Latest Wiring Devices Articles

When to Use Metal Conduit vs PVC? Compare EMT/rigid for grounding, EMI shielding, impact strength, and heat; choose PVC for corrosion resistance, wet locations, direct burial, UV exposure, and chemical environments per NEC.

When to Use Metal Conduit vs PVC?

Use metal for grounding, EMI shielding, and impact; use PVC for corrosion resistance, wet or buried runs, and chemicals.

✅ Metal: grounding, EMI shielding, high impact/heat, indoor industrial

✅ PVC: corrosion-proof, wet locations, direct burial, chemical plants

✅ Follow NEC: fitting types, bonding, derating, temperature limits

Did you know that a seemingly simple choice like conduit material can make or break your electrical installation? Selecting the right conduit, whether metal or PVC, is crucial for ensuring safety, longevity, and code compliance in any electrical project. While both materials serve the essential function of protecting and routing electrical wires, they each possess unique characteristics that make them suitable for different environments and applications. This article dives deep into the metal conduit vs PVC debate, exploring their key differences, advantages, disadvantages, and installation considerations to help you make informed decisions for your next project. For a broader understanding of how conduit selection relates to wire types, see this guide to electrical cables for planning your layout.

What are the key differences between metal conduit and PVC, and when should each be used?

Metal conduit, often made from galvanized steel, is renowned for its robust strength and ability to withstand impacts, making it the go-to choice for industrial settings, construction sites, and areas prone to physical stress.  Furthermore, metal conduit provides inherent grounding capabilities, adding an extra layer of safety by providing a low-resistance path for fault currents to flow to ground. This is critical in preventing electrical shocks and equipment damage. Within the metal family, EMT (Electrical Metallic Tubing) offers a lighter-duty option that still provides reliable protection for many commercial runs.

On the other hand, PVC conduit shines in its resistance to corrosion and moisture. This lightweight and non-conductive material is ideal for underground installations, damp locations like basements, and areas exposed to harsh chemicals. PVC's ease of installation, thanks to its flexibility and simple joining methods, makes it a favorite for DIYers and contractors alike. Understanding how materials interact with current is useful, and the basics outlined in what conducts electricity help explain why PVC’s non-conductive properties enhance certain safety strategies.

In what environments is metal conduit preferred over PVC?

Think heavy-duty! Metal conduit reigns supreme in environments where physical protection is paramount. Industrial facilities with heavy machinery, construction zones with potential for impact, and areas with high vibration all benefit from the ruggedness of metal conduit.  Moreover, in hazardous locations where flammable gases or vapors may be present, metal conduit provides an added layer of protection by containing sparks or arcs that could ignite an explosion. In such high-risk settings, pairing raceways with appropriately rated equipment like metal-clad switchgear can further improve resilience and fault containment.

When is PVC conduit a better choice than metal conduit?

PVC conduit takes the lead when corrosion is a concern. Underground installations, where moisture and soil conditions can wreak havoc on metal, are prime candidates for PVC. Similarly, in areas exposed to chemicals or saltwater, PVC's resistance to corrosion ensures the longevity and integrity of the electrical system.  Its lightweight nature also makes it easier to handle and install in tight spaces or overhead applications.

How does the installation process differ between metal conduit and PVC conduit?

Installing metal conduit often involves specialized tools like threading machines and conduit benders.  The rigid nature of metal conduit requires careful planning and precise cuts to ensure proper alignment and secure connections. While more labor-intensive, the resulting installation is incredibly robust and durable. For installers mastering field techniques, the step-by-step guidance on how to bend conduit can reduce errors when laying out offsets and saddles.

PVC conduit, in contrast, offers a more DIY-friendly installation experience.  Simple hand tools like hacksaws and PVC cutters are sufficient for cutting and shaping the conduit.  Joining sections is typically done with solvent cement, creating a watertight and secure bond.  PVC's flexibility also allows for easier navigation around obstacles and bends. Once raceways are in place, best practices for pulling and terminating conductors in accordance with conductor and cable installation standards help ensure long-term reliability.

What are the cost considerations when choosing between metal conduit and PVC?

