system can be combined with a current transformer measuring circuit without adding an additional device.

3. The current transformer fault self-diagnosis method does not affect the real-time measurement of the current and the measurement result when the fault self-diagnosis is carried out.

Drawings

Fig. 1 is a functional block diagram of a fault self-diagnosis system of a current transformer of the present invention.

Fig. 2 is an equivalent circuit diagram of a current transformer fault self-diagnosis system of the present invention in practical use.

Fig. 3 is a flow chart of the fault self-diagnosis method of the current transformer of the invention.

Fig. 4 is an equivalent circuit diagram of a measuring circuit of the fault self-diagnosis system for the current transformer of the present invention.

Fig. 5 is an equivalent circuit diagram of the fault diagnosis circuit of the fault self-diagnosis system of the current transformer of the present invention.

In the figure: 1-a sine wave generator; 2-a power supply module; 3-supply control switch VT 1; 4-a controller module; 5-measurement control switch VT 2; 6-measuring the resistance R₁(ii) a 7-voltage dividing resistor R₂(ii) a 8-current transformer secondary side coil internal resistance R₃(ii) a 9-dashed box; 10-secondary side equivalent current I_S2(ii) a 11-Secondary side inductance L of current transformer₁(ii) a 12-a current transformer; 13-primary side line current I_S1。

Detailed Description

The present invention will be described in further detail below with reference to the accompanying drawings.

As shown in FIG. 1, the resistance R is measured₁(6) Connected to the two terminals of the secondary side of the current transformer, in order to explain the system principle as a whole, the current transformer (12) and the primary side line current I shown in fig. 2 need to be added to the system shown in fig. 1_S1(13) Performing equivalent circuit conversion to convert the current transformer (12) and the primary side line current I_S1(13) The equivalent circuit shown in the dashed box (9) of fig. 2 is simplified by the norton's theorem. Wherein R is₃Is the internal resistance of the secondary side coil of the current transformer, I_S2Is a primary side line current I_S1(13) Secondary side equivalent current of, L₁Is a secondary side inductor of the current transformer. Secondary side equivalent current I_S2(10) One end of the secondary side inductor L of the current transformer₁(11) One end of the first and second side are connected in parallel with the ground, and the equivalent current I of the secondary side_S2(10) And the other end of the current transformer and a secondary side inductor L₁(11) Is connected to the other end of the current path and is connected to the current pathInternal resistance R of secondary side coil of inductor₃(8) Is connected with one end of the current transformer, and the secondary side coil internal resistance R of the current transformer₃(8) And the other end of (2) and a measuring resistor R₁(6) One end of (1) and a voltage dividing resistor R₂(7) Is connected with the sampling pin of the controller module (4) and measures the resistance R₁(6) The other end of the resistor is grounded, and a voltage dividing resistor R₂(7) The other end of the second end is connected with a sine wave generator (1). The power supply module (2) is connected with the controller module (4), the power supply module (2) is connected with a source electrode of the power supply control switch VT1(3), a drain electrode of the power supply control switch VT1(3) is connected with the sine wave generator (1), and a grid electrode of the power supply control switch VT1(3) is connected with a control pin 1 of the controller module (4). Measuring the drain of the control switch VT2(5) and the voltage dividing resistance R₂(7) Is connected to the gate of the measurement control switch VT2(5) to the control pin 2 of the controller module (4), and the source of the measurement control switch VT2(5) is grounded.

Wherein the secondary side equivalent current I_S2(10) The calculation formula of (a) is as follows:

I_S2＝I_S1N₁/N₂

in the above formula, N₁Is the number of primary turns of the current transformer, N₂The number of turns of the secondary side of the current transformer.

Secondary side inductance L of current transformer₁(11) The simplified calculation formula of (c) is as follows:

L₁＝N₂ ²Aμ/l

in the above formula, a is the sectional area of the current transformer core, l is the magnetic path length of the core, and μ is the magnetic permeability of the core.

The flow chart of the current transformer fault self-diagnosis method is shown in fig. 3, and comprises the following steps:

step 1) after the system is installed on site, the system enters a fault diagnosis mode to obtain u_b(1)；

And 2) entering a normal measurement mode. Starting a fault diagnosis mode at regular time, entering the step (3) when the set time is reached, and otherwise, repeating the step 2);

step 3) entering a fault diagnosis mode to obtain u_b(n)；

Step 4) utilizing a digital wave trap to separate a sine wave component U with the frequency of f from sampling data U of a sampling pin of a controller module_bAfter filtering, calculating the primary side line current I_S1(13) (ii) a The filtering function of the digital wave trap is realized by software of the controller module.

