CN104236702B - Loosened inside power transformer and judge system and method - Google Patents

Abstract

The invention discloses a system for judging the internal looseness of a power transformer and a method thereof. The system for judging the internal looseness of a power transformer and a preliminary positioning system includes a signal conditioning circuit, a data acquisition instrument and a data analysis module connected in sequence, and also includes three vibration sensors, The three vibration sensors are respectively connected to the data acquisition instrument through the signal conditioning circuit; the three vibration sensors respectively correspond to the three-phase vibration signals of the power transformer. The acquisition instrument transmits the collected vibration signals to the data analysis module, and the data analysis module stores and processes the vibration signals and performs fault judgment. According to the variation characteristics of the vibration signal with the degree of looseness, the invention uses the 100Hz signal in the vibration signal to judge the loose fault of the transformer.

Description

Internal Looseness Judgment System and Method of Power Transformer

technical field

The invention belongs to the technical field of intelligent substations, and in particular relates to a system for judging internal looseness of a power transformer and a method thereof.

Background technique

The loose deformation of the iron core and winding of the power transformer will pose a huge threat to the safe operation of the transformer. Therefore, it is very important to monitor the operation status of the transformer online and find hidden troubles in time. The state monitoring method of the power transformer based on the vibration signal is convenient to realize, the monitoring system has no electrical connection with the transformer, and does not affect the normal operation of the equipment. The prior art studies transformer vibration, analyzes the change of the 100Hz signal in the vibration signal of the oil tank after the transformer internal iron core fails, and analyzes the influence of transformer voltage and current changes on vibration. However, because the magnitude of the 100Hz signal does not have a linear relationship with the iron core fault, or even a monotonic relationship, the internal part of the transformer is loose, and the fundamental vibration component of the oil tank will increase in some positions, and may decrease in some positions, the law is not clear, directly Judgment remains difficult. Through research, it was found that the 50Hz, 150Hz, and 300Hz signals changed significantly after the transformer iron core/winding loosening fault, and the iron core loosening diagnosis was proposed based on the relationship between the 300Hz, 150Hz, and 50Hz components in the vibration signal, which improved the diagnostic accuracy. However, the overall value of the 50Hz, 150Hz, and 300Hz signals is very small, and the requirements for vibration monitoring accuracy are relatively high.

Through further research, the vibration signal on the surface of the oil tank is the vector superposition of the vibration signals generated by the vibrations inside the transformer at the measuring points on the surface of the oil tank. The amplitude of the fundamental frequency component of the vibration signal is linear to the square of the no-load voltage and the square of the current under load; The amplitude of the 100Hz fundamental frequency component of the vibration signal at the corresponding position of the core/winding on the top or bottom of the fuel tank is larger than normal, and becomes larger with the increase of the looseness of the iron core. The other two-phase iron cores/windings are on the top of the fuel tank The vibration amplitude of the vibration point corresponding to the measuring point on the surface or bottom decreases first and then increases as the looseness of the iron core increases. According to this rule, the core winding looseness can be judged, and the looseness can be preliminarily located.

Contents of the invention

In order to solve the technical problems existing in the background technology, the present invention aims to provide a system and method for judging internal looseness of power transformers. According to the variation characteristics of vibration signals with the degree of looseness, the 100Hz signal in the vibration signal is used to judge the looseness fault of the transformer.

The internal looseness judgment system of the power transformer includes a signal conditioning circuit, a data acquisition instrument and a data analysis module connected in sequence, and also includes three vibration sensors, and the three vibration sensors are respectively connected to the data acquisition instrument through the signal conditioning circuit; the three The three vibration sensors correspond to the three-phase vibration signals of the power transformer respectively. The vibration signals are amplified, filtered and denoised by the signal conditioning circuit and sent to the data acquisition instrument. The data acquisition instrument transmits the collected vibration signals to the data analysis module. The data analysis module The vibration signal is stored and processed, and fault judgment is carried out.

