An example how to calculate voltage drop and size of electrical cable

Input information

Electrical details:

Electrical load of 80KW, distance between source and load is 200 meters, system voltage 415V three phase, power factor is 0.8, permissible voltage drop is  5%, demand factor is 1.

Cable laying detail:

Cable is directed buried in ground in trench at the depth of 1 meter. Ground temperature is approximate 35 Deg. Number of cable per trench is 1. Number of run of cable is 1 run.

Soil details:

Thermal resistivity of soil is not known. Nature of soil is damp soil.

Ok, let’s dive into calculations…

• Consumed Load = Total Load · Demand Factor:
  Consumed Load in KW = 80 · 1 = 80 KW
• Consumed Load in KVA = KW/P.F.:
  Consumed Load in KVA = 80/0.8 = 100 KVA
• Full Load Current = (KVA · 1000) / (1.732 · Voltage):
  Full Load Current = (100 · 1000) / (1.732 · 415) = 139 Amp.

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New Cable Bushing Maximizes Density, Minimizes Installation Headaches

More cables, less space. That’s the challenge faced by anyone trying to bring all the necessary power and signal connections into today’s increasingly complex electronics enclosures. But help is on the way, thanks to a new multi-cable bushing system that debuted last month at the Hannover Fair.

Called SKINTOP® Cube Multi, the new cable bushing allows combinations of up to 23 electrical cables or pneumatic lines to pass directly through the enclosure wall. Like our earlier multi-cable bushings, SKINTOP Cube Multi system places a rigid, glass-reinforced nylon frame into an standard-sized cutout in the enclosure wall. Inside this rectangular frame is an polycarbonate insert with gel-filled hole for the cables or lines to pass through.

Innovative Sealing Mechanism

The elastomeric gel represents SKINTOP Cube Multi’s key technical breakthrough and an industry first. The gel allows the cables to be easily inserted through the holes. Yet at the same time, the gel’s elastomeric properties create a lasting seal around the cables and provide strain relief.

Available in two versions for now with more sizes to come, Cube Multi maximizes wire density for a given size cutout. For example, one version can pack 23 cables, ranging in size from 6 to 9 mm, into 36 x 112 mm cutout, which is the standard size for a 24-pin industrial connector.

The second version squeezes two fewer cables—or pneumatic lines—into the same cutout. But it supports more varied combinations with room for nine 3 to 6 mm cables, nine 6 to 9 mm cables, two 9 to 13 mm cables and one 13 to 16 mm cable.

Technical Specifications Cube Multi is a new product, so you should expect its technical specifications to evolve over time. For now, the specs include: 

* Protection to IP 65. 

* Operating temperature range from –30 to 100ºC 

* UL 94 V–2 flame rating.

 

Selection Of Number Of Cable Cores With Emphasis On Sizing Parameters

Dependance On Installation Site

The selection of number of cable cores basically depends on the type of system where it is going to be installed.

Generally we have two types of systems:

1. A perfectly balanced system and
2. A system with some degree of unbalance (or Unbalanced System).

Generally cable sizing includes below parameters:

1. Cable installation conditions and the load it will carry
2. Continuous current rating of the cable
3. Voltage drop and short circuit considerations
4. Earth fault loop impedance

Here, I am going to describe that how the number of cores can be selected.

3-Core Cables

These cables are used generally for a perfect balanced 3-phase system. When the currents on the 3-live wires of a 3-phase system are equal and at an exact 120° phase angle, then the system is said to be balanced. The 3-phase loads are identical in all respects with no need of a neutral conductor.

An important example of 3-phase load is electric motor and that is why, they are fed through 3-Core cables in most cases.

3.5-Core Cables

A 3-phase system may have a neutral wire. This wire allows the 3-phase system to be used at higher voltages while it will still support lower voltage single phase loads.
It is not likely in such cases that the loads will be identical, so the neutral will carry the out-of-balance current of the system. The greater the degree of imbalance, the larger the neutral current.

3-5-core cable construction (figure by mitesh-raval.blogspot.com)

When there is some degree of unbalance and the amount of fault current is very small, then 3.5 core cables are used. In these types of cables, a neutral of reduced cross section as compared to the 3-main conductors is used, which is used to carry the small amount of unbalanced currents.

4-Core Cables

When there is severe out-of-balance conditions, the amount of fault current will raise to a very high level. Generally in the case of linear loads, the neutral only carries the current due to imbalance between the phases.

4-core PVC insulated and sheathed copper conductor power cable

The non-linear loads such as switch-mode power supplies, computers, office equipment, lamp ballasts and transformers on low loads produce third order harmonic currents (Definition of Harmonics and Their Origin) which are in the phase of all the supply phases.
These currents do not cancel at the star point of a three-phase system as do normal frequency currents, but add up, so that the neutral carries very heavy third harmonic currents.

That is why the neutral of the cable feeding the equipment are not reduced and made with cross sectional area same as that of the main conductor to carry this high amount of current.

5 and 6-Core Cables

Some conditions may arrive when the amount of fault (neutral) current becomes very large than the phase currents. When the load concerned to this type of situation is fed through a multi-core cable, it is necessary to use a 5-Core or 6-Core Cable.

