A transformer oil having reduced naphthene content and its preparation method and use

Abstract

This application relates to the field of transformer oil technology, specifically to a transformer oil with reduced cycloalkane content, its preparation method, and its application. The transformer oil contains 50-75 wt% alkanes and 30-50 wt% cycloalkanes. It has a fraction A with a distillation range of 270℃-360℃ and a fraction B with a distillation range above 360℃, wherein the weight ratio of fraction A to fraction B is 35-85:10-60, and the total amount of fraction A and fraction B accounts for more than 90 wt% of the transformer oil's weight. The resulting transformer oil meets the requirements of ASTM D3487 and GB 2536-2011 standards, satisfying both domestic and North American market demands.

Description

Technical Field

[0001] This application relates to the field of transformer oil technology, specifically to a transformer oil with reduced cycloalkane content, its preparation method, and its application. Background Technology

[0002] Transformer oil is a heat-conducting medium used in transformers or similar electrical equipment as an electrical insulation medium and to conduct heat energy of electrical equipment. It plays a role in insulation protection, heat dissipation and cooling, and arc extinguishing. It is one of the important raw materials in the power industry.

[0003] Domestic and international transformer oil standards include IEC 60296, ASTM D3487, BS148, JIS C 2320, AS 1767.1, and GB 2536. Different countries' transformer oil standards are revised or formulated according to their respective national conditions. However, except for the American ASTM D3487, the others are basically modified versions of the International Electrotechnical Commission's IEC 60296 transformer oil standard.

[0004] Because the requirements and testing methods for oil specifications in ASTM D3487 differ significantly from those in IEC 60296, most products on the market that meet the ASTM D3487 standard are naphthenic transformer oils. However, since petroleum resources are non-renewable, naphthenic crude oil accounts for only 2% of total petroleum resources, and some naphthenic resources are of poor quality with polycyclic aromatic hydrocarbon (PCA) content greater than 3%.

[0005] Chinese Patent CN 115247095 A discloses a transformer oil suitable for instrument transformers, comprising hydrorefined base oil, antioxidants, and aromatic compounds. By rationally adjusting the content of each component of the transformer oil, the gas evolution index of the transformer oil can meet the requirements of ASTM D3487 standard. However, the high amount of added aromatic compounds results in a polycyclic aromatic hydrocarbon (PCA) content greater than 3%, which fails to meet the PCA requirements of GB2536-2011 and ASTM D3487. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, this application provides a transformer oil with reduced cycloalkane content, its preparation method and application.

[0007] The inventors have discovered that by adjusting the base oil formulation, and thereby controlling the content of alkanes and cycloalkanes in transformer oil, as well as the total amount and proportion of fraction A (270℃-360℃) and fraction B (boiling range above 360℃), a transformer oil with excellent kinematic viscosity, flash point, and breakdown voltage properties was prepared, while also exhibiting a reduced cycloalkanes content, effectively reducing the transformer oil's dependence on naphthenic base oils. Furthermore, existing transformer oils contain more than 3% polycyclic aromatic hydrocarbons.

[0008] The technical solution of this application is as follows.

[0009] In a first aspect, the present invention provides a transformer oil with a reduced cycloalkane content, wherein the %C of alkanes in the transformer oil is [missing information]. P 50-75%; Cycloalkanes %C N 30-50%; the transformer oil includes fraction A with a distillation range of 270℃-360℃ and fraction B with a distillation range above 360℃; the weight ratio of fraction A to fraction B is 35-85:10-60;

[0010] In some embodiments of this application, the transformer oil contains 50-67 wt% alkanes and 30-45 wt% cycloalkanes.

[0011] In some embodiments of this application, the distillation range of fraction B is above 360°C to about 450°C, preferably above 360°C to about 435°C.

