CN109932676A - Abnormal detection method of voltage transformer circuit - Google Patents

Abstract

The invention discloses a method for detecting abnormality of a voltage transformer loop. The voltage transformer loop comprises a voltage transformer connected with a three-phase transmission line, two first converters connected with the voltage transformer, two first modulo a converter, a CPU and an alarm; the two first converters are respectively connected with the three-phase of the two secondary coils of the same type of the voltage transformer; the two first converters are respectively electrically connected with the two first analog-to-digital converters , the CPU is respectively electrically connected with the two first analog-to-digital converters and the alarm. The present invention has the characteristics of not performing blocking, without changing the action strategy mechanism of the relay protection, improving the reliability of the relay protection, high detection efficiency and good accuracy.

Description

Abnormal detection method of voltage transformer circuit

technical field

The invention relates to the technical field of power system relay protection, in particular to an abnormal detection method of a voltage transformer loop with high detection efficiency and good accuracy.

Background technique

Whether the analog sampling circuit of the relay protection voltage transformer of the power system is normal or not is directly related to the protection reliability, and the detection function of the abnormal circuit is an important guarantee for the correct operation of the protection device.

The normal operation of the relay protection device is equipped with corresponding relay protection components, analyzes the real-time state quantity of the power system during the operation of the power system, judges the operating state of the power system, and handles power system faults and abnormal conditions that endanger safe operation.

The judging process of judging whether the loop is abnormal through the positive and negative sequence components of the electrical quantity sampling data and the corresponding logical relationship is relatively complicated, and different logical judgment conditions are required in specific cases.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings of the complex detection method of the analog quantity sampling loop abnormality of the relay protection voltage transformer in the prior art, and the need for different logical judgment conditions under specific circumstances, and to provide a detection method with high detection efficiency and accuracy. Abnormal detection method of voltage transformer circuit with good performance.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for detecting abnormality of a voltage transformer loop, the voltage transformer loop comprises a voltage transformer connected with a three-phase transmission line, two first converters connected with the voltage transformer, two first analog-to-digital converters, and a CPU. and the alarm device; the two first converters are respectively connected with the three-phase of the two secondary coils of the same type of the voltage transformer; the two first converters are respectively electrically connected with the two first analog-to-digital converters, and the CPU is respectively connected with The two first analog-to-digital converters are electrically connected to the alarm; the steps are as follows:

(1-1) Two sets of three-phase voltages are drawn from the two secondary coils of the same type of the voltage transformer;

(1-2) Connect the two sets of three-phase voltages to two converters, respectively, and the two converters convert the two sets of three-phase voltages into the first group of weak voltage signals U _A1 , U _B1 , U _C1 and the second group respectively Weak voltage signals U _A2 , U _B2 , U _C2 ;

(1-3) Two analog-to-digital converters perform analog-to-digital conversion on the first group of weak voltage signals and the second group of weak voltage signals to obtain the digital sampling data of the two groups of weak voltage signals;

(1-4) The CPU compares the digital sampling data of the two groups of weak voltage signals to determine whether the voltage transformer circuit is abnormal.

The logic of the abnormal detection of the analog quantity sampling loop of the traditional relay protection voltage transformer is complicated. The judgment condition is related to the operating state of the equipment, and is not clearly distinguished from the fault quantity. The judgment process has a certain delay, and the simulation of the relay protection voltage transformer is judged. After the quantity sampling circuit is abnormal, the corresponding protection needs to be blocked.

For many large-scale generator-transformation units and power transmission and transformation equipment, the configuration of voltage transformers is often drawn from multiple sets of secondary coils. The analysis of the relationship between them, as a method of judging whether the state of the voltage sampling circuit is abnormal, is based on simple value judgment, and is suitable for various equipment situations. By selecting the voltage of the voltage transformer in the normal state, the protection can not be blocked, and the action strategy mechanism of the relay protection does not need to be changed, which can improve the reliability of the relay protection.

The invention utilizes the configuration characteristics of the current main equipment voltage transformer to compare the sampling data between the two sets of the same type coils of the voltage transformer at the same installation point. When the deviation of the two sets of data does not exceed the threshold value, the loop is considered to be normal, otherwise it is a loop abnormal.

