A liquid compensation system for a natural ester transformer

Abstract

A liquid compensation system for a natural ester transformer, comprising an oil tank and an oil conservator. The space in the oil conservator provides an expansion space for the natural ester insulating oil. Obtain the volume V of the natural ester insulating oil used for filling in the oil tank, as well as the minimum value T1 and the maximum value T2 of the operating temperature T of the transformer. Divide the operating temperature range of the natural ester insulating oil into three intervals, and substitute the expansion coefficients of the three intervals into the formula: V1 = V * [(t1 - T1) * Y1 + (t2 - t1) * Y2 + (T2 - t2) * Y3] to calculate and obtain the volume V1 of the oil conservator. A fault alarm device triggered when the natural ester insulating oil is abnormally used is provided on the pipeline system connecting the oil conservator and the oil tank. The present invention can accurately obtain the required expansion space of the oil conservator and reduce costs.

Description

Technical Field

[0001] The present invention relates to the field of power transformer products, and particularly to a liquid compensation system for a natural ester transformer. Background Art

[0002] Existing low-voltage products do not have the process requirement of vacuum pumping on site, resulting in relatively low product performance. With the gradual increase of users' requirements for product performance and the popularization of on-site process requirements such as vacuum pumping, especially the need for pressure balance and protection is gradually emerging. The existing technologies and related product structures have the following defects when applied to natural ester transformers: First, the design of the oil conservator is relatively simple, designed according to the maximum expansion coefficient of natural ester insulating oil, which makes the volume of the oil conservator relatively large. The large-volume oil conservator not only causes waste of space, but also increases the difficulty of the coordinated installation of the oil conservator and the oil tank due to its large volume. At the same time, the large-volume oil conservator reduces the insulation distance of the live parts of the transformer, posing a safety hazard to the transformer; Second, natural ester insulating oil is different from mineral oil. Compared with mineral oil, natural ester insulating oil cannot be directly in contact with air, is prone to oxidation, has a large viscosity, and the expansion coefficient of natural ester insulating oil is not a fixed coefficient. Directly using the existing transformer liquid level compensation and protection system for mineral oil is not conducive to solving the pressure balance of natural ester insulating oil transformers; Third, a perfect protection system for protecting natural ester insulating oil is not set up. Once a failure occurs, there is no relevant protection equipment. If it cannot be discovered in time, it will cause the oxidation and deterioration of natural ester insulating oil, resulting in a decline in performance and seriously endangering the normal operation of the transformer. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a liquid compensation system for a transformer that occupies less space and is suitable for natural ester insulating oil.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A liquid compensation system for a natural ester transformer includes an oil tank and an oil conservator arranged on the upper part of the oil tank. A pipeline system is provided between the oil conservator and the oil tank. The natural ester insulating oil in the oil conservator and the natural ester insulating oil in the oil tank are kept in communication through the pipeline system. The space in the oil conservator provides compensation and expansion space for the natural ester insulating oil;

[0006] Obtain the volume V of the natural ester insulating oil used to fill the oil tank and the minimum value T 1 and the maximum value T 2 ;

[0007] The operating temperature t of the natural ester insulating oil filled in the oil tank is between t 0 -t N between, select the temperature t1 , t 2 , and t 0 < t 1 < t 2 < t N , the temperature t 1 , t 2 divides the operating temperature range of the natural ester insulating oil into three temperature ranges, namely t 0 - t 1 range, t 1 - t 2 range, t 2 - t N range. The lowest value T of the transformer operating temperature 1 falls within t 0 - t 1 range, and the highest value T 2 falls within at the same time t 2 - t N range. At the same time, obtain the expansion coefficients Y of the natural ester insulating oil in the t 0 - t 1 range, t 1 - t 2 range, t 2 - t N range, and calculate the volume V of the conservator (1) according to formula (I): 1 , Y 2 , Y 3 . According to formula (I): 1 :

[0008] V 1 = V * [(t 1 - T 1 ) * Y 1 + (t 2 - t 1 ) * Y 2 + (T 2 - t 2 ) * Y 3 (I).