[0012] According to some embodiments of this application, the total amount of fraction A and fraction B accounts for more than 90 wt% of the transformer oil weight. This results in a low content of low-boiling-point components, which is beneficial for improving the flash point and gas evolution performance of the transformer oil. The percentage of the total amount of fraction A and fraction B to the transformer oil weight can be 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, or a range thereof. In some preferred embodiments, the total amount of fraction A and fraction B accounts for 90-99 wt% of the transformer oil weight, preferably 92-98 wt%.

[0013] The fraction with a distillation range of 270℃-360℃ contains 35%-40% cycloalkanes and 60%-63% alkanes; the fraction with a distillation range above 360℃ contains 42%-43% cycloalkanes and 55%-56% alkanes.

[0014] As described in the background section, all transformer oils meeting the ASTM D3487 standard are naphthenic transformer oils. However, naphthenic crude oil accounts for only 2% of total petroleum resources, and some naphthenic resources are of poor quality, resulting in a relative shortage of oils meeting the ASTM D3487 standard in the market. Alkane base oils, on the other hand, do not meet the requirements of the ASTM D3487 standard. Different distillation fractions have different properties. By screening petroleum fractions by temperature and combining them with low-temperature performance, flash point, and kinematic viscosity, transformer oils that meet multiple standards can be obtained, thus achieving a combination of functions.

[0015] According to some embodiments of this application, the aromatic hydrocarbon content in the transformer oil is less than 5 wt%, preferably 1-5 wt%. The aromatic hydrocarbons are mostly derived from anti-gas evolution improvers, with a small portion originating from the distillate itself. By controlling the aromatic hydrocarbon content, the polycyclic aromatic hydrocarbon (PCA) content (mass fraction) is ensured to be less than 3%, thus expanding the applicability of the transformer oil.

[0016] According to some embodiments of this application, the flash point of the transformer oil is higher than 145°C; preferably, the flash point of the transformer oil is between 145°C and 155°C; further, the flash point of the transformer is 148°C, 149°C, 150°C, 151°C, 153°C, or 155°C.

[0017] According to some embodiments of this application, and measured according to GB / T 265, the kinematic viscosity of the transformer oil at 100°C is 3 mm. 2 The kinematic viscosity of the transformer oil at 100°C is 3.0 mm³ / s or less. 2 / s, 2.9mm 2 / s, 2.8mm 2 / s, 2.7mm 2 / s, 2.6mm 2 / s, 2.5mm 2 / s, 2.4mm 2 / s, 2.3mm 2 / s, 2.2mm 2 / s, 2.1mm 2 / s, 2.0mm 2 / s, 1.9mm 2 / s, 1.8mm 2 / s, 1.7mm 2 / s, 1.6mm 2 / s, 1.5mm 2 / s or a range thereof; preferably 2-3mm 2 / s, more preferably 2.2 to 2.7 mm 2 / s.

[0018] According to some embodiments of this application, the kinematic viscosity of the transformer oil at 0°C is 60 mm⁻¹. 2 The kinematic viscosity of the transformer oil at 0°C is 60 mm³ / s or less. 2 / s, 59mm 2 / s, 58mm 2 / s, 57mm 2 / s, 56mm 2 / s, 55mm 2 / s, 54mm 2 / s, 53mm 2 / s, 52mm 2 / s, 51mm 2 / s, 50mm 2 / s, 45mm 2 / s, 40mm 2 / s, 35mm 2 / s, 30mm 2 / s, 25mm 2 / s, 20mm 2 / s, 15mm 2 / s or a range thereof; preferably 40–60 mm 2 / s, more preferably 45-60mm 2 / s.

[0019] According to some embodiments of this application, the kinematic viscosity at 40°C is 10 mm. 2 The kinematic viscosity of the transformer oil at 40°C is below 10 mm² / s. 2 / s, 9mm 2 / s, 8mm 2 / s, 7mm 2 / s, 6mm 2 / s, 5mm 2 / s, 4mm 2 / s, 3mm 2 / s, 2mm 2 / s, 1mm 2 / s or a range thereof; preferably 1 to 10 mm 2 / s, more preferably 5-10mm 2 / s. The viscosity of the transformer oil in this application meets the requirements for medium and low temperatures, and satisfies the application conditions of transformers at medium and low temperatures.

