Active early warning method for internal pressure of transformer

Abstract

The invention relates to a transformer internal pressure active early warning method which comprises the following steps: S1, detecting oil pressure at a quick-acting oil pressure relay, integrating a pressure sensor in the quick-acting oil pressure relay, and accurately detecting the internal pressure of the transformer at the quick-acting oil pressure relay in real time; s2, oil pressure calculation at a quick-acting oil pressure relay: calculating the oil level height of an oil conservator according to the scale of an oil level gauge of the transformer, and calculating the oil pressure at the quick-acting oil pressure relay of the transformer; and S3, active early warning of the internal pressure of the transformer is carried out, comparative analysis is carried out according to the detected and calculated oil pressure, whether the internal pressure of the transformer is normal or not is judged, and active early warning is carried out according to an analysis result. Under the condition of no contact with transformer insulating oil, a real-time monitoring function of the internal pressure of the transformer can be realized, and other pressure relays do not need to be additionally arranged; through a pressure sensor integrated with the quick-acting oil pressure relay, early warning of leakage of the pressure relief valve or faults before action and early warning of the quick-acting oil pressure relay before action are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer pressure monitoring, and in particular relates to an active early warning method for transformer internal pressure. Background Art

[0002] Transformers are important equipment for power transmission. During operation, they may experience abnormal internal pressure due to various reasons, resulting in serious failures, which seriously affect the safe and stable operation of transformers. For example, during operation, the respirator of the transformer is blocked and the transformer loses its ability to "breathe". At this time, if the oil temperature of the transformer continues to rise, the volume of the insulating oil expands, causing the internal pressure of the transformer to continue to rise. This not only increases the pressure-bearing strength of the transformer oil tank, but also easily causes the pressure relief valve to spray oil in severe cases. When the oil level of the transformer body is too high, the oil level gauge cannot correctly alarm due to abnormalities. When the oil level reaches the limit of the oil conservator, the transformer oil conservator loses the ability to adjust the oil level, which will also cause the internal pressure of the transformer to continue to rise. In severe cases, it is easy to cause the pressure relief valve to spray oil. When the pulley of the corrugated external oil conservator is stuck and the oil temperature of the transformer is reduced, negative pressure will appear inside. At this time, if the stress of the negative pressure inside the transformer on the pulley of the expander inside the oil conservator exceeds the friction of the stuck pulley, the pulley will be suddenly released, which will cause the internal pressure of the transformer to change suddenly and cause the transformer heavy gas to malfunction, etc.

[0003] From the above situation, it can be seen that transformer internal pressure monitoring is crucial to the safe and stable operation of the transformer. Traditional transformers use pressure relief valves and quick-acting oil pressure relays to protect the transformer from abnormal internal pressure. When the internal oil pressure of the transformer increases to the opening pressure of the pressure relief valve, the pressure relief valve opens instantly to release the pressure to protect the transformer oil tank. However, the traditional pressure relief valve only has the function of pressure relief and cannot monitor the pressure changes inside the transformer in real time. The quick-acting oil pressure relay is installed according to the needs, and the quick-acting oil pressure relay acts according to the speed of the oil pressure rise inside the transformer. From the protection principle of the quick-acting oil pressure relay, it can be seen that the quick-acting oil pressure relay can only send an alarm signal according to the speed of change of the internal pressure of the transformer, but is insensitive to slow changes in oil pressure and has no protective effect.

[0004] As can be seen from the above, the traditional transformer uses a combination of a pressure relief valve and a fast-acting oil pressure relay to protect the transformer, which cannot achieve the real-time monitoring function of the internal pressure of the transformer. Although the pressure relief valve can achieve pressure relief and the fast-acting oil pressure relay can achieve the protection of the oil pressure change speed, the traditional protection method has the following defects:

[0005] 1. It is impossible to monitor the internal pressure value of the transformer in real time, and it is impossible to provide effective guidance for the operation and maintenance of the transformer.

[0006] 2. It is not possible to conduct a comprehensive analysis and assessment based on the changes in the internal pressure of the transformer, and is unable to implement the active early warning function for the internal pressure of the transformer based on the changes in the internal pressure of the transformer.

[0007] 3. It is not sensitive to changes in the internal pressure of the transformer caused by problems such as breather blockage, high oil level, and corrugated expander pulley jam, and it is unable to provide timely warning and effective protection against these potential faults.

[0008] 4. It is impossible to determine whether the pressure relief function and the quick-acting oil pressure relay are working normally and whether the oil tank strength design is reasonable due to the faulty transformer. Summary of the invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for active early warning of transformer internal pressure.

