The Science Behind Cable Shielding and EMI Protection

By JianYunCable -

 

Table of Contents

1. What Is EMI and Why It Matters

Electromagnetic interference (EMI), also known as radio-frequency interference (RFI), refers to unwanted signals from sources such as motors, radios, and switching power supplies that disrupt cable performance. These interferences can lead to data errors or system malfunctions.

2. How Cable Shielding Works

Shielding encloses conductors in conductive layers that function as a Faraday cage, reflecting and absorbing EMI, then directing it to ground. This process minimizes both incoming interference and outward emissions.

3. Shield Types: Foil, Braid, Spiral, Combo

Shield TypeCoverageFrequency RangeStrengthsLimitations
Foil (Al/Mylar)100%High frequencyLightweight, full coverageLow flex life, fragile
Braid (Copper)70–95%Low–mid frequencyDurable, flexible, mechanically strongHeavier, gaps allow some EMI
Spiral/Serve85–95%Low frequencyVery flexible, easy terminationsPoor high-frequency protection
Foil + Braid Combo≈100%All frequency rangesBest overall protectionHeavier, thicker, higher cost

Foil shielding is ideal for high frequencies; braid offers mechanical durability; spiral enhances flexibility; and combination layers provide high performance across all frequency ranges.

4. Grounding & Termination Best Practices

Effective shielding requires proper grounding. Use 360° contact with the chassis to minimize inductance, avoiding pigtails. For enhanced high-frequency suppression, consider adding ferrite beads at cable ends.

5. Physics of Shielding

  • Reflection: Conductive layers reflect electric fields through induced currents.
  • Absorption: Some EMI energy is converted to heat within the shield.
  • Skin Effect: High-frequency currents flow near the shield’s surface, allowing small gaps in braid to remain effective if minimal relative to wavelength.

6. Where Shielding Matters Most

  • Industrial Environments: Shields signals from interference caused by heavy machinery and power lines.
  • Medical & Aerospace: Critical systems demand near-perfect shielding for reliability.
  • Data & Audio: Twisted-pair and XLR cables use shielded pairs to reduce crosstalk and EMI.

7. Conclusion

Effective EMI protection requires selecting the appropriate shield type based on frequency range and flexibility needs, ensuring proper grounding, and using multiple layers when necessary. These measures are critical for maintaining signal integrity across various industries.

Source: JianYunCable.

Comments

Post a Comment

Popular posts from this blog

Understanding Voltage Levels and Cable Types in China's Power Industry

By JianYunCable -
Image
  In China's electrical power industry, voltage levels play a critical role in determining the type of cables used and their applications. Common voltage grades include 220V, 380V, 1kV, 10kV, 35kV, 110kV, 220kV, and 500kV. These are broadly categorized into three groups: low voltage, medium voltage, and high voltage. This article explores the differences between low-voltage and high-voltage cables, their structures, uses, production processes, and how to distinguish them in practice. Voltage Classifications in China Low Voltage (LV):  Typically 220V and 380V, primarily used for household electricity and small-scale applications. Medium Voltage (MV):  Ranges from 1kV to 35kV, serving as an intermediary for industrial and local distribution networks. High Voltage (HV):  Starts at 35kV and above (e.g., 110kV, 220kV, 500kV), mainly employed for long-distance power transmission. These classifications dictate the design and construction of cables to ensure safety and effic...
Read more

Comparison of Flame Retardant Standards for Electric Wires and Cables

By JianYunCable -
Image
  ​ Introduction With the increasing demand for  fire safety in electric wires and cables ,  flame retardant standards  play a critical role in preventing  fire hazards and the spread of flames . This paper compares the  domestic and international flame retardant standard systems , focusing on  GB/T 19666-2019  and  GB 31247-2014 , and analyzes the  key technical indicators, sample burning methods, and combustion test parameters . 1. Current Standards for Flame Retardant Cables 1.1 International Standards (IEC 60332 Series) IEC 60332-1-1:2015 ,  IEC 60332-1-2:2004 , and  IEC 60332-1-3:2004  focus on the  flame spread height  based on  non-metal content in cables . China adopts these standards through  GB/T 18380-2022 , which aligns with  IEC 60332 . 1.2 Chinese National Standards GB/T 19666-2019 : General rules for flame-retardant and fire-resistant electric wires and optical cables. GB 31247-2014 ...
Read more

What Are Trailing Cables and Where Are They Used?

