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The discussions of the single core armored cable

Information Source:Henan Huadong Cable Co., Ltd  Release date:2014-02-11 1 The problem
By test and analysis of field data and the data collected showed that, single core wire armoured cable structure design, material selection and operation rationality problems gradually attracted people's attention. Armoured single core wire armoured cable loss more and more cause for concern, trouble and economic loss to many projects with single core armored cable at. Sensitivity and importance of user attention than thinking cable factory on this issue. The data [1] discusses this problem and gives the laying single core wire armoured cable line. And put forward the single core cable steel wire armored by magnetic separation structure and there is different "strange" products. Should be geared to international standards, to cancel the copper wire magnetic separation structure.
60 time metaphase laying the Shanghai Huangpu River cable, select Italy Pirelli 220kV oil filled lead PE sheath aluminum alloy wire armoured, the non-magnetic armour, eliminate the loss of magnetic wire can increase the transportation capacity. Abroad also has the hard copper alloy wire armoring (the original author think non-magnetic armour is misleading). The late 60's Nanjing and Anqing 110KV oil filled single core cable project envisaged production non-magnetic armour, because no domestic aluminum alloy wire products, use the design of magnetic separation copper wire. In the steel wire armored evenly distributed among 3 to 4 copper wire is a single core cable does not form a closed magnetic circuit. Since then until now domestic super high pressure single core cable used in all magnetic structure of armoured. (this is originated from our country subject to verification - abstractor has).
The article also cited several introduced project in 1987, Guangdong Humen 220KV oil filled lead PE sheathed steel wire armored PLP outer sheath cable. By the Japanese Sumitomo delivery. The phi 8 mm galvanized steel wire 45 root. In order to improve the transport capacity, in the lead set with the PE sheath with 24 flat conductor 240mm2. Return conductor's role is to reduce the metal sleeve to reduce resistance, increase the transmission capacity of sheath loss. The 1989 Xiamen Jimei Gaoqi cross strait submarine cable, 220Kv1 × 630mm2 copper core oil filled lead HDPE protective layer of steel wire armored PLP outer sheath cable. By the French Al Carter delivery. The Φ 7.6mm galvanized steel wire 41 root. In 1998, Beijing Power Supply Bureau laying the cable, 15kV 1 × 300mm2 copper core XLPE lead sheathed steel wire armored PE external protecting layer cable. By the French Al Carter delivery. Armoured with φ 7 mm galvanized steel wire 23 root. Manufacturers that galvanized steel surface, the arrangement is not very tight, steel wire is the outer layer of preservatives (such as Li Qing) filled, will not form a closed magnetic loop, does not produce additional sheath loss.
The structure of domestic single core AC submarine cable wire armoured since the beginning of the 60's has been using magnetic steel structure design. While the single core AC submarine cables all foreign imports of steel wire galvanized steel wire used in the design, manufacturing plant that from the theory and the actual operation of the record can need not take the magnetic isolation design. In order to make the structure and foreign products in China cable is similar, the author's point of view is to abolish the magnetic structure. Not only is the 110kV cable, XLPE cable should be modified accordingly.
The above is the domestic and foreign HV and EHV cables for single core armored structure underwater laying condition. For 35kV and below the national standard cable with copper wire magnetic structure, so each manufacturing plant is the basic standard. The design department and department also choose this kind of cable. The problem is in the.
Zhenhai Refining & Chemical second thermal power station of No. 1 generator and transformer is used in 8.7/10kV1 * 500mm2 YJV32 φ 3.15 galvanized steel wire armoring, magnetic separation and 4 copper wire. Cable burned besides laying of cable, wire is one of the reasons causing the burnt.
A power plant with 1 × 400mm2 YJV32 XLPE cable 15, each with 5 parallel. (don't analyze the selection of cable type is reasonable.) After the trial operation found that current carrying capacity is far less than the current carrying capacity of design. The user is a steel wire armored loss is too large. We propose to do experiment. This paper is aimed at the construction of single core armored cable for load flow test. With the data and the field test data test to speak. From the point of armor material and operation to provide information for future rational design of cable structure.
2 The test and field test data
2.1 experimental and computational data
Simulation of a cable line engineering test. 8.7/15 kV 1 × 400 mm2 YJV32 XLPE insulated single core armored cable. The sample size are shown in table 2-1.
Note: a conductor shielding layer with thickness of 0.8 mm. insulation shielding layer with thickness of 0.6 mm. copper strip thickness 0.2mm. Bag with a thickness of 0.2mm.
The wire diameter φ 2.5mm 4 root diameter wire evenly divided as magnetic isolation.
The air laying, different arrangement download flow test data and relevant parameters are listed in table 2- 2.
Note: * according to the measurement of the surface of different parts, temperature difference.
* * s - between adjacent cable axis distance. De – outer diameter of cable
According to IEC 60287 standard according to the sample size was calculated ampacity of single core armored cable, the calculation results are shown in table 2-3.  
Note: * AC resistance conductor operating temperature of (/m)
* * armouring wire loss (according to the test when shield loss calculated value calculated from).
The plane arrangement, the center of the cable spacing of 2 cable outer diameter (De).
2.2 field data
A project field cable arrangement as shown in figure 2-1. Test data after finishing summary as follows. According to the No. 1 to No. 2 unit current distribution data to calculate the cable core and surface temperature are listed in table 2-4 and table 2-5. The following parameters calculation of the conductor temperature and surface temperature of the:
According to the measured current and projected wire core temperature and surface temperature. The parameter is the parameter YJV32 value of cable (such as AC resistance and thermal resistance) and test parameters (such as wire loss etc.).
