CN114446598A - Converter transformer protection device and method based on strain characteristics of explosion-proof material - Google Patents

Abstract

The converter transformer protection device and method based on the strain characteristics of the explosion-proof material comprise an oil pressure starting unit, a strain protection unit, a trip unit and a porous metal explosion-proof unit capable of absorbing energy; the porous metal explosion-proof unit and the tripping unit are connected with the strain protection unit, the strain protection unit is connected with the oil pressure starting unit, and the oil pressure starting unit is arranged on the wall of the converter transformer box. According to the invention, whether the internal insulation oil pressure strong characteristic quantity and the porous material strain characteristic quantity of the converter transformer reach threshold values or not is judged by using the oil pressure starting unit and the strain protection unit, so that the state change of the converter transformer can be discriminated quickly and reliably, and internal faults can be eliminated. Meanwhile, the porous explosion-proof unit is used for absorbing fault energy, so that the pressure intensity of insulating oil is effectively reduced, the strain of the tank wall is reduced, the deformation degree of the converter transformer is reduced, and the effect of improving the explosion-proof performance of the converter transformer is achieved.

Description

Converter transformer protection device and method based on strain characteristics of explosion-proof materials

technical field

The invention belongs to the technical field of non-electrical protection of power system converter transformers, and in particular relates to a converter transformer protection device and method based on the strain characteristics of explosion-proof materials.

Background technique

Transformer is an important equipment in the power system, equipped with differential protection, current quick-break protection, over-current protection, overload protection, zero-sequence current protection, over-excitation protection and other electrical protection and gas protection and other non-electrical protection. Compared with electrical quantity protection, non-electrical quantity protection not only makes up for the deficiency of electrical quantity protection by virtue of its sensitivity advantage, but also is widely used in power system, which broadens the existing ideas of relay protection research.

On the one hand, the electrical quantity protection is to identify the fault through the protection criterion after the fault occurs, and issue a tripping action signal to quickly remove the fault, so as to avoid further damage to the power equipment or further impact on the system. However, due to the inherent time limit of fault identification and fault removal in electrical quantity protection, transformer faults often evolve into fire and explosion accidents within this inherent time limit.

On the other hand, since the 1920s, according to the special structure and fault characteristics of the transformer, the transformer gas protection based on oil flow rate and gas generation has been invented to protect various types of internal faults outside the sensitive area of electrical quantity. Buchholz protection depends on the correct operation of the Buchholz relay. The currently widely used Buchholz relay is still the basic principle and mechanical structure of the Buchholz relay a hundred years ago, but the traditional Buchholz relay threshold value is determined only by experience, lacking theoretical guidance and support, and due to the long-term non-electrical protection It has not been widely used in the industry. Attention, its performance has been difficult to meet the demand, and its correct action rate is also at a low level. Due to the external short-circuit impact of the transformer, the faulty tripping of the heavy gas protection of the main transformer and the fuel injection accident of the pressure release valve frequently occur, which have a great impact on the safe operation of the power grid.

In summary, in view of the complex physical environment and phenomena of transformer faults, a relay protection method that can quickly and reliably identify and remove converter transformer faults is urgently needed. Converter transformer to avoid explosion and fire accident.

SUMMARY OF THE INVENTION

In view of the above problems, the purpose of the present invention is to provide a converter transformer protection device and method based on the strain characteristics of explosion-proof materials, which can improve the mechanical properties and explosion-proof performance of the converter transformer. By monitoring, analyzing and recording the porous metal material inside the converter transformer The strain characteristics of the converter transformer can be identified and removed, the converter transformer can be protected, and the operation reliability of the converter transformer can be improved.

For achieving the above object, the present invention adopts the following technical scheme:

A converter transformer protection device based on the strain characteristics of explosion-proof materials, including an oil pressure starting unit, a strain protection unit, a trip unit, and a porous metal explosion-proof unit capable of absorbing energy;

Both the porous metal explosion-proof unit and the trip unit are connected with the strain protection unit, the strain protection unit is connected with the oil pressure starting unit, and the oil pressure starting unit is installed on the wall of the converter transformer.

Further, the porous metal explosion-proof unit is placed inside the converter transformer, and the insulating oil pressure sensor is connected to the inner wall of the converter transformer.

Further, the porous metal explosion-proof unit includes a porous metal explosion-proof membrane, and the porous metal explosion-proof membrane includes a front panel, a rear panel, and several closed-cell foam metal layers disposed between the front panel and the rear panel.