[0009] Further, at different operating temperatures t, the expansion coefficient Y of the natural ester insulating oil filled in the fuel tank satisfies the following formula:

[0010] Y = 0.00075 + 0.0000065 * (t + 20) (II);

[0011] where the operating temperature t takes the intermediate temperature values of the t 0 - t 1 range, the intermediate temperature values of the t 1 - t 2 range, and the intermediate temperature values of the t 2 - t NSubstitute the intermediate temperature value of the interval into formula (II) to calculate the expansion coefficient Y of the natural ester insulating oil in the t 0 -t 1 interval of the natural ester insulating oil 1 ,t 1 -t 2 interval of the natural ester insulating oil 2 and t 2 -t N interval of the natural ester insulating oil 3 。

[0012] Furthermore, the t 1 -t 2 interval can be divided into 2 - 6 intervals. Substitute the intermediate temperature value of each interval into formula (II) to calculate the expansion coefficient of each interval, and obtain the average value Y' of the sum of the expansion coefficients of all intervals. Use Y' to replace Y 2 and substitute it into formula (I).

[0013] Furthermore, a fault alarm device is provided on the pipeline system connecting the conservator and the oil tank.

[0014] Furthermore, the fault alarm device includes a gas relay. The gas relay is provided with a gas collection and analysis module and an alarm module. When the gas collection and analysis module detects abnormal decomposition of the natural ester insulating oil, the alarm module of the gas relay is triggered to issue an alarm.

[0015] Furthermore, the fault alarm device includes a shut-off valve. The shut-off valve remains open during normal use of the pipeline system. When the shut-off valve detects a leak in the oil tank, the shut-off valve automatically closes.

[0016] Furthermore, the pipeline system includes a main pipeline provided with a fault alarm device and a standby pipeline parallel to the main pipeline. The main pipeline is connected between the conservator and the oil tank. Both ends of the standby pipeline are respectively connected to the main pipeline at both ends of the fault alarm device. The standby pipeline is provided with a closing device. The closing device is opened when the main pipeline is in a closed state, so that the conservator and the oil tank are temporarily connected through the standby pipeline.

[0017] Furthermore, a capsule protection device is provided inside the conservator. The capsule protection device is used to isolate the natural ester insulating oil inside the conservator from the air. The capsule protection device includes a sealed capsule and a leak alarm device. A gas is filled inside the capsule and the capsule is floating on the surface of the natural ester insulating oil. When the capsule leaks, the leak alarm device is triggered to issue an alarm.

[0018] Furthermore, the leakage alarm device includes a liquid sensor, an alarm unit, and a control cable. The control cable is connected between the alarm unit and the liquid sensor. The liquid sensor extends into the capsule, and the alarm unit is arranged outside the conservator. After the liquid sensor detects that the capsule leaks, it transmits a leakage signal to the alarm unit, and the alarm unit issues an alarm.

[0019] Furthermore, the leakage alarm device includes a gas sensor, an alarm unit, and a control cable arranged in the conservator. The gas sensor is connected to the alarm unit through the control cable; the gas sensor is located at the bottom end of the side wall of the conservator, and the detection end of the gas sensor floats on the surface of the natural ester insulating oil and is between the capsule and the natural ester insulating oil. After the capsule leaks, when the gas content in the conservator detected by the detection end reaches a certain volume, the gas sensor transmits a leakage signal to the alarm unit through the control cable, and the alarm unit issues an alarm.