As preferably, (1-4) comprises the steps:

U _A1 , U _B1 , U _C1 and U _A2 , U _B2 , U _C2 are compared using the following formulas to obtain and

in, is the vector of U _A1 , is the vector of U _A2 , The A-phase vector difference of the two groups of weak voltage signals, is the vector of U _B1 , is the vector of U _B2 , is the B-phase vector difference of the two groups of weak voltage signals, is the vector of U _C1 , is the vector of U _C2 , The C-phase vector difference of the two groups of weak voltage signals, U _NORMAL is the rated voltage of the voltage transformer;

When MAX(|ΔU _A |, |ΔU _B |, |ΔU _C |)>15%U _NORMAL , the CPU judges that the voltage transformer loop is abnormal, and controls the alarm to give an alarm.

Preferably, it also includes a second converter and a second digital-to-analog converter, the second converter is connected to the three-phase of another secondary coil of the same type of the voltage transformer, and the second converter is electrically connected to the second digital-to-analog converter. connected, the second digital-to-analog converter is electrically connected to the CPU; the second digital-to-analog converter outputs auxiliary voltage sampling data U _A3 , U _B3 , and U _C3 ;

Use step (1-4) to compare U _A3 , U _B3 , U _C3 with U _A1 , U _B1 , U _C1 and U _A2 , U _B2 , U _C2 respectively, if the sampled data of auxiliary voltage is the same as U _A1 , U _B1 When comparing with U _C1 , it is judged that the voltage transformer circuit is abnormal, and when the auxiliary voltage sampling data is compared with U _A2 , U _B2 , U _C2 , it is judged that the voltage transformer circuit is normal, then the CPU will U _A1 , U _B1 , U _C1 is discarded, and U _A2 , U _B2 , and U _C2 are regarded as normal voltage quantities.

Therefore, the present invention has the following beneficial effects: no blocking is required, no need to change the action strategy mechanism of the relay protection, and the reliability of the relay protection can be improved; the detection efficiency is high and the accuracy is good.

Description of drawings

Fig. 1 is a kind of principle block diagram of the present invention;

Figure 2 is a circuit diagram of the present invention.

In the figure: voltage transformer 1, first converter 2, first analog-to-digital converter 3, CPU 4, alarm 5, second converter 6, second digital-to-analog converter 7.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

The embodiment shown in FIG. 1 and FIG. 2 is a method for detecting abnormality of a voltage transformer loop. The voltage transformer loop includes a voltage transformer 1 connected to a three-phase transmission line, and two first and second voltage transformers connected to the voltage transformer. Converter 2, two first analog-to-digital converters 3, CPU 4 and alarm 5; the two first converters are respectively connected with the three-phase of the two secondary coils of the same type of the voltage transformer; the two first converters The device is electrically connected to the two first analog-to-digital converters respectively, and the CPU is electrically connected to the two first analog-to-digital converters and the alarm device respectively; the steps are as follows:

(1-1) Two sets of three-phase voltages are drawn from the two secondary coils of the same type of the voltage transformer;

(1-2) Connect the two sets of three-phase voltages to two converters, respectively, and the two converters convert the two sets of three-phase voltages into the first group of weak voltage signals U _A1 , U _B1 , U _C1 and the second group respectively Weak voltage signals U _A2 , U _B2 , U _C2 ;

(1-3) Two analog-to-digital converters perform analog-to-digital conversion on the first group of weak voltage signals and the second group of weak voltage signals to obtain the digital sampling data of the two groups of weak voltage signals;

The analog-to-digital conversion of the relay protection voltage includes full-cycle Fourier integration algorithm, half-cycle Fourier integration algorithm, etc. according to different needs. Among them, the full-cycle Fourier integration algorithm requires a period of sampling time, that is, for a 50Hz power system, there are 20 milliseconds of sampling data. window time, while the half-cycle Fourier integration algorithm is a 10-millisecond sampled data window time. The analog-to-digital conversion of the circuit abnormality detection device can also complete its basic functions if the analog-to-digital conversion module used for protection is the same. The analog-to-digital conversion module of the detection device adopts the half-cycle Fourier integral algorithm, which reduces the sampling data window time and makes the abnormal judgment of the voltage sampling loop faster.

(1-4) The CPU compares the digital sampling data of the two groups of weak voltage signals to determine whether the voltage transformer circuit is abnormal.