PVC conduit generally enjoys a lower upfront cost compared to metal conduit. The material itself is less expensive, and the simpler installation process translates to reduced labor costs. However, the long-term cost-effectiveness depends on the specific application. In environments where corrosion is a major factor, PVC's longevity can lead to significant savings on repairs and replacements down the line. Evaluating lifecycle cost should also account for conductor selection in buried runs, and insights on copper for underground transmission can inform decisions about durability and losses over time.

The "metal conduit vs PVC" decision ultimately hinges on the specific demands of your electrical project.  Metal conduit offers unparalleled strength and grounding capabilities, making it ideal for harsh and hazardous environments. PVC conduit counters with its corrosion resistance, ease of installation, and cost-effectiveness, making it suitable for underground, damp, and corrosive locations. By carefully considering the factors discussed in this article, you can confidently choose the right conduit material to ensure a safe, reliable, and code-compliant electrical installation.

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Examples of load devices include resistive heaters and lamps, inductive motors and transformers, and capacitive power supplies, drawing AC/DC power in electrical circuits and affecting power factor, efficiency, and voltage regulation.

What Are Examples of Load Devices?

Typical loads include resistive heaters and lamps, inductive motors, and capacitive supplies in AC/DC systems.

✅ Resistive: heaters, incandescent lamps, toasters

✅ Inductive: AC motors, compressors, solenoids

✅ Capacitive: capacitor banks, switch-mode PSUs

Examples of Load Devices Include: Load devices play a crucial role in electrical systems by consuming power and converting it into other forms of energy, such as heat, light, or mechanical motion. Understanding examples of load devices is essential for both engineers and electricians working with various types of circuits. These devices range from simple light bulbs to complex electric motors, and they impact the overall performance and efficiency of an electrical system. By exploring different types of load devices and their applications, you can gain a deeper understanding of how power is distributed and utilized in residential, commercial, and industrial settings. For foundational definitions and context, the concept of an electric load is explained in the what is electric load resource, which clarifies how loads relate to sources and circuits.

What Are Load Devices in an Electrical System?

A load device is any electrical component or appliance that consumes power from a power source to perform work. These devices are the endpoint in a circuit where the flow of electric current is converted into some form of output, such as heat, light, motion, or sound. The behavior and performance of these devices are critical in both residential and industrial applications, as they directly affect the overall operation of power systems. Standard terminology used to describe loads and power quality is outlined in the electricity terms glossary, aiding consistent interpretation across projects.

Electrical loads are categorized based on how they use power. The three primary categories of electrical loads are resistive loads, inductive loads, and capacitive loads. Understanding these categories helps in assessing how different devices function and their impact on an electrical circuit.

What Are Some Common Examples of Load Devices?

Resistive loads are devices that primarily convert electrical energy into heat. The resistance in these loads limits the flow of current, causing energy to dissipate in the form of heat. Resistive loads include devices such as incandescent light bulbs, electric heaters, and ovens. These devices are simple in their operation, with no moving parts and no creation of magnetic fields. For a deeper look at characteristics and examples, see this overview of resistive load behavior and its implications for power quality.

Inductive loads operate by using electromagnetic fields to perform mechanical work. Devices that fall into this category include electric motors, fans, and transformers. These devices have coils or windings that create magnetic fields when current passes through them, enabling them to perform tasks like moving or transforming electrical energy. Inductive loads are common in industrial settings where machines with moving parts are in operation. Practical distinctions among motors, transformers, and solenoids are summarized in the inductive load guide with notes on starting currents and power factor.

Capacitive loads store electrical energy in an electric field and release it as needed. Capacitors, which are often used in power correction applications, are common examples of capacitive loads. These loads do not typically consume electrical energy in the same way that resistive and inductive loads do, but they play an essential role in maintaining balance in power systems applications. Design considerations for power factor correction are outlined in the capacitive load reference for typical facility applications.

How Do Load Devices Impact Electrical Systems?

The impact of different devices on an electrical system depends largely on their type. Resistive loads tend to have a steady and predictable effect on a system, with minimal interference with the flow of electric current. These loads are relatively straightforward to manage and usually have little impact on system stability.