The present invention also includes a looseness judgment method based on the above-mentioned internal looseness judgment system of the power transformer, which is used for judgment and preliminary positioning of the iron core looseness of the power transformer, and the method is carried out under no-load operation of the power transformer, including the following steps, wherein Steps (1)-(4) are to measure the loosening threshold when determining that the power transformer is fault-free, and steps (5)-(6) are to detect loosening faults in routine maintenance:

(1) The sampling frequency and sampling time are preset, and the data acquisition instrument continuously samples the vibration signals detected by each vibration sensor for at least 3 times;

(2) According to the sampling frequency and sampling time, the vibration signal of each vibration sensor is intercepted in the whole cycle;

(3) The data analysis module filters the vibration signal intercepted throughout the cycle, and then performs time-frequency conversion to obtain the frequency spectrum component amplitude at 100 Hz in the vibration signal sampled by each vibration sensor;

(4) Get the arithmetic mean value of the frequency spectrum component amplitude at 100Hz in the vibration signal of each vibration sensor multiple sampling, obtain the frequency spectrum component average amplitude of 100Hz in the vibration signal of each vibration sensor sampling, the average amplitude Values are multiplied by a certain multiple to obtain the loosening thresholds CR _1A , CR _1B , and CR _1C of the three-phase iron cores of the power transformer, and store the loosening thresholds in the data analysis module;

(5) Repeat steps (1)-(3) to re-obtain the amplitude of the frequency spectrum component at 100 Hz in each vibration signal sampled by each vibration sensor. When the amplitude of the frequency spectrum component is greater than the loosening threshold of the corresponding phase iron core of the vibration sensor, enter step (6), otherwise return to step (5);

(6) The ratio of the amplitude of the frequency spectrum component at 100Hz in the vibration signal sampled by each vibration sensor to the looseness threshold of the corresponding phase iron core is expressed as λ _1A , λ _1B and λ _1C respectively:

When the largest ratio among the three ratios is greater than 2, and the other two ratios are not greater than 1, it is judged that there is obvious iron core looseness in the power transformer, and the phase iron core of the power transformer corresponding to the largest ratio is loose;

When the largest ratio among the three ratios is greater than 2, and at least one ratio of the other two ratios is greater than 1, it is only judged that there is obvious iron core looseness in the power transformer;

When the largest ratio among the three ratios is greater than 1 and less than 2, it can only be judged that there is a slight iron core looseness in the power transformer;

When the largest ratio among the three ratios is not greater than 1, it is judged that there is no iron core looseness in the power transformer.

Wherein, the time-frequency transform in the above step (3) adopts Fourier transform.

Wherein, the certain multiple in the above step (4) is 1.2 to 2 times.

The present invention also includes a looseness judgment method based on the above-mentioned power transformer internal looseness judgment system, the method is used for the judgment and preliminary positioning of the power transformer winding looseness, and the method is carried out under the load operation of the power transformer, including the following steps, wherein the steps ( 1)-(4) is to measure the loosening threshold when determining that the power transformer is fault-free, and steps (5)-(6) are to detect loosening faults in routine maintenance:

(1) The sampling frequency and sampling time are preset, and the data acquisition instrument continuously samples the vibration signals detected by each vibration sensor for at least 3 times;

(2) According to the sampling frequency and sampling time, the vibration signal of each vibration sensor is intercepted in the whole cycle;

(3) The data analysis module filters the vibration signal intercepted throughout the cycle, and then performs time-frequency conversion to obtain the frequency spectrum component amplitude at 100 Hz in the vibration signal sampled by each vibration sensor;

(4) Get the arithmetic mean value of the frequency spectrum component amplitude value at 100 Hz in the vibration signal of each vibration sensor sampling multiple times, obtain the frequency spectrum component average value of 100 Hz place in the vibration signal sampled by each vibration sensor, the average amplitude Values are multiplied by a certain multiple to obtain the loosening thresholds CR _2A , CR _2B , and CR _2C of the three-phase windings of the power transformer, and store the loosening thresholds in the data analysis module;

(5) Repeat steps (1)-(3) to re-obtain the amplitude of the frequency spectrum component at 100 Hz in each vibration signal sampled by each vibration sensor. When the amplitude of the spectral component of the vibration sensor is greater than the looseness threshold of the corresponding phase winding of the vibration sensor, enter step (6), otherwise return to step (5);

(6) The ratio of the amplitude of the frequency spectrum component at 100Hz in the vibration signal sampled by each vibration sensor to the looseness threshold of the corresponding phase winding is expressed as λ _2A , λ _2B and λ _2C respectively:

When the largest ratio among the three ratios is greater than 2, and the remaining two ratios are not greater than 1, it is judged that there is obvious winding looseness in the power transformer, and the phase winding of the power transformer corresponding to the largest ratio is loose;

When the largest ratio among the three ratios is greater than 2, and at least one ratio of the other two ratios is greater than 1, it is only judged that there is obvious winding looseness in the power transformer;

When the largest ratio among the three ratios is greater than 1 and less than 2, it is only judged that there is a slight winding looseness in the power transformer;

When the largest ratio among the three ratios is not greater than 1, it is judged that there is no winding looseness in the power transformer.