[0020] A liquid compensation system for a natural ester transformer according to the present invention provides compensation and expansion space for the natural ester insulating oil in the fuel tank through the conservator, divides the operating temperature of the natural ester insulating oil into three intervals, and then calculates the volume of the conservator according to the expansion coefficients of each interval, which can accurately calculate the required space of the conservator, avoid designing a conservator with more redundant space, is beneficial to reducing the design cost of the conservator, and simplifies the design process of the conservator volume. Compared with the existing conservator obtained by rough estimation, the conservator in the present invention can provide expansion space for the natural ester insulating oil in terms of volume, and will not occupy too much space due to having redundant expansion space, which is beneficial to reducing costs and improving the safety of the transformer; the conservator is arranged on the upper part of the fuel tank and is filled with part of the natural ester insulating oil in the conservator, and this ensures that the natural ester insulating oil always fills the fuel tank; further, a fault alarm device is arranged on the pipeline system between the conservator and the fuel tank and is triggered when the natural ester insulating oil is used abnormally.

[0021] In addition, the fault alarm device includes a gas relay and a shut-off valve. The gas relay issues an alarm when the natural ester insulating oil decomposes abnormally, and the shut-off valve will automatically close when the fuel tank leaks; a capsule protection device for keeping the natural ester insulating oil isolated from air is arranged in the conservator. The capsule protection device can prevent the natural ester insulating oil from contacting air and avoid the deterioration of the natural ester insulating oil. At the same time, the capsule in the capsule protection device will trigger the leakage alarm device after leaking, which is beneficial to timely maintenance and ensures the safe operation of the transformer. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of a liquid compensation system for a natural ester transformer according to the present invention;

[0023] Figure 2 It is a schematic structural diagram of a liquid compensation system for a natural ester transformer of the present invention;

[0024] Figure 3 It is a schematic structural diagram of a liquid compensation system for a natural ester transformer of the present invention;

[0025] Figure 4 It is a schematic structural diagram of a capsule protection device in a liquid compensation system for a natural ester transformer of the present invention;

[0026] Figure 5 It is a schematic structural diagram of a capsule protection device in a liquid compensation system for a natural ester transformer of the present invention. Detailed implementation manners

[0027] The following details the design method of the conservator 1 of the transformer and, in combination with the Figures 1 to 5 embodiments given, further illustrates the detailed implementation manners of a liquid compensation system for a natural ester transformer of the present invention. The liquid compensation system for a natural ester transformer of the present invention is not limited to the descriptions of the following embodiments.

[0028] A liquid compensation system for a natural ester transformer includes an oil tank 2 and a conservator 1 provided at the upper part of the oil tank 2. A pipeline system is provided between the conservator 1 and the oil tank 2. The natural ester insulating oil in the conservator 1 is kept in communication with the natural ester insulating oil in the oil tank 2 through the pipeline system. The space in the conservator 1 provides a compensation and expansion space for the natural ester insulating oil;

[0029] Obtain the volume V of the natural ester insulating oil used for filling in the oil tank 2 and the minimum value T 1 and the maximum value T 2 ;

[0030] The operating temperature t of the natural ester insulating oil filled in the oil tank 2 is between t 0 -t N . Select the temperatures t 1 , t 2 , and t 0 <t 1 <t 2 <t N . The temperatures t 1 , t 2 divide the operating temperature range of the natural ester insulating oil into three temperature ranges, namely the t 0 -t 1 range, the t 1 -t 2 range, and the t 2 -t N range. The minimum value T 1 of the transformer operating temperature falls into t0 -t 1 Interval, the highest value T 2 Falls within at the same time t 2 -t N Interval, and obtain t at the same time 0 -t 1 Interval, t 1 -t 2 Interval, t 2 -t N Coefficient of expansion Y of natural ester insulating oil in the -t interval 1 , Y 2 , Y 3 , the volume V of the conservator (1) is calculated according to the formula (I) 1 :[[]]END]]

[0031] V 1 = V * [(t 1 -T 1 ) * Y 1 +(t 2 -t 1 ) * Y 2 +(T 2 -t 2 ) * Y 3 (I).