Further, the strain protection unit includes a strain sensor, a strain amplifier and a second judgment element; wherein, the strain sensor is connected with the strain amplifier, and the strain amplifier is connected with the second judgment element; the porous metal explosion-proof unit, the trip unit and the oil pressure starting unit are all connected with The second judgment element is connected.

Further, the strain sensor is arranged between adjacent closed-cell metal foam layers; the sampling frequency of the strain sensor is 20 kHz.

Further, the density of the closed-cell metal foam layer is distributed from large to small in the direction from the insulating oil to the inner wall of the converter transformer.

Further, the closed-cell foam metal layer includes a first porous metal layer and a second porous metal layer, the density of the first porous metal layer is 0.54 g/cm ³ , and the density of the second porous metal layer is 0.27 g/cm ³ .

Further, the oil pressure starting unit includes a connected insulating oil pressure sensor and a first judging element; the insulating oil pressure sensor is arranged on the inner wall of the converter transformer and is in contact with the insulating oil.

A protection method for a converter transformer protection device based on the strain characteristics of explosion-proof materials, comprising the following steps:

Step 1: Measure the real-time oil pressure through the insulating oil pressure sensor placed on the inner wall of the converter transformer, and obtain the characteristic quantity of the real-time pressure of the insulating oil;

Step 2: Determine whether the characteristic quantity of the insulating oil pressure of the converter transformer exceeds the oil pressure starting threshold value, if it exceeds the oil pressure threshold value, go to step 3, otherwise return to step 1;

Step 3: Measure the real-time strain characteristics of the porous metal explosion-proof layer to obtain real-time strain characteristics;

Step 4: Determine whether the real-time strain characteristic quantity exceeds the strain protection threshold value, if the real-time strain characteristic quantity exceeds the strain protection threshold value, go to step 5, otherwise return to step 1;

Step 5: Send out the strain trip signal, and store the transient oil pressure of insulating oil and transient strain data of porous material for 500ms before and after the trip.

Compared with the prior art, the present invention has the following beneficial effects:

The invention utilizes the porous metal explosion-proof unit installed inside the converter transformer to absorb internal fault energy, reduce the insulating oil pressure, increase the overall pressure-bearing limit of the converter transformer, and improve the explosion-proof performance of the converter transformer. At the same time, the porous metal explosion-proof unit itself has a simple structure and is easy to implement, and the closed-cell structure also meets the use environment of oil pollution inside the converter transformer. The invention utilizes the strain sensor installed between the porous metal layers to quickly sense the strain characteristic quantity under the internal fault of the converter transformer, and meets the complex environment of high temperature, oil pollution and strong electromagnetic in the converter transformer in terms of accuracy and use range. The device of the invention is independent of the power system, does not generate harmonic interference during operation and use, and does not affect the operation of the power system.

The invention uses the oil pressure starting unit and the strain protection unit to judge whether the characteristic quantity of the insulating oil pressure inside the converter transformer and the characteristic quantity of the strain of the porous material reach the threshold value, so as to realize the rapid and reliable identification of the state change of the converter transformer, and remove the internal Fault. At the same time, the porous explosion-proof unit is used to absorb the fault energy, which can effectively reduce the pressure of the insulating oil, reduce the strain of the box wall, reduce the deformation degree of the converter transformer, and achieve the effect of improving the explosion-proof performance of the converter transformer.

Description of drawings

Figure 1 is a schematic diagram of a converter transformer protection device based on the strain characteristics of explosion-proof materials.

Figure 2 is a partial schematic diagram of a porous metal explosion-proof unit.

FIG. 3 is a flow chart of a converter transformer protection method based on the strain characteristics of explosion-proof materials.

FIG. 4 shows the measured strain characteristics of the porous metal material according to the present invention.

Figure 5 shows the measured insulating oil pressure of the present invention.

In the figure, 1 is the porous metal explosion-proof unit, 2 is the strain protection unit, 3 is the trip unit, 4 is the oil pressure starting unit, 5 is the tap changer, 6 is the porous metal explosion-proof membrane, 7 is the converter transformer, and 8 is the front The panel, 9 is the rear panel, 10 is the first porous metal layer, 11 is the second porous metal layer, and 12 is the strain sensor.

Detailed ways

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

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the related drawings. The preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure is provided.

In addition, when an element in the present invention is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for the purpose of illustration only and do not represent the only embodiment.

Referring to FIG. 1 , a converter transformer protection device based on the strain characteristics of explosion-proof materials includes a porous metal explosion-proof unit 1 , an oil pressure starting unit 4 , a strain protection unit 2 and a trip unit 3 . Among them, the tap changer 5 is an important component of the converter transformer.

