結合行業規范（GB/T 12706、IEC 60502等）及動態內容，電力電纜相關知識解析如下：

　　Based on industry standards (GB/T 12706, IEC 60502, etc.) and the latest technological developments, the analysis of knowledge related to power cables is as follows:

　　一、電力電纜基礎1.電纜與架空線對比電力線路按結構分為架空線路和電纜線路兩種，架空線路的導線通過大氣、絕緣子實現電氣絕緣隔離，大地為地電極。電纜線路的導線通過絕緣材料隔離后被封閉在接地的金屬屏蔽內部。特性架空線路電纜線路絕緣介質大氣+絕緣子固態絕緣材料屏蔽方式無屏蔽，大地作地電極金屬屏蔽層接地敷設環境暴露于大氣埋地/管廊/隧道電壓等級全范圍（220V~1000kV）中高壓為主（1kV~500kV）補充說明：電纜的金屬屏蔽層兼具電場均化與短路電流通道功能，是保障的核心設計。

　　1、 Power cable foundation 1. Comparison between cables and overhead lines Power lines are divided into two types according to their structure: overhead lines and cable lines. The wires of overhead lines are electrically insulated and isolated through the atmosphere and insulators, and the earth is the ground electrode. The wires of the cable line are isolated by insulation material and enclosed inside a grounded metal shield. Characteristics: Overhead power lines, cable lines, insulation media, atmosphere+insulator, solid insulation material, shielding method, unshielded, earth electrode, metal shielding layer, grounding, laying environment exposed to atmosphere, buried/pipe gallery/tunnel voltage level, full range (220V~1000kV), mainly medium high voltage (1kV~500kV). Additional explanation: The metal shielding layer of the cable has both electric field homogenization and short-circuit current channel functions, which is the core design to ensure safety.

　　2.電壓等級與標識我國電壓等級劃分為：220/380V、3kV、6kV、10kV、35kV、110kV、220kV、330kV、500kV、750kV、1000kV等，并劃分為輸電電壓與配電電壓兩類。

　　2. Voltage levels and identification: China's voltage levels are divided into two categories: 220/380V, 3kV, 6kV, 10kV, 35kV, 110kV, 220kV, 330kV, 500kV, 750kV, 1000kV, etc., and are divided into transmission voltage and distribution voltage.  ? ??

　　我國電纜產品的電壓等級包括：0.6/1、1/1、3.6/6、6/6、6/10、8.7/10、8.7/15、12/15、12/20、18/20、18/30、21/35、26/35、36/63、48/63、64/110、127/220、190/330、290/500kV共19種。標準電壓（U?/U）：U，導體對地額定電壓（如10kV系統U?=8.7kV）；U，系統線電壓（如10kV）。電纜額定電壓(U0/U)的選定是由系統的不同接地方式決定的，接地方式影響：接地類型適用U?/U特點直接接地64/110kV及以上單相短路電流大小電阻接地12/20kV~48/63kV限制過電壓消弧線圈接地3.6/6kV~18/30kV補償電容電流不接地≤8.7/10kV短時允許帶故障運行3.導體規格電纜導體截面積有：1.5、2.5、4、6、10、16、25、35、50、70、95、120、150、185、240、300、400、500、630、800、1000、1200、1400、1600、1800、2000、2500mm2，共27種。

　　The voltage levels of cable products in China include: 0.6/1, 1/1, 3.6/6, 6/6, 6/10, 8.7/10, 8.7/15, 12/15, 12/20, 18/20, 18/30, 21/35, 26/35, 36/63, 48/63, 64/110, 127/220, 190/330, and 290/500kV, totaling 19 types. Standard voltage (U ?/U): U, rated voltage of the conductor to ground (such as U ?=8.7kV for a 10kV system); U， System line voltage (such as 10kV). The selection of cable rated voltage (U0/U) is determined by different grounding methods of the system, and the grounding method affects: the grounding type is suitable for U ?/U characteristics, directly grounded 64/110kV and above single-phase short-circuit current size, resistance grounded 12/20kV~48/63kV, overvoltage arc suppression coil grounded 3.6/6kV~18/30kV, compensation capacitor current not grounded ≤ 8.7/10kV, short-term fault operation is allowed. 3. Conductor specifications: Cable conductor cross-sectional area includes: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630, 800, 1000, 1200, 1400, 1600, 1800. There are a total of 27 types, including 2000 and 2500mm2.