By JianYunCable -
Image
  Table of Contents What Are Trailing Cables? Construction and Features Key Benefits of Trailing Cables Applications of Trailing Cables Limitations of Trailing Cables Trailing vs. Standard Cables Comparison Table Tips for Choosing Trailing Cables Conclusion What Are Trailing Cables? Trailing cables, also known as reeling cables or mining trailing cables, are specialized, highly flexible electrical cables designed to power mobile or frequently moving equipment in demanding industrial environments. Engineered to withstand mechanical stresses such as bending, twisting, stretching, and coiling, these cables ensure a reliable connection between power sources and equipment like excavators, cranes, and draglines. They are commonly used in industries such as mining, construction, and heavy manufacturing, where durability and safety are critical. Trailing cables comply with standards like AS/NZS 1747 (for mining cables) and IEC 60245, offering features like flame retardancy and grounding fo...
Read more

Understanding Low Voltage Power Cables: A Comprehensive Guide

By JianYunCable -
Image
Low voltage (LV) power cables are an essential component of modern electrical systems, facilitating the safe and efficient transmission of electricity for a wide range of applications. Defined as cables with a rated voltage not exceeding 0.6/1 kV (600 volts for DC or 1000 volts for AC), they are widely used in residential, commercial, and industrial settings. This article explores the key aspects of LV power cables, addressing common questions from multiple angles—design, applications, materials, and challenges—while providing clear answers backed by scientific principles and practical insights. What Are Low Voltage Power Cables ? Low voltage power cables are electrical cables designed to transmit power or signals at voltages up to 0.6/1 kV. Unlike high voltage (HV) cables, which handle large-scale power distribution (typically above 1 kV), or medium voltage (MV) cables (3-35 kV), LV cables cater to localized power needs, such as household wiring, industrial machinery, ...
Read more

Medium Voltage Cable Life Expectancy: Factors and Insights

By JianYunCable -
Image
Table of Contents What Are Medium Voltage Cables? What Is the Life Expectancy of MV Cables? Factors Affecting MV Cable Life Expectancy Single-Core and Multi-Core MV Cables MV Cable Insulation Comparison Table Maintenance Tips to Extend MV Cable Life Conclusion What Are Medium Voltage Cables ? Medium voltage (MV) cables are electrical cables designed to transmit power at voltages ranging from 3.6 kV to 35 kV, bridging the gap between low voltage (up to 1 kV) and high voltage (above 50 kV) systems. They are critical for power distribution in urban and rural networks, industrial facilities, mining operations, and transportation systems like railways. MV cables typically feature copper or aluminum conductors, insulation (often cross-linked polyethylene, or XLPE), and protective layers like metall...
Read more

4 AWG Wire: Definition, Specifications, Ampacity, and MM² Equivalent

By JianYunCable -
Image
  Table of Contents What is 4 AWG Wire? 4 AWG Wire Specifications Ampacity of 4 AWG Wire 4 AWG Wire in MM² Applications of 4 AWG Wire Summary of 4 AWG Wire Characteristics Tips for Selecting 4 AWG Wire Conclusion What is 4 AWG Wire? 4 AWG wire refers to a conductor sized according to the American Wire Gauge (AWG) system, a standardized method for measuring wire diameters in North America. The AWG system assigns smaller gauge numbers to thicker wires with greater current-carrying capacity. A 4 AWG wire is a relatively large conductor, suitable for high-current, low-voltage applications in residential, commercial, and industrial settings. It is commonly made of copper or aluminum, with copper offering higher conductivity and aluminum providing cost savings for larger installations. 4 AWG wire is used in applications requiring significant power delivery, such as service entrances or heavy equipment, as discussed in prior articles on AWG, 2 AWG vs. 2/0 AWG, and medium voltage cables. 4...
Read more

Optimized Design of Smooth Aluminum Sheath Thickness for High-Voltage Cables Using the Short-Circuit Capacity Method

