In medium-voltage distribution cable manufacture, Jiangsu Dewei XLPE YJ-10 is specified as the insulation core in triple-extruded power-cable constructions rated 6/10 kV, 8.7/15 kV, and 12/20 kV under IEC 60502-2 and GB/T 12706.2. The compound enters the insulation extruder as a ready-to-use peroxide-curable polyethylene pellet with a density of 0.91–0.93 g/cm³ when determined by ISO 1183-1. In an 8.7/15 kV core, the three-layer construction typically combines a conductor screen of 0.8 mm, the YJ-10 insulation layer of 4.5 mm nominal thickness, and an insulation screen of 1.0 mm; the resulting radial layer distribution is therefore approximately 0.8:4.5:1.0. The downstream process is a continuous catenary vulcanization line with dry nitrogen pressure held at 1.0–1.5 MPa, zoned tube temperatures from 160°C at the inlet to 240–250°C in the curing zone, and conductor preheating that raises the copper or aluminum core to 80–100°C before triple coextrusion. Practical line experience shows that the melt temperature measured at the breaker plate must remain below 125°C; exceeding this threshold initiates premature peroxide decomposition, observable as surface grain, die drool, and localized gel particles. After the curing tube, the core is degassed for 24–72 h at 70–80°C under forced ventilation to strip dicumyl peroxide byproducts such as cumyl alcohol and acetophenone before the metallic screen and outer sheath are applied. Routine electrical verification includes partial discharge measurement at 1.73 U₀ and a high-voltage test according to the cable standard. Finished products are three-core armoured distribution cables installed in urban ring circuits, wind-farm collector systems, and industrial feeder connections. Continuous conductor temperature is limited to 90°C, with a short-circuit upper limit of 250°C for 5 s; the insulation is not intended for continuous contact with mineral oil, strong oxidizing acids, or direct flame exposure. Scorch control is governed by the decomposition kinetics of the peroxide package: dicumyl peroxide has a half-life of approximately 1 h at 135°C and 1 min at 175°C, so the extruder temperature envelope is the most sensitive boundary. If head pressure falls or the melt temperature rises above 125°C, resin may crosslink before exiting the die and accumulate as hard particles behind the breaker plate. Operators monitor head pressure and screen-pack differential pressure continuously because a differential pressure increase across a production shift signals gel build-up and requires a screen change.

What Constraints Arise When YJ-10 Runs at Thin-Wall Dimensions in 0.6/1 kV Building Wire?

Low-voltage building cable is the highest-volume downstream segment for 0.6/1 kV insulated conductors under IEC 60502-1, and YJ-10 is extruded at wall thicknesses that range from 0.7 mm for small conductor cross-sections to 1.6 mm for large service-entrance conductors. The processing constraint is not crosslinking speed but melt confinement in a thin annulus; production lines using a single-screw extruder with an L/D of 25:1 and a barrier screw maintain a temperature profile of 105°C in the feed section, 115–125°C in the metering section, and a head temperature below 125°C. Copper or aluminum conductors are preheated to 80–100°C to prevent rapid polymer skin freezing and eccentricity drift. The ratio of insulation thickness to conductor diameter changes from approximately 0.39 on a 2.5 mm² copper conductor to below 0.10 on a 300 mm² compacted aluminum conductor, which affects heat transfer during pressure curing. The extruded core passes through a dry-cure tube with line speeds typically between 20 m/min and 150 m/min depending on wall thickness and cross-section, while the peroxide decomposition must be completed before the core leaves the cooling section. The final building wire is subjected to a 3.5 kV AC routine voltage test for 5 min according to IEC 60502-1 for 0.6/1 kV cables, or to an equivalent spark test at the insulation line. End products include single-core non-sheathed building wires for fixed installation in conduit, flat twin-and-earth constructions with an outer PVC sheath, and multi-core control cables in residential and commercial switchboards. YJ-10 is not flame-retardant by itself; building-construction fire classification is achieved by the outer sheath, and the insulation should not be exposed to hot bitumen, aromatic solvents, or continuous contact with plasticized PVC at temperatures above 70°C because low-molecular-weight plasticizer migration may reduce interfacial adhesion. If pellets show surface condensation after storage at a relative humidity above 60%, pre-drying in a dehumidified hopper at 70°C for 2 h is required before extrusion to avoid steam voids at the conductor-insulation interface.

When a 1.5 kV DC Photovoltaic Cable Uses a Thermoset Crosslinked Polyolefin Insulation

When YJ-10 is evaluated for single-core photovoltaic link cables rated 1.5 kV DC under EN 50618 and TÜV 2Pfg 1169, the acceptance path is the long-term damp-heat and ultraviolet sequence rather than the conventional medium-voltage partial-discharge test. The insulation is applied over tinned copper conductors according to flexible class 5 of IEC 60228, with insulation thickness set by the product standard; common DC solar cables use an insulation wall of 0.5–1.2 mm across standard cross-sections. The extrusion process for thin-walled photovoltaic insulation requires a low-shear screw, a melt temperature held below 125°C, and conductor preheating to 70–90°C. Because YJ-10 is a peroxide-curable system, the insulated core must be degassed after curing before a halogen-free outer sheath is applied; residual peroxide decomposition products such as acetophenone may otherwise collect at the insulation-sheath interface and reduce long-term adhesion under thermal cycling. The final photovoltaic cable is subjected to the EN 50618 durability test programme, which includes long-term thermal endurance, damp heat, ozone, cold bend, and UV weathering; published data for YJ-10 in this specific photovoltaic construction is limited, so qualification testing must be performed before production, especially if the application demands halogen-free and low-smoke performance. The compound’s conventional XLPE formulation should not be assumed to pass the more restrictive flame-propagation or acid-gas emission limits unless the cable design places all fire-performance requirements on the sheath. End products are single-core module interconnect cables, combiner-box-to-inverter DC feeders, and ground-mounted or rooftop array wiring. The operational boundary is 90°C continuous conductor temperature, with the additional constraint that the outer sheath must provide the required UV resistance and the connector interface must be free of residual byproduct films.