　　截面積分級常用范圍35~240mm?（占90%用量），大電流應用≥1000mm?需采用分割導體結構減少集膚效應。絞合結構，如下：二、電纜結構深度解析1.分層功能與材料電纜的基本結構，主要包括如下：結構層功能關鍵材料技術要點導體層傳輸電能退火銅/鋁緊壓系數≥0.9絕緣層電氣隔離XLPE/EPR/油浸紙厚度∝U?等級屏蔽層電場均化半導電交聯料界面光滑度≤5μm護套層機械防護PE/PVC/無鹵阻燃料阻燃等級IEC 60332?電纜導體芯數有：單芯、兩芯、三芯、四芯、五芯，計5種。單芯和三芯電纜基本結構，圖示如下：

　　The commonly used range for cross-sectional area classification is 35-240mm ? (accounting for 90% of usage), and for high current applications ≥ 1000mm ?, a segmented conductor structure should be used to reduce skin effect. Twisted structure, as follows: 2. Deep analysis of cable structure: 1. Layered function and material. The basic structure of the cable mainly includes the following: structural layer, functional key materials, technical points, conductor layer, transmission of electrical energy, annealing, copper/aluminum compression coefficient ≥ 0.9, insulation layer, electrical isolation, XLPE/EPR/oil immersed paper thickness ∝ U ? level, shielding layer, electric field homogenization, semiconductive cross-linking material, interface smoothness ≤ 5 μ m, sheath layer, mechanical protection, PE/PVC/halogen-free flame retardant grade, IEC 60332. The number of cable conductors includes: single core, two core, three core, four core, five core, totaling five types. The basic structure of single core and three core cables is shown in the diagram below:

　　2.絕緣材料電纜絕緣層的作用是，將線芯與大地以及不同相的線芯間在電氣上彼此隔離，從而保證電能輸送。從1kV到500 kV的各種電力電纜中，交聯聚乙烯是當前應用廣的一種絕緣材料，電纜主要絕緣介質的型式結構：橡膠絕緣乙丙橡膠電纜使用電壓已達150kV。聚氯乙烯絕緣介損大，含氯，運行溫度低，一般只用于6kv及以下電壓等級，將被淘汰。聚乙烯絕緣熔融溫度低(70℃)，工作電壓達500kV。交聯聚乙烯通過化學或物理方法將聚乙烯分子鏈間相互交聯。運行溫度可達90℃，短路時導電線芯允許的溫度可達250℃。極大地提高了電纜的載流量和短路容量。其工作電壓達500kV。?電纜絕緣層的厚度大小，主要與電纜電壓U0的等級有關，詳見下圖：3.電纜保護層電纜保護層的質量好壞，對電纜的使用壽命有很大影響。保護層按加強層、鎧裝層和外被層結構順序，以兩個阿拉伯數字表示，每一個數字表示所采用的主要材料。內護層更是重要的保護，其代號如下表：

　　2. The function of the insulation layer of the insulation material cable is to electrically isolate the wire core from the ground and the wire cores of different phases, thereby ensuring the transmission of electrical energy. Among various power cables ranging from 1kV to 500 kV, cross-linked polyethylene is currently the most widely used insulation material. The main insulation medium structure of the cable is rubber insulated ethylene propylene rubber cable, with a maximum operating voltage of 150kV. Polyvinyl chloride insulation has high dielectric loss, chlorine content, low operating temperature, and is generally only used for voltage levels of 6kV and below, and will be phased out. Polyethylene insulation has a low melting temperature (70 ℃) and a maximum operating voltage of 500kV. Cross linked polyethylene is crosslinked between polyethylene molecular chains through chemical or physical methods. The maximum operating temperature can reach 90 ℃, and the maximum temperature allowed for the conductive core during short circuit can reach 250 ℃. Greatly improves the safety current carrying capacity and short-circuit capacity of the cable. Its maximum working voltage reaches 500kV. The thickness of the cable insulation layer is mainly related to the level of cable voltage U0, as shown in the following figure: 3. The quality of the cable protection layer has a great impact on the service life of the cable. The protective layer is represented by two Arabic numerals in the order of reinforcement layer, armor layer, and outer layer structure, with each numeral indicating the main material used. The inner protective layer is even more important for protection, and its code is shown in the following table:

　　4.屏蔽層電纜屏蔽層，實質上是一種改善電場分布的措施。沒有金屬護套的擠包絕緣電纜，除半導電屏蔽層外，還要增加用銅帶或銅絲繞包的金屬屏蔽層，這個金屬屏蔽層的作用，在正常運行時通過電容電流;當系統發生短路時，作為短路電流的通道，同時也起到屏蔽電場的作用。三層共擠工藝：導體屏蔽+絕緣+絕緣屏蔽同步擠出，界面缺陷。金屬屏蔽類型：銅帶繞包厚度≥0.1mm銅絲編織截面≥25mm?（滿足短路熱穩定）三、電纜附件技術電纜附件，主要包括終端頭與中間接頭。終端頭是將電纜與其他電氣設備連接的部件；中間接頭是將兩根電纜連接起來的部件。良好的電纜附件，線芯連接主要是聯接電阻小而且聯接穩定，能經受起故障電流的沖擊；長期運行后其接觸電阻不應大于電纜線芯本體同長度電阻的1.2倍。電纜附件的絕緣性能應不低于電纜本體，所用絕緣材料的介質損耗要低。電纜附件的種類繁多，具有不同類型的特點及局限性，一般不能相互取代。

　　4. The shielding layer of a cable is essentially a measure to improve the distribution of electric fields. For extruded insulated cables without a metal sheath, in addition to the non-conductive shielding layer, a metal shielding layer wrapped with copper tape or wire should be added. The function of this metal shielding layer is to pass capacitive current during normal operation; When a short circuit occurs in the system, it serves as a channel for short-circuit current and also shields the electric field. Three layer co extrusion process: simultaneous extrusion of conductor shielding, insulation, and insulation shielding to eliminate interface defects. Metal shielding type: Copper tape wrapping thickness ≥ 0.1mm, copper wire weaving cross-section ≥ 25mm ? (meeting short-circuit thermal stability). 3. Cable accessory technology: Cable accessories, mainly including terminal heads and intermediate joints. Terminal head is a component that connects cables with other electrical equipment; The intermediate joint is a component that connects two cables together. A good cable accessory, the core connection is mainly characterized by low connection resistance and stable connection, which can withstand the impact of fault current; After long-term operation, its contact resistance should not exceed 1.2 times the resistance of the same length of the cable core body. The insulation performance of cable accessories should not be lower than that of the cable body, and the dielectric loss of the insulation material used should be low. There are various types of cable accessories with different characteristics and limitations, and they generally cannot be replaced by each other.

　　2.高壓終端解析?瓷套式戶外電纜終端主要由接線柱、應力錐、應力錐罩、瓷套和尾管等零件組成，應力錐采用橡膠材料橡膠注橡成型，瓷套采用高強度、大小傘裙結構，外形呈錐形，具有很好的防污閃特性。內部采用彈簧錐托定位結構，使應力錐和硅油隔離開，克服了應力錐由于材料老化帶來的彈性松弛、應力錐與電纜外半導電層接觸不良等弊病，提高了應力錐壽命。?復合管套式戶外電纜終端外絕緣由環氧玻璃纖維管及硅橡膠雨裙組成的復合套管，內部結構與瓷套式終端相近，具有瓷套式終端的全部優點，同時具有優良的防爆性能，重量輕，便于裝卸運輸，極利于安裝操作。

　　2. Analysis of High Voltage Terminals ? Ceramic sleeve outdoor cable terminals are mainly composed of terminal posts, stress cones, stress cone covers, ceramic sleeves, and tailpipes. The stress cones are made of rubber material and molded by rubber injection molding, while the ceramic sleeves are made of high-strength, large-sized umbrella skirts with a conical shape and excellent anti pollution flashover characteristics. The internal use of a spring cone support positioning structure separates the stress cone from the silicone oil, overcoming the drawbacks of elastic relaxation caused by material aging and poor contact between the stress cone and the outer semiconductive layer of the cable, and improving the service life of the stress cone. The external insulation of the composite sleeve outdoor cable terminal is composed of epoxy glass fiber tube and silicone rubber rain skirt composite sleeve. The internal structure is similar to that of the porcelain sleeve terminal, and it has all the advantages of the porcelain sleeve terminal. At the same time, it has excellent explosion-proof performance, light weight, easy loading and unloading transportation, and is extremely conducive to installation and operation.