U _A1 , U _B1 , U _C1 and U _A2 , U _B2 , U _C2 are compared using the following formulas to obtain and

in, is the vector of U _A1 , is the vector of U _A2 , The A-phase vector difference of the two groups of weak voltage signals, is the vector of U _B1 , is the vector of U _B2 , is the B-phase vector difference of the two groups of weak voltage signals, is the vector of U _C1 , is the vector of U _C2 , C-phase vector difference of the two groups of weak voltage signals, U _NORMAL is the rated voltage of the voltage transformer;

When MAX(|ΔU _A |, |ΔU _B |, |ΔU _C |)>15%U _NORMAL , the CPU judges that the voltage transformer loop is abnormal, and controls the alarm to give an alarm.

1. Assuming that the main electrical equipment and the voltage transformer circuit are in normal operation, the two sets of voltage data sampled by the detection device are both normal rated voltages, and the phases are consistent. At this time, the difference between the two is ideally not. greater than the sum of their respective maximum allowable errors.

For example: for a generator to protect the outlet of the machine end The two groups of the same type of pressure change, the transmission accuracy is 0.5, the allowable transmission error of the two normal transmission is ± 0.5%, the difference between the two is not more than 1% at most, considering the sampling by the detection device The possible error, the difference between the two is generally not more than 5%.

2. Assuming that the equipment is indeed in a system failure state, the voltage transformer circuit is in normal operation, and the two sets of voltage data sampled by the detection device have a large change at the same time, this change should still meet its accuracy requirements, and the situation is in a normal operating state resemblance.

3. Assuming that the equipment is in normal operation, one of the voltage transformer circuits is in an abnormal state, and the two sets of voltage data sampled by the detection device, one is in a normal state and the other is in an abnormal state, and the storage of the two is relatively large. deviation.

For example: for the C-phase single-phase disconnection, the three-phase phase-to-phase voltage changes from the original three 100V as follows:

U _ab = 100(V)

U _bc =U _ca =100/2=50(V)

There will be a large deviation in the two sets of voltage quantity data sampled by the detection device.

4. Assuming that the equipment is in a system failure state, one of the voltage transformer loops is in an abnormal state, and two sets of voltage data are sampled by the detection device, one set is the voltage change in the fault state, and the other set is the fault state. And the voltage when the voltage transformer circuit is abnormal.

Assuming that the C-phase voltage drops to 70% of the original voltage when a C-phase single-phase ground fault occurs, and the C-phase disconnection occurs in a group of voltage transformer circuits at this time, it can be seen from the above example that the abnormal voltage deviation of the voltage transformer circuit is still there. More than 30%, and the sampling error deviation is generally not more than 5%, the deviation of the comparison between the two is mainly still the abnormal voltage deviation of the voltage transformer loop, including part of the sampling error deviation.

As shown in FIG. 1, it also includes a second converter 6 and a second digital-to-analog converter 7, the second converter is connected to the three-phase of another secondary coil of the same type of the voltage transformer, and the second converter is connected to the second The digital-to-analog converter is electrically connected, and the second digital-to-analog converter is electrically connected to the CPU; the second digital-to-analog converter outputs auxiliary voltage sampling data U _A3 , U _B3 , and U _C3 ;

Compare U _A3 , U _B3 , U _C3 with U _A1 , U _B1 , U _C1 :

calculate

When MAX(|ΔU _A |, |ΔU _B |, |ΔU _C |)>15%U _NORMAL , the CPU judges that the voltage transformer loop is abnormal;

Compare U _A3 , U _B3 , U _C3 with U _A2 , U _B2 , U _C2 :

calculate:

When MAX(|ΔU _A |, |ΔU _B |, |ΔU _C |)≤15%U _NORMAL , the CPU judges that the voltage transformer circuit is normal, the CPU discards U _A1 , U _B1 , and U _C1 , and discards U A1 , U B1 , and U C1, and sets U _A2 , U _B2 , U _C2 as the normal voltage.

If the voltage loop does not have auxiliary voltage sampling data, the positive and negative sequence components of the traditional electrical sampling data and the corresponding logical relationship judgment method can also be used for auxiliary correction, select the data of the faulty voltage sampling loop, and discard this group of data. The protection device takes the normal voltage of the sampling circuit.