By JianYunCable -
Image
  Introduction High-voltage and ultra-high-voltage underground power cables require  metal sheaths  to provide  mechanical protection, waterproofing, and electrical shielding . A  smooth aluminum sheath  offers advantages over traditional  corrugated aluminum sheaths , including  better electrical contact and lower risk of insulation failure . However, if the aluminum sheath  thickness is not optimized , it may  wrinkle during bending , compromising cable performance. This study introduces a  short-circuit capacity-based design method  for determining the  optimal aluminum sheath thickness , ensuring both  mechanical durability and electrical safety . 1. Influence of Aluminum Sheath Thickness on Cable Performance 1.1 Wrinkling and Mechanical Stability When designing aluminum sheath thickness, using values from  corrugated aluminum sheaths  can lead to  wrinkling  after bending, especially in  ...
Read more

0.6/1kV CU/XLPE/PVC Cable

By JianYunCable -
Image
  0.6/1kV CU/XLPE/PVC Cable Introduction Conductors Copper conductor Insulation XLPE (Cross-Linked Polyethylene) Outer Sheath PVC (Polyvinyl Chloride) Application These cables are used for electricity supply in low voltage installation system. They are suitable for installation in indoors and outdoors, in cable ducts, under ground, in power and switching stations, local energy distributions, industrial plants, where there is no risk of mechanical damage. Product Parameters Single core(unarmoured) Nominal Cross Section Diameter of Conductor (Approx.) Nominal Insulation Thickness Nominal Sheath Thickness Overall Diameter (Approx.) mm² mm mm mm mm 1x1.5 1.4 0.7 1.4 5.6 1x2.5 1.8 0.7 1.4 6 1x4 2.3 0.7 1.4 6.5 1x6 2.8 0.7 1.4 7 1x10 3.6 0.7 1.4 7.8 1x16 4.5 0.7 1.4 8.7 1x25 5.6 0.9 1.4 10.2 1x35 6.7 0.9 1.4 11.3 1x50 8 1 1.4 12.8 1x70 9.4 1.1 1.4 14.4 1x95 11 1.1 1.5 16.1 1x120 12.4 1.2 1.5 17.8 1x150 13.8 1.4 1.6 19.8 1x185 15.3 1.6 1.6 21.8 1x240 17.5 1.7 1.7 24.4 1x300 19.5 1.8 1.8 ...
Read more

Understanding LSOH Cables: Safety and Applications

By JianYunCable -
Image
  Table of Contents What Are LSOH Cables? How Are LSOH Cables Constructed? LSOH vs. PVC Cables: Key Differences Single-Core and Multi-Core LSOH Cables What Are the Applications of LSOH Cables? LSOH vs. PVC Comparison Table Safety and Selection Tips for LSOH Cables Conclusion What Are LSOH Cables? Low Smoke Zero Halogen (LSOH) cables, also referred to as LSZH, LS0H, LSFH, or OHLS, are specialized electrical cables designed to enhance safety during fire events. Unlike traditional cables, LSOH cables emit minimal smoke and no halogen gases when exposed to flames, reducing risks of toxic inhalation and equipment corrosion. These cables are critical in environments where fire safety is paramount, such as public buildings, transportation systems, and confined spaces. Their halogen-free composition makes them an environmentally friendly choice, aligning with modern safety and sustainability standards. How Are LSOH Cables Constructed? LSOH cables are engineered with materials that prioriti...
Read more

Understanding Voltage Levels and Cable Types in China's Power Industry

By JianYunCable -
Image
  In China's electrical power industry, voltage levels play a critical role in determining the type of cables used and their applications. Common voltage grades include 220V, 380V, 1kV, 10kV, 35kV, 110kV, 220kV, and 500kV. These are broadly categorized into three groups: low voltage, medium voltage, and high voltage. This article explores the differences between low-voltage and high-voltage cables, their structures, uses, production processes, and how to distinguish them in practice. Voltage Classifications in China Low Voltage (LV):  Typically 220V and 380V, primarily used for household electricity and small-scale applications. Medium Voltage (MV):  Ranges from 1kV to 35kV, serving as an intermediary for industrial and local distribution networks. High Voltage (HV):  Starts at 35kV and above (e.g., 110kV, 220kV, 500kV), mainly employed for long-distance power transmission. These classifications dictate the design and construction of cables to ensure safety and effic...
Read more

All Cable Products-Henan Province Jianyun Cable Co., Ltd.

Loading...