　　?GIS電纜終端分插拔式與裝配式，兩者在頂部密封處理與尾管結構有所不同，其他主要結構一致；由于GIS是在全封閉的環境下運行，可以免受大氣條件與污穢的影響，加上SF6氣體的良好絕緣特性，所以GIS的外絕緣采用環氧樹脂套管，內絕緣采用應力錐加彈簧錐托頂緊結構，且為全干式，無需加任何絕緣澆注劑，杜絕了運行中漏油現象。?整體預制式電纜終端（柔性干式戶外終端）在工廠整體預制成型，內部復合了半導電硅橡膠應力錐，與瓷套式、復合套管式相比，結構大大簡化，安裝時只需按要求處理好電纜本體后，將終端主體套入電纜端頭位置即可，安裝極為方便，可傾斜安裝在架空線塔上，且具有無油、防爆、重量輕等特點。?高壓電纜絕緣接頭與直通接頭插入式裝配型絕緣接頭，接頭主體主絕緣為高性能絕緣樹脂，采用真空澆注成型工藝與金屬保護殼成型為一個整體，連接金具為插拔式免模壓結構，安裝極為方便。?高壓電纜分支接頭整體插拔式高壓分支接頭，分支主體是由熱固性樹脂或絕緣橡膠真空注射而成的一整體實心模件，無需添加絕緣澆注劑或絕緣氣體，主體外殼為金屬構件，防水，防潮，耐機械應力，安裝為全插拔式，直接將各相電纜插入分支主體即可，可埋于地下，也可安裝在電纜溝或電纜井內。

　　GIS cable terminals are divided into plug-in and assembled types, with differences in top sealing treatment and tailpipe structure, while other main structures are the same; Due to the fact that GIS operates in a fully enclosed environment, it can be protected from atmospheric conditions and pollution. In addition, SF6 gas has good insulation properties. Therefore, the external insulation of GIS adopts epoxy resin sleeves, and the internal insulation adopts a stress cone and spring cone support structure, which is fully dry and does not require any insulation casting agent, eliminating oil leakage during operation. ? The overall prefabricated cable terminal (flexible dry-type outdoor terminal) is prefabricated and formed in the factory as a whole, with a semi conductive silicone rubber stress cone composite inside. Compared with the porcelain sleeve type and composite sleeve type, the structure is greatly simplified. When installing, only the cable body needs to be processed according to the requirements, and the terminal body can be inserted into the cable end position. The installation is extremely convenient, and it can be installed at an angle on the overhead line tower, and has the characteristics of oil-free, explosion-proof, and lightweight. High voltage cable insulation joints and straight through joints are plug-in assembly type insulation joints. The main insulation of the joint body is high-performance insulation resin, which is formed by vacuum casting technology and metal protective shell as a whole. The connecting fittings are plug-in and non molded structures, making installation extremely convenient. High voltage cable branch joint integral plug-in type high voltage branch joint, the branch body is a solid module made of thermosetting resin or insulating rubber vacuum injection, without the need to add insulation casting agent or insulation gas. The main body shell is a metal component, waterproof, moisture-proof, and resistant to mechanical stress. It is installed as a fully plug-in type, and the cables of each phase can be directly inserted into the branch body. It can be buried underground or installed in cable trenches or cable wells.

　　四、電纜試驗技術1.試驗分類標準試驗類型執行主體依據標準核心項目例行試驗制造廠GB/T 3048局部放電、耐壓交接試驗安裝單位DL/T 596交流耐壓、護層測試狀態檢修試驗運維單位Q/GDW 11316紅外測溫、介質損耗2.關鍵試驗方法局部放電檢測脈沖電流法，靈敏度0.1pC。高頻CT法，抗干擾能力強。護層故障定位跨步電壓法，定位精度±0.5m。電流脈沖法，適用長距離電纜。警示：XLPE電纜禁用直流耐壓，殘余電荷可導致運行擊穿（CIGRE 21-03報告證實）。

　　4、 Cable testing technology 1. Test classification standard Test type Execution subject according to standard Core project Routine test Manufacturing plant GB/T 3048 Partial discharge, withstand voltage handover test Installation unit DL/T 596 AC withstand voltage, protective layer test status Maintenance test Operation and maintenance unit Q/GDW 11316 Infrared temperature measurement, dielectric loss 2. Key test method Partial discharge detection Pulse current method, sensitivity 0.1pC. High frequency CT method, strong anti-interference ability. Step voltage method for fault location of protective layer, with a positioning accuracy of ± 0.5m. Current pulse method, suitable for long-distance cables. Warning: XLPE cables are prohibited from DC withstand voltage, as residual charges can cause operational breakdown (confirmed by CIGRE 21-03 report).