Thermal Ageing and Hot-Set Behaviour in Motor Lead and Control Cable Insulation

For motor leads, variable-frequency-drive motor wiring, and control-cable cores, the central qualification test for YJ-10 is the hot-set test under 0.2 MPa at 200°C as described in IEC 60811-507; a crosslinked insulation must show hot elongation no greater than 175% and a permanent set no greater than 15%. The extrusion line for these smaller conductors often uses a semi-tubing pressure die and a single-screw extruder at an L/D of 20:1 to 25:1, with screen packs of 40/60/80 mesh to trap lightly crosslinked gels. The insulation wall for 0.6/1 kV control cable ranges from 0.6 mm to 1.0 mm, and the ratio of insulation thickness to overall core diameter is smaller than in medium-voltage cable; therefore hot-set sampling is taken from the fastest-moving reel and the slowest-moving reel of each extrusion run to detect batch-to-batch variation in peroxide dispersion. The downstream application is thermally demanding because inverter-fed motors impose repetitive high-frequency voltage spikes that can initiate partial discharges at voids or microporosity in the insulation wall. YJ-10 exhibits a volume resistivity of at least 10¹⁴ Ω·cm at 20°C and a dissipation factor below 0.001 at 50 Hz when measured under IEC 62631-3-1 and IEC 60250, but these values are measured on fully cured, void-free slabs; the cable maker must verify that extrusion pressure and cooling do not introduce voids. End products include XLPE-insulated motor lead wires, panel wiring, and multicore control cables for machine tools and automated production cells. The operational boundary is continuous conductor temperature 90°C; when the cable is routed through hydraulic oil reservoirs or exposed to polar solvents, an oil-resistant elastomer or fluoropolymer insulation is required because conventional XLPE is not formulated for immersion in these fluids. In addition, antioxidants in YJ-10 are consumed by long-term exposure to copper ions; direct contact with bare copper at temperatures above 110°C during processing can accelerate oxidative ageing.

Submersible pump cable insulation produced from YJ-10 is assessed primarily for water-tree growth because the flooded installation environment applies alternating electrical stress in the presence of moisture. The standard laboratory method for evaluating water-tree development in crosslinked insulation is ASTM D6097, which subjects moulded plaques or cable specimens to a defined electrical field and temperature in a conductive water environment. In an actual submersible cable, the copper or tinned-copper conductor is insulated at thicknesses from 0.7 mm to 1.5 mm depending on pump motor voltage and conductor size; the insulation is then covered by a moisture-resistant sheath, but water vapour ingress through the sheath remains the long-term failure driver. Extrusion of the insulation layer uses a pressure-cure line with nitrogen at 1.0–1.5 MPa, and melt temperatures are held below 125°C to avoid microvoid nucleation around decomposed peroxide residues. After curing, the cable is degassed at 70–80°C for at least 24 h to remove byproducts that would otherwise form hydrophilic sites at the insulation-sheath interface. Field experience with XLPE submersible pump cables shows that the most common failure location is the splice or the motor lead entry point, where mechanical damage or incomplete void elimination creates a high-gradient region for water-tree initiation. The finished product is installed in deep-well irrigation pumps, submersible sump pumps, and downhole pressure-monitoring leads. YJ-10 is a conventional XLPE insulation, not a water-tree-retardant grade, so specifications that require utility-grade water-tree-retardant formulations should not substitute YJ-10 without comparative long-term wet aging data; published data for YJ-10 under long-duration wet electrical ageing is limited.

For Overhead Covered Conductors Exposed to Pollution and UV, Tracking Resistance Governs Service Life

Overhead distribution lines use a bare aluminum conductor covered with an extruded XLPE layer to reduce phase-to-ground faults from incidental tree contact and wind-induced conductor clashing. The covering is not a primary rated insulation in the same sense as a medium-voltage cable because the conductor remains at system potential and the outside surface is exposed; utility specifications generally require covering thicknesses from 1.5 mm to 3.5 mm for conductor sizes up to 240 mm². The extrusion process uses a pressure die with a sheath-type crosshead, a conductor preheat temperature of 80–100°C, and a curing tube temperature profile that may be 20–30°C lower than in cable insulation to prevent sag of the thick covering before crosslinking. Tracking resistance is evaluated under IEC 60587 by subjecting specimens to an electrolyte contaminant and a defined electrical stress; a covering that fails by surface tracking creates conductive carbon paths, which lead to flashover and line tripping during fog or light rain. The outer surface of YJ-10 is not inherently UV-stable; long-term outdoor exposure requires a co-extruded black stabilized polyethylene skin or the incorporation of a weathering package, and utilities commonly specify carbon black content of 2–3 wt% in the outer covering layer for UV stability. End products are covered overhead line conductors for rural distribution feeders, forested mid-span sections, and temporary construction-site power lines. The operational limitation is that the covered conductor should not be treated as fully insulated: line maintenance must still use rated personal protective equipment and isolation procedures, and the covering is not intended for continuous immersion or direct contact with sharp metallic edges. Published comparative tracking and erosion data for YJ-10 under the full IEC 60587 thousand-hour sequence is limited; qualification for overhead service should include a utility-specific contamination test protocol.