Voltage marking and materials 4.1 Rated voltage The rated voltage is the reference voltage used for cable design and cable performance testing. The rated voltage U0/U (Um) of the cable in this document is marked as follows: U0/U (Um) = 3.6/6 (7.2) kV, 6/6 (7.2) kV, 6/10 (12) kV, 8.7/10 (12) kV, 8.7/15 (17.5) kV, 12/20 (24) kV, 18/20 (24) kV, 18/30 (36) kV, 21/35 (40.5) kV, 26/35 (40.5) kV. In the rated voltage marking U0/U (Um) of the cable:
——U0 is the rated power frequency voltage between the conductor and the ground or metal shield for which the cable is designed;
——U is the rated power frequency voltage between the conductors for which the cable is designed;
——Um is the maximum value of the "maximum system voltage" that can be used by the equipment (according to GB/T156). The rated voltage of the cable for a given application should be suitable for the operating conditions of the system where the cable is located. In order to facilitate the selection of cables, the system is divided into the following three categories:
——Class A cable: When any phase conductor of this system contacts the ground or grounding conductor, it can be separated from the system within 1 minute;
——Class B cable: This type of system can be operated for a short time in the event of a single-phase grounding fault, and the grounding fault time should not exceed 1h according to the provisions of JB/T8996; for the cables included in this document, the fault-carrying operation time should not exceed 8h or longer under any circumstances; the total duration of grounding faults in any year should not exceed 125h;
——Class C cable: includes all systems that do not belong to Class A or Class B. When the system ground fault cannot be automatically cleared immediately, the excessive electric field strength applied to the cable insulation during the fault will shorten the cable life to a certain extent. If the system is expected to operate frequently under a persistent ground fault state, the system can be classified as Class C. For cables used in three-phase systems, the recommended value of U0 is shown in Table 1. T/HSXLXH003—2023 Table 1 Recommended values of rated voltage U0 System maximum voltage Um kV Rated voltage U0 kV Class A, Class B Class C 7.2 3.6 6.0 12.0 6.0 8.7 17.5 8.7 12.0 24.0 12.0 18.0 36.0 18.0 21.0 40.5 21.0 26.0 4.2 Insulating compound Table 2 gives the maximum conductor temperature of the insulating compound cable in this document. Table 2 Maximum operating temperature of conductors for cables with insulation mixtures Insulation mixture code Maximum conductor temperature during normal operation ℃ Normal operation short circuit (maximum duration 5s) Polypropylene insulation P 105 250 The temperatures in Table 2 are determined by the inherent characteristics of the insulation mixture. Other factors are also important to consider when using these data to calculate the rated current. For example, in normal operation, if a cable directly buried underground is operated under continuous load (100% load factor) according to the maximum conductor temperature shown in Table 2, the thermal resistance coefficient of the soil around the cable will exceed the original value after a certain period of time due to soil drying, so the conductor temperature may exceed the maximum temperature. If such operating conditions can be anticipated, appropriate precautions should be taken. For guidance on continuous load current carrying capacity, refer to JB/T10181. For guidance on short-circuit temperature, refer to IEC60986IEC61443. 4.3 Sheath mixtures Table 3 gives the maximum conductor temperatures for cables with different types of sheath mixtures in this document. Table 3 Maximum conductor temperature of cables with different types of sheath mixtures Sheath mixture code Maximum conductor temperature during normal operation ℃ Polyvinyl chloride (PVC) H-105105 Halogen-free low smoke flame retardant (LSF) H-105W105 Table 13 Requirements for cable insulation performance Test item No. (mixture code see 4.2) Unit PP 1 Mechanical properties before aging (9.1 in CB/T2951.11-2008 1.1 Tensile strength, minimum N/mm2 18 1.2 Elongation at break, minimum 400 Mechanical properties after air oven aging (8.1 in GB/T2951.12-2008 2.1 Treatment conditions 2.1.1 Temperature (deviation ±3K) 135 2.1.2 Duration 168 2.2 Tensile strength after aging, minimum N/mm2 15 2.3 Elongation at break after aging, minimum 400 High temperature pressure test (GB/T2951.31-2008 Chapter 8) 3.1 Pressure calculation coefficient k 0.7 3.2 Temperature (deviation +2K) ℃ 130 3.3 Time 6 3.4 Maximum indentation depth 10 "Low temperature performance test (GB/T2951.14-2008 Chapter 8) is not tested before aging" 4.1 Low temperature tensile test of dumbbell pieces 4.1.1 Temperature (deviation ±2K) -25 4.1.2 Elongation at break, minimum 20 5 Water absorption test (GB/T2951.13-2008 Chapter 9.2 Weight method) 5.1 Temperature (deviation ±2K) ℃ 85 5.2 Duration h 336 5.3 Maximum weight increase mg/cm' 0.5 6 Shrinkage test (GB/T2951.13-2008 Chapter 10) 6.1 Length between markings L mm 200 6.2 Temperature (deviation ±3K) ℃ 130 6.3 Duration h 1 6.4 Maximum allowable shrinkage % 4 4.3 Sheath mixture Table 3 gives the maximum conductor temperature of cables with different types of sheath mixtures in this document. Table 3 Maximum conductor temperature of cables with different types of sheath mixtures Sheath mixture code Maximum conductor temperature during normal operation ℃ Polyvinyl chloride (PVC) H-105105 Halogen-free low smoke flame retardant (LSF) H-105W105 4.4 Working temperature 4.4.1 The maximum long-term temperature allowed for the conductor during normal operation of the cable is 105℃. 4.4.2 In case of short circuit (the maximum duration should not exceed 5s), the maximum temperature allowed for the cable conductor is 250℃. T/HSXLXH003—2023 5 Conductor The conductor shall be the first or second type of metal-plated or non-metal-plated annealed copper conductor in accordance with GB/T3956, or the first or second type of aluminum or aluminum alloy conductor. The conductor may also be a longitudinal water-blocking structure. The specific chemical composition of the aluminum alloy conductor is shown in Appendix A of GB/T31840.2. The various properties of the conductor shall comply with the provisions of 5.3 and 5.4 of GB/T31840.2. 6 Insulation 6.1 Material The insulation shall be a polypropylene extruded material. 6.2 Insulation thickness The nominal thickness of insulation is shown in Table 4. The thickness of any isolation layer or semi-conductive shielding layer outside the conductor or insulation shall not be included in the insulation thickness. The rated voltage 6/6kV, 8.7/10kV, 18/20kV cables in Table 4 are exactly the same as the 6/10kV, 8.7/15kV, 18/30kV cables, see Table 1 for details. Table 4 Nominal thickness of polypropylene insulation Nominal cross-sectional area of conductor mm2 Nominal thickness of insulation at rated voltage U0/U (Um) kV mm 3.6/6 (7.2) 6/6 (7.2) 6/10 (12) 8.7/10 (12) 8.7/15 (17.5) 12/20 (24) 18/20 (24) 18/30 (36) 21/35 (40.5) 26/35 (40.5) 25 35 50～185 240 300 400 500～1600 2.5 2.5 2.6 2.8 3.0 3.2 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 4.5 4.5 4.5 4.5 4.5 4.5 5.5 5.5 5.5 5.5 5.5 8.0 8.0 8.0 8.0 8.0 9.3 9.3 9.3 9.3 9.3 10.5 10.5 10.5 10.5 Note 1: It is not advisable to use any conductor cross-sectional area smaller than that given in the table. If a smaller cross-sectional area is required, the conductor diameter may be increased (see 7.2) or the insulation thickness may be increased by using a conductor screen to limit the maximum electric field strength applied to the insulation at the test voltage to the value calculated for the smallest conductor size given in the table. Note 2: For conductors with a nominal cross-sectional area greater than 1000 mm2, the insulation thickness may be increased to avoid mechanical damage during installation and operation. 7 Screening 7.1 General All cables shall have a metallic screen over the insulated core. The screen of the insulated core of a single-core or three-core cable shall consist of a conductor screen and an insulation screen. 7.2 Conductor shielding The conductor shielding shall be a non-metallic semi-conductive material, consisting of extruded thermoplastic semi-conductive material or first wrapping a semi-conductive tape on the conductor and then extruding a semi-conductive material. The extruded semi-conductive layer shall be tightly bonded to the insulation, and its interface with the insulation layer shall be smooth, without obvious twisted wire convexity, and shall not have sharp corners, particles, burns or scratches. 