　　3.電纜試驗方法介紹

　　3. Introduction to Cable Testing Methods

　　（1）絕緣電阻試驗在進行電纜的絕緣電阻測量時需要對電纜的外皮以及芯線之間或者外皮之間或芯線之間的絕緣電阻進行測量。測量絕緣電阻的基本原理和普通電阻的測量相似，也是在試品的兩端加上一個較為穩定的直流電壓，然后通過測量儀器將試品過的電流大小和時間的關系表示出來，從而經過換算可以得到電纜試樣的絕緣電阻隨時間變化的曲線，在曲線上可以得出某個特定時間的絕緣電阻值。對于容量比較大的電纜來說，通常情況下吸收比的概念更能說明問題，因此用它來代替絕緣電阻測量的結果。在工程實際測量之中，通常用兆歐表作為測量設備。?主絕緣絕緣電阻測量：?主絕緣絕緣電阻值參考標準：?外護套絕緣電阻測量：試驗目的是檢測電纜在救設后或運行中外護套是否損傷或受潮。外護套破損的原因有:敷設過程中受拉力過大或彎曲過度;敷設或運行中由于施工和交通運輸等直接外力作用;終端/中間接頭受內部應力、自然拉力、電動力作用;白蟻吞噬、化學物質腐蝕等。測量方法:三芯電纜三相共用外護套，只進行一次測量;單芯電纜分別在每一相測量，非被試相及金屬線芯(導體)接地。采用500V兆歐表，大容量數字兆歐表(如:短路電流>3mA)GB50150-2006、Q/CSG10007-2004要求外護套絕緣電阻值不低于0.5M/km。注意問題：兆歐表“L”端引線和“E”端引線應具有可靠的絕緣。測量前后均應對電纜金屬護層充分放電，時間約2-3分鐘。若用手搖式兆歐表，未斷開高壓引線前，不得停止搖動手柄。電纜不接試驗設備的另一端應派人看守，不準人靠近與接觸。

　　(1) When conducting insulation resistance tests on cables, it is necessary to measure the insulation resistance between the outer sheath and core wires, or between the outer sheath and core wires. The basic principle of measuring insulation resistance is similar to that of measuring ordinary resistance. It is to apply a relatively stable DC voltage at both ends of the test sample, and then use a measuring instrument to represent the relationship between the current flowing on the test sample and time. After conversion, the curve of the insulation resistance of the cable sample over time can be obtained, and the insulation resistance value at a specific time can be obtained on the curve. For cables with relatively large capacity, the concept of absorption ratio is usually more indicative, so it is used to replace the results of insulation resistance measurement. In practical engineering measurement, a megohmmeter is usually used as a measuring device. ? Measurement of main insulation resistance: ? Reference standard for main insulation resistance value: ? Measurement of outer sheath insulation resistance: The purpose of the test is to detect whether the outer sheath of the cable is damaged or damp after rescue or operation. The reasons for damage to the outer sheath include: excessive tension or bending during installation; Due to direct external forces such as construction and transportation during installation or operation; The terminal/intermediate joint is subjected to internal stress, natural tension, and electric force; Termite ingestion, chemical corrosion, etc. Measurement method: Three core cable with three-phase shared outer sheath, only one measurement is conducted; Single core cables are measured separately at each phase, with the non tested phase and metal core (conductor) grounded. Using a 500V megohmmeter, it is recommended to use a high-capacity digital megohmmeter (such as short-circuit current>3mA). GB50150-2006 and Q/CSG10007-2004 require the outer sheath insulation resistance value to be no less than 0.5m/km. Attention: The "L" terminal lead and "E" terminal lead of the megohmmeter should have reliable insulation. Before and after measurement, the metal protective layer of the cable should be fully discharged for about 2-3 minutes. If using a hand cranked megohmmeter, do not stop shaking the handle until the high voltage lead is disconnected. The other end of the cable that is not connected to the testing equipment should be guarded by someone, and no one is allowed to approach or come into contact with it.

　　（2）泄漏電流試驗泄漏電流試驗的基本原理是通過測量直流電壓作用下電纜試品中流過的電流大小發現電纜中存在的絕緣缺陷問題。一般情況下，電纜絕緣的直流耐壓試驗和泄漏電流試驗是同時開展的，在泄漏電流試驗中需要在試品的高壓側安裝適當的微安表。該試驗和絕緣電阻試驗的基本原理幾乎完全相同，所不同的就是該試驗中用高壓整流裝置供作為直流電源，試驗中指示電流的裝置是微安表。絕緣是否良好的指標是依據微安表顯示的泄漏電流來反映的。

　　(2) The basic principle of leakage current test is to detect insulation defects in the cable by measuring the current flowing through the cable sample under the action of DC voltage. In general, the DC withstand voltage test and leakage current test of cable insulation are carried out simultaneously. In the leakage current test, an appropriate microampere meter needs to be installed on the high-voltage side of the test sample. The basic principle of this test is almost identical to that of the insulation resistance test, except that a high-voltage rectifier device is used as the DC power source in this test, and a microampere meter is used to indicate the current in the test. The indicator of good insulation is reflected by the leakage current displayed on the microampere meter.