After being judged by the voltage transformer circuit abnormality detection device, the corresponding signal can be output to the voltage transformer circuit abnormality protection device to shield the abnormal voltage sampling data of the corresponding circuit, or the sampling data of the voltage transformer circuit abnormality detection device can be directly passed through the network. to the relay protection device.

The implementation of the abnormality detection of the voltage transformer loop using the electronic voltage transformer in the present invention can be further simplified, and the links before the analog-to-digital conversion are reduced.

According to Article 8.4.8 of DL/T 1543-2016 Electronic Voltage Transformer Selection Guide: In addition to the dual protection channels meeting the accuracy required by GB/T 20840.7, the instantaneous value is required to be sampled, that is, in the same frame message (the larger value -smaller value)/smaller value×100%<2%, so the threshold value can be set lower when the abnormal detection of the voltage transformer loop using the electronic voltage transformer is implemented in the present invention.

Under certain conditions, the abnormality detection device of the voltage transformer circuit can be integrated with the relay protection device, so that the abnormality detection device of the voltage transformer circuit can become an integral part of the relay protection device.

It should be understood that this embodiment is only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (3)

1. an abnormal detection method of a voltage transformer circuit, it is characterized in that, the voltage transformer circuit comprises the voltage transformer (1) connected with the three-phase transmission line, and the two first converters (2) connected with the voltage transformer ), two first analog-to-digital converters (3), a CPU (4) and an alarm device (5); the two first converters are respectively connected with the three-phase of the two secondary coils of the same type of the voltage transformer; two The first converters are respectively electrically connected with the two first analog-to-digital converters, and the CPU is respectively electrically connected with the two first analog-to-digital converters and the alarm; the steps are as follows: (1-1) Two sets of three-phase voltages are drawn from the two secondary coils of the same type of the voltage transformer; (1-2) Connect the two sets of three-phase voltages to two converters, respectively, and the two converters convert the two sets of three-phase voltages into the first group of weak voltage signals U _A1 , U _B1 , U _C1 and the second group respectively Weak voltage signals U _A2 , U _B2 , U _C2 ; (1-3) Two analog-to-digital converters perform analog-to-digital conversion on the first group of weak voltage signals and the second group of weak voltage signals to obtain the digital sampling data of the two groups of weak voltage signals; (1-4) The CPU compares the digital sampling data of the two groups of weak voltage signals to determine whether the voltage transformer circuit is abnormal. 2. the abnormal detection method of the voltage transformer loop according to claim 1 is characterized in that, (1-4) comprises the steps: U _A1 , U _B1 , U _C1 and U _A2 , U _B2 , U _C2 are compared using the following formulas to obtain and in, is the vector of U _A1 , is the vector of U _A2 , The A-phase vector difference of the two groups of weak voltage signals, is the vector of U _B1 , is the vector of U _B2 , is the B-phase vector difference of the two groups of weak voltage signals, is the vector of U _C1 , is the vector of U _C2 , The C-phase vector difference of the two groups of weak voltage signals, U _NORMAL is the rated voltage of the voltage transformer; When MAX(|ΔU _A |, |ΔU _B |, |ΔU _C |)>15%U _NORMAL , the CPU judges that the voltage transformer loop is abnormal, and controls the alarm to give an alarm. 3. The abnormality detection method of the voltage transformer loop according to claim 2, characterized in that, further comprising a second converter (6) and a second digital-to-analog converter (7), the second converter and the voltage transformer The three-phase connection of another secondary coil of the same type, the second converter is electrically connected to the second digital-to-analog converter, and the second digital-to-analog converter is electrically connected to the CPU; the second digital-to-analog converter outputs auxiliary voltage sampling data U _A3 , U _B3 , U _C3 ; Use step (1-4) to compare U _A3 , U _B3 , U _C3 with U _A1 , U _B1 , U _C1 and U _A2 , U _B2 , U _C2 respectively, if the sampled data of auxiliary voltage is the same as U _A1 , U _B1 When comparing with U _C1 , it is judged that the voltage transformer circuit is abnormal, and when the auxiliary voltage sampling data is compared with U _A2 , U _B2 , U _C2 , it is judged that the voltage transformer circuit is normal, then the CPU will U _A1 , U _B1 , U _C1 is discarded, and U _A2 , U _B2 , and U _C2 are regarded as normal voltage quantities.