[0032] A liquid compensation system for a natural ester transformer of the present invention provides compensation and expansion space for the natural ester insulating oil in the fuel tank 2 through the conservator 1, divides the operating temperature of the natural ester insulating oil into three intervals, and then calculates the volume of the conservator 1 according to the expansion coefficients of each interval, can accurately calculate the space required by the conservator 1, avoid designing a conservator 1 with more redundant space, is beneficial to reducing the design cost of the conservator 1, and simplifies the design process of the volume of the conservator 1.

[0033] Provide an optimal embodiment to obtain the volume V of the natural ester insulating oil filled in the fuel tank 2 and the lowest value T and the highest value T of the transformer operating temperature 1 and the highest value T 2 ;

[0034] The operating temperature t of the natural ester insulating oil filled in the fuel tank 2 is between t 0 -t N , the transformer selects the temperatures t 1 , t 2 , and t 0 < t 1 < t 2 < t N , the temperatures t 1 , t 2 divide the operating temperature interval of the natural ester insulating oil into three temperature intervals, which are respectively t 0-t 1 Interval, t 1 -t 2 Interval, t 2- t N Interval, the minimum value T of the transformer operating temperature 1 Falls within t 0- t 1 Interval, the maximum value T 2 Falls within simultaneously t 2- t N Interval, simultaneously obtain t 0 -t 1 Interval, t 1 -t 2 Interval, t 2 -t N Coefficient of expansion Y of natural ester insulating oil in the interval 1 , Y 2 , Y 3 , Calculate the volume V of the conservator 1 obtained according to formula (I) 1 :

[0035] V 1 = V * [(t 1 - T 1 ) * Y 1 +(t 2 - t 1 ) * Y 2 +(T 2 - t 2 ) * Y 3 (I).

[0036] Generally speaking, the minimum operating temperature T of the transformer 1 Is -20 °C, the maximum operating temperature T 2 Is 120 °C. Taking a certain soybean-based natural ester insulating oil as an example for the natural ester insulating oil, the operating temperature t filled in the fuel tank 2 varies between t 0 - t N Among them, the temperature of t 0 Is equal to the minimum operating temperature T of the transformer 1 , That is, t 0 = T 1 = -20 °C; the temperature of t N Is equal to the maximum operating temperature T of the transformer 2 , That is, t N = T 2 = 120 °C. Preferably t 1 = 40 °C, t 2 = 80 °C. At this time, t 0 - t 1 Interval, t 1 - t 2 Interval, t2 -t N The intervals are -20°C - 40°C, 40°C - 80°C, and 80°C - 120°C respectively.

[0037] Obtain the expansion coefficients Y in three stages 1 、Y 2 and Y 3 , the expansion coefficient Y can be obtained through multiple measurements or by calculation. In the present invention, the expansion coefficient Y can optionally be obtained by formula (II),

[0038] Y = 0.00075 + 0.0000065 * (t + 20) (II);

[0039] In formula (II), t represents the operating temperature of the natural ester insulating oil. When calculating the expansion coefficient Y1 in the t 0 -t 1 interval, select the middle value of t 0 -t 1 interval and substitute it into formula (II). In the present invention, substitute the middle value of 10°C in the range of -20°C - 40°C to obtain Y1 = 0.000945; when calculating the expansion coefficient Y2 in the t 1 -t 2 interval, select the middle value of t 1 -t 2 interval and substitute it into formula (II), substitute the middle value of 60°C in the range of 40°C - 80°C to obtain Y2 = 0.00114; when calculating the expansion coefficient Y3 in the t 2 -t N interval, select the middle value of t 2 -t N interval and substitute it into formula (II), substitute the middle value of the range of 80°C - 120°C to obtain Y3 = 0.0014; substitute the calculated Y1, Y2, and Y3 into formula (I) to get V1 = V * (60 * 0.000945 + 40 * 0.00114 + 40 * 0.0014) = 0.1583V.

