A method for calculating the air filling volume of corrugated aluminum sheathed power cable air tightness test

Abstract

The present invention discloses a method for calculating the air filling volume of a corrugated aluminum sheath power cable air tightness test, comprising the following steps: providing a corrugated aluminum sheath power cable, which comprises, from the inside to the outside, a conductor, an inner semi-conductive shield, an insulation, an outer semi-conductive shield, a semi-conductive buffer water-blocking layer, a corrugated aluminum sheath and a non-metallic outer sheath; obtaining the volume V of the internal gap per unit length of the corrugated aluminum sheath 1 , obtain the volume V of the semi-conductive buffer water-blocking layer wrapped per unit length 2 , get the volume V of the insulated wire core per unit length wrapped with insulation 3 , get the volume V of the conductor gap after twisting per unit length 4 ; Calculate the gas volume V of the corrugated aluminum sheathed power cable air tightness test, V = (V 1 ‑V 2 ‑V 3 +V 4 )×l, where V is in L; V 1 、V 2 、V 3 、V 4 The unit is L / km; l is the number of products to be tested, unit is km. The technical problem solved by the present invention is to develop a calculation method that can accurately calculate the capacity of nitrogen filled in the air tightness test of corrugated aluminum sheathed power cable.

Description

Technical Field

[0001] The invention relates to the technical field of cable manufacturing inspection and testing, and in particular to a method for calculating the air filling volume of a corrugated aluminum sheathed power cable air tightness test. Background Art

[0002] The power industry is the most important basic energy industry in the development of the national economy. With the continuous growth of electricity consumption in the whole society, high-voltage and ultra-high-voltage cables are often used in urban underground power transmission grids. Corrugated aluminum sheathed power cables are widely used in high-voltage and ultra-high-voltage cable structures due to their good mechanical properties and bending ability, excellent conductivity and moisture resistance. In addition to carrying the short-circuit current of transmission system failures, the corrugated aluminum sheath also prevents water molecules from entering the cable, reduces the failure rate of the transmission system, and prolongs the service life of the cable. Therefore, an air tightness test is required after the production of the corrugated aluminum sheath is completed to ensure that the corrugated aluminum sheath is continuous and tight. Usually, the air tightness test requires that there is no leakage for 2 hours after filling with nitrogen (N2) at a pressure of 0.40±0.05MPa.

[0003] However, the existing corrugated aluminum sheathed power cable manufacturers cannot accurately calculate the gas filling capacity of the corrugated aluminum sheathed power cable, nor can they determine the volume of nitrogen filled in when conducting air tightness tests. The commonly used method is to first fill a certain amount of nitrogen based on work experience, let it stand until the pressure in each part of the corrugated aluminum sheathed power cable is consistent, and then check whether nitrogen needs to be supplemented or released to achieve the pressure required by the test. Repeated nitrogen replenishment leads to an increase in the test cycle and low efficiency; the release of nitrogen after the pressure is too high causes a waste of nitrogen in the test consumables.

[0004] Therefore, those skilled in the art are committed to developing a calculation method that can accurately calculate the capacity of the corrugated aluminum sheathed power cable to be filled with nitrogen during the air tightness test. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the present invention discloses a method for calculating the inflation volume of a corrugated aluminum sheathed power cable during an air tightness test. The technical problem to be solved is to provide a method for accurately calculating the capacity of nitrogen filled in a corrugated aluminum sheathed power cable during an air tightness test.

[0006] To achieve the above object, the present invention provides a method for calculating the air filling volume of a corrugated aluminum sheathed power cable air tightness test, comprising the following steps:

[0007] 1) A corrugated aluminum sheathed power cable is provided, which comprises, from inside to outside, a conductor (1), an inner semi-conductive shield (2), an insulation (3), an outer semi-conductive shield (4), a semi-conductive buffer water-blocking layer (5), a corrugated aluminum sheath (6) and a non-metallic outer sheath (7);

[0008] 2) Obtaining the volume V1 of the internal gap per unit length of the corrugated aluminum sleeve (6);

[0009] 3) obtaining the volume V2 of the semi-conductive buffer water-blocking layer (5) wrapped per unit length;

[0010] 4) obtaining the volume V3 of the insulating wire core per unit length wrapped with insulation (3);

[0011] 5) obtaining the volume V4 of the gap of the conductor (1) after twisting per unit length;

[0012] 6) Calculate the volume V of the corrugated aluminum sheath (6) for the air tightness test of power cables.

