Shielded cables

A shielded cable contains one or more conductive or semiconductive layers around a circuit or cable core. The purpose of that layer depends on the cable. In control, instrumentation and VFD circuits, a metallic foil, braid or combination may help manage electromagnetic interference and provide a defined high-frequency return path when correctly terminated. In medium-voltage power cable, conductor and insulation screens control the electric field, while a metallic screen may also form part of the protective-earth or fault-current path. These functions are not interchangeable, and "shielded cable" is not a complete specification.

Industrial users search for shielded cable when signals are unstable near motors and drives, when a VFD motor feeder must control conducted and radiated noise, or when a medium-voltage circuit requires screened phases and a coordinated grounding system. Applications range from crane control and offshore instrumentation to mining equipment, tunnel power distribution, mobile substations and converter-fed motors. The right design depends on circuit type, frequency content, voltage, fault duty, movement, route, grounding architecture and environmental exposure.

TEBAOFLEX's Shielded Cable range includes products spanning several distinct groups. Low-voltage signal and control applications are represented, for example, by the IEEE 1580 Type P and NEK 606 BFOU/RFOU marine-offshore families and the individually screened NGFLCGOU flat festoon cable. VFD-related products include the screened rubber VFD Mining Cable and dedicated Type P VFD constructions by model; take the voltage from the selected datasheet and quotation. Medium-voltage and mining products include Type SHD-GC, Type MP-GC, AS/NZS 1972, SANS Type 61/63/611/622/633/66 families, GSEYQY and XSEYQY tunnel cables, and multiple VDE/DIN flexible mining and reeling designs. Filter this range by function before comparing dimensions or electrical rating.

For a control or instrumentation circuit, first define the signal: analogue measurement, thermocouple, digital control, alarm, encoder or another system. Then consider source impedance, signal level, cable length, nearby noise sources and routing. Individual screens can separate circuits within a multicircuit cable; an overall screen can address external coupling; some designs use both. The screen needs a termination and bonding method consistent with the equipment manufacturer's EMC plan. Available options include screened constructions, but foil, braid, coverage and attenuation remain construction-specific.

For a VFD output circuit, screening is only part of the cable system. PWM switching can produce high-frequency common-mode current and transient voltage stress. Cable selection should consider drive voltage, motor current, conductor size, run length, carrier frequency, insulation system, phase and protective-earth symmetry, screen construction and termination at the drive and motor. The VFD Mining Cable construction has three power conductors, a three-way protective-earth arrangement and an overall tinned-copper braid. IEEE 1580 Type P also includes dedicated VFD configurations by model. Take voltage, armour, fire performance and approvals from the selected construction.

Medium-voltage screening serves different electrical duties. Medium-voltage constructions use semiconductive conductor screens, EPR or XLPE insulation, semiconductive insulation screens and copper wire, tape or braid screens. Some flexible mining designs use individual copper screens as protective-earth conductors; Type SHD-GC combines individually shielded phases with grounding and ground-check conductors; tunnel feeder products may add armour or steel-wire braid for mechanical protection. Screen cross-section, fault-current capability, bonding, earth arrangement, accessory compatibility and termination design must be coordinated with the power system. Low-voltage EMI guidance should not be copied into this context.

Movement changes screen selection. A foil can provide high coverage but may not suit the same repeated bending duty as a flexible braid; a braid's wire size, angle and coverage affect both flexibility and electrical behaviour. Reeling, trailing and festoon products need a complete flexible construction in which the screen, conductor lay-up and sheath move together. Specify the screen together with dynamic bend radius, torsion, tensile load, speed and cycle frequency.

The outer system still has to survive the environment. State oil, water, mud, salt, sunlight, ozone, temperature, abrasion and flame or low-smoke requirements. Available sheath systems include elastomeric, TPU, PVC, SHF2 halogen-free and other materials depending on model. Armour or reinforcement provides mechanical protection and acts as an EMI screen only where the cable construction and termination design assign it that role.

Standards and approvals in this range span IEEE 1580, NEK 606, DIN VDE, SANS, AS/NZS, ICEA and MSHA-related products. These references define different scopes. Before specifying shield effectiveness, certification or project approval, request the exact cable designation, voltage, model marking, test basis and approval document.

For an RFQ, provide circuit function, voltage, current and frequency content; conductor and pair/triad arrangement; individual or overall screen requirement; grounding and termination drawing; screen fault-current requirement for power cable; cable length and route; separation from noise sources; fixed, festoon, reeling or trailing movement; bend radius and tensile duty; armour, sheath and environment; governing standard; approval/document requirement; destination and quantity. Use the TEBAOFLEX products within the appropriate signal, VFD or medium-voltage screen group, with construction-specific data attached to the enquiry.