[0040] The present invention preferably obtains the t 0 -t 1 interval, t 1 -t 2 interval, t 2 -t N interval expansion coefficients Y 1 、Y 2 、Y 3 , that is, the expansion coefficients in the three intervals of -20°C - 40°C, 40°C - 80°C, and 80°C - 120°C are 0.000767, 0.000797, and 0.000825 respectively. Substitute Y 1 、Y2 and Y 3 Substitute into formula (I), and calculate to obtain V = 0.1111 * V. It should be noted that there is a certain range of error between the measured value and the result obtained by calculation according to the formula. In particular, there is also a certain range of error in the result calculated after the formula is split. However, there is no doubt that the result calculated according to the formula is more accurate.

[0041] Of course, t 1 and t 2 can also be other temperature values. The three temperature intervals can be three unequal parts. Preferably, the t 1 -t 2 interval can be divided into 2 - 6 intervals. Substitute the intermediate temperature value of each interval into formula (II) to calculate the expansion coefficient of each interval, and obtain the average value Y' of the sum of the expansion coefficients of all intervals. Use Y' to replace Y 2 and substitute it into formula (I). Of course, the t 1 -t 2 interval can also be divided into more intervals.

[0042] As Figures 1 - 5 shown, a liquid compensation system for a transformer includes an oil tank 2 and an oil conservator 1 designed according to the above formula. Part of natural ester insulating oil is filled in the oil conservator 1 to isolate the natural ester insulating oil in the oil conservator 1 from air. The oil conservator 1 is arranged on the upper part of the oil tank 2. A pipeline system is provided between the oil conservator 1 and the oil tank 2. The natural ester insulating oil in the oil conservator 1 and the natural ester insulating oil in the oil tank 2 are kept connected through the pipeline system. The space in the oil conservator 1 provides an expansion space for the natural ester insulating oil. A fault alarm device is provided on the pipeline system connecting the oil conservator 1 and the oil tank 2, and the fault alarm device is triggered when the natural ester insulating oil is used abnormally.

[0043] Compared with the existing oil conservator 1 obtained by rough estimation, the oil conservator 1 in the present invention can not only provide an expansion space for the natural ester insulating oil in terms of volume, but also will not occupy too much space due to having excessive expansion space, which is beneficial to reducing costs and improving the safety of the transformer. The oil conservator 1 is arranged on the upper part of the oil tank 2 and part of natural ester insulating oil is filled in the oil conservator 1 to ensure that the natural ester insulating oil always fills the oil tank 2. A fault alarm device is provided on the pipeline system between the oil conservator 1 and the oil tank 2 and is triggered when the natural ester insulating oil is used abnormally.

[0044] Combined with the attached Figures 1 - 5Detailed introduction: A liquid compensation system for a transformer includes an oil conservator 1 filled with partially natural ester insulating oil. The natural ester insulating oil in the oil conservator 1 isolates air and avoids deterioration after contacting air. Preferably, a capsule protection device that can isolate the natural ester insulating oil from air is provided in the oil conservator 1. The oil conservator 1 is arranged on the upper part of the oil tank 2, and a pipeline system is provided between the oil conservator 1 and the oil tank 2. The natural ester insulating oil in the oil conservator 1 is kept in communication with the natural ester insulating oil in the oil tank 2 through the pipeline system. The space in the oil conservator 1 provides an expansion space for the natural ester insulating oil. By arranging the oil conservator 1 on the upper part of the oil tank 2 and keeping the oil tank 2 in communication with the oil conservator 1, since the oil conservator 1 is always filled with partially natural ester insulating oil, it can be ensured that the natural ester insulating oil in the oil tank 2 is always in a full state. Therefore, only by ensuring that the oil conservator 1 isolates air can it be ensured that the natural ester insulating oil in the oil tank 2 does not contact air. A fault alarm device is provided on the pipeline system connecting the oil conservator 1 and the oil tank 2. The fault alarm device will be triggered when the natural ester insulating oil is abnormally used, which is beneficial for the staff to timely detect the fault.