Step 5) R ═ u_b(n)/u_b(1) If R is less than or equal to R_SETReporting the fault of the current transformer, and then turning to the step 2); if R is>R_SETAnd directly turning to the step 2). Wherein R is u obtained in the failure diagnosis mode_b(n) and u_b(1) Ratio of (A) to (B), R_SETIs a default value set by the system.

The fault diagnosis mode comprises the following steps: the control pin 2 of the controller module (4) controls the measurement control switch VT2(5) to be turned off, the control pin 1 of the controller module (4) controls the power supply control switch VT1(3) to be turned on, and the sine wave generator (1) outputs a sine wave signal U with fixed voltage amplitude and frequency of 1Hz_sThe sampling pin of the controller module (4) collects voltage data as U, the sampling period is 1/f, DFT analysis is carried out on U, and sine wave vector U with frequency f is obtained_bAmplitude of u_bAnd (n) is the number of times of calculation.

The normal measurement mode includes the steps of: the control pin 1 of the controller module (4) controls the power supply control switch VT1(3) to be turned off, the control pin 2 of the controller module (4) controls the measurement control switch VT2(5) to be turned on, the sampling pin of the controller module (4) collects voltage data U', and primary side line current I is calculated_S1(13)。

When the system works in a normal measurement mode, the power supply control switch VT1(3) is turned off, the measurement control switch VT2(5) is turned on, an equivalent circuit diagram of the measurement circuit is shown in FIG. 4, the sampling pin of the controller module (4) collects voltage data U', and primary side line current I is carried out_S1(13) And (4) calculating. When the current transformer fails, for example, the iron core of the current transformer is corroded, mu is reduced, so that the secondary side inductance L of the current transformer is caused₁(11) The size is reduced; in the case of a current transformer which is artificially modified, for example, a short-circuit wire is added to the primary side or the secondary side of the current transformerOr when a short-circuit ring is added on the through hole of the through mutual inductor, a coil of a closed loop is generated on the magnetic core, so that the secondary side inductance L of the current mutual inductor₁(11) And sharply becomes smaller. In FIG. 4, the equivalent current of the secondary side I_S2(10) Fixing if current transformer secondary side inductance L₁(11) When the inductance is reduced, the current flows through a secondary side inductance L of the current transformer₁(11) Becomes larger and flows through the measuring resistor R₁(6) And a voltage dividing resistor R₂(7) The current of (2) becomes small, U' becomes small, and the primary side line current I is finally measured_S1(13) And becomes smaller.

When the system works in a fault diagnosis mode, the power supply control switch VT1(3) is closed, the measurement control switch VT2(5) is turned off, and the system has a sine wave generator (1) and a secondary side equivalent current I_S2(10) Two independent power supplies. Analyzing by adopting a superposition theorem when the secondary side equivalent current I_S2(10) When the device works independently, the sine wave generator (1) is in short circuit, the equivalent circuit of the system is still as shown in figure 4, and the voltage data acquired by the sampling pin of the controller module (4) at the moment is set to be U_aThe same as the voltage data U' of the normal measurement mode. When the sine wave generator (1) works independently, the equivalent current I of the secondary side_S2(10) Open circuit, the equivalent circuit of the system is as shown in fig. 5, and the voltage data collected by the sampling pin of the controller module (4) at this time is set to be U_b. According to the superposition theorem, in the fault diagnosis mode, the controller module (4) samples a pin to acquire a voltage U which is equal to U_a+U_b. Due to U_bIs U_sLinear voltage division, frequency and U of_sUniformly, using digital wave trap to convert specific frequency U in U_bFiltering, in this case, U is equal to U_aU', and then calculating the primary side line current I_S1(13) Is consistent with the calculation result of the normal measurement mode. Therefore, the current transformer fault self-diagnosis method does not affect the real-time measurement of the current and the measurement result when the fault self-diagnosis is carried out.

For analyzing U when current transformer fails_bIn conjunction with FIG. 5, vector U is derived from the divider rule_bAnd vector U_sThe relationship of (a) is as follows:

further transformation is as follows:

order toThen vectorDie ofPhase angleVector quantityDie ofPhase angleThenAndangle of (2)

Order vectorEquation (1) transforms to the following form:

secondary side inductance L of current transformer when current transformer fails₁(11) The size of the composite material is reduced,the size of the mixture is increased, and the mixture is,becomes smaller, namely < theta becomes smaller. When in useAndthe included angle between the two becomes smaller,when the gain is increased, according to the vector addition algorithm,and is increased. If it isIncrease, and U_sThe mode (2) is kept constant, and U is known from the formula (2)_bBecome smaller in modulus, i.e. U_bAmplitude u of_b(n) becomes smaller. When u is_b(n) and an initial value u_b(0) Is less than the set value R_SET(R_SET<1) And reporting the fault of the current transformer.