[0020] According to some embodiments of this application, fraction A and fraction B are derived from crude oil and / or petroleum hydrorefining processes.

[0021] According to some embodiments of this application, the transformer oil further includes antioxidants and anti-gas evolution improvers;

[0022] According to some embodiments of this application, the amount of the antioxidant is 0.01-0.30 wt%.

[0023] According to some embodiments of this application, the antioxidant includes phenolic antioxidants, preferably 2,6-di-tert-butyl-p-cresol.

[0024] According to some embodiments of this application, the amount of the anti-gas evolution improver is 0.3-0.6 wt%.

[0025] According to some embodiments of this application, the anti-gas evolution improver includes alkylbenzene and benzyltoluene, preferably alkylbenzene and / or benzyltoluene.

[0026] According to some embodiments of this application, the anti-gas evolution improver is selected from alkylbenzene and / or benzyltoluene, which can ensure that the polycyclic aromatic hydrocarbon (PCA) content (mass fraction) is 2.2-2.7%.

[0027] According to some embodiments of this application, as determined by GB / T 3535, the pour point of the transformer oil is -40℃ to -60℃, and the pour point of the transformer oil is within the range of -40℃, -41℃, -40℃-42℃, -43℃, -44℃-45℃, -46℃, -47℃, -48℃, 49℃, -50℃, -51℃, -52℃, -53℃, -54℃, -55℃, -56℃, -57℃, -58℃, -59℃, -60℃, or a combination thereof; preferably -42℃ to -48℃.

[0028] According to some embodiments of this application, such as those measured according to ASTM D2300, the gas evolution of the transformer oil is no greater than +30 mm. 3 / min, the gas evolution rate of the transformer oil is +30mm 3 / min, +29mm 3 / min

[0029] +28mm 3 / min, +27mm 3 / min, +26mm 3 / min, +25mm 3 / min, +24mm 3 / min, +23mm 3 / min

[0030] +22mm 3 / min, +21mm 3 / min, +20mm 3 / min, +19mm 3 / min, +18mm 3 / min, +17mm 3 / min

[0031] +16mm 3 / min, +15mm 3 / min, +14mm 3 / min, +13mm 3 / min, +12mm 3 / min, +11mm 3 / min

[0032] +10mm 3 / min, +9mm 3 / min, +8mm 3 / min, +7mm 3 / min, +6mm 3 / min, +5mm 3 / min or the range of composition; preferably +10 to +30mm 3 / min, more preferably +20-+30mm 3 / min.

[0033] According to some embodiments of this application, such as those measured according to SH / T 0604, the relative density of the transformer oil at 15°C is not greater than 910, preferably 800-910.

[0034] According to some embodiments of this application, such as those measured according to ASTM D1816, at 60 Hz, with VDE electrodes and a gap of 0.040 inches, the breakdown voltage is above 20 kV, preferably 30-60 kV, more preferably 45-55 kV; at 60 Hz, with VDE electrodes and a gap of 0.080 inches, the breakdown voltage is above 40 kV, preferably 50-80 kV, more preferably 60-80 kV.

[0035] According to some embodiments of this application, such as those measured according to ASTM D1816, at 25°C, with a 1-inch gap between the needle negative electrode and the spherical surface, the breakdown voltage under pulse is above 150kV, preferably 150-200kV.

[0036] A second aspect of this application protects a method for preparing the aforementioned transformer oil, wherein the method comprises: mixing a naphthenic base oil with a distillation range of 280±10℃-360±10℃, an alkyl base oil with a distillation range of 280±10℃-425±10℃, an optional antioxidant, and an optional anti-gas evolution improver.