[0010] The present invention solves the technical problem by the following technical solutions:

[0011] A method for active early warning of transformer internal pressure, the method comprising the following steps:

[0012] S1. Oil pressure detection at the quick-acting oil pressure relay. A pressure sensor is integrated in the quick-acting oil pressure relay to accurately and real-time detect the internal pressure of the transformer at the quick-acting oil pressure relay.

[0013] S2. Calculate the oil pressure at the quick-acting oil pressure relay. Calculate the oil level height of the oil storage cabinet according to the scale of the transformer oil level gauge, and calculate the oil pressure at the quick-acting oil pressure relay of the transformer;

[0014] S3. Active early warning of transformer internal pressure: compare and analyze the oil pressure obtained through detection and calculation to determine whether the internal pressure of the transformer is normal, and issue an active early warning based on the analysis results.

[0015] Moreover, the S1 is specifically:

[0016] A miniature gas pressure sensor is arranged in the upper air chamber I of the transformer, an expander and a micro switch connected in sequence are arranged at the center of the lower air chamber II of the transformer, a pressure sensor is arranged at the upper end of the expander, and the upper end of the pressure sensor is connected to the top of the bellows of the upper air chamber I of the transformer through a spring, and the miniature gas pressure sensor and the micro switch are both connected to the terminal block at the bottom end of the transformer. When the oil pressure inside the transformer increases, the corresponding oil chamber pressure increases, and the insulating oil compresses the separation bellows of the quick-acting oil pressure relay, and the separation bellows transmits the pressure to the spring. The pressure of the spring is transmitted to the pressure sensor to cause deformation, and at the same time compresses the gas in the air chambers I and II, so that the miniature gas pressure sensor detects the pressure, and the internal pressure P of the transformer is calculated by detecting the spring pressure and the pressure in the air chamber I.

[0017] The air pressure P1 inside the air chamber I is detected by a micro gas pressure sensor. The pressure sensor is subjected to a pressure of F through a spring. The pressure-bearing area on the top of the bellows is S. The internal oil pressure of the transformer, i.e., the internal pressure P of the oil chamber, is:

[0018]

[0019] Moreover, the S2 is specifically:

[0020] The transformer oil level gauge is installed at the bottom of one side of the transformer body oil conservator. When the oil level inside the oil conservator is 0, the angle β between the oil level gauge connecting rod and the horizontal line is 0. The connecting rod angle β increases with the increase of the oil level. As the connecting rod angle β increases, the oil level gauge drives the dial pointer to rotate through mechanical gears and magnetic transmission. The angle α between the pointer on the dial and the 0 scale oil level increases accordingly. Then:

[0021] β=λ×α (2)

[0022] Where: λ is the proportional coefficient of angle conversion;

[0023] According to the oil level indication of the oil level gauge, calculate the oil level height H of the main oil storage tank, and according to the trigonometric function, get:

[0024] H=L×sinβ (3)

[0025] Where: L is the length of the oil level gauge connecting rod.

[0026] Substituting formula (2) into formula (3), we get:

[0027] H=L×sin(λ×α) (4)

[0028] After calculating the oil level, according to the liquid pressure calculation formula, the pressure P' at the quick-acting oil pressure relay is calculated as:

[0029] P'=ρ×g×(H+h)=ρ×g×[L×sin(λ×α)+h] (5)

[0030] Where: ρ is the density of transformer oil, g is the acceleration of gravity, and h is the height from the bottom of the main oil storage cabinet to the quick-acting oil pressure relay;

[0031] Because transformer oil changes pressure according to temperature, its volume expansion rate α is known. When the temperature changes, the mass m of transformer oil does not change. Therefore, before and after the temperature changes:

[0032] m=ρ×V=(ρ-Δρ)×[V×(1+α×ΔT)] (6)

[0033] Where: V is the volume of transformer oil, △T is the temperature difference, △ρ is the density correction;

[0034] According to formula (6), the density correction value △ρ is:

[0035]

[0036] Substituting formula (7) into formula (5), we get:

[0037]

[0038] Moreover, the S3 is specifically:

[0039] 3.1. When the internal detection pressure P or calculated pressure P' of the transformer is greater than or equal to the sealing pressure of the pressure relief valve, an early warning message is issued, indicating that the internal pressure of the transformer is abnormal;