However, inductive loads can present challenges due to their reliance on magnetic fields. When inductive loads are in operation, they create a lag between voltage and current, which can reduce overall efficiency in the system. For example, an electric motor requires more current to start than to run, and the fluctuating demands can strain an electrical system, especially if multiple inductive loads are used simultaneously. Where motors run for three hours or more, classification as a continuous load informs conductor sizing and protective device settings.

Capacitive loads also affect system performance, though their impact is typically seen in how they interact with other loads, particularly inductive ones. Capacitors are often used to offset the lag created by inductive loads, thereby improving the power factor of a system. In essence, capacitive and inductive loads work together to stabilize electrical systems by balancing the timing of voltage and current.

How Do Load Devices Influence Power Quality and Electrical Performance?

The performance and efficiency of an electrical system depend heavily on the balance of types of electrical loads within it. Resistive loads, with their stable and linear energy consumption, tend to have minimal effect on power quality. On the other hand, inductive loads, such as electric motors, can introduce issues like voltage drops, power factor degradation, and harmonic distortion, which can negatively impact the overall performance of a system. Evaluating utilization over time with the load factor metric helps identify demand peaks and efficiency opportunities.

When inductive loads are in operation, the relationship between current and voltage becomes misaligned, often leading to reduced efficiency. In large-scale power systems applications, this can lead to increased energy losses and potential overheating of equipment. To mitigate these effects, power systems often employ capacitive loads for power factor correction, which helps realign the current and voltage, reducing energy waste and improving overall system stability.

The distribution of resistive, inductive, and capacitive loads in a system also plays a role in electrical performance. In a well-designed system, the right balance of these loads ensures smooth operation, with minimal losses and disturbances. However, if the loads are improperly balanced, issues like voltage sags, surges, or even equipment failure can occur. Maintaining proper load management is key to avoiding these problems and ensuring efficient operation across all devices.

In summary, load devices, including resistive loads, inductive loads, and capacitive loads, play crucial roles in electrical systems by converting electrical power into functional output. Each type of device has a different effect on system performance. Resistive loads include simple, heat-generating devices that have minimal impact on system efficiency, while inductive loads like electric motors can create challenges by introducing inefficiencies and power quality issues. Capacitive loads, on the other hand, are vital for stabilizing systems, particularly in power systems applications that involve a significant number of inductive devices.

Understanding these fundamental principles of load behavior is essential for ensuring the reliable operation of electrical systems. Whether in residential, commercial, or industrial settings, proper management of load devices contributes to the overall efficiency and safety of electrical circuits.

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Cable handling and testing procedures ensure safe installation, correct bend radius, proper termination, and compliance via insulation resistance, continuity, and hipot tests, TDR fault locating, grounding checks, and IEC/IEEE standards adherence.

What Are Cable Handling and Testing Procedures?

Standard methods for safe cable installation and verification using insulation resistance, continuity, and hipot tests.

✅ Control bend radius, pulling tension, and strain relief per datasheets.

✅ Run IR, continuity, and hipot tests using calibrated meters and VLF.

✅ Document results to IEC 60502, IEEE 400.2, and site QA/QC.

PRE-INSTALLATION

To ensure safety during cable installation and reliability once the cable is installed, you should confirm the following prior to installation: • The cable selected is proper for your application • The cable has not been damaged in transit or storage Review all applicable state and national codes to verify that the cable chosen is appropriate for the job. Also, consult your local building authority. Next, you must identify any existing cable damage and prevent any further damage from occurring. This is done through proper cable inspection, handling and storage. Consulting resources such as a guide to electrical cable classifications can help verify selections before work begins.

CABLE INSPECTION

Inspect every cable reel for damage before accepting the shipment. Be particularly alert for cable damage if:

• A reel is laying flat on its side
• Several reels are stacked
• Other freight is stacked on a reel
• Nails have been driven into reel flanges to secure shipping blocks
• A reel flange is damaged • A cable covering is removed, stained or damaged
• A cable end seal is removed or damaged
• A reel has been dropped (hidden damage likely)

For older distribution systems, an assessment overview of XLPE and PILC cables outlines common defect modes to consider during receipt inspection.

CABLING HANDLING

Remove all nails and staples from the reel flanges before moving a reel, and avoid all objects that could crush, gouge or impact the cable when moving. NEVER use the cable as a means to move a reel. When unreeling, observe recommended bending radii, use swivels to prevent twisting and avoid overruns.