[0037] According to some embodiments of this application, the cycloalkyl base oil comprises: 0.5-2.5 wt% aromatic hydrocarbons, 30-40 wt% alkanes, and 60-70 wt% cycloalkanes; preferably, the cycloalkyl base oil comprises: 0.5-2 wt% aromatic hydrocarbons, 30-36 wt% alkanes, and 60-66 wt% cycloalkanes; more preferably, the cycloalkyl base oil comprises: 0.5-1.5 wt% aromatic hydrocarbons, 33-36 wt% alkanes, and 62.8-65.8 wt% cycloalkanes.

[0038] According to some embodiments of this application, the alkyl base oil comprises: 0.5-2.5 wt% aromatic hydrocarbons, 45-60 wt% alkanes, and 35-50 wt% cycloalkanes; preferably, the alkyl base oil comprises: 0.5-2 wt% aromatic hydrocarbons, 50-60 wt% alkanes, and 40-50 wt% cycloalkanes; more preferably, the alkyl base oil comprises: 0.5-1.5 wt% aromatic hydrocarbons, 50-56 wt% alkanes, and 42.8-48.8 wt% cycloalkanes.

[0039] According to some embodiments of this application, the anti-gas evolution improver includes alkylbenzene derivatives and benzyltoluene derivatives, preferably alkylbenzene and / or benzyltoluene;

[0040] According to some embodiments of this application, the antioxidant includes phenolic antioxidants, preferably 2,6-di-tert-butyl-p-cresol.

[0041] According to some embodiments of this application, the transformer oil comprises the following raw materials in parts by weight: 70-90 parts of non-cycloalkyl base oil, 5-20 parts of cycloalkyl base oil, 0.05-0.30 parts of antioxidant, and 2-10 parts of anti-gas evolution improver.

[0042] The third aspect of this application protects the use of the aforementioned transformer oil in the field of transformers.

[0043] Beneficial effects of this application

[0044] By screening petroleum fractions by temperature and considering their low-temperature performance, flash point, and kinematic viscosity, transformer oils that meet multiple standards are obtained, achieving a synergistic effect. This solves the problem of naphthenic acid resource scarcity. Furthermore, by adding anti-gas evolution improvers and antioxidants, the transformer oil's polycyclic aromatic hydrocarbon (PCA) content, flash point, gas evolution properties, pour point, and other properties meet the requirements of ASTM D3487 and GB2536-2011 standards, satisfying both domestic and North American market demands. Detailed Implementation

[0045] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0046] Example 1

[0047] This embodiment illustrates a transformer oil with reduced cycloalkane content and its preparation method.

[0048] S1: 798g of crude oil and / or petroleum hydrorefined at 290±10℃-390±10℃ (1.20% aromatic content, 55.2% alkane content, 43.6% cycloalkanes) from Sinopec Gaoqiao and 100g of crude oil and / or petroleum hydrorefined at 280±10℃-360±10℃ (1.20% aromatic content, 35.0% alkane content, 63.8% cycloalkanes) from Sinopec Jingmen Petrochemical were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0049] S2: Add 2.6g of 2,6-di-tert-butyl-p-cresol and 80g of alkylbenzene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 1.

[0050] Example 2

[0051] This embodiment illustrates a transformer oil with reduced cycloalkane content and its preparation method.

[0052] S1: 927g of Sinopec Yanshan crude oil and / or petroleum hydrorefined at 280±10℃-425±10℃ (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) and 50g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined at 280±10℃-360±10℃ (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% cycloalkanes) were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0053] S2: Add 2.6g of 2,6-di-tert-butyl-p-cresol and 20g of benzyltoluene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 2.

[0054] Example 3

[0055] This embodiment illustrates a transformer oil with reduced cycloalkane content and its preparation method.