Both the porous metal explosion-proof unit 1 and the trip unit 3 are connected to the strain protection unit 2, and the strain protection unit 2 is connected to the oil pressure starting unit 4, and the oil pressure starting unit 4 is installed on the wall of the converter transformer box.

Referring to FIG. 2 , the porous metal explosion-proof unit 1 includes a porous metal explosion-proof membrane 6 . The porous metal explosion-proof membrane 6 includes a front panel 8 , a rear panel 9 , and several closed-cell foam metal layers disposed between the front panel 8 and the rear panel 9 . Each closed-cell foam metal layer has different densities, and the density is determined by the oil pressure fluctuation characteristics under the internal fault of the converter transformer. According to the calculation of oil pressure amplitude and closed-cell metal yield strength, the density of each layer of closed-cell foam metal is selected.

The porous metal explosion-proof unit 1 is placed inside the converter transformer 7 , and the porous metal explosion-proof unit 1 is closely connected with the wall surface of the converter transformer 7 . The first porous metal layer 10 is close to the insulating oil, and the second porous metal layer 11 is close to the tank wall of the converter transformer 7 .

The oil pressure starting unit 4 includes an insulating oil pressure sensor and a first judging element.

The strain protection unit 2 includes a strain sensor 12, a strain amplifier and a second judgment element. Wherein, the strain sensor 12 and the second judgment element are both connected with the strain amplifier, and the second judgment element is also connected with the first judgment element of the oil pressure starting unit 4 . After the second judging element receives the signal sent by the first judging element in the hydraulic starting unit 4, the strain sensor 12 measures the strain characteristic amount in real time, and after being amplified by the strain amplifier, it is input to the second judging element, and the strain characteristic amount is realized by the second judging element The amplitude is compared with the preset protection threshold value. If it exceeds the protection threshold value, the second judgment element sends a signal to the trip unit 3; otherwise, the second judgment element does not send a signal and continues to wait for the first Judge the signal of the component. The sampling frequency of the strain sensor 12 is 20 kHz.

The insulating oil pressure sensor is located on the box wall of the converter transformer, the insulating oil pressure sensor is in direct contact with the insulating oil, and the first judgment element of the insulating oil pressure sensor is connected. The oil pressure starting unit 4 directly measures the insulating oil pressure through the pressure sensor, and compares the amplitude of the measurement result with the set starting threshold value through the first judging element. The second judgment element of the protection unit 2; otherwise, it does not reach the starting state, and continues to measure the insulating oil pressure. The oil pressure start threshold P _set is set as:

为第一整定系数，取1.5。K_err是误差系数。Among them, P _max is the maximum oil pressure under the normal operation of the converter transformer,

is the first setting coefficient, taking 1.5. _Kerr is the error coefficient.

Both the porous metal explosion-proof unit 1 and the trip unit 3 are connected to the first judgment element.

The dynamic sliding window algorithm is used to identify the discrete data of the converter transformer tank strain characteristic quantity ε(t) within a window length and record the real-time data to obtain the discrete sequence ε ₁ , ε ₂ ... ε _N .

i＝1,2,...,N

i=1,2,...,N

Suppose the current time is t and the window length is N.

通过将当前值与平均值之间的差值与前一个总和相加来计算得到累加总和S_i。即Calculate the mean of discrete series

The cumulative sum Si is calculated by adding the difference between the current value and the mean value to the previous _sum . which is

Where S ₀ =0, take the largest three items in the accumulated sum Si and record them as S _m1 , S _m2 , and S _m3 , and obtain the root mean _square value S _m ;

After receiving the signal sent by the oil pressure starting unit 4, the strain protection unit 2 judges the abrupt change in the surface strain ε(t) of the converter transformer tank by calculating the root mean square value S _m at the current moment. If the strain protection criterion S _m (t) is satisfied, )≥S _set , that is, the root mean square value S _m of the porous metal strain characteristic quantity ε(t) of the inner wall of the converter transformer tank is greater than or equal to the converter transformer strain protection action setting value S _set , then the strain protection unit sends a trip signal to the trip unit 3 .

Among them, the setting value S _set of the converter transformer strain protection action is set according to the maximum value S _max of the surface deformation strain of the converter transformer tank when the converter transformer is running at the maximum load:

S _set =K _re1 S _max

In the formula, K _re1 is the first reliability coefficient of the sliding window, which is taken as 1.2.

After receiving the signal sent by the strain protection starting unit 2, the strain mutation monitoring unit determines whether the surface strain ε(t) of the converter transformer tank is significantly increased. According to the judgment result, the converter transformer corresponds to the protection action.