[0013] V=(V1-V2-V3+V4)×l

[0014] Wherein, V is the air tightness test filling capacity of the product to be tested, in L; the units of V1, V2, V3, and V4 are all L / km; l is the number of products to be tested, in km.

[0015] Preferably, the volume V1 of the internal gap per unit length of the corrugated aluminum sleeve (6) is calculated as follows:

[0016]

[0017] in,

[0018] D2 is the base diameter of the corrugated aluminum sleeve, in mm;

[0019] p is the corrugation pitch of the corrugated aluminum sleeve, unit: mm;

[0020] r is the longitudinal curvature radius of the corrugated aluminum sleeve, in mm, which is calculated according to the following formula:

[0021]

[0022] h is the depth of corrugated aluminum sleeve, unit: mm;

[0023] t is the corrugation coefficient of the corrugated aluminum sleeve, which is calculated according to the following formula:

[0024]

[0025] Where, δ is the average thickness of the corrugated aluminum sleeve, unit: mm;

[0026] D3 is the average outer diameter of the corrugated aluminum sleeve, in mm.

[0027] Preferably, the volume V2 of the semi-conductive buffer water-blocking layer (5) wrapped per unit length is calculated as follows:

[0028]

[0029] Wherein, m is the amount of semi-conductive buffer water-blocking tape per unit length, in kg / km;

[0030] ρ is the volume density of the semi-conductive buffer water-blocking tape, unit: g / cm 3 .

[0031] Preferably, the calculation method of the volume V3 of the insulating core per unit length is:

[0032]

[0033] Wherein, D1 is the average outer diameter of the insulated wire core, in mm.

[0034] Preferably, the volume V4 of the gap of the conductor (1) after twisting per unit length is calculated as follows:

[0035]

[0036] Among them, D0 is the average diameter of the conductor, unit is mm; S0 is the actual cross-sectional area of ​​the conductor, unit is mm 2 .

[0037] Preferably, the bulk density ρ of the semiconductive buffer water-blocking tape should be the ratio of weight to volume of the solid part, measured by a buoyancy method solid density tester, and the solution in the tester is anhydrous ethanol.

[0038] The beneficial effects of the present invention are:

[0039] Through the above step-by-step calculation method, the capacity of nitrogen (N2) filled in the corrugated aluminum sheathed power cable during the air tightness test can be accurately calculated, and there is no need to repeatedly replenish nitrogen, which shortens the test cycle and improves the test efficiency. It also avoids the waste of nitrogen in the test consumables caused by the release of excessive pressure of nitrogen (N2), greatly reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the radial structure of the corrugated aluminum sheathed power cable of the present invention;

[0041] Figure 2 This is a schematic diagram of the longitudinal structure of the corrugated aluminum sheathed power cable of the present invention;

[0042] Figure 3 It is a schematic diagram of the local corrugation of the corrugated aluminum sleeve of the present invention.

[0043] In the above figures: 1. conductor; 2. inner semi-conductive shield; 3. insulation; 4. outer semi-conductive shield; 5. semi-conductive buffer water-blocking layer; 6. corrugated aluminum; 7. non-metallic outer sheath. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific manner, and therefore cannot be understood as limiting the present invention. The terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0045] like Figure 1 As shown, the present invention provides a method for calculating the air filling amount of a corrugated aluminum sheathed power cable air tightness test, comprising the following steps:

[0046] 1) A corrugated aluminum sheath power cable is provided, which comprises, from inside to outside, a conductor 1, an inner semi-conductive shield 2, an insulation 3, an outer semi-conductive shield 4, a semi-conductive buffer water-blocking layer 5, a corrugated aluminum sheath 6 and a non-metallic outer sheath 7; the calculation of the filling capacity of the air tightness test of the corrugated aluminum sheath power cable to be tested is to calculate the volume of the internal gap of the corrugated aluminum sheath 6 of the product to be tested, and the principle is to subtract the volume of the solid materials of each internal structural layer from the total volume inside the corrugated aluminum sheath 6 of the product to be tested.