Figure 2-1 cable arrangement diagram
Table 2-4 of unit 1 in 31 MW 1800 A
* each line consists of three single core cable in triangular arrangement, there is a gap between each other.
* due to impedance caused by the uneven distribution of current.
* each line consists of three single core cable in triangular arrangement, there is a gap between each other.
* due to impedance caused by the uneven distribution of current.
3.1 load flow decreased
First of single core wire armoured cable at the same temperature and the same environmental conditions why carrying capacity than the armoured cable is much smaller load flow? One of the main reasons is sheathed wire loss too big. Hysteresis and eddy current loss of steel wire in triangle arrangement is more than 3 times the core loss. Planar arrangement is more than 2 times the core loss. Even the separation (cable laying between the center distance is larger than 2 times of the cable diameter of), more than 2 times the wire loss and core loss. Load flow is non steel wire armored ampacity of single core cable 57% (contact triangle arrangement) and 64% (clearance for the 1 outer diameter of cable plane arrangement). Considering the thermal resistance, in cable than non steel wire armored cable with cross section diameter is much larger (about 1.2 times). The air laying its external thermal resistance than the steel wire armored cable with small (about 0.80%). Although the steel wire armored much lining layer resistance, the absolute value of external resistance decreases with the increase of almost offset. So the shield loss plays a role here. This is the main reason for the reduced load flow.
3.2 The armoured loss
Why single core cable steel wire armored loss so big? The loss is mainly due to hysteresis and eddy current loss plays a decisive role. These losses are associated with the strength of the magnetic field, and the magnetic field strength and core current. When the wire single when there is no circulation loss, armored. The cable is equivalent to the infinite long straight wire, electric wire core in current in the cable wire in electric field is far greater than the other adjacent cable current in the wire in the wire, that loss is mainly caused by the cable core current. Three single core triangular arrangement operation for three-phase system and three single core triangular arrangement series running on the Dan Xiang system, according to table 2-2 test data (Dan Xiang) and field measurement data (three-phase) to reflect the current carrying capacity and the two parameters of the temperature of steel wire armored loss both in the triangle array is close. This is just the set of data. To be unable to carry on the three-phase system test conditions. Through the table to calculate the temperature parameter 3-1 can at least show test data of single-phase cable triangular arrangement (ampacity) and three-phase system in the field aligned current measurement mode is similar.
Note: ① test and field cable are triangular arrangement, but the scene is separated by a rubber strips in the triangle.
The calculated value (calculated according to the current and resistance).
In order to facilitate comparison of the equivalent test data of 2-2 has been converted into the ambient temperature of 38.5 ℃ value.
The surface temperature of the triangle cable groups with different parts vary greatly, the data in the table is for reference only.
The 3.3 magnetic isolation is a false concept
Through the experiment and field data show that, single core wire armoured its magnetic structure is not effective. The wire is a magnetic material, copper wire is non-magnetic material, in the conductor with alternating current through the wire, in part because of a copper wire insertion may cause magnetic aberration, but cannot interrupt. Alternating electromagnetic field in the wire due to changes in magnetization always lag behind the strength of the magnetic field (hysteresis), phase ferromagnets repeatedly magnetized magnets in molecular changes continually, molecular vibration intensified, to heat, the temperature increases. The molecular vibration energy is supplied by the magnetic field of current power supply maintenance. In the alternating magnetic field wire also produced should be current, the current in the wire body itself closed form vortex. Because the resistance is very small, the swirl intensity can be large, is the release of large amounts of heat wire. The heat is also due to the magnetic field current power supply to maintain the supply. Through the experiment and field measurement show that the magnetic structure is a false concept. From the quantitative calculation is relatively complex, calculation method of shield loss and core loss equal only to cable interval 10m submarine single core wire armoured cable is proposed in the IEC 60287 standard. In the absence of calculation method through the experiment to solve the best single core armored cable current carrying capacity. For the problem under consideration, using experimental method to solve the problem is to accord with the standard of IEC principle. Fortunately, Shanghai Cable Research Institute in 60's built the cable ampacity test base, now has been converted in accordance with national requirements of the test chamber. There is a set of test equipment load flow. In addition to the general cable, special cable service for testing performance of heat.
Conclusion
Through the above analysis, at least you can achieve two harvest:
1 single core armored cable ampacity is far less than the same section non armoured single core cable, do not press the unarmored cable select load flow (can say traffic load 100% manufacturers to provide all the wrong).
2 steel wire armored loss is far greater than the core loss, magnetic isolation structure is actually a dummy, not work. Magnetic separation is a false concept.
To sum up, the single core armored cable for armored magnetic loss caused to reduce load flow. This is the disadvantage of single core armored cable fatal. But the single core armored cable and it can bear tension and strong external mechanical force, but also an indispensable product. As the rivers and lakes the laying of submarine cables. Therefore, recommended:
1 single core cable non-magnetic armour (such as stainless steel wire, copper alloy or aluminum alloy wire), this is not misleading.
2 must choose the galvanized steel wire and steel wire, coated with anticorrosive layer, wire between the spaced apart from each other. [1] said that foreign manufacturers to magnetic effect. But the author thinks no much difference between the wire and the magnetic effect. You can do an experiment to verify. Comment is not here.
3 in addition to rivers and sea bottom and under great tension of special circumstances, usually not easy to use single core armored cable, such as tunnel, bracket, not withstand external mechanical force and or can be expected is not too big.
In addition, proposed to amend the single core cable standard steel wire armored cables with copper wire magnetic isolation structure is changed into non-magnetic material as armoured wire.
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