Wherein, the load current of the power transformer when detecting the loose fault is kept equal to the load current of the power transformer when the loose threshold is measured.

Among them, if there is a deviation between the load current of the power transformer when the loose fault is detected and the load current of the power transformer when the loose threshold is measured, the following formula is used to convert the amplitude of the frequency spectrum component of the vibration signal at 100 Hz:

In the above formula, A _x is the amplitude of the frequency spectrum component of the vibration signal at 100 Hz under any load current, A ₁₀₀ is the equivalent value of A _x , and I _2* is the per unit value of the load current of the power transformer when detecting loose faults.

The beneficial effect brought by adopting the above-mentioned technical scheme:

The invention can conveniently judge the looseness of the iron core and the winding of the power transformer, and can preliminarily locate the looseness position. The present invention utilizes the component amplitude at 100 Hz in the vibration signal, and since the 100 Hz component amplitude in the transformer vibration signal is relatively large, it does not require high precision of the measurement system and has strong anti-interference ability.

Description of drawings

Fig. 1 is a system structure block diagram of the present invention;

Fig. 2 is a schematic diagram of the position of the vibration sensor of the hanging core type power transformer of the present invention.

detailed description

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings.

The system structural block diagram of the present invention as shown in Figure 1, the internal looseness judgment system of power transformer, comprises the signal conditioning circuit, data acquisition instrument and data analysis module connected successively, also comprises 3 vibration sensors, and described 3 vibration sensors pass through respectively The signal conditioning circuit is connected with the data acquisition instrument; the three vibration sensors respectively correspond to the three-phase vibration signals of the power transformer. The vibration signal is transmitted to the data analysis module, and the data analysis module stores and processes the vibration signal and performs fault judgment.

In this embodiment, the three vibration sensors are firmly bonded on the surface of the fuel tank with glue. When the detected power transformer is a hanging core type power transformer, the three vibration sensors are respectively set on the top surface of the power transformer oil tank and the three positions corresponding to the three-phase windings of the power transformer, as shown in Figure 2, No. 1, No. 2 and No. 3 are 3 A vibration sensor installation location. When the detected power transformer is a hanger-type power transformer, three vibration sensors are respectively arranged at three positions corresponding to the bottom surface of the oil tank of the power transformer and the three-phase winding of the power transformer.

The present invention also includes a method for judging loose iron cores based on the above system, and the method is carried out under no-load operation of the power transformer, including the following steps, wherein steps (1)-(4) are measured when the power transformer is determined to be fault-free Loose threshold, steps (5)-(6) are to detect loose faults in routine maintenance:

(1) The sampling frequency and sampling time are preset, and the data acquisition instrument continuously samples the vibration signals detected by each vibration sensor for at least 3 times;

(2) According to the sampling frequency and sampling time, the vibration signal of each vibration sensor is intercepted in the whole cycle;

(3) The data analysis module filters the vibration signal intercepted throughout the cycle, and then performs time-frequency conversion to obtain the frequency spectrum component amplitude at 100 Hz in the vibration signal sampled by each vibration sensor;

(4) Get the arithmetic mean value of the frequency spectrum component amplitude value at 100 Hz in the vibration signal of each vibration sensor sampling multiple times, obtain the frequency spectrum component average value of 100 Hz place in the vibration signal sampled by each vibration sensor, the average amplitude Values are multiplied by a certain multiple to obtain the loosening thresholds CR _1A , CR _1B , and CR _1C of the three-phase iron cores of the power transformer, and store the loosening thresholds in the data analysis module;

(5) Repeat steps (1)-(3) to re-obtain the amplitude of the frequency spectrum component at 100 Hz in each vibration signal sampled by each vibration sensor. When the frequency spectrum component amplitude is greater than the loosening threshold of the corresponding phase iron core of the vibration sensor, enter step (6), otherwise return to step (5);

(6) The ratio of the amplitude of the frequency spectrum component at 100Hz in the vibration signal sampled by each vibration sensor to the looseness threshold of the corresponding phase iron core is expressed as λ _1A , λ _1B and λ _1C respectively:

When the largest ratio among the three ratios is greater than 2, and the other two ratios are not greater than 1, it is judged that there is obvious iron core looseness in the power transformer, and the phase iron core of the power transformer corresponding to the largest ratio is loose;

When the largest ratio among the three ratios is greater than 2, and at least one ratio of the other two ratios is greater than 1, it is only judged that there is obvious iron core looseness in the power transformer;

When the largest ratio among the three ratios is greater than 1 and less than 2, it can only be judged that there is a slight iron core looseness in the power transformer;

When the largest ratio among the three ratios is not greater than 1, it is judged that there is no iron core looseness in the power transformer.