[0056] S1: 925g of Sinopec Gaoqiao crude oil and / or petroleum hydrorefined at 290±10℃-390±10℃ (1.20% aromatic content, 55.2% alkane content, 43.6% cycloalkanes) and 55g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined at 280±10℃-360±10℃ (1.20% aromatic content, 35.0% alkane content, 63.8% cycloalkanes) were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0057] S2: Add 2.8g of 2,6-di-tert-butyl-p-cresol and 18g of benzyltoluene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 3.

[0058] Example 4

[0059] This embodiment illustrates a transformer oil with reduced cycloalkane content and its preparation method.

[0060] S1: 748g of Sinopec Yanshan crude oil and / or petroleum hydrorefined at 290±10℃-390±10℃ (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) and 150g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined at 280±10℃-360±10℃ (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% cycloalkanes) were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0061] S2: Add 2.8g of 2,6-di-tert-butyl-p-cresol and 100g of alkylbenzene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 4.

[0062] Comparative Example 1

[0063] This comparative example is used to illustrate transformer oil and its preparation method.

[0064] Unlike Example 4, no antioxidant was added; transformer oil sample 5 was obtained.

[0065] Comparative Example 2

[0066] This comparative example is used to illustrate transformer oil and its preparation method.

[0067] Unlike Example 4, no anti-gas evolution improver was added; transformer oil sample 6 was obtained.

[0068] Comparative Example 3

[0069] This comparative example is used to illustrate transformer oil and its preparation method.

[0070] Unlike Example 4, no anti-gas evolution improver or antioxidant was added; transformer oil sample 7 was obtained.

[0071] Comparative Example 4

[0072] This comparative example is used to illustrate transformer oil and its preparation method.

[0073] 898g of Sinopec Yanshan crude oil and / or petroleum hydrorefined alkyl base oil fraction (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) at 290±10℃-390±10℃ was mixed with 2.8g of 2,6-di-tert-butyl-p-cresol and 100g of alkylbenzene as an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 8.

[0074] Comparative Example 5

[0075] This comparative example is used to illustrate transformer oil and its preparation method.

[0076] 979g of Sinopec Gaoqiao crude oil and / or petroleum hydrorefined alkyl base oil fraction (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) at 390±10℃-425±10℃ was mixed with 2.8g of 2,6-di-tert-butyl-p-cresol and 18g of benzyltoluene, an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 9.

[0077] Comparative Example 6

[0078] This comparative example is used to illustrate transformer oil and its preparation method.

[0079] 917g of Sinopec Gaoqiao crude oil and / or petroleum hydrorefined alkyl base oil fraction (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) at 200±10℃-290±10℃ was mixed with 2.6g of 2,6-di-tert-butyl-p-cresol and 80g of alkylbenzene as an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 10.

[0080] Comparative Example 7

[0081] This comparative example is used to illustrate transformer oil and its preparation method.

[0082] 897g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined naphthenic base oil fraction (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% naphthenes) was mixed with 2.8g of 2,6-di-tert-butyl-p-cresol and 100g of alkylbenzene as an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 11.

[0083] Comparative Example 8

[0084] This comparative example is used to illustrate transformer oil and its preparation method.

[0085] 979g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined naphthenic base oil fraction (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% naphthenes) was mixed with 2.8g of 2,6-di-tert-butyl-p-cresol and 18g of benzyltoluene, an anti-gas evolution improver, at 200±10℃-280±10℃. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 12.

[0086] Comparative Example 9

[0087] This comparative example is used to illustrate transformer oil and its preparation method.

[0088] 917g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined naphthenic base oil fraction (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% naphthenes) was mixed with 2.6g of 2,6-di-tert-butyl-p-cresol and 80g of alkylbenzene as an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 13.

[0089] Comparative Example 10

[0090] This comparative example is used to illustrate transformer oil and its preparation method.