[0040] 3.2. When the pressure change of the transformer internal detection pressure P per unit time is greater than or equal to 80% of the setting limit of the quick-acting oil pressure relay, an early warning message is issued, indicating that the transformer internal pressure is abnormal;

[0041] 3.3. When the deviation between the internal detection pressure P of the transformer and the calculated pressure P' of the transformer is greater than or equal to 10%, an early warning message is issued, indicating that the internal pressure of the transformer is abnormal;

[0042] 3.4. When the internal detection pressure P of the transformer is greater than or equal to the maximum value of the calculated pressure P' inside the transformer, that is, the maximum pressure value calculated corresponding to the highest oil level of the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value;

[0043] 3.5. When the internal detection pressure P of the transformer is less than or equal to the minimum value of the calculated pressure P' inside the transformer, that is, the minimum pressure value calculated corresponding to the lowest oil level in the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value.

[0044] The advantages and beneficial effects of the present invention are:

[0045] 1. The present invention integrates the pressure sensor into the quick-acting oil pressure relay, and can realize the real-time monitoring function of the internal pressure of the transformer without contact with the transformer insulating oil, without installing other pressure relays.

[0046] 2. The present invention can realize early warning of leakage or pre-action failure of the pressure relief valve and pre-action warning of the quick-acting oil pressure relay through the pressure sensor integrated in the quick-acting oil pressure relay.

[0047] 3. The present invention can compare and analyze the detected internal pressure value of the transformer with the pressure value calculated according to the oil level of the oil storage cabinet, so as to judge the abnormal internal pressure of the transformer caused by faults such as respirator blockage and false oil level, realize the active early warning function of abnormal internal pressure of the transformer, and ensure the safe and stable operation of the transformer.

[0048] 4. When the internal pressure of the transformer is abnormal, the severity of the internal fault of the transformer can be judged according to the pressure value detected by the pressure sensor, and it can be judged whether the strength design of the transformer oil tank is reasonable, whether the pressure relief valve operates normally, and whether the oil pressure quick-acting relay operates normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the arrangement of the internal pressure sensor of the transformer of the present invention;

[0050] Figure 2 It is a schematic diagram of the oil level detection principle of the oil level gauge of the present invention. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0052] A method for active early warning of internal pressure of a transformer, characterized in that the steps of the method are:

[0053] S1. Oil pressure detection at the quick-acting oil pressure relay. A pressure sensor is integrated in the quick-acting oil pressure relay to accurately and real-time detect the internal pressure of the transformer at the quick-acting oil pressure relay.

[0054] like Figure 1 As shown, the transformer is divided into an upper chamber 18 and a lower chamber 13. The upper chamber 18 contains an oil chamber 4. A separation bellows 5 is provided on the inner wall of the oil chamber. A spring 3 is connected to the middle of the separation bellows 5. The bottom end of the spring 3 is connected to a pressure sensor 16. The lower end of the pressure sensor is connected to an expander 15 and a micro switch 14 in sequence. A test hole cover 2 and a vent plug 1 are provided at the top of the oil chamber 4. An air chamber 17 is provided in the oil chamber 4. A miniature gas pressure sensor 17 is provided in the air chamber 17. The miniature gas pressure sensor 17 and the micro switch 14 are both connected to the terminal block 11 at the bottom end of the transformer. A mounting flange 6 is provided on the side wall of the oil chamber 4. A balancing pinhole 8 is provided between the upper chamber 18 and the lower chamber 13 of the transformer.

[0055] A miniature gas pressure sensor 17 is arranged in the upper air chamber I7 of the transformer, and an expander 15 and a micro switch 14 connected in sequence are arranged at the center of the lower air chamber II10 of the transformer. A pressure sensor 16 is arranged at the upper end of the expander 15, and the upper end of the pressure sensor 16 is connected to the top of the bellows 5 of the upper air chamber I7 of the transformer through a spring 3. The miniature gas pressure sensor 17 and the micro switch 14 are both connected to the terminal block 11 at the bottom end of the transformer. When the internal oil pressure of the transformer increases, the pressure of the corresponding oil chamber 4 increases, and the insulating oil compresses the separation bellows 5 of the quick-acting oil pressure relay. The separation bellows transmits the pressure to the spring 3, and the pressure of the spring 3 is transmitted to the pressure sensor 16 to cause deformation, and at the same time compresses the gas in the air chamber I7 and the air chamber II10, so that the miniature gas pressure sensor 17 detects the pressure, and the internal pressure P of the transformer is calculated by detecting the pressure of the spring 3 and the pressure in the air chamber I7.