7.3 Insulation shielding The insulation shielding shall be composed of a combination of a non-metallic semi-conductive layer and a metal layer. T/HSXLXH003—2023 Each insulating core shall be directly extruded with a non-metallic thermoplastic semi-conductive layer that is tightly bonded to the insulating core or can be peeled off, and its interface with the insulation layer shall be smooth, and shall not have sharp corners, particles, burns or scratches. If necessary, a layer of semi-conductive tape may be wrapped on each insulating core. The metal shielding layer shall be wrapped on the outside of each insulating core and shall comply with the requirements of Chapter 10. 8 Core, lining and filling of three-core cable 8.1 General requirements The core of a three-core cable is related to the rated voltage of the cable. 8.2 to 8.4 are not applicable to the cable core of single-core cable with sheath. 8.2 Lining and filling 8.2.1 Structure The lining can be extruded or wrapped. Round insulated core cables can only use wrapped lining when the gaps between the insulated cores are filled. The lining can be tightened with a suitable tape before extruding. 8.2.2 Materials The materials used for the lining and filling should be adapted to the operating temperature of the cable and compatible with the cable insulation material. Except for longitudinal water-blocking cables, the lining and filling should be made of non-hygroscopic materials. The lining and filling of halogen-free cables shall comply with the provisions of Table 15. 8.2.3 Thickness of extruded lining See Table 5 for the nominal thickness of the extruded lining. Table 5 Nominal thickness of extruded lining layer Unit: mm Assumed diameter of cable core Nominal thickness of extruded lining layer >25.0 >35.0 >45.0 >60.0 >80.0 =25.0 =35.0 =45.0 =60.0 =80.0 1.0 1.2 1.4 1.6 1.8 2.0 8.2.4 Wrapped lining layer When the assumed diameter of the cable core is 40.0mm or less, the nominal thickness of the wrapped lining layer is 0.4mm; when it is greater than 40.0mm, it is 0.6mm. The wrapped lining layer is made of a single or multiple tapes wrapped in overlapping layers, and the cable core or the lower layer of tape should not be exposed. When multiple tapes are wrapped, each tape should be wrapped in overlapping layers. 8.3 Cable with a metal layer (see Chapter 9) The cable core should be covered with an inner lining layer. The inner lining layer and filler should comply with the provisions of 8.2. If each insulated core of the cable is semi-conductively shielded and covered with a metal layer, the inner lining layer shall be made of semi-conductive material, and the filler may also be made of semi-conductive material. The covered metal layer is not applicable to cables with a rated voltage U of 35kV. 8.4 Cables with phase-separated metal layers (see Chapter 9) The metal layers of each insulated core shall be in contact with each other. If the cable has another wrapped metal layer of the same metal material outside the phase-separated metal shielded core (see Chapter 9), the cable core shall be covered with an inner lining layer. The inner lining layer and filler shall comply with the provisions of 8.2. The inner lining layer and filler may also be made of semi-conductive material. When the metal materials used for the phase separation and the covered metal layer are different, they shall be separated by an extruded isolation sleeve of any material specified in 13.2. If the cable does not have a covered metal layer (see Chapter 9), the inner lining layer may be omitted as long as the cable shape remains round. T/HSXLXH003—2023 9 Metal layers of single-core or three-core cables This document includes the following types of metal layers: a) Metal shield (see Chapter 10); b) Concentric conductor (see Chapter 11); c) Metal armor (see Chapter 12). The metal layer should be composed of one or more of the above forms and should be non-magnetic when wrapped on a single-core cable or a separate insulated core of a three-core cable. Measures can be taken to provide longitudinal water-blocking properties around the metal layer. 