[0091] 977g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined naphthenic base oil fraction (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% naphthenes) at 280±10℃-350±10℃ was mixed with 2.6g of 2,6-di-tert-butyl-p-cresol and 20g of benzyltoluene, an anti-gas evolution improver. The mixture was stirred at 40℃ at a rate of 800 rpm until homogeneous, yielding transformer oil sample 14.

[0092] Comparative Example 11

[0093] This comparative example is used to illustrate transformer oil and its preparation method.

[0094] S1: 748g of Sinopec Yanshan crude oil and / or petroleum hydrorefined at 290±10℃-390±10℃ (1.20% aromatic content, 55.2% alkane content, 43.6% cycloalkanes) and 150g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined at 280±10℃-400±10℃ (1.20% aromatic content, 35.0% alkane content, 63.8% cycloalkanes) were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0095] S2: Add 2.8g of 2,6-di-tert-butyl-p-cresol and 100g of alkylbenzene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 15.

[0096] Comparative Example 12

[0097] This comparative example is used to illustrate transformer oil and its preparation method.

[0098] S1: 748g of Sinopec Yanshan crude oil and / or petroleum hydrorefined at 200±10℃-290±10℃ (1.20% aromatic hydrocarbon content, 55.2% alkane content, 43.6% cycloalkanes) and 150g of Sinopec Jingmen Petrochemical crude oil and / or petroleum hydrorefined at 280±10℃-360±10℃ (1.20% aromatic hydrocarbon content, 35.0% alkane content, 63.8% cycloalkanes) were stirred at 30℃ at a rate of 800 rpm until homogeneous to obtain the first mixture;

[0099] S2: Add 2.8g of 2,6-di-tert-butyl-p-cresol and 100g of alkylbenzene, an anti-gas evolution improver, to the first mixture obtained in step S1. Stir at 40°C at a speed of 800 rpm until homogeneous to obtain transformer oil sample 16.

[0100] Implementation Results Example

[0101] I. The performance of the four samples prepared in Examples 1-4 was tested according to the standard. The specific results are shown in Table 1.

[0102] Table 1 Performance analysis of the four samples prepared in Examples 1-4

[0103]

[0104]

[0105]

[0106] 2. The performance of the four samples prepared in Examples 4-7 and Comparative Examples 1-9 was tested according to the standard. The specific results are shown in Table 1.

[0107] Table 2 Comparative analysis of the effects of samples prepared in Examples 4-7 and Comparative Examples 1-9

[0108]

[0109] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A transformer oil with reduced cycloalkane content, characterized in that, The transformer oil contains 50-75 wt% alkanes and 30-50 wt% cycloalkanes. The transformer oil has a fraction A with a distillation range of 270℃-360℃ and a fraction B with a distillation range above 360℃. The weight ratio of fraction A to fraction B is 35-85:10-60, and the total amount of fraction A and fraction B accounts for more than 90 wt% of the weight of the transformer oil, preferably 90-99 wt%, and more preferably 92-98 wt%.

2. The transformer oil according to claim 1, characterized in that, The transformer oil contains 50-67 wt% alkanes and 30-45 wt% cycloalkanes. And / or, the aromatic hydrocarbon content in the transformer oil is less than 5 wt%, preferably 1-5 wt%; And / or, the flash point of the transformer oil is higher than 145°C; preferably, the flash point of the transformer oil is between 145°C and 155°C. And / or, according to GB / T 265, the kinematic viscosity of the transformer oil at 100°C is 3 mm. 2 Below / s, preferably 2-3mm 2 / s, more preferably 2.2 to 2.7 mm 2 / s; kinematic viscosity at 0℃ is 60 mm² / s; 2 Below / s, preferably 40-60mm 2 / s, more preferably 45-60mm 2 / s; kinematic viscosity at 40℃ is 10 mm⁻¹ 2 Below / s, preferably 1 to 10 mm 2 / s, more preferably 5-10mm 2 / s.