In this embodiment, the time-frequency transformation in the above step (3) adopts Fourier transform, and the certain multiple in step (4) is 1.2 to 2 times.

The present invention also includes a method for judging loose windings of power transformers. The steps of this method are consistent with the method for judging and preliminary positioning of loose iron cores of power transformers above. The only difference is that when judging loose iron cores, the power transformer must be under no load. When judging that the winding is loose, the power transformer must be in the running state of the load.

When judging the winding looseness, the load current of the power transformer when the looseness fault is detected and the load current of the power transformer when the looseness threshold is measured should be kept equal. If it cannot be kept equal, the following formula needs to be used to convert the amplitude of the frequency spectrum component of the vibration signal at 100Hz:

In the above formula, A _x is the amplitude of the frequency spectrum component of the vibration signal at 100 Hz under any load current, A ₁₀₀ is the equivalent value of A _x , and I _2* is the per unit value of the load current of the power transformer when detecting loose faults.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (5)

1. The looseness judgment method based on the internal looseness judgment system of the power transformer, the internal looseness judgment system of the power transformer includes a signal conditioning circuit, a data acquisition instrument and a data analysis module connected in sequence, and also includes 3 vibration sensors, and the 3 vibration sensors The sensors are respectively connected to the data acquisition instrument through the signal conditioning circuit; the three vibration sensors respectively correspond to the three-phase vibration signals of the power transformer. The instrument transmits the collected vibration signal to the data analysis module, and the data analysis module stores and processes the vibration signal, and performs fault judgment; it is characterized in that: the method is used for the judgment and preliminary positioning of the loose iron core of the power transformer, and the method It is carried out under no-load operation of the power transformer, including the following steps: (1) The sampling frequency and sampling time are preset, and the data acquisition instrument continuously samples the vibration signals detected by each vibration sensor for at least 3 times; (2) According to the sampling frequency and sampling time, the vibration signal of each vibration sensor is intercepted in the whole cycle; (3) The data analysis module filters the vibration signal intercepted throughout the cycle, and then performs time-frequency conversion to obtain the frequency spectrum component amplitude at 100 Hz in the vibration signal sampled by each vibration sensor; (4) Get the arithmetic mean value of the frequency spectrum component amplitude value at 100 Hz in the vibration signal of each vibration sensor sampling multiple times, obtain the frequency spectrum component average value of 100 Hz place in the vibration signal sampled by each vibration sensor, the average amplitude Values are multiplied by 1.2 to 2 times to obtain the loosening thresholds CR _1A , CR _1B , and CR _1C of the three-phase iron cores of the power transformer respectively, and store the loosening thresholds in the data analysis module; (5) When it is necessary to detect the looseness of the power transformer, repeat steps (1)-(3) to re-obtain the amplitude of the frequency spectrum component at 100 Hz in each vibration signal sampled by each vibration sensor. When a certain vibration sensor has at least When the frequency spectrum component amplitude at 100 Hz of its sampled vibration signal is greater than the looseness threshold of the corresponding phase iron core of the vibration sensor for two consecutive times, enter step (6), otherwise return to step (5); (6) The ratio of the amplitude of the frequency spectrum component at 100Hz in the vibration signal sampled by each vibration sensor to the looseness threshold of the corresponding phase iron core is expressed as λ _1A , λ _1B and λ _1C respectively: When the largest ratio among the three ratios is greater than 2, and the other two ratios are not greater than 1, it is judged that there is obvious iron core looseness in the power transformer, and the phase iron core of the power transformer corresponding to the largest ratio is loose; When the largest ratio among the three ratios is greater than 2, and at least one ratio of the other two ratios is greater than 1, it is only judged that there is obvious iron core looseness in the power transformer; When the largest ratio among the three ratios is greater than 1 and less than 2, it can only be judged that there is a slight iron core looseness in the power transformer; When the largest ratio among the three ratios is not greater than 1, it is judged that there is no iron core looseness in the power transformer. 2. The looseness judgment method based on the internal looseness judgment system of the power transformer according to claim 1, characterized in that: the time-frequency transformation in step (3) adopts Fourier transform. 