10 Metal shield 10.1 Structure The metal shield should consist of one or more metal strips, concentric layers of metal wires, or a combination of metal wires and metal strips. The metal shield can be a metal sleeve or an armor that complies with the provisions of 10.2 in the case of a turnkey shield. When selecting the metal shield material, special consideration should be given to the possibility of corrosion, not only for mechanical safety but also for electrical safety. The overlap and gap of the metal shield wrapping should comply with the provisions of 10.2. 10.2 Requirements 10.2.1 The resistance of the copper wire shield in the metal shield shall comply with the provisions of GB/T3956 when applicable. The nominal cross-sectional area of the copper wire shield shall be determined according to the fault current capacity. 10.2.2 The copper wire shield is composed of sparsely wound soft copper wires. The surface can be tightened with reversely wrapped copper wires or copper tapes. The average gap between adjacent copper wires should not be greater than 4mm. The definition and calculation of the average gap between adjacent copper wires shall comply with the provisions of 6.5.2 in GB/T11017.2. 10.2.3 The copper tape shield shall consist of an overlapping soft copper tape. The nominal overlap rate between the overlapping copper tapes is 15%, and the minimum overlap rate shall not be less than 5%. Other structures may be used when required. The soft copper tape of the shielding raw material shall be selected in accordance with the provisions of GB/T11091. The nominal thickness of the copper tape is:
——Single-core cable: ≥0.12mm;
——Three-core cable: ≥0.10mm. The minimum thickness of the copper tape shall not be less than 90% of the nominal value. 10.2.4 The metal shield of cables with a rated voltage U of 35 kV and a nominal cross-sectional area of 500 mm2 and above shall adopt a copper wire shielding structure. 11 Concentric conductor 11.1 Structure The gap between concentric conductors shall comply with the provisions of 10.2.2. When selecting the structure and materials of concentric conductors, special consideration shall be given to the possibility of corrosion, not only for mechanical safety but also for electrical safety. 11.2 Requirements The size, structure and resistance value requirements of concentric conductors shall comply with the provisions of 10.2. 11.3 Use If a concentric conductor structure is required, the concentric conductor layer can be directly coated on the semi-conductive insulating shielding layer or on the appropriate inner lining layer for single-core cables. 12 Metal armor 12.1 Metal armor types The armor types in this document are as follows: a) flat metal wire armor; b) round metal wire armor; c) bimetallic tape armor. T/HSXLXH003—2023 d) Aluminum alloy interlocking armor Note: Aluminum alloy interlocking armor is only applicable to cables below 35kV. 12.2 Materials Round metal wire or flat metal wire should be galvanized steel wire, stainless steel wire (non-magnetic), copper wire or tinned copper wire, aluminum wire or aluminum alloy wire. Metal strips should be galvanized steel strips, stainless steel strips (non-magnetic), aluminum strips or aluminum alloy strips. Steel strips should be industrial grade hot-rolled or cold-rolled steel strips. Aluminum alloy strips for interlocking armor should comply with the provisions of Appendix C in GB/T31840.2-2015. In the case where the armor steel wire layer is required to meet the minimum conductivity, the armor layer may contain sufficient copper wire or tinned copper wire to ensure that the requirements are met. When selecting armor materials, especially when the armor is used as a shielding layer, special consideration should be given to the possibility of corrosion, not only for mechanical safety but also for electrical safety. Unless a special structure is used, the armor used for single-core cables in AC systems should be made of non-magnetic materials. Note: Even if a special structure is used for the armor of single-core cables mainly made of magnetic materials for AC systems, the current carrying capacity of the cable will still be greatly reduced. 