[0045] Preferably, as Figures 1 - 3 shown, the pipeline system includes a main pipeline 31 provided with a fault alarm device and a standby pipeline 32 parallel to the main pipeline 31. The main pipeline 31 is connected between the oil conservator 1 and the oil tank 2. Both ends of the standby pipeline 32 are respectively connected to the main pipeline 31 at both ends of the fault protection system. The standby pipeline 32 is provided with a closing device. The closing device is opened when the main pipeline 31 is in a closed state, so that the oil conservator 1 and the oil tank 2 are temporarily connected through the standby pipeline 32, ensuring that the transformer can operate without power interruption during regular inspection and maintenance. Preferably, butterfly valves are provided on the main pipeline 31 at both ends of the fault alarm system, and a ball valve is provided on the standby pipeline 32. During normal operation, the butterfly valve of the main pipeline 31 is opened to make the main pipeline 31 operate normally, and the ball valve is closed to close the standby pipeline 32. During regular inspection and maintenance, by closing the butterfly valve and opening the ball valve, the main pipeline 31 is closed, and the oil tank 2 and the oil conservator 1 are connected through the standby pipeline 32.

[0046] The fault alarm device includes a gas relay 41 and a cut-off valve 42. The gas relay 41 is located on one side close to the oil tank 2, and the cut-off valve 42 is located on one side close to the conservator 1. The gas relay 41 is provided with a gas collection and analysis module and an alarm module. When the gas collection and analysis module detects abnormal decomposition of natural ester insulating oil, the alarm module of the gas relay 41 is triggered to issue an alarm. The principle is as follows: Since natural ester insulating oil will operate with the transformer for about 30 - 50 years, its molecules will undergo natural or fault decomposition under high temperature and high voltage in the transformer. The gas components of fault decomposition are different from those of natural decomposition. The gas collection and analysis module of the gas relay 41 can provide gas collection and quantification alarm for this part. When the fault gas accumulates to a certain amount, the alarm module of the gas relay 41 is triggered to issue an alarm signal for maintenance personnel to judge the fault.

[0047] The cut-off valve 42 remains open during normal use of the pipeline system. When the cut-off valve 42 detects a leak in the oil tank 2, the cut-off valve 42 automatically closes. A preset value is set for the cut-off valve 42. When the flow rate of natural ester insulating oil in the pipeline system exceeds the preset value of the cut-off valve 42, the pressure difference generated when the natural ester insulating oil flows through will trigger the cut-off valve 42 to automatically close and issue an alarm. Usually, only when there is a leak will the flow rate of natural ester insulating oil be too fast to cause the cut-off valve 42 to close, and it is considered that there is a leak when the flow rate is too fast. When the flow rate of natural ester insulating oil is below the preset value, the cut-off valve 42 remains open to ensure the normal flow of natural ester insulating oil due to thermal expansion and contraction. Of course, a flow rate regulating device is configured for the cut-off valve 42, and the trigger preset value of the cut-off valve 42 can be adjusted according to the toilet pressure difference or setting convention. The model of the cut-off valve 42 is the RDR MK II type cut-off valve 42 of COMEM Company.

[0048] Preferably, a capsule protection device is arranged in the conservator 1. The capsule protection device is used to isolate the natural ester insulating oil in the conservator 1 from the air. The capsule protection device includes a sealed capsule 51 and a leakage alarm device. A gas is filled in the capsule 51 and the capsule 51 is floatingly arranged on the surface of the natural ester insulating oil. The capsule 51 is similar to a balloon. The inlet of the capsule 51 is communicated with the outside. Usually, air is filled in the capsule 51. In this way, the inlet of the capsule 51 can be directly communicated with the air. The capsule 51 plays a role in balancing the atmospheric pressure of the conservator 1. When the natural ester insulating oil in the transformer expands, the oil volume in the conservator 1 increases, causing the gas in the capsule 51 to be discharged. When the temperature of the transformer decreases and the natural ester insulating oil shrinks, the oil volume in the conservator 1 decreases. Affected by the negative pressure, the capsule 51 begins to inhale air and expand. Usually, a dry gas is filled in the capsule 51. Preferably, a drying device 54 is arranged to keep the gas in the capsule 51 dry. When the capsule 51 leaks, the leakage alarm device is triggered to send an alarm. There are two alarm principles for the leakage alarm device.