If the route includes tray systems, follow best practices for installing cable in cable trays to minimize damage during pulling and dressing.

CABLE INSTALLATION

A survey of customer complaints revealed that 92% of the cables in question failed due to mechanical damage. When does mechanical damage usually occur? During installation. In fact, most cables are subjected to more mechanical stress during installation than they ever experience in actual operation. Needless to say, handling and pulling your cable according to manufacturer’s recommendations is extremely important. There are five main considerations in any cable installation:

• Ambient temperature
• Equipment
• Conduit fill
• Mechanical fit in raceway
• Physical limitations

For detailed field methods and safety precautions, refer to installation guidance for conductors and cables to plan equipment, pulling tensions and lubricant use.

AMBIENT TEMPERATURE

Low temperatures are a cause for concern when installing cable. The following are temperatures below which cable should not be installed.

PHYSICAL LIMITATIONS TRAINING AND BENDING

Training is the positioning of cable which is not under tension. Bending is the positioning of cable which is under tension. When installing cable, the object is to limit these forces so that the cable’s physical and electrical characteristics are maintained for the expected service life. The recommended limits are:

• Tables per National Electric Code (see tables at right)
• Tables per ICEA/NEMA (see pg 100)
• A non-shielded cable can tolerate a sharper bend than a shielded cable can. This is especially true for cables having helical metal tapes which, when bent too sharply, can separate, buckle and cut into the insulation.

Beyond bend limits, using properly rated cable cleats helps restrain short-circuit forces and protect insulation integrity in tray and ladder runs.

The problem is compounded by the fact that most tapes are under jackets which conceal such damage. The shielding bedding tapes or extruded polymers have sufficient conductivity and coverage initially to pass acceptance testing, then fail prematurely due to corona at the shield/insulation interface. Remember that offsets are bends.

CABLE TESTING

Prior to performing the “Hi-Pot” tests, it is recommended that all insulated conductors should be meggered (insulation resistance tests) – See the formula below. The test voltage should be increased in steps of 10kV, or minimum of 5 steps. The duration at each step should be long enough for the current to reach a steady value (1 minute suggested).

For context on acceptance and maintenance test choices, see an overview of power cable testing that compares DC, VLF and tan delta applications.

The test current will momentarily increase for each voltage increment due to charging of the capacitance and the dielectric absorption characteristics of the insulation. Stabilized current should be recorded at each step. The maximum test voltage should be maintained for 15 minutes (new cable, shielded)/5 minutes (non-shielded). Leakage current should be recorded each minute after the maximum test voltage has been reached. Increase of leakage current at any step point may be an indication of a cable insulation problem.

To trend condition over time and pinpoint localized issues, power cable diagnostics techniques integrate partial discharge, VLF and oscillating-wave tests for actionable insights.

Failure of the cable or cable accessories may result unless the voltage is rapidly reduced. Otherwise, the leakage current should stabilize after about 5 minutes. Leakage current is essentially a function of the construction and length of cable but it can be influenced by the test conditions (wind and humidity) as well as the test apparatus (leads).

Typical leakage currents in the order of 100 – 150 microamperes are not unusual. A defective installation is identified by high or fluctuating leakage current with time, at a fixed DC voltage. All testing should be performed by qualified personnel taking all appropriate safety precautions.

From: Wire and Cable and Wiring Methods Handbook, Vol 3, The Electricity Forum

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Assessment of XLPE and PILC Cables covers diagnostics, condition monitoring, insulation testing, partial discharge analysis, tan delta, VLF, sheath integrity checks, and lifecycle asset management to enhance reliability, safety, and fault prevention.

What Is the Assessment of XLPE and PILC Cables?

A systematic evaluation using diagnostics to determine cable condition, risks, and maintenance needs.

✅ Conduct PD, VLF, and tan delta tests to gauge insulation health.

✅ Analyze sheath integrity, TDR traces, and thermography for defects.

✅ Score asset condition to plan maintenance, refurbishment, or replacement.