12.3 Application of armor 12.3.1 Single-core cable There should be an extruded or wrapped inner lining layer under the armor layer of single-core cables, and the thickness should comply with the provisions of 8.2.3 or 8.2.4. 12.3.2 Three-core cable When three-core cables need to be armored, the armor should be covered on the inner lining layer that complies with the provisions of 8.2. 12.3.3 Isolation sleeve When the metal layer under the armor is different from the armor material, a material specified in 13.2 should be used to extrude an isolation sleeve to separate them. The isolation sleeve should withstand the spark test specified in GB/T3048.10. If an isolation sleeve is used under the armor layer, it can replace the inner lining layer or be attached to the inner lining layer. Cables with a longitudinal water-blocking structure around the metal layer do not need to use isolation sleeves. The nominal thickness of the isolation sleeve shall be calculated according to formula (1): Ts=0.02Du+0.6 (1) Where: Ts——nominal thickness of the isolation sleeve, in millimeters (mm); Du——hypothetical diameter in front of the isolation sleeve, in millimeters (mm). The calculation shall be carried out in accordance with the provisions of Appendix A, and the calculation result shall be rounded to 0.1mm in accordance with the provisions of Appendix B. When the calculated value of the nominal thickness of the cable isolation sleeve is less than 1.2mm, the nominal thickness of the isolation sleeve shall be 1.2mm. 12.4 Sizes of armored metal wires and armored metal strips The following nominal sizes shall be preferred for armored metal wires and armored metal strips:
——Round metal wire (thin): diameter 0.8mm, 1.25mm, 1.6mm, 2.0mm, 2.5mm, 3.15mm;
——Round metal wire (thick): diameter 4.0mm;
——Flat metal wire: thickness 0.8mm;
——Steel strip: thickness 0.2mm, 0.5mm, 0.8mm;
——Aluminum strip or aluminum alloy strip: thickness 0.5mm, 0.8mm;
——Aluminum alloy strip for chain armor: thickness 0.5mm, 0.6mm, 0.7mm. 12.5 Relationship between cable diameter and armor layer size The nominal diameter of armored round metal wire and the nominal thickness of armored metal strip are shown in Table 5, Table 6 and Table 7 respectively. T/HSXLXH003—2023 Table 5 Nominal diameters of armored round metal wires (in millimeters) Assumed diameter before armoring Nominal diameter of armored metal wire— >10.0 >15.0 >25.0 >35.0 >60.0 ≤10.0 ≤15.0 ≤25.0 ≤35.0 ≤60.0 0.8 1.25 1.6 2.0 2.5 3.15,4.0 Table 6 Nominal diameters of armored metal strips (in millimeters) Assumed diameter before armoring Nominal thickness of metal strips Steel strip Aluminum strip or aluminum alloy strip >30.0 >70.0 ≤30.0 ≤70.0 0.2 0.5 0.8 0.5 0.5 0.8 Table 7 Nominal thickness of aluminum alloy strips for interlocking armor Cable outer diameter before armoring d/mm Thickness of aluminum alloy strip/mm >20 >40 ≤20 ≤40 0.5 0.6 0.7 When the assumed diameter of the cable before armoring is greater than 15.0 mm, the nominal thickness of the flat metal wire shall be 0.8 mm. Flat metal wire armoring shall not be used when the assumed diameter of the cable is 15.0 mm or less. 12.6 Round metal wire or flat metal wire armoring The metal wire armoring shall be tight, even if the gap between adjacent metal wires is small. If necessary, a galvanized steel strip with a nominal thickness of at least 0.3 mm may be sparsely wound around the flat metal wire armoring and round metal wire armoring. The deviation of the steel strip thickness shall comply with the provisions of 16.6.3. When thick round metal wire armoring is used, when the calculated value of the nominal thickness of the isolation sleeve or lining layer under the armoring is less than 2.0 mm, the nominal thickness of the isolation sleeve or lining layer shall be 2.0 mm. 12.7 Bimetallic tape armoring When bimetallic tape armoring and a wrapped lining layer in accordance with 8.2 are used, the lining layer shall be reinforced with a wrapping pad. If the thickness of the armored metal tape is 0.2mm, the total thickness of the inner lining layer and the additional tape cushion