[0047] 2) Obtain the volume V1 of the internal gap of the corrugated aluminum sleeve 6 per unit length,

[0048]

[0049] in,

[0050] D2 is the base diameter of the corrugated aluminum sleeve 6, in mm;

[0051] p is the corrugation pitch of the corrugated aluminum sleeve 6, in mm;

[0052] r is the longitudinal curvature radius of the corrugated aluminum sleeve 6, in mm, which is calculated according to the following formula:

[0053]

[0054] h is the corrugated aluminum sleeve 6 corrugation depth, unit: mm;

[0055] t is the corrugation coefficient of the corrugated aluminum sleeve 6, which is calculated according to the following formula:

[0056]

[0057] Where, δ is the average thickness of the corrugated aluminum sleeve 6, unit: mm;

[0058] D3 is the average outer diameter of the corrugated aluminum sleeve after 6, in mm;

[0059] 3) Obtain the volume V2 of the semi-conductive buffer water-blocking layer wrapped per unit length,

[0060]

[0061] Wherein, m is the amount of semi-conductive buffer water-blocking tape per unit length, in kg / km;

[0062] ρ is the volume density of the semi-conductive buffer water-blocking tape, unit: g / cm 3 ;

[0063] 4) Obtain the volume V3 of the insulating wire core per unit length wrapped with insulation 3,

[0064]

[0065] Wherein, D1 is the average outer diameter of the insulated wire core, in mm;

[0066] 5) Obtain the volume V4 of the gap of conductor 1 after twisting per unit length,

[0067]

[0068] Where D0 is the average diameter of conductor 1, in mm; S0 is the actual cross-sectional area of ​​conductor 1, in mm 2 ;

[0069] 5) Calculate the volume V of the corrugated aluminum sheath 6 power cable air tightness test,

[0070] V=(V1-V2-V3+V4)×l

[0071] Wherein, V is the gas filling capacity of the product to be tested for air tightness test, in L;

[0072] V1 is the volume per unit length of the corrugated aluminum sleeve 6, in L / km;

[0073] V2 is the volume of the wrapped buffer layer per unit length, in L / km;

[0074] V3 is the volume of the insulated core per unit length, in L / km;

[0075] V4 is the volume of the gap between the stranded conductors per unit length, in L / km;

[0076] l is the number of products to be tested, in km.

[0077] In the above step 3), the bulk density ρ of the semi-conductive buffer water-blocking tape should be the ratio of weight to volume of the solid part, measured by a buoyancy method solid density tester, and the solution in the tester is anhydrous ethanol.

[0078] In the above embodiment, through the above step-by-step calculation method, the capacity of the corrugated aluminum sheath 6 power cable filled with nitrogen (N2) can be accurately calculated during the air tightness test, and there is no need to repeatedly replenish nitrogen, which shortens the test cycle and improves the test efficiency. It also avoids the waste of nitrogen in the test consumables caused by the release of excessive pressure of nitrogen (N2), greatly reducing the production cost.

[0079] Specific embodiments are listed below:

[0080] Provide a rated voltage of 64 / 110kV, single core, copper conductor with a nominal cross-sectional area of ​​800㎜ 2 , cross-linked polyethylene insulated corrugated aluminum sheathed polyethylene outer sheathed power cable, expressed as: YJLW0364 / 110kV 1×800, the quantity l is 0.66km, and the amount m of semi-conductive buffer water-blocking tape per unit length is 329.9kg / km.

[0081] The results show that: the diameter D0 of conductor 1 is 34.0㎜, the outer diameter D1 of the insulated core is 71.0㎜, the actual cross-sectional area S0 of conductor 1 is 812.0㎜2, the base circle diameter D2 of the corrugated aluminum sleeve 6 is 81.5㎜, the average outer diameter D3 of the back of the corrugated aluminum sleeve 6 is 94.5㎜, the average thickness of the corrugated aluminum sleeve 6 is 2.0㎜, the rib pitch p of the corrugated aluminum sleeve 6 is 27.5㎜, the rib depth h of the corrugated aluminum sleeve 6 is 4.5㎜, and the bulk density of the semi-conductive buffer water-blocking tape is 1.283g / ㎝3.