Specifically, if the strain mutation protection criterion S _m (t)≥S _set is satisfied, the strain protection unit 2 further distinguishes whether it is an external short-circuit fault or an internal fault of the converter transformer. Under external faults, the strain characteristic of the porous metal inside the converter transformer box is positively correlated with the ride-through current during external faults. The greater the fault ride-through current, the greater the strain. Therefore, the strain protection with braking characteristics is adopted, and the action strain ε _set is automatically adjusted according to the braking strain ε _res , that is, the following formula, the maximum setting value ε _set.max is:

为整定可靠系数，取1.3。整定值过低容易造成保护误动，所以在制动应变量ε_res小于等于整定应变量最小值对应的制动应变量

时，整定应变量最小值ε_set.min为：Among them, ε _res.max is the strain variable under the most severe external fault,

To set the reliability factor, take 1.3. If the setting value is too low, it is easy to cause the protection to malfunction, so when the braking strain ε _res is less than or equal to the braking strain corresponding to the minimum setting strain

When , the minimum value of the setting strain variable ε _set.min is:

为可靠系数，取1.5，ε_u.max为换流变压器正常运行下泡沫金属层应变最大突变值。这样，制动特性的数学表达式为：in,

is the reliability coefficient, which is taken as 1.5, and ε _u.max is the maximum abrupt change of the strain of the foam metal layer under the normal operation of the converter transformer. Thus, the mathematical expression for the braking characteristic is:

In the formula, ε _set.r is the strain protection threshold value, ε _set.min is the minimum value of the strain amount, ε _res is the braking strain amount, and ε _res.g is the braking strain amount corresponding to the minimum value of the strain amount.

The braking characteristic slope K is:

After receiving the signal sent by the strain protection unit 2, the trip unit 3 sends a trip signal and stores the transient strain data of the converter transformer box.

The strain sensor 12 is disposed between adjacent closed-cell metal foam layers for measuring the strain characteristics of the porous metal material.

Preferably, the closed-cell foam metal layer consists of two layers, which are a first porous metal layer 10 and a second porous metal layer 11 respectively, and the metal density of the first porous metal layer 10 is greater than that of the second porous metal layer 11 . density. Specifically, the density of the first porous metal layer 10 is 0.54 g/cm ³ , and the density of the second porous metal layer 11 is 0.27 g/cm ³ . A strain sensor 12 is provided between the first porous metal layer 10 and the second porous metal layer 11 .

After receiving the signal from the strain protection unit 2, the trip unit 3 sends a trip signal and stores the transient oil pressure and transient strain data of porous explosion-proof.

Referring to Figure 3, the converter transformer protection method based on the strain characteristics of explosion-proof materials includes the following steps:

Step 1: After the device is powered on and started, read the preset oil pressure start threshold P _set and strain protection threshold ε _set.r

Step 2: measure the real-time oil pressure through the insulating oil pressure sensor placed on the wall of the converter transformer, quickly sense the real-time change of the oil pressure, and read the real-time pressure characteristic value P(t) of the insulating oil;

Step 3: Determine whether the characteristic quantity P(t) of the insulating oil pressure of the converter transformer exceeds the oil pressure start threshold value P _set by the first judgment element of the oil pressure start unit. If it exceeds the oil pressure threshold value, it is considered that the start state is reached and Go to step 4, otherwise it is considered that the startup state has not been reached, and return to step 2; avoid the interference influence of external faults on the single strain characteristic quantity, and improve the reliability of the converter transformer protection.

Step 4: Measure the strain characteristics of the porous metal through the strain sensor placed between the porous metal foam layers, and indirectly and quickly obtain the strain characteristics under the internal fault of the converter transformer, avoiding external impact or shaking when directly measuring the strain characteristics of the converter transformer wall. The influence of measurement can improve the accuracy of converter transformer protection judgment and the reliability of protection. Read the real-time strain characteristic quantity ε(t) of the porous material; if the strain mutation protection criterion S _m (t) ≥ S _set is satisfied, go to step 5; otherwise, return to step 2;

Step 5: Determine whether the amplitude of the real-time strain characteristic ε(t) of the porous metal explosion-proof layer exceeds the strain protection threshold _εset.r by the second judgment element of the strain protection unit, and if it exceeds the strain protection threshold, go to step 6, Otherwise, go back to step 2;

Step 6: Send a strain trip signal through the trip unit, and store the transient oil pressure of the insulating oil and the transient strain data of the porous material for 500ms before and after the trip, and the whole device is reset.