[0049] Provide the first leakage alarm device, as Figure 4 shown, the leakage alarm device includes a liquid sensor 52, an alarm unit and a control cable. The control cable is connected between the alarm unit and the liquid sensor 52. The liquid sensor 52 extends into the capsule 51. The alarm unit is arranged outside the conservator 1. Usually, an oil level gauge is arranged in the conservator 1 in cooperation. After the capsule 51 leaks, part of the natural ester insulating oil enters the capsule 51, triggering the liquid sensor 52. At this time, the liquid sensor 52 detects that the capsule 51 leaks and transmits a leakage signal to the alarm unit, and the alarm unit issues an alarm.

[0050] Provide the second leakage alarm device, as Figure 5 shown, the leakage alarm device includes a gas sensor 53 arranged in the conservator 1, an alarm unit and a control cable. The gas sensor 53 is connected to the alarm unit through the control cable; the gas sensor 53 is located at the bottom end of the side wall of the conservator 1. The detection end of the gas sensor 53 floats on the surface of the natural ester insulating oil and is between the capsule 51 and the natural ester insulating oil. The detection end can change with the change of the liquid level of the natural ester insulating oil. After the capsule 51 leaks, air flows into the conservator 1. When the detection end detects that the gas content in the conservator 1 reaches a certain volume, usually used to detect the volume of air, the gas sensor 53 transmits a leakage signal to the alarm unit through the control cable box and the alarm unit issues an alarm.

[0051] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as falling within the protection scope of the present invention.

Claims

1. A liquid compensation system for a natural ester transformer, characterized in that: it includes an oil tank (2) and an oil conservator (1) arranged on the upper part of the oil tank (2). A pipeline system is provided between the oil conservator (1) and the oil tank (2). The natural ester insulating oil in the oil conservator (1) is kept in communication with the natural ester insulating oil in the oil tank (2) through the pipeline system. The space in the oil conservator (1) provides a compensation and expansion space for the natural ester insulating oil; Obtain the volume V of the natural ester insulating oil filled in the fuel tank (2) and the minimum value T of the operating temperature T of the transformer 1 and the maximum value T 2 ; The operating temperature t of the natural ester insulating oil filled in the fuel tank (2) is within the temperature t 0 -t N Between, select the temperature t 1 、t 2 And t 0 <t 1 <t 2 <t N The temperature t 1 、t 2 Divide the operating temperature range of the natural ester insulating oil into three temperature ranges, which are t 0 -t 1 Range, t 1 -t 2 Range, t 2 -t N Range, the lowest value T of the transformer operating temperature 1 Falls into t 0 -t 1 Range, the highest value T 2 Falls into and t 2 -t N Range, and obtain t at the same time 0 -t 1 Range, t 1 -t 2 Range, t 2 -t N The expansion coefficient Y of the natural ester insulating oil in the range 1 , Y 2 、Y 3 , Calculate the volume V of the oil conservator (1) according to formula (I) 1 : V 1 = V * [(t 1 - T 1 ) * Y 1 + (t 2 - t 1 ) * Y 2 + (T 2 - t 2 ) * Y 3 (I).

