Shreenath_GoSwitchgear_UAE
·
Follow
5 min read
·
Jun 13,
--
Within the Dubai control panel manufacturing industry, it is essential to follow certain standards and methods for selecting the right cable size for switchgear, process control and automation applications. It is quintessential to be aware of cable ratings, types, materials, characteristics, and basic cable construction to understand problems related to cable systems. This not only helps in solving problems related to electrical cable systems but also provides a safe and reliable electrical power system, safeguarding the devices and their operators.
Goswitchgear.com will guide you through this process with some quick tips and methods to be able to select the right cable size and brief you through the cable types as well.
Note that Dubai electrical switchgear industry follows DIN and BS standards for most of the electrical installations. Other Emirates within UAE follow similar standards, though it is always essential to check with local building companies or authorities such DEWA, ADDC (Abu Dhabi Distribution Company) or AADC (Al-Ain Distribution company). The focus of this article is primarily for low voltage copper conductor cables and wires as offered here!
Cable installation incorporates the type and location of installation of the cables. The cables could be placed outdoors or indoors. Outdoors cables can further be classified if they are underground or above, and also, on the location of the electrical cabinet. Cable management or protection systems such as conduit, trunking, or cable trays, can also affect the selection of cables.
Cable construction is one of the primary criteria for sorting or classifying cables into different types.
Factors that determine cable construction are:
Insulation
The layer that touches the conductor directly is known as insulation. It plays a vital role in the selection of cables, as it determines the maximum temperature of the cable during operation. There are various insulation materials such as PVC, XLPE, and EPR. PVC has a max operating temperature of 70°C, EPR and XLPE have 90°C. Other factors such as flexibility also play a vital role. EPR is a type of rubber and is more flexible than XLPE. Along with these factors, the most primordial one is cost. For the same length, size, current rating (both short time and continuous current rating) and voltage rating, the cost of XLPE would be much higher than PVC insulated cable.
Note that goswitchgear.com provides PVC flexible cables, which are heat resistant and flame retardant (HFFR). They have high insulation resistance, high heat resistance and are RoHS compliant.
Conductor and Cores
Conductor materials such as copper and aluminium are given precedence due to their chemical and physical properties. Aluminium conductors have more critical consideration factors than copper conductors.
There are single-core and multi-core conductors available in the Dubai switchgear industry. Single-core cables can have a higher current carrying capacity due to the fact that they can dissipate heat better than multi-core cables. But multicore cables provide the ease of installing multiple conductors at one go, saving time. Moreover, multi-core cables are less susceptible to damage caused by mechanical stresses due to high inrush currents and short circuit currents.
Our webshop provides single core unsheathed cable by Havells and SM cables, Malta. The number of cores and conductor finally depends on factors such as type of installation, and current and voltage rating.
After determining installation conditions, environmental conditions, load requirements, cable length and circuit conditions, the next step is to determine the current carrying capacity, followed by voltage drop.
Table 1 shows the current-carrying capacities for PVC single-core unsheathed and unarmoured copper cables at a conductor working temperature of 70°C and ambient temperature of 30°C.
Table 1 Current-Carrying capacity for low voltage copper conductor.The voltage drop can be calculated only once the length of the cable is known. The drop is measured in mV/A/m and conveys the potential drop across the running cable in the system, or desired part of the system.
Mingda supply professional and honest service.
Table 2 shows the max voltage drop for single-core copper wires. r,x, and z are resistance, reactance and impedance respectively.
In the UAE electrical industry, standard practice is to have a maximum voltage drop of 2.5% -8% across the cable run. Please note that a range of values is mentioned since it could be vary based on the Emirates local electrical regulations set by organizations such as DEWA, or AADC. For instance, if the supply voltage is 415V, then the voltage drop cannot exceed 10.375V (2.5%).
Table 2 Voltage drop (Per Amp Per Meter)The following formulas in Box 1 will help in calculating the voltage drop. Here, Vmax is the max permissible voltage drop in the circuit (V), L is the length of the cable (m), I is the current (A), Vd is the max voltage drop in the circuit (mV/A/m), Vds is the voltage drop of the selected cable (mV/A/m) and Vt is the total voltage drop in the circuit (V).
Table 1 and Table 2 will help you select the right cable size and Buy PVC single-core cables by Havells from goswitchgear.com. After calculating the size using both methods, the one with a higher conductor cross-sectional area or size has to be selected.
Remember that the smaller the cable size, the longer the cable and the higher the voltage drop. If the voltage drop exceeds the max permissible voltage drop (2.5% in this case), then the cable size has to be increased.
Other factors such as, ambient temperature-correction factor for PVC cables, and the number of circuits-correction factor has to be selected for further optimizing the cable size. The tables provided consider conductor operating temperature at 70°C and the cables are a part of just one operating circuit. These factors will be discussed in the coming articles of our blog/knowledge centre.
Keep following our blog to stay updated and get more valuable insights to build an efficient low voltage control panel in the UAE.
References.