　　（3）直流耐壓試驗直流耐壓試驗是傳統的檢測直流電纜絕緣缺陷的重要方法，其基本原理是將直流電壓施加在電纜的主絕緣上，這個直流電壓要求比電纜的正常工作電壓高，將這個電壓保持一段時間并且電壓值盡量恒定，如果被試電纜試樣能在這段時間經受這樣高的直流電壓而不出現擊穿的現象，則可以判定其符合要求，這種試驗能夠發現絕緣嚴重的缺陷，從而及時采取措施而避免事故的發生。直流耐壓試驗電路原理接線圖，如下圖：交聯聚乙烯絕緣電纜電性能優良，已成為紙絕緣電纜的替代品。按高壓試驗的通用原則，被試品上所施加的試驗電壓場強應模擬高壓電器的運行狀況。這對檢驗交聯聚乙烯絕緣電纜效果不明顯，而且還可能產生負作用。如在電纜附件內，在交流電壓下，絕緣機械損傷等缺陷處易發生擊穿，在直流電壓下則不會。直流耐壓試驗模擬高壓交聯電纜的運行工況，其試驗效果差，并且有一定的危害性。直流耐壓試驗不能有效地發現高壓交聯聚乙烯主絕緣電纜的缺陷，因此不宜用于測試；交流耐壓試驗是檢驗交聯電纜絕緣質量的有效手段。準確有效的掌握電纜各部位的運行狀況有利于提高電纜的運行，減少電纜在運行中的故障。

　　(3) DC withstand voltage test is an important traditional method for detecting insulation defects in DC cables. Its basic principle is to first apply a DC voltage to the main insulation of the cable, which is required to be higher than the normal operating voltage of the cable. The voltage should be maintained for a period of time and kept as constant as possible. If the tested cable sample can withstand such high DC voltage during this period without breakdown, it can be judged to meet the requirements. This test can detect serious insulation defects and take timely measures to avoid accidents. The schematic diagram of the DC withstand voltage test circuit is as follows: Cross linked polyethylene insulated cables have excellent electrical performance and have become a substitute for paper insulated cables. According to the general principles of high-voltage testing, the test voltage field strength applied to the test object should simulate the operating conditions of high-voltage electrical appliances. This is not very effective in testing cross-linked polyethylene insulated cables and may also have negative effects. If in cable accessories, insulation mechanical damage and other defects are most prone to breakdown under AC voltage, but not under DC voltage. The DC withstand voltage test simulates the operating conditions of high-voltage cross-linked cables, but its test effect is poor and has certain hazards. The DC withstand voltage test cannot effectively detect defects in high-voltage cross-linked polyethylene main insulated cables, so it is not suitable for testing; The AC withstand voltage test is an effective means of inspecting the insulation quality of cross-linked cables. Accurately and effectively understanding the operating conditions of various parts of the cable is beneficial for improving the safe operation of the cable and reducing cable failures during operation.

　　（4）交流耐壓試驗下圖為交流耐壓試驗的原理圖。該試驗通過檢測在交流高壓下試品的絕緣性能發現其中存在的缺陷和問題。規定如果被試電纜能夠承受工頻試驗電壓一分鐘而不發生擊穿以及絕緣閃絡或者其他異常問題，則可以判斷該電纜絕緣良好。圖中R1的作用是限制被試電纜放電時變壓器的短路電流，使之低于允許值，并且高壓繞組的電壓梯度需低于危險值;R2的作用是限制球隙放電的電流大小;調壓變壓器的作用是對試驗電壓的幅值大小以及電壓上升和下降的速度等進行調節;試驗變壓器的選擇方面可以使用單臺或者串級的試驗變壓器，具體依照試驗具體情況而定。?主絕緣交流耐壓試驗典型缺陷:?

　　(4) The schematic diagram of the AC withstand voltage test is shown below. This experiment discovered defects and issues in the insulation performance of the test sample under high AC voltage. According to national regulations, if the tested cable can withstand the power frequency test voltage for one minute without breakdown, insulation flashover or other abnormal problems, it can be judged that the cable has good insulation. The function of R1 in the figure is to limit the short-circuit current of the transformer during the discharge of the tested cable, so that it is lower than the allowable value, and the voltage gradient of the high-voltage winding needs to be lower than the dangerous value; The function of R2 is to limit the current size of the ball gap discharge; The function of a voltage regulating transformer is to adjust the amplitude of the test voltage and the speed of voltage rise and fall; The selection of test transformers can be either single or series, depending on the specific test situation.? Typical defects of main insulation AC withstand voltage test:?