2. The liquid compensation system for a natural ester transformer according to claim 1, characterized in that : at different operating temperatures t, the expansion coefficient Y of the natural ester insulating oil filled in the oil tank (2) satisfies the following formula: Y = 0.00075 + 0.0000065 * (t + 20) (II); where the operating temperature t is respectively taken as the intermediate temperature value in the range of t 0 -t 1 range, the intermediate temperature value in the range of t 1 -t 2 range, and the intermediate temperature value in the range of t 2 -t N range are substituted into formula (II) to calculate the expansion coefficient Y of the natural ester insulating oil at t 0 -t 1 range, the expansion coefficient Y of the natural ester insulating oil at t 1 , t 1 -t 2 range, and the expansion coefficient Y of the natural ester insulating oil at t 2 and t 2 -t N range. 3 .

3. The liquid compensation system for a natural ester transformer according to claim 2, characterized in that: The value of t 1 -t 2 is divided into 2 - 6 intervals. The intermediate temperature value of each interval is substituted into formula (II) to calculate the expansion coefficient of each interval, and the average value Y' of the sum of the expansion coefficients of all intervals is obtained. Y' is used to replace Y 2 and substituted into formula (I).

4. The liquid compensation system for a natural ester transformer according to claim 1, characterized in that: a fault alarm device is provided on the pipeline system connecting the oil conservator (1) and the oil tank (2).

5. The liquid compensation system for a natural ester transformer according to claim 4, characterized in that : the fault alarm device includes a gas relay (41). The gas relay (41) is provided with a gas collection and analysis module and an alarm module. When the gas collection and analysis module detects abnormal decomposition of the natural ester insulating oil, the alarm module of the gas relay (41) is triggered to issue an alarm.

6. The liquid compensation system for a natural ester transformer according to claim 4, characterized in that : the fault alarm device includes a shut-off valve (42). The shut-off valve (42) remains open during normal use of the pipeline system. When the shut-off valve (42) detects a leak in the oil tank (2), the shut-off valve (42) automatically closes.

7. The liquid compensation system for a natural ester transformer according to claim 4, characterized in that: the pipeline system includes a main pipeline (31) provided with a fault alarm device and a standby pipeline (32) connected in parallel with the main pipeline (31). The main pipeline (31) is connected between the oil conservator (1) and the oil tank (2). Both ends of the standby pipeline (32) are respectively connected to the main pipeline (31) at both ends of the fault alarm device. The standby pipeline (32) is provided with a closing device. The closing device is opened when the main pipeline (31) is in a closed state, so that the oil conservator (1) and the oil tank (2) are temporarily connected through the standby pipeline (32).

8. The liquid compensation system for a natural ester transformer according to claim 4, characterized in that: a capsule protection device is arranged in the oil conservator (1). The capsule protection device is used to isolate the natural ester insulating oil in the oil conservator (1) from the air. The capsule protection device includes a sealed capsule (51) and a leak alarm device. A gas is filled in the capsule (51) and the capsule (51) is floating on the surface of the natural ester insulating oil. When the capsule (51) leaks, the leak alarm device is triggered to issue an alarm.

9. The liquid compensation system for a natural ester transformer according to claim 8, It is characterized in that: The leakage alarm device includes a liquid sensor (52), an alarm unit and a control cable. The control cable is connected between the alarm unit and the liquid sensor (52). The liquid sensor (52) extends into the capsule (51). The alarm unit is arranged outside the conservator (1). After the liquid sensor (52) detects the leakage of the capsule (51), it transmits a leakage signal to the alarm unit and the alarm unit issues an alarm.

10. A liquid compensation system for a natural ester transformer according to claim 8, It is characterized in that: The leakage alarm device includes a gas sensor (53) arranged in the conservator (1), an alarm unit and a control cable. The gas sensor (53) is connected to the alarm unit through the control cable. The gas sensor (53) is located at the bottom end of the side wall of the conservator (1). The detection end of the gas sensor (53) floats on the surface of the natural ester insulating oil and is between the capsule (51) and the natural ester insulating oil. After the capsule (51) leaks, when the detection end detects that the gas content in the conservator (1) reaches a certain volume, the gas sensor (53) transmits a leakage signal to the alarm unit through the control cable box and the alarm unit issues an alarm.

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