3. The transformer oil according to claim 1 or 2, characterized in that, The distillation range of fraction B is from 360°C to about 450°C, preferably from 360°C to about 435°C. And / or, fraction A and fraction B are derived from the hydrorefining process of crude oil and / or petroleum.

4. The transformer oil according to any one of claims 1-3, characterized in that, The transformer oil also includes antioxidants and anti-gas evolution improvers; The amount of the antioxidant is 0.01-0.30 wt%; And / or, the antioxidant includes phenolic antioxidants, preferably 2,6-di-tert-butyl-p-cresol; The amount of the gas evolution resistance improver is 0.3-0.6 wt%; And / or, the anti-gas evolution improver includes alkylbenzene derivatives, benzyltoluene derivatives, preferably alkylbenzene and / or benzyltoluene.

5. The transformer oil according to any one of claims 1-4, characterized in that, As determined according to GB / T 3535, the pour point of the transformer oil is -40°C to -60°C, preferably -42°C to -48°C; And / or, as determined according to ASTM D2300, the gas evolution of the transformer oil is not greater than +30 mm. 3 / min, preferably 10-30mm 3 / min, more preferably 20-30mm 3 / min. And / or, as determined according to SH / T 0604, the relative density of the transformer oil at 15°C is not greater than 910, preferably 800-910.

6. The transformer oil according to any one of claims 1-5, characterized in that, According to ASTM D1816, at 60 Hz, with VDE electrodes and a gap of 0.040 inches, the breakdown voltage is above 20 kV, preferably 30-60 kV, and more preferably 45-55 kV; at 60 Hz, with VDE electrodes and a gap of 0.080 inches, the breakdown voltage is above 40 kV, preferably 50-80 kV, and more preferably 60-80 kV. And / or, as determined according to ASTM D1816, at 25°C, with a 1-inch gap between the needle negative electrode and the sphere, the breakdown voltage under pulse is above 150kV, preferably 150-200kV.

7. A method for preparing transformer oil according to any one of claims 1-6, wherein, The preparation method includes: mixing a naphthenic base oil with a distillation range of 280±10℃-360±10℃, an alkyl base oil with a distillation range of 280±10℃-425±10℃, an optional antioxidant, and an optional anti-gas evolution improver.

8. The preparation method according to claim 7, characterized in that, The cycloalkyl base oil comprises: 0.5-2.5 wt% aromatic hydrocarbons, 30-40 wt% alkanes, and 60-70 wt% cycloalkanes; preferably, the cycloalkyl base oil comprises: 0.5-2 wt% aromatic hydrocarbons, 30-36 wt% alkanes, and 60-66 wt% cycloalkanes; more preferably, the cycloalkyl base oil comprises: 0.5-1.5 wt% aromatic hydrocarbons, 33-36 wt% alkanes, and 62.8-65.8 wt% cycloalkanes. And / or, the alkyl base oil comprises: 0.5-2.5 wt% aromatic hydrocarbons, 45-60 wt% alkanes and 35-50 wt% cycloalkanes; preferably, the alkyl base oil comprises: 0.5-2 wt% aromatic hydrocarbons, 50-60 wt% alkanes and 40-50 wt% cycloalkanes; more preferably, the alkyl base oil comprises: 0.5-1.5 wt% aromatic hydrocarbons, 50-56 wt% alkanes and 42.8-48.8 wt% cycloalkanes; And / or, the anti-gas evolution improver includes alkylbenzene derivatives, benzyltoluene derivatives, preferably alkylbenzene and / or benzyltoluene; And / or, the antioxidant includes phenolic antioxidants, preferably 2,6-di-tert-butyl-p-cresol.

9. The preparation method according to claim 7 or 8, characterized in that, 70-90 parts by weight of alkyl base oil, 5-20 parts by weight of naphthenic base oil, 0.05-0.30 parts by weight of antioxidant, and 2-10 parts by weight of anti-gas evolution improver.

10. The application of the transformer oil according to any one of claims 1-9 in the field of transformers.

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