GE Energy uses non-destructive diagnostic technology to measure the overall health of a power cable, to reveal existing cable defects through partial discharge testing, and to predict the future life expectancy of the cable. Cable testing helps our customers to be proactive in preventing costly forced service outages while optimizing their capital budgeting for replacement programs. This offering applies to medium- and high-voltage shielded power cable (5-25 kV XLPE cables and 5-500 kV PILC cables) with a maximum length of 1.5 to two miles. The cables to be tested can be overhead, in cable trays, in duct bank, or buried. The GE Energy solution includes both general condition assessment and partial-discharge technologies. This paper will address only the general condition assessment technology. For a broader overview of techniques for asset condition assessment, see the Electricity Forum's power cable diagnostics guide for context on PD detection and lifecycle modeling.

DIAGNOSTICS OF XLPE (CROSS-LINKED POLYETHYLENE) CABLES

One of the major causes of failures in XLPE insulated cables is water-treeing. Water-tree deterioration process is very slow (5-50 years) and can vary from cable to cable, among different designs, and also among individual cables of same design. Earlier studies have shown that the dielectric response, obtained by dielectric spectroscopy measurements performed at high voltage levels, is correlated to water-tree content and breakdown voltage. Higher losses and increasing non-linearity of frequency response are associated with lower breakdown voltage. Understanding the relationship between dielectric losses and the principles in insulation resistance explained can help interpret slope changes and voltage dependence more confidently.

Water-tree measurement on XLPE cable requires an IDA 200* insulation diagnostics unit with the IDA HVU (High Voltage Unit) option. The diagnostic approach is based on extent of non-linearity of XLPE cable insulation. In performing a general condition assessment on XLPE cable, the dielectric spectroscopy technology shows the severity of water-trees in the insulation. The water-tree aging process is very slow, but it is important to understanding the degree of damage to the insulation. A heavily aged cable can fail catastrophically if the insulation stress is increased quickly (i.e. lightning impulses or faults). The HVU is used with the IDA 200 system to increase the output voltage up to 30 kV (21 kVrms). The main application for this combination is for diagnosis of water-tree deteriorated extruded power cables. The system works equally well when other types of non-linear materials are to be characterized. Field crews should follow established cable handling and testing procedures to ensure safe setup of the IDA 200 and HVU in energized environments.

DIAGNOSTICS OF PAPER INSULATED (PILC) CABLES

The three most commonly seen problems in PILC cables are partial discharge (cable itself and joints), moisture ingress, and thermal aging and resulting increase of moisture content (not dangerous by itself). In performing a general condition assessment on paper-insulated cable, the dielectric spectroscopy technology allows for estimation of average moistening of the insulation. Moreover, the presence of other defects, such as developing short-circuit due to carbonizing of paper, may be identified. Measurements on PILC cables are normally performed with the IDA 200 system only. Test voltage is by default 140 Vrms and frequency range 0.01-1000 Hz. Frequency response of a paper insulated cable can reveal worsening of insulation condition which is caused, for example, by an increase of moisture content. For locating and characterizing PD sources in substations and vaults, modern FLIR PD acoustic imaging can provide rapid screening before detailed dielectric assessment.

TECHNICAL DESCRIPTION OF IDA 200

The system (IDA 200) measures the impedance of a specimen at a variable voltage and frequency. A Digital Signal Processing (DSP) unit generates a test signal with the desired frequency. This signal is amplified with an internal amplifier and then applied to the specimen. The voltage over and the current through the specimen are measured with high accuracy using a voltage divider and an electrometer (ampere meter). The diagnostic measurement is performed by applying a relatively low voltage (up to 140 Vrms). The IDA 200 system measures the capacitance and dielectric losses at discrete frequencies both above and below the main frequency (output signals with frequencies from 0.1 mHz to 1 kHz are available). By avoiding the main frequency and its harmonics, an efficient filtering of their corruptive effects is enabled. These measurement strategies align with best-practice power cable test methods used across utilities for benchmarking insulation performance.

The diagnostic measurement is performed by applying a relatively low voltage (up to 140 Vrms). The IDA 200 system measures the capacitance and dielectric losses at discrete frequencies both above and below the main frequency (output signals with frequencies from 0.1 mHz to 1 kHz are available). By avoiding the main frequency and its harmonics, an efficient filtering of their corruptive effects is enabled.