In response to an arc fault inside the converter transformer, the density of the first porous metal layer 10 is 0.54 g/cm ³ , and the density of the second porous metal layer 11 is 0.27 g/cm ³ .

Figures 4 and 5 show the measured results of the converter transformer integrated protection device based on the strain characteristics of metal materials. It can be seen from FIG. 4 and FIG. 5 that the present invention can measure the insulating oil pressure in the oil tank and the strain of the porous metal material in the porous explosion-proof unit through the insulating oil pressure sensor and the strain sensor.

Through the organic combination and reasonable arrangement of the porous metal explosion-proof unit, the oil pressure starting unit, the strain protection unit, and the trip unit, the present invention makes the entire protection device and method simple in structure, easy to implement and high in sensitivity.

The above content is a further detailed description of the present invention in conjunction with the specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field of the present invention, without departing from the present invention , some simple deductions or substitutions can also be made, all of which should be regarded as belonging to the invention and the scope of patent protection determined by the submitted claims.

Claims (9)

1. The converter transformer protection device based on the strain characteristics of the explosion-proof material is characterized by comprising an oil pressure starting unit (4), a strain protection unit (2), a trip unit (3) and a porous metal explosion-proof unit (1) capable of absorbing energy;

the porous metal explosion-proof unit (1) and the trip unit (3) are connected with the strain protection unit (2), the strain protection unit (2) is connected with the oil pressure starting unit (4), and the oil pressure starting unit (4) is installed on the wall of the converter transformer box.

2. The converter transformer protection device based on the strain characteristics of the explosion-proof material as claimed in claim 1, wherein the porous metal explosion-proof unit (1) is arranged inside the converter transformer (7) and is connected with the inner wall of the converter transformer (7).

3. The converter transformer protection device based on the strain characteristic of the explosion-proof material is characterized in that the porous metal explosion-proof unit (1) comprises a porous metal explosion-proof membrane (6), and the porous metal explosion-proof membrane (6) comprises a front panel (8), a rear panel (9) and a plurality of closed-cell foam metal layers arranged between the front panel (8) and the rear panel (9).

4. The converter transformer protection device based on the strain characteristic of the explosion-proof material is characterized in that the strain protection unit (2) comprises a strain sensor (12), a strain amplifier and a second judgment element; wherein the strain sensor (12) is connected with a strain amplifier, and the strain amplifier is connected with the second judgment element; the porous metal explosion-proof unit (1), the trip unit (3) and the oil pressure starting unit (4) are connected with the second judgment element.

5. The converter transformer protection device based on the strain characteristics of the explosion-proof material as claimed in claim 4, wherein the strain sensor (12) is arranged between adjacent closed-cell foam metal layers; the sampling frequency of the strain sensor (12) is 20 kHz.

6. The converter transformer protection device based on the strain characteristics of the explosion-proof material as recited in claim 1, wherein the density of the closed-cell foam metal layer is distributed from large to small from the insulating oil to the inner wall of the converter transformer (7).

7. The converter transformer protection device based on the strain characteristics of the explosion-proof material as recited in claim 1 or 6, wherein the closed-cell foam metal layer comprises a first porous metal layer (10) and a second porous metal layer (11), and the density of the first porous metal layer (10) is 0.54g/cm³The density of the second porous metal layer (11) is 0.27g/cm³。

8. The converter transformer protection device based on the strain characteristics of the explosion-proof material is characterized in that the oil pressure starting unit (4) comprises an insulated oil pressure sensor and a first judgment element which are connected; the insulating oil pressure intensity sensor is arranged on the inner wall of the converter transformer (7) and is in contact with the insulating oil.

9. A protection method of a converter transformer protection device based on strain characteristics of an explosion-proof material is characterized by comprising the following steps:

step 1: measuring real-time oil pressure through an insulating oil pressure sensor arranged on the inner wall of the converter transformer to obtain the characteristic quantity of the real-time pressure of the insulating oil;

step 2: judging whether the strong characteristic quantity of the converter transformer insulation oil pressure exceeds an oil pressure starting threshold value or not, if so, entering a step 3, otherwise, returning to the step 1;

and step 3: measuring the real-time strain characteristic of the porous metal explosion-proof layer to obtain a real-time strain characteristic quantity;

and 4, step 4: judging whether the real-time strain characteristic quantity exceeds a strain protection threshold value, if so, entering a step 5, otherwise, returning to the step 1;

and 5: and sending a strain trip signal, and simultaneously storing the transient oil pressure of the insulating oil and the transient strain data of the porous material for 500ms before and after tripping.

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