　　（5）介質損耗試驗介質損耗角正切試驗是檢測絕緣缺陷的有效方法。在試驗時，通過在絕緣上施加交流電壓可以檢測絕緣的損耗大小，如果電纜的絕緣出現老化變質或受潮等現象時，通過檢測電纜電流有功分量變大的現象可以判斷絕緣損耗的增大。同時，因為損耗和有功電流以及電纜絕緣的體積均有直接關系，因此不同大小的絕緣其損耗也不同，為了排除該因素的影響，在實際中一般采用另一個指標tgδ 來衡量。tgδ 的大小可以用很多種方法來進行測量，其中傳統上一般采用西林電橋法即平衡測量法來檢測介質損耗角正切的大小。由于技術不斷發展，出現了更為方便的測量方法，例如角差法就是其中的一種，它用直接測量的方式判斷電壓電流之間的夾角，從而方便的得到介質損耗角正切的大小，正因為如此，角差法在當前的介質損耗角正切的試驗中得到了越來越廣泛的應用。

　　(5) Dielectric loss test and dielectric loss tangent test are effective methods for detecting insulation defects. During the experiment, the magnitude of insulation loss can be detected by applying AC voltage to the insulation. If the insulation of the cable deteriorates or becomes damp, the increase in insulation loss can be determined by detecting the increase in the active component of the cable current. At the same time, because losses are directly related to active current and the volume of cable insulation, the losses of insulation of different sizes are also different. In order to eliminate the influence of this factor, another indicator, tg δ, is generally used to measure in practice. The magnitude of TG δ can be measured in many ways, among which the traditional method is to use the Xilin bridge method, also known as the balance measurement method, to detect the magnitude of the dielectric loss tangent. Due to the continuous development of technology, more convenient measurement methods have emerged, such as the angle difference method, which uses direct measurement to determine the angle between voltage and current, thus easily obtaining the magnitude of the dielectric loss tangent. Therefore, the angle difference method has been increasingly widely used in current dielectric loss tangent experiments.

　　（6）局部放電試驗電纜絕緣在局部放電試驗可以利用局部放電時產生的一系列的電、聲、光、熱等現象進行檢測。主要的檢測內容應該包括以下幾個方面:應該根據試驗現象判斷是否有局部放電現象的發生即定性測量;如果有局部放電的話要能檢測出放電量的多少即定量測量，這是重要的環節;產生局部放電時的起始放電和熄滅的電壓值必須能靈敏的進行檢測;另外如果有局部放電的話應該找到放電的部位。局部放電有很多試驗方法，可以從大體上將其分為電和非電的兩大類，再進行精確分類的話可以分為超聲波法、光側發、RIV法、射頻檢測法、脈沖電流法、DGA法、介質損耗法、電氣檢測法等，其中電氣檢測法是當前應用的廣泛的方法，能同時檢測出是否存在局部放電以及放電的強弱。

　　(6) Partial discharge test: Cable insulation can be tested using a series of electrical, acoustic, optical, and thermal phenomena generated during partial discharge testing. The main detection contents should include the following aspects: firstly, the occurrence of partial discharge phenomenon should be judged based on the test phenomenon, that is, qualitative measurement; If there is partial discharge, the most important step is to be able to detect the amount of discharge and measure it quantitatively; The initial discharge and extinguishing voltage values during partial discharge must be sensitively detected; Additionally, if there is partial discharge, the location of the discharge should be identified. There are many testing methods for partial discharge, which can be roughly divided into two categories: electrical and non electrical. If accurately classified, they can be divided into ultrasonic method, optical side emission, RIV method, radio frequency detection method, pulse current method, DGA method, dielectric loss method, electrical detection method, etc. Among them, electrical detection method is currently the most widely used method, which can simultaneously detect the presence and strength of partial discharge.

　　（7）絕緣油試驗充油電纜的電纜油是其中重要的絕緣介質，因此可以通過對油樣進行預防性試驗以對電纜的絕緣性能有一個大致的了解。對油樣進行預防性試驗時其試驗內容有很多，有色譜分析、tgδ 測量、含水量測試、交流擊穿強度試驗等等。在進行油樣試驗時，要從電纜中采集油樣，而這一環是整個油樣測試中相當重要的環節，直接影響了后面的測試結果。在采集油樣時應該本著這樣一種原則，即任何時候都不能讓灰塵和水分等雜質進入油樣而影響試驗的結果，因此在采集時需要遵守相關規定并且十分謹慎。在采集油樣時應該在電纜中距離供油點較遠的那一端進行采集，如果要采集的電纜段的兩端均有供油，則哪一邊油壓較低就應在哪一段采集，采集出來的油樣需要進行干燥處理并且放置于廣口瓶內。