3. The looseness judgment method based on the internal looseness judgment system of the power transformer, the internal looseness judgment system of the power transformer includes a signal conditioning circuit, a data acquisition instrument and a data analysis module connected in sequence, and also includes 3 vibration sensors, and the 3 vibration sensors The sensors are respectively connected to the data acquisition instrument through the signal conditioning circuit; the three vibration sensors respectively correspond to the three-phase vibration signals of the power transformer, and the vibration signal is amplified, filtered and noise-reduced by the signal conditioning circuit and then transmitted to the data acquisition instrument. The instrument transmits the collected vibration signal to the data analysis module, and the data analysis module stores and processes the vibration signal, and performs fault judgment; it is characterized in that: the method is used for the judgment and preliminary positioning of the loose winding of the power transformer, and the method is It is carried out under the load operation of the power transformer, including the following steps: (1) The sampling frequency and sampling time are preset, and the data acquisition instrument continuously samples the vibration signals detected by each vibration sensor for at least 3 times; (2) According to the sampling frequency and sampling time, the vibration signal of each vibration sensor is intercepted in the whole cycle; (3) The data analysis module filters the vibration signal intercepted throughout the cycle, and then performs time-frequency conversion to obtain the frequency spectrum component amplitude at 100 Hz in the vibration signal sampled by each vibration sensor; (4) Get the arithmetic mean value of the frequency spectrum component amplitude value at 100 Hz in the vibration signal of each vibration sensor sampling multiple times, obtain the frequency spectrum component average value of 100 Hz place in the vibration signal sampled by each vibration sensor, the average amplitude Values are multiplied by 1.2 to 2 times to obtain the loosening thresholds CR _2A , CR _2B , and CR _2C of the three-phase windings of the power transformer respectively, and store the loosening thresholds in the data analysis module; (5) When it is necessary to detect the looseness of the power transformer, repeat steps (1)-(3) to re-obtain the amplitude of the frequency spectrum component at 100 Hz in each vibration signal sampled by each vibration sensor. When a certain vibration sensor has at least When the amplitude of the frequency spectrum component at 100 Hz of the vibration signal sampled for two consecutive times is greater than the looseness threshold of the corresponding phase winding of the vibration sensor, enter step (6), otherwise return to step (5); (6) The ratio of the amplitude of the frequency spectrum component at 100Hz in the vibration signal sampled by each vibration sensor to the looseness threshold of the corresponding phase winding is expressed as λ _2A , λ _2B and λ _2C : When the largest ratio among the three ratios is greater than 2, and the remaining two ratios are not greater than 1, it is judged that there is obvious winding looseness in the power transformer, and the phase winding of the power transformer corresponding to the largest ratio is loose; When the largest ratio among the three ratios is greater than 2, and at least one ratio of the other two ratios is greater than 1, it is only judged that there is obvious winding looseness in the power transformer; When the largest ratio among the three ratios is greater than 1 and less than 2, it is only judged that there is a slight winding looseness in the power transformer; When the largest ratio among the three ratios is not greater than 1, it is judged that there is no winding looseness in the power transformer. 4. The method for judging looseness based on the internal looseness judging system of the power transformer according to claim 3, characterized in that: the load current of the power transformer when the looseness fault is detected is kept equal to the load current of the power transformer when the looseness threshold is measured. 5. The method for judging looseness based on the internal looseness judging system of the power transformer according to claim 3 is characterized in that: if there is a deviation between the load current of the power transformer when detecting a loose fault and the load current of the power transformer when measuring the looseness threshold, then use the following The formula converts the amplitude of the frequency spectrum component of the vibration signal at 100Hz: <mrow> <msub> <mi>A</mi> <mn>100</mn> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <msubsup> <mi>I</mi> <mrow> <mn>2</mn> <mo>*</mo> </mrow> <mn>2</mn> </msubsup> </mfrac> <msub> <mi>A</mi> <mi>x</mi> </msub> </mrow> In the above formula, A _x is the amplitude of the frequency spectrum component of the vibration signal at 100 Hz under any load current, A ₁₀₀ is the equivalent value of A _x , and I _2* is the per unit value of the load current of the power transformer when detecting loose faults.