[0056] The internal air pressure P1 of the air chamber I7 is detected by the micro gas pressure sensor 17. The pressure sensor 16 is subjected to a pressure F through the spring 3. The pressure-bearing area at the top of the bellows 5 is S. The internal oil pressure of the transformer, i.e., the internal pressure P of the oil chamber 4, is:

[0057]

[0058] S2. Calculate the oil pressure at the quick-acting oil pressure relay. Calculate the oil level height of the oil storage cabinet according to the scale of the transformer oil level gauge, and calculate the oil pressure at the quick-acting oil pressure relay of the transformer;

[0059] The transformer oil level gauge is installed at the bottom of one side of the transformer body oil conservator. When the oil level inside the oil conservator is 0, the angle β between the oil level gauge connecting rod and the horizontal line is 0. The connecting rod angle β increases with the increase of the oil level. As the connecting rod angle β increases, the oil level gauge drives the dial pointer to rotate through mechanical gears and magnetic transmission. The angle α between the pointer on the dial and the 0 scale oil level increases accordingly. Then:

[0060] β=λ×α (2)

[0061] Where: λ is the proportional coefficient of angle conversion;

[0062] According to the oil level indication of the oil level gauge, calculate the oil level height H of the main oil storage tank, and according to the trigonometric function, get:

[0063] H=L×sinβ (3)

[0064] Where: L is the length of the oil level gauge connecting rod.

[0065] Substituting equation 2 into equation 3, we get:

[0066] H=L×sin(λ×α) (4)

[0067] After calculating the oil level, according to the liquid pressure calculation formula, the pressure P' at the quick-acting oil pressure relay is calculated as:

[0068] P'=ρ×g×(H+h)=ρ×g×[L×sin(λ×α)+h] (5)

[0069] Where: ρ is the density of transformer oil, g is the acceleration of gravity, and h is the height from the bottom of the main oil storage cabinet to the quick-acting oil pressure relay;

[0070] Because transformer oil changes pressure according to temperature, its volume expansion rate α is known. When the temperature changes, the mass m of transformer oil does not change. Therefore, before and after the temperature changes:

[0071] m=ρ×V=(ρ-Δρ)×[V×(1+α×ΔT)] (6)

[0072] Where: V is the volume of transformer oil, △T is the temperature difference, △ρ is the density correction;

[0073] According to formula 6, the density correction value △ρ is:

[0074]

[0075] Substituting equation 7 into equation 5, we get:

[0076]

[0077] S3. Active early warning of transformer internal pressure: compare and analyze the oil pressure obtained through detection and calculation to determine whether the internal pressure of the transformer is normal, and issue an active early warning based on the analysis results.

[0078] 3.1. When the internal detection pressure P or calculated pressure P' of the transformer is greater than or equal to the sealing pressure of the pressure relief valve, an early warning message is issued, indicating that the internal pressure of the transformer is abnormal;

[0079] 3.2. When the pressure change of the transformer internal detection pressure P per unit time is greater than or equal to 80% of the setting limit of the quick-acting oil pressure relay, an early warning message is issued, indicating that the transformer internal pressure is abnormal;

[0080] 3.3. When the deviation between the internal detection pressure P of the transformer and the calculated pressure P' of the transformer is greater than or equal to 10%, an early warning message is issued, indicating that the internal pressure of the transformer is abnormal;

[0081] 3.4. When the internal detection pressure P of the transformer is greater than or equal to the maximum value of the calculated internal pressure P' of the transformer, that is, the maximum pressure value calculated corresponding to the highest oil level of the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value.

[0082] 3.5. When the internal detection pressure P of the transformer is less than or equal to the minimum value of the calculated pressure P' inside the transformer, that is, the minimum pressure value calculated corresponding to the lowest oil level in the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value.

[0083] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for active early warning of internal pressure of a transformer, characterized in that: The steps of the method are: S1. Oil pressure detection at the quick-acting oil pressure relay. A pressure sensor is integrated in the quick-acting oil pressure relay to accurately and real-time detect the internal pressure of the transformer at the quick-acting oil pressure relay. S2. Calculate the oil pressure at the quick-acting oil pressure relay. Calculate the oil level height of the oil storage cabinet according to the scale of the transformer oil level gauge, and calculate the oil pressure at the quick-acting oil pressure relay of the transformer; S3. Active early warning of transformer internal pressure: compare and analyze the oil pressure obtained through detection and calculation to determine whether the internal pressure of the transformer is normal, and issue an active early warning based on the analysis results.