DATA INTERPRETATION XLPE CABLES

The IDA 200 system helps to identify water-treeing in an extruded power cable. There are four different responses that will help to determine the health of the cable: low losses and no voltage dependence, VDP response, TLC response and LC response. LOW LOSSES AND NO VOLTAGE DEPENDENCE Graph 1 is an example showing capacitance changes in a cable having good overall health (dry cable). The cable was frequency swept from 0.1 Hz to 1 Hz at 3kV and 6kV. When the voltage is varied from 3kV to 6kV, the capacitance remains relatively the same, thus indicating a good condition of the cable. Moreover, when the 3kV and 6kV tests were performed, the frequency response was repeatable showing that the cable behaves consistently when voltage is varied. Similar condition-monitoring principles are applied in transformer oil testing to trend dielectric strength and contaminants across a fleet.

VDP RESPONSE

A voltage dependent increase of capacitance and loss. Graph 2 displays the capacitance changes that show a dry cable vs. a moist cable. Both cables were frequency swept from 0.1 Hz to 1 Hz at 3kV and 6kV. When looking at the dry cable, the voltage is varied from 3kV to 6kV and the capacitance stays relatively the same, thus indicating a good condition of the cable. If we look at the moist cable, when the voltage is varied from 3kV to 6kV, the capacitance increases with voltage. Looking at the moist cable, when the 3kV, 4.5kV and 6kV tests were performed, the frequency response is also not repeatable indicating water-treeing is present in this cable.

CONCLUSION

The IDA 200 test set can be used to help identify watertreeing in XLPE as well as moistening of the PILC cables. By identifying water-treeing in XLPE cables, increased moisture content in PILC cables and other defects in both types of cables, customers will have the ability to create a cost effective maintenance program for their cables and thus increase the reliability of their network. Informed by these diagnostics, utilities can integrate power transformer health checks into broader maintenance strategies for substations and feeders.

From: Wire and Cable and Wiring Methods Handbook, Vol 3, The Electricity Forum

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Installation of conductors and cables ensures compliant wiring, routing, and terminations with proper ampacity, insulation, grounding, shielding, and bend radius control per NEC/IEC standards, using conduit, cable trays, pull tension limits, and labeling.

What Is Installation of Conductors and Cables?

Engineering process of routing, securing, and terminating electrical wiring to code with proper protection and testing.

✅ Size conductors for ampacity, voltage drop, and derating.

✅ Maintain bend radius, pull tension, and tray/conduit fill limits.

✅ Ensure grounding, bonding, labeling, and NEC/IEC compliance.

1. SINGLE- VS MULTI-CONDUCTOR CONSTRUCTIONS

It is generally accepted that armoured cable installations are more economical than pipe and wire installations, as wire pulling and conduit installation are not required. Armoured cables are readily available in single- and multi-conductor constructions. Various aspects should be considered when selecting either type. While single conductor cables might initially seem more economical, a summary analysis will reveal technical constraints such as voltage drop and installed costs that can substantially reduce any real cost advantages. Some of these technical concerns are outlined below. For a broader overview of cable types and selection factors, see the guidance in Know Your Electrical Cables for context on materials, ratings, and applications.

COST OF MATERIAL

Cost analyses show multi-conductors to be more cost effective than single-conductors for many installations. Although single-conductors have higher ampacities, they require proportionally more insulation, armored and jacketing material than a comparable multi-conductor installation. Good procurement should be paired with proper cable handling and testing procedures to avoid damage that can erase anticipated savings.

COST OF LABOUR

With single-conductors each phase must be installed separately, whereas all phases are installed at once when using multi-conductor cables. Using appropriately spaced cable cleats can also speed installation in trays while improving safety and phase grouping control.

VOLTAGE DROP

In multi-conductor cables, phase conductors (and neutral conductor, where present) are twisted together, for the minimum possible spacing. This geometry leads to the lowest inductive reactance and voltage drop. In single-conductor circuits, phase conductors are laid out in parallel. The extra thickness of the jacket and armour (where present), and the separation required to obtain more favourable free air ratings, lead to greater inductive reactance and voltage drop. These impedance effects become especially critical in long runs typical of copper underground transmission where cumulative reactance, loss, and voltage regulation must be tightly controlled.

