A 38/66kV high voltage cable is designed for power networks with a nominal voltage of 66 kV between phases and 38 kV between a phase conductor and earth. The designation commonly appears as 38/66(72.5) kV, where the value in parentheses identifies the highest system voltage for which the cable design is intended. These cables are typically insulated with cross-linked polyethylene (XLPE) and incorporate conductor screens, insulation screens, and a metallic screen to manage electrical stress and provide a path for fault current. The correct specification depends on the network, installation conditions, applicable standards, and the complete cable system—not voltage designation alone.
This guide is for utility engineers, EPC contractors, procurement teams, distributors, and project owners evaluating 38/66kV cable for transmission or sub-transmission projects. It outlines the main cable components, common material options, selection factors, and supplier questions that help turn a project requirement into a usable technical specification. It is an orientation guide, not a substitute for system design or project-specific engineering review.
In the designation U0/U, U0 is the rated voltage between a conductor and earth, while U is the rated voltage between conductors. For a 38/66kV cable, these values are 38 kV and 66 kV respectively. Some specifications also show Um, the highest voltage for equipment, as in 38/66(72.5) kV; confirm the required designation against the network data and the governing standard.
For procurement, voltage rating is only one part of the specification. Conductor material and cross-section, insulation thickness, metallic screen design, sheath, installation method, and required tests all affect the cable selection. A cable should be assessed together with its joints, terminations, bonding arrangement, and protection design.
A typical single-core 38/66kV XLPE cable is built in layers, with each component performing a distinct electrical or mechanical function. Exact designs vary by manufacturer, standard, and project specification. The following overview describes common elements, not a universal construction for every project.
The conductor carries the load current and is commonly made from copper or aluminium. The appropriate cross-section depends on factors such as current demand, installation conditions, permissible voltage drop, short-circuit duty, and future operating requirements. A semiconductive conductor screen is applied over the conductor to provide a smooth electrical boundary between the conductor and insulation.
XLPE is widely used as the main insulation in high voltage cable designs. It separates the energized conductor from the grounded metallic screen and is manufactured with semiconductive layers on both sides to support a controlled electric field. Typical XLPE designs use a maximum conductor temperature of 90°C for continuous operation and up to 250°C for short-circuit conditions, but the permitted values must be confirmed for the selected cable, duration, and applicable standard.
A metallic screen may use copper wires, a copper tape, or another specified arrangement. It provides a grounded layer around the insulation and is part of the system’s earth-fault and bonding design. The outer sheath protects the cable against environmental and installation-related damage; armour may be specified where mechanical protection is required, subject to the installation design.
| Component | Common options | Selection consideration |
|---|---|---|
| Conductor | Copper or aluminium | Electrical load, installation, and project requirements |
| Insulation | XLPE in common designs | Rated voltage, manufacturing specification, and test requirements |
| Metallic screen | Copper wires, tape, or specified alternatives | Fault-current duty and bonding arrangement |
| Outer protection | Sheath; armour where required | Buried, duct, tunnel, or other installation conditions |
38/66kV cables are used in high voltage power networks where underground or protected cable routes are appropriate. Potential applications include connections between substations, utility network sections, power plant connections, and industrial installations. Whether this rating is suitable depends on the project’s system voltage, load, fault level, route, and network operating requirements.
Installation conditions should be reviewed early. Direct burial, duct installation, tunnels, and indoor cable routes can impose different thermal, mechanical, and environmental demands. For single-core cables, the route layout and bonding method also affect the design; coordinate these details with the system designer rather than selecting the cable from voltage and conductor size alone.
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Provide the nominal system voltage, highest system voltage, frequency, earthing arrangement, and applicable national or project standards. IEC 60840 is commonly referenced for extruded-insulation power cables and accessories within its stated voltage scope, but the project specification should determine which standard and edition apply. Confirm whether the requirement covers the cable only or also accessories and system-level testing.
Share the design current, expected load profile, short-circuit current and duration, route length, installation method, ambient or soil conditions, and any grouping with other circuits. These inputs support engineering checks for ampacity, thermal performance, voltage drop, and screen duty. Do not assume that a conductor size suitable for one route will be suitable for another with different installation conditions.
State conductor material and cross-section, insulation and sheath requirements, metallic screen details, and whether armour is needed. Identify required routine, sample, type, or project-specific tests in the purchase specification, and ask the supplier to state the proposed test scope and documentation. Test requirements and acceptance criteria should be agreed before production rather than inferred from a product description.
Confirm whether joints, terminations, link boxes, or other accessories are in the supply scope. Check compatibility with the cable construction, conductor size, screen arrangement, and installation environment. Also coordinate drum lengths, route segmentation, handling limits, delivery schedule, and documentation so the supplied cable can be received and installed as planned.
There is no single reliable price or lead time for every 38/66kV cable order. Cost can vary with conductor material and size, cable construction, order quantity, accessory scope, testing requirements, packaging, and delivery destination. Minimum order quantities and production schedules are supplier- and project-dependent, so buyers should request a quotation based on a complete technical specification and required delivery dates.
To make quotations easier to compare, issue the same technical schedule to each bidder and ask suppliers to list deviations separately. Request pricing by cable type and length, clarify included tests and documents, and confirm how any requested design changes affect cost and schedule. This helps distinguish a like-for-like offer from one based on different assumptions.
At Zhongdong Cable Co., Ltd., we support B2B buyers by reviewing cable requirements and discussing construction, materials, documentation, and delivery scope for quotation. Share your project voltage, applicable specification, installation method, conductor requirements, estimated quantity, and destination to help us assess the request. Final design details and availability should be confirmed against the project requirements and order schedule.
A 38/66kV cable is selected for a network voltage requirement, but its suitability depends on the complete electrical and installation design. XLPE insulation, conductor screens, insulation screens, metallic screens, and protective sheaths are common construction elements, while conductor material, screen duty, armour, and accessories vary by project. Typical thermal limits such as 90°C continuous and 250°C short-circuit operation are design-dependent values that must be verified for the specific cable.
To move from evaluation to a supplier enquiry, prepare the network data, applicable standard, route and installation conditions, conductor requirements, test scope, estimated quantity, and delivery target. Ask suppliers to confirm construction, deviations, accessories, and documentation in writing. Zhongdong Cable Co., Ltd. can use these details to discuss a project-specific 38/66kV cable quotation and clarify the information needed for technical review.
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