layer shall be the nominal value of 8.2 plus 0.5mm; if the thickness of the armored metal tape is greater than 0.2mm, the total thickness of the inner lining layer and the additional tape cushion layer shall be the specified value of 8.2 plus 0.8mm. The measured value of the total thickness of the wrapped inner lining layer and the additional tape cushion layer shall not be less than 80% of the specified value minus 0.2mm. The metal tape armor shall be spirally wrapped in two layers so that the center line of the outer metal tape is roughly above the gap of the inner metal tape, and the gap rate of each layer of metal tape shall not be greater than 50% of the width of the metal tape. 13 Outer sheath 13.1 Overview All cables shall have an outer sheath. The outer sheath is usually black, but other colors other than black may be used according to the agreement between the supply and demand parties to adapt to the specific environment in which the cable is used. The outer sheath of the cable wrapped on the armor, metal shield or concentric conductor shall withstand the spark test specified in GB/T3048.10. 13.2 Material T/HSXLXH003-2023 The outer sheath shall be made of thermoplastic material (polyvinyl chloride, halogen-free low-smoke flame-retardant material) in accordance with the requirements of Table 3. If the cable is required to prevent the spread of flames, generate less smoke and no halogen gas release in the event of a fire, a halogen-free low-smoke flame-retardant sheath material shall be used. The outer sheath of halogen-free low-smoke flame-retardant (H-105W) cables shall comply with the provisions of Table 15. The outer sheath shall be compatible with the cable operating temperature specified in 4.4. For outer sheaths used under special conditions (e.g. for termite prevention), it may be necessary to use chemical additives, but these additives should not include materials that are harmful to humans and the environment. Note: For example, materials that are not desirable as additives include 1):
——Chloromethylnaphthalene (aldrin): 1, 2, 3, 4, 10, 10-hexachloro-1, 4, 4a, 5, 8, 8a-hexahydro-1, 4, 5, 8-dimethylnaphthalene;
——Oxychloromethylnaphthalene (dieldrin): 1, 2, 3, 4, 10, 10-hexachloro-6, 7-epoxy-1, 4, 4a, 5, 6, 7, 8, 8a-octa-1, 4, 5, 8-dimethylnaphthalene;
——Hexachlorobenzene (hexachlorobenzene): 1, 2, 3, 4, 5, 6, -hexachloro-cyclohexane γ isomer. 13.3 Thickness If not otherwise specified, the nominal thickness of the extruded outer sheath shall be calculated according to formula (2): tos = 0.035Dos + 1.0 (2) Where: tos - nominal thickness of the outer sheath, in millimeters (mm); Dos - assumed diameter of the cable before extrusion of the sheath, in millimeters (mm). The value calculated according to formula (2) shall be rounded to 0.1 mm in accordance with the provisions of Appendix B. When the calculated value of the nominal thickness of the outer sheath of a single-core cable is less than 1.4 mm, the nominal thickness of the outer sheath shall be 1.4 mm. When the calculated value of the nominal thickness of the outer sheath of a multi-core cable is less than 1.8 mm, the nominal thickness of the outer sheath shall be 1.8 mm. Table 13 Cable insulation performance requirements No. (mixture code see 4.2) Unit PP 1 Mechanical properties before aging (9.1 in CB/T2951.11-2008) 1.1 Tensile strength, minimum N/mm2 18 1.2 Elongation at break, minimum 400 Mechanical properties after air oven aging (8.1 in GB/T2951.12-2008) 2.1 Treatment conditions 2.1.1 Temperature (deviation ±3K) 135 2.1.2 Duration 168 2.2 Tensile strength after aging, minimum N/mm2 15 2.3 Elongation at break after aging, minimum 400 High temperature pressure test (8.1 in GB/T2951.31-2008) 3.1 Pressure calculation coefficient k 0.3.2 Temperature (deviation +2K) ℃ 130 3.3 Time 3.4 Maximum indentation depth 10 Low temperature performance test (Chapter 8 of GB/T2951.14-2008) is conducted before aging. 4.1 Low temperature tensile test of dumbbell plates 4.1.1 Temperature (deviation ±2K) 25 4.1.2 Elongation at break, minimum 20
T/HSXLXH 003-2023 history
2023T/HSXLXH 003-2023 Power cables with polypropylene insulation for rated voltages from 6 kV (Um = 7.2 kV) up to 35 kV (Um = 40.5 kV)