MAGNETIC FIELDS AND HARMONICS

Magnetic fields in harmonic frequencies of ascending order can cause unpredictable effects with sensitive electronic equipment such as computers and instrumentation. Expensive techniques such as shielding and filtering of power supplies often represent the only corrective solution. The mutual cancellation effect on magnetic fields of the fundamental (usually 60 hz) frequency is not necessarily extended to fields created by harmonic currents. The magnetic fields having frequencies of the third harmonic, or multiples of the third harmonic, reinforce rather than cancel, and this typically leads to higher magnetic field magnitude in the region surrounding single conductor cables.

This effect is greatly diminished in four-conductor constructions where the fields generated by the neutral conductors cancel the fields of the phase conductors. Harmonics are multiples of the original frequency (60 Hz) and can result from chopping of the waveforms of solid-state devices. Examples of such types of equipment include fluorescent lighting ballasts, dimmers, motor controls, and various other types of industrial control equipment. Odd harmonics (3rd, 5th, 7th, etc.) may cause damaging over-voltages spikes. Care should also be taken when selecting clamps and connectors. These should be made of non-ferrous materials to avoid overheating from magnetic hysteresis and eddy current losses produced by circulating magnetic fields. Given that third harmonics will amplify these effects, it is especially important to properly balance currents between parallel conductors of the same phase. Balancing third harmonic currents is almost impossible with single conductors. Special consideration should thus be given to multi-conductors, and especially to 4-conductor cable assemblies that can inherently balance harmonic currents. Understanding the role of the neutral conductor is central to managing triplen harmonics, return currents, and thermal loading in multi-conductor systems.

2. INSTALLATION OF SINGLE-CONDUCTOR

AC90, ACWU90 AND TECK90 CABLES

In circuits rated 425 amps and larger, it is necessary to isolate the armour from the grounded metal of the enclosure and the armour of the other circuit conductors. Similarly, the armour must be adequately and continuously insulated from grounded metal such as tray or struts. The most satisfactory way to accomplish this is by means of an outer jacket over the armour. At the remote end of the cable, closest to the point of utilization, armour and bonding conductor will carry a significant potential difference to ground whenever current flows in the central conductor. A spark could be generated if the armour is grounded through accidental contact with grounded metal. The opening of a sheath circuit that has been accidentally grounded in this manner can produce a spark with considerable energy loss – an unexpected hazard for maintenance crews or non-electrical trades people working in the area. Single-conductor circuits in hazardous location are not recommended due to the risk of sparking initiated by standing voltages on the armour. When these circuits are supported in trays, refer to installation of cable in cable trays to verify support spacing, bonding practices, and separation from grounded metallic elements.

CIRCUITS RATED UP TO 425 AMPS INCLUSIVE

On any AC system, currents flowing in the centre conductor will induce small currents in the concentrically applied bonding wires and in the interlocked armour. For circuit ampacities up to and including 425 amps, these induced currents do not affect the cable ampacity and may be neglected. We recommend terminating the cables as follows: the bonding wires of all cables entering the equipment enclosure should be bunched and connected to the bonding screw of the terminal (2), the armour of each cable should be attached to the entry plate by means of an approved connector, and the entry plate should be aluminum or some other non-magnetic conducting material. Coordination with the facility’s grounding electrode conductor will further support fault clearing performance and reduce stray sheath currents.

From: Wire and Cable and Wiring Methods Handbook, Vol 3, The Electricity Forum

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Know your electrical cables with guidance on wire types, gauges, insulation, voltage ratings, amperage, grounding, color codes, NEC compliance, copper vs aluminum conductors, shielding, and safe installation best practices for home and industrial applications.

What Is Know Your Electrical Cables?

An expert guide to identify cable types, match ratings to loads, and install wiring safely to code.

✅ Choose correct gauge, insulation, and voltage rating

✅ Distinguish THHN, NM-B, MC, and flexible cord types

✅ Follow NEC color codes, grounding, and ampacity limits

The electrical conductors strung between the poles and towers of overhead powerlines are usually bare wires without an insulation covering. An electrical cable is generally defined as being an insulated electrical conductor. This information sheet does not discuss uninsulated wires and focuses only on insulated cables.