2. The transformer internal pressure active early warning method according to claim 1 is characterized by: The S1 is specifically: A micro gas pressure sensor (17) is arranged in the upper chamber I (7) of the transformer, an expander (15) and a micro switch (14) connected in sequence are arranged at the center of the lower chamber II (10) of the transformer, a pressure sensor (16) is arranged at the upper end of the expander (15), the upper end of the pressure sensor (16) is connected to the top of the bellows (5) of the upper chamber I (7) of the transformer through a spring (3), and the micro gas pressure sensor (17) and the micro switch (14) are both connected to the transformer The terminal block (11) at the bottom, when the oil pressure inside the transformer increases, the pressure in the corresponding oil chamber (4) increases, the insulating oil compresses the separation bellows (5) of the quick-acting oil pressure relay, the separation bellows transmits the pressure to the spring (3), the pressure of the spring (3) is transmitted to the pressure sensor (16) to produce deformation, and at the same time compresses the gas in the air chamber I (7) and the air chamber II (10), so that the micro gas pressure sensor (17) detects the pressure, and the internal pressure P of the transformer is calculated by detecting the pressure of the spring (3) and the pressure in the air chamber I (7). The internal air pressure P1 of the air chamber I (7) is detected by a micro gas pressure sensor (17). The pressure sensor (16) is subjected to a pressure F through a spring (3). The pressure-bearing area of ​​the top of the bellows (5) is S. The internal oil pressure of the transformer, i.e., the internal pressure P of the oil chamber (4), is:

3. The transformer internal pressure active early warning method according to claim 1 is characterized in that: The S2 is specifically: The transformer oil level gauge is installed at the bottom of one side of the transformer body oil conservator. When the oil level inside the oil conservator is 0, the angle β between the oil level gauge connecting rod and the horizontal line is 0. The connecting rod angle β increases with the increase of the oil level. As the connecting rod angle β increases, the oil level gauge drives the dial pointer to rotate through mechanical gears and magnetic transmission. The angle α between the pointer on the dial and the 0 scale oil level increases accordingly. Then: β=λ×α (2) Where: λ is the proportional coefficient of angle conversion; According to the oil level indication of the oil level gauge, calculate the oil level height H of the main oil storage tank, and according to the trigonometric function, get: H=L×sinβ (3) Where: L is the length of the oil level gauge connecting rod. Substituting formula (2) into formula (3), we get: H=L×sin(λ×α) (4) After calculating the oil level, according to the liquid pressure calculation formula, the pressure P' at the quick-acting oil pressure relay is calculated as: P'=ρ×g×(H+h)=ρ×g×[L×sin(λ×α)+h] (5) Where: ρ is the density of transformer oil, g is the acceleration of gravity, and h is the height from the bottom of the main oil storage cabinet to the quick-acting oil pressure relay; Because transformer oil changes pressure according to temperature, its volume expansion rate α is known. When the temperature changes, the mass m of transformer oil does not change. Therefore, before and after the temperature changes: m=ρ×V=(ρ-Δρ)×[V×(1+α×ΔT)] (6) Where: V is the volume of transformer oil, △T is the temperature difference, △ρ is the density correction; According to formula (6), the density correction value △ρ is: Substituting formula (7) into formula (5), we get:

4. The transformer internal pressure active early warning method according to claim 1 is characterized by: The S3 is specifically: 3.

1. When the internal detection pressure P or calculated pressure P' of the transformer is greater than or equal to the sealing pressure of the pressure relief valve, an early warning message is issued, indicating that the internal pressure of the transformer is abnormal; 3.

2. When the pressure change of the transformer internal detection pressure P per unit time is greater than or equal to 80% of the setting limit of the quick-acting oil pressure relay, an early warning message is issued, indicating that the transformer internal pressure is abnormal; 3.

3. When the deviation between the transformer internal detection pressure P and the transformer internal calculation pressure P' is greater than or equal to 10%, an early warning message is issued, indicating that the transformer internal pressure is abnormal; 3.

4. When the internal detection pressure P of the transformer is greater than or equal to the maximum value of the calculated pressure P' inside the transformer, that is, the maximum pressure value calculated corresponding to the highest oil level of the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value; 3.

5. When the internal detection pressure P of the transformer is less than or equal to the minimum value of the calculated pressure P' inside the transformer, that is, the minimum pressure value calculated corresponding to the lowest oil level in the oil conservator, an early warning message is issued, and the internal pressure of the transformer reaches the alarm boundary value.

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