March 6, / General, 101 learning, Installation and testing, Best Practices
Both shielded and unshielded twisted-pair copper cable comes in either stranded or solid wire versions. There are plenty of considerations when it comes to choosing one or the other, including standards, environment, application, and cost. Lets take a look at the differences and considerations, so you can decide whether stranded copper wire or solid copper wire cable is right for your specific installation.
Stranded and solid wire cable differ in key ways, including construction, flexibility, and performance.
In a stranded cable, each of the eight copper conductors are made up of multiple strands of small-gauge wires that are wound together concentrically in a helix, much like a rope. Stranded wire is typically specified as two numbers, with the first number representing the quantity of strands and the second representing the gauge. For example, a 7X32 (sometimes written as 7/32) indicates that there are 7 strands of 32 AWG wire that make up the conductor.
In a solid cable, each of the eight conductors are made up of a single larger-gauge wire. Solid wire is specified by just one gauge number to indicate the size of the conductor, such as 24 AWG. Whether its a one-, two-, or four-pair cable, the gauge of the solid conductor is the specification for the cable.
Beyond the way they're made, another key difference between stranded and solid wire cable is flexibility.
A less-obvious difference between stranded and solid wire cable is performance.
Now that you understand the differences between stranded and solid wire cable, lets cover what you need to consider when making a choice.
Which type of wire is the best choice depends on the installation's requirements.
When it comes to 90-meter horizontal permanent links, theres no choice: whether it's shielded or unshielded twisted pair, both TIA and ISO/IEC standards require solid wire cable. Stranded cable (24 and 26 AWG) is limited to patch cords and 10-meter lengths within a 100-meter channel.
Because stranded cables are more flexible and can withstand bending, they make excellent patch cords for equipment connections and cross-connects where cables are frequently bent and manipulated; at just 10 meters of the channel, the increased insertion loss and resistance arent a factor in the overall channel performance. However, smaller 28 AWG stranded patch cords that have even more insertion loss and resistance due to their smaller gauge do have some limitations get the Skinny on 28 AWG Patch Cords to learn more.
Open office environments, however, are special situations; theyre faced with regular reconfigurations and may require a more flexible cabling system. In those installations, the standards allow stranded patch cords to take up more than 10 meters of the channel. However, if youre using more than 10 meters of stranded cable in a channel, industry standards require de-rating the overall channel length to accommodate for the greater insertion loss and DC resistance.
When it comes to de-rating stranded cable per industry standards, the overall gauge is a factor: higher-gauge (thinner) cables have a higher de-rating factor. The de-rating for 26 AWG stranded cable is 0.5, while 24 AWG is only 0.2, and 22 AWG stranded cables require no de-rating at all.
Here are the calculations to determine overall channel length, where H=horizontal cable length, D=de-rating factor, C= total stranded cable length and T=total channel length.
For example, if youre using 60 meters of horizontal solid category 6A cable and 40 meters of stranded 24 AWG category 6A patch cable with a 0.2 de-rating factor, the total length of the channel must be reduced to 97.5 meters. (If you prefer the actual math: total stranded cable length = [105-60]/[1 + 0.2], or 37.5, and total channel length = 60+37.5, or 97.5 meters.) If youre using 26 AWG stranded cable with a 0.5 de-rating, the channel length needs to be reduced to 90 meters.
While stranded cable is the norm for patch cords at patching areas in the telecommunications room (TR) and at the work area (perhaps longer than 10 meters in open offices), a primary application to consider in todays LANs warrants the use of solid patch cords: Power over Ethernet (PoE). When PoE is delivered over twisted-pair copper cable, some of the power dissipates as heat. When power dissipates as heat, the cable temperature increases. With higher insertion loss and DC resistance, stranded patch cords are more likely to exhibit degraded transmission performance at elevated temperatures.
While not typically a concern in environmentally controlled spaces like the TR, stranded patch cords could become an issue once you start connecting devices in the ceiling think wireless access points, security cameras, LED lights, and more. In best practice, if the environment isnt temperature controlled and the cable doesnt have to bend much, solid cable patch cords should be used. If you do use stranded patch cords in uncontrolled environments, its better to keep them short (about 5 meters or less). And when it comes to higher-temperature environments, industry standards require de-rating channel length for that, too; more cables in a bundle, each generating more heat, can require even more length de-rating (though there can be An Exception to Every Rule).
While more strands in a conductor mean greater flexibility, a higher strand count also means a higher price. To keep costs down, stranded category 6 and category 6A cable are designed to strike a balance: enough strands to maintain proper flexibility, but not so many that it creates a dramatic price difference. You dont have to compromise performance (or standards compliance) by selecting stranded wire cable instead of solid for environments and applications for which its not suited. Keep your stranded cables in environmentally controlled areas that require greater flexibility, and use solid wire cable where rugged performance (and little bending) is required.
Whether its patch cords, permanent links, or channels, you can configure a Fluke Networks Versiv tool to certify the cable's performance.
View the Versiv Configurator
For more information, please visit BS Standard Cable .