[0082] Substitute the known parameters into the formula:

[0083]

[0084] The longitudinal curvature radius r of the corrugated aluminum sleeve 6 is 23.3 mm;

[0085] Substitute the known parameters into the formula:

[0086]

[0087] The corrugation coefficient t is 10.1;

[0088] Substitute the known parameters into the formula:

[0089]

[0090] The volume V1 of the internal gap per unit length of the aluminum sleeve is 6067.1L / km.

[0091] Substitute the known parameters into the formula:

[0092]

[0093] The volume V2 of the semi-conductive buffer water-blocking layer wrapped per unit length is 257.1 L / km.

[0094] Substitute the known parameters into the formula:

[0095]

[0096] The volume of the insulated core per unit length V3 is 3959.2L / km.

[0097] Substitute the known parameters into the formula

[0098]

[0099] The volume V4 of the gap per unit length of the twisted conductor is 95.9L / km.

[0100] Substitute the known parameters into the formula:

[0101] V=(V1-V2-V3+V4)×l

[0102] The air tightness test filling capacity V of the product to be tested is 1284.8L.

[0103] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for calculating the air volume of a corrugated aluminum sheathed power cable air tightness test, characterized in that: The steps include: 1) A corrugated aluminum sheathed power cable is provided, which comprises, from inside to outside, a conductor (1), an inner semi-conductive shield (2), an insulation (3), an outer semi-conductive shield (4), a semi-conductive buffer water-blocking layer (5), a corrugated aluminum sheath (6) and a non-metallic outer sheath (7); 2) Obtaining the volume V1 of the internal gap per unit length of the corrugated aluminum sleeve (6); 3) obtaining the volume V2 of the semi-conductive buffer water-blocking layer (5) wrapped per unit length; 4) obtaining the volume V3 of the insulating wire core per unit length wrapped with insulation (3); 5) obtaining the volume V4 of the gap of the conductor (1) after twisting per unit length; 6) Calculate the volume V of the corrugated aluminum sheath (6) for the air tightness test of power cables. V=(V1-V2-V3+V4)×l Wherein, V is the air tightness test filling capacity of the product to be tested, in L; the units of V1, V2, V3, and V4 are all L / km; l is the number of products to be tested, in km; The volume V1 of the internal gap per unit length of the corrugated aluminum sleeve (6) is calculated as follows: in, D2 is the base diameter of the corrugated aluminum sleeve, in mm; p is the corrugation pitch of the corrugated aluminum sleeve, unit: mm; r is the longitudinal curvature radius of the corrugated aluminum sleeve, in mm, which is calculated according to the following formula: h is the depth of corrugated aluminum sleeve, unit: mm; t is the corrugation coefficient of the corrugated aluminum sleeve, which is calculated according to the following formula: Where, δ is the average thickness of the corrugated aluminum sleeve, unit: mm; D3 is the average outer diameter of the corrugated aluminum sleeve, in mm; The volume V2 of the semi-conductive buffer water-blocking layer (5) wrapped per unit length is calculated as follows: Wherein, m is the amount of semi-conductive buffer water-blocking tape per unit length, in kg / km; ρ is the volume density of the semi-conductive buffer water-blocking tape, unit: g / cm 3 ; The calculation method of the volume V3 of the insulating core per unit length is: Wherein, D1 is the average outer diameter of the insulated wire core, in mm; The volume V4 of the gap of the conductor (1) after twisting per unit length is calculated as follows: Among them, D0 is the average diameter of the conductor, unit is mm; S0 is the actual cross-sectional area of ​​the conductor, unit is mm 2 .

2. The method for calculating the air filling volume of the corrugated aluminum sheathed power cable air tightness test according to claim 1, characterized in that: The bulk density ρ of the semi-conductive buffer water-blocking tape should be the ratio of weight to volume of the solid part, measured by a buoyancy method solid density tester, and the solution in the tester is anhydrous ethanol.

Images