　　(7) The cable oil of the oil filled cable is an important insulation medium in the insulation oil test, so preventive testing of the oil sample can provide a rough understanding of the insulation performance of the cable. When conducting preventive tests on oil samples, there are many test contents, including chromatographic analysis, TG δ measurement, moisture content testing, AC breakdown strength testing, and so on. When conducting an oil sample test, the first step is to collect the oil sample from the cable, which is a crucial step in the entire oil sample testing process and directly affects the subsequent test results. When collecting oil samples, the principle should be followed that at no time should impurities such as dust and moisture enter the oil sample and affect the test results. Therefore, it is necessary to comply with relevant regulations and be very cautious when collecting. When collecting oil samples, they should be collected at the end of the cable that is farther away from the oil supply point. If both ends of the cable section to be collected have oil supply, the oil sample should be collected at the section with lower oil pressure. The collected oil sample needs to be dried and placed in a wide mouthed bottle.

　　（8）交叉互聯系統試驗有單芯電纜組成的三相輸電系統中，金屬護層接地方式有a兩端接地、b單端接地、c交叉互聯接地等3種接地方式，如下圖。交叉互聯性能檢驗交接試驗采用的方式，應作為特殊試驗項目。使所有互聯箱連接片處于正常工作位置，在每相電纜導體中通以大約100A的三相平衡試驗電流。在保持試驗電流不變的情況下，測量靠近交叉互聯箱處的金屬套電流和對地電壓。測量完后將試驗電流降零，切斷電源。然后將靠近的交叉互聯箱內的連接片重新連接成模擬錯誤連接的情況，再次將試驗電流升100A，并再測量該交叉互聯箱處的金屬套電流和對地電壓。測量完后將試驗電量降零，切斷電源，將該交叉互聯箱中的連接片復原正確的連接位置。再將試驗電流升100A，測量電纜線路上所有其它交叉互聯箱處的金屬套電流和對地電壓。?五、敷設要求與電纜載流量修正1.敷設要求彎曲半徑控制單芯電纜≥20D（D=電纜直徑）；多芯電纜≥15D交叉互聯接地分段長度300~600m（110kV）接地電流不平衡度＜10%在線監測技術分布式光纖測溫（DTS）精度±1℃；護層環流監測閾值＜10A2.電纜載流量修正影響因素修正系數K計算式土壤熱阻0.8~1.2I'=I·√(K_θ)并列敷設0.7~0.9I'=I·K_d電纜間距1.0~1.1間距≥2D時取1.0依據IEC 60287標準計算，D為電纜外徑。

　　(8) In a three-phase transmission system composed of single core cables, there are three grounding methods for the metal protective layer in the cross interconnection system test: a two end grounding, b single end grounding, and c cross interconnection grounding, as shown in the following figure. The recommended method for cross connection performance testing and handover testing should be considered as a special test item. Place all interconnection box connectors in their normal working position and conduct a three-phase balanced test current of approximately 100A in each phase cable conductor. Measure the metal sleeve current and ground voltage closest to the cross junction box while keeping the test current constant. After measurement, reduce the test current to zero and cut off the power supply. Then reconnect the connecting piece in the nearest cross junction box to simulate a misconnection situation, increase the test current to 100A again, and measure the metal sleeve current and ground voltage at the cross junction box. After measuring, reduce the test power to zero, cut off the power, and restore the connecting pieces in the cross interconnection box to the correct connection position. Finally, increase the test current to 100A and measure the metal sheath current and ground voltage at all other cross interconnection boxes on the cable line.? 5、 Installation requirements and cable current carrying capacity correction: 1. Installation requirements: The bending radius of the single core cable should be controlled to be ≥ 20D (D=cable diameter); Multi core cable ≥ 15D cross interconnection grounding section length 300~600m (110kV), grounding current imbalance<10%, online monitoring technology distributed fiber optic temperature measurement (DTS) accuracy ± 1 ℃; The monitoring threshold for protective layer circulation is less than 10A2. The calculation formula for the correction factor K of cable current carrying capacity correction is soil thermal resistance 0.8~1.2I '=I ·√ (K0θ). When laid in parallel 0.7~0.9I'=I ·K0d, the cable spacing is 1.0~1.1. When the spacing is ≥ 2D, 1.0 is taken according to IEC 60287 standard calculation, and D is the outer diameter of the cable.

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