This information sheet is not meant to provide the reader with an in-depth knowledge of cable sizing, selection or methods of installation. It is meant to provide:

1. A general appreciation of the factors that should be generally considered when confronted with cabling information; and

2. A general understanding on what is involved in sizing and installing electrical cables.

For procedural guidance on field workmanship, the installation of conductors and cables resource outlines good practice without prescribing specific designs.

THEORY

The sole function of an electric cabling system is the transfer of electric power. The load to be supplied can vary from a small indicating lamp to a large generator transformer.

For background on how materials conduct charge, the conductor of electricity overview clarifies current flow and resistance considerations.

Any cabling system must meet the following requirements:

SAFETY

1. The cable must be able to withstand the voltage to which it will normally be subjected; Routine power cable test methods validate insulation integrity under expected stresses.

2. A cabling system must be installed in such a manner that it presents no danger to any person likely to come in contact with the cables; Practical cable handling and testing procedures help verify these safety measures during commissioning.

3. The cables must not develop a hazard by induction, or through other means, in other equipment; and

4. The type of insulation must suit the type of installation and the environment. The temperature rating of the cable must be suited to ambient conditions. Also, if the cable is to be installed where it is subject to direct sunlight, resistance to UV becomes a factor. If the cable is to be installed in an area where it is subject to flammable dust or liquid, additional factors must be considered. Design notes for aerial cable installations highlight UV exposure and clearances in outdoor runs.

CONDUCTOR SIZING

The cables must be able to conduct power in a manner that will allow the connected device to operate to its full capacity. The cable must be able to conduct the full load current without causing any significant voltage drop at the terminals of the load connection. In considering this factor, the starting current requirements of the connected device have also to be taken into consideration and the cable must be able to withstand a fault on the system to which it is connected.

INSTALLATION REQUIREMENTS

1. The installation of cables Wiring Rules;

2. The cable support must protect the cable from any reasonable chance of damage; and

3. The cable also must be protected from the detrimental effects of the environment in which the cable is installed.

Guidance on installation of cable in cable trays addresses support spacing and mechanical protection.

CABLE CONSTRUCTION

CONDUCTORS

Copper and aluminium are the materials most used for conductors. Aluminium conductors of cross-sectional area less than 16 mm2 have proved difficult to terminate due to their tendency to ‘cold flow’. Therefore below 16 mm2, aluminium cables are not generally used.

Copper is a better conductor than aluminium. To achieve the same current flow as a copper conductor, an aluminium conductor would need to have 1.6 times the cross sectional area. Because of the equivalent aluminium conductor requiring a larger cross sectional area than that of copper, the size of the cable is larger. This will result in greater space required to terminate an aluminium conductor than a copper conductor of equivalent current carrying capacity. The termination of an aluminium conductor requires great care to avoid problems due to the formation of aluminium oxide on the metal surface, which will interfere with the conductivity of the termination. In underground networks, copper underground transmission applications often exploit copper's higher conductivity for compact routing.

Normally aluminium conductors cost less than copper conductors. Aluminium conductors have approximately half the specific gravity as copper conductors.

The decision on which conductor to be used in the cable will require the above factors to be considered.

INSULATION

The type of insulation is influenced by a number of factors such as:

1. The maximum operating voltage of the cable; and

2. The temperature the cable has to withstand. This influences the quality and type of the insulation, coverings, sheathings, insulating sleeves on connections and sealing compounds used on the cable.

The current carrying capacity for Mineral Insulated Metal Sheathed (MIMS) cables are based on an operating temperature of 100°C for the external surface of either bare metal sheathed or served cables. Higher continuous operating temperatures are permissible for bare metal sheathed cables, dependEnt upon factors such as:

1. The suitability of the cable terminations and mountings;

2. The location of the cable away from the combustible materials;

3. The location of the cable away from areas where there is a reasonable chance of persons touching the exposed surface; and

4. Other environmental and external influences. The minimum temperature of use of MIMS cables will be dependent on the cable seal used and manufacturer’s recommendations should be followed.

From: Wire and Cable and Wiring Methods Handbook, Vol 3, The Electricity Forum

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