5-core PVC insulated and sheathed copper conductor power cable

In this condition, two (or three) conductors can be used in parallel formation to carry the high amount of generated unbalanced currents.

Protecting Cables From Oil Damage

Of all the chemical exposures that can affect the life and performance of electrical cables, oil is one of the most damaging. Used as a coolant and lubricant in many industrial and infrastructure settings, oil can inflict molecular damage on the polymers used for cable insulation.

Degradation Happens. When insulation polymers are exposed to oil over time, two degradation mechanisms can occur. Some polymer formulations will absorb the oil, causing the polymer to swell and soften. A loss of tensile properties results. Other polymers will lose their plasticizers when exposed to oil, causing a loss of flexibility and elongation.

Either way, oil exposure renders many polymer compounds ineffective as insulators. This attack on polymer properties can result in downtime, costly repairs and, in the worst case, hazardous electrical conditions.

Temperature extremes and other chemical exposures can exacerbate the damage caused by oils. The greater the intensity of the oil exposure and the operating temperatures, the faster oil will degrade insulating polymers.

Lasting Damage. Once it gets underway, oil damage is not reversible. But it can be prevented by selecting cables with inherent oil resistance.

Without a deep knowledge of the specific polymer compounds used in the cable you’re considering, it can be difficult to know which products can stand up to oils and for how long. Making matters worse, individual polymer formulations may not offer equivalent performance even if they have the same family name. Not all PVCs are created equal, for instance.

And that’s why testing is so important. To avoid oil resistance problems, engineers should pay close attention to UL tests, which help determine how a cable will react in the industrial oil environment.

 

Cable Connectivity Solutions for designing a more efficient and flexible factory of the future

Flexible production with "plug & produce"

Industry is currently undergoing a fundamental change: we are seeing the integration of all components of the value chain into the corporate network. The radical changes associated with this sea change do not just affect companies in the IT sector, even if the development of intelligent factories is often seen primarily in terms of IT. Even manufacturers of cables and connectors can make a considerable contribution to this new era with intelligent solutions, thereby supporting industry and increasing efficiency and flexibility.

Machines, plants and devices are made "intelligent" by connecting them to one another using the "Internet of Things". The resulting cyber-physical systems form the basis of the intelligent factory of the future - its vision: to generate maximum flexibility and efficient production with batch size 1. Cyber-physical systems are functional units with embedded hardware, software and mechanics. The fact that they are capable of communicating with one another is opening up new horizons for plant and machinery manufacturers, who can break plants down into individual modules that only have to be programmed and tested once. Depending on the customer's requirements, a mechanical engineer can then assemble the standardized modules in a flexible and personalized way and feed in the data that is required for production - plug & produce.

This leads to fundamental changes in the cabling of an industrial plant. A network cable no longer ends in the control cabinet; instead, it is run directly to the motor of a machine, for example. For the manufacturers of connection technology, this means that the cables with inserts that have previously been used primarily in office environments now need to be suitable for industrial applications. The cables must be able to withstand high mechanical stress, extreme temperatures, vibrations and contamination. In this kind of environment, they may also be exposed to aggressive media. Ethernet cables used in industrial applications must also be shielded against much stronger EMC interference, such as that found in the vicinity of motors or live cables that are generating an electromagnetic field.

"We are certain that the "fourth industrial revolution", by which we mean the increasing networking within production facilities and the associated transition to a more flexible type of production, as well as the increasing customization of product variants, will be the defining development in German industry over the next few years", says Siegbert Lapp, Member of the Board at Lapp Holding AG. Because of this conviction and its aspiration to help fashion the industrial production methods of the future, the Lapp Group is taking part in a number of research projects on the topic. Together with project partners, Lapp is researching "production work 4.0" under the leadership of the Fraunhofer IAO. The research mainly focuses on the following questions: how could the work environment look in a factory of the future, what kind of tasks will factory workers undertake and how can they be supported in fulfilling their tasks? "This is important for understanding the entire production system, that is the plants and operators. We want to use our findings to develop solutions that are even more suitable for the factory of the future," explains Siegbert Lapp.

In addition to this, Lapp is involved in the SmartFactory^KL e.V. technology initiative run by the German Research Center for Artificial Intelligence (DFKI). The SmartFactory^KL is a demonstration factory inside a laboratory, where researchers from the DFKI can use technologies for the intelligent factory of tomorrow in a production environment as close as possible to the real world. The DFKI and the companies involved hope that the resulting findings will help to realize the vision of the new industrial era, with totally flexible factories manufacturing heavily customizable products. The solutions developed in this context aim to support companies in achieving resource efficient and ergonomic production, with dynamic integration of their customers and business partners into the value chain.

Lapp is taking the lead on the quality inspection module for the research and demonstration platform, which will involve testing innovative cabling and connection solutions for data network cables. Quality inspection includes the use of a high-resolution camera, which raises a particular challenge in itself as it must be able to transfer data consistently and reliably at the highest data rate in the demanding conditions of a production environment. In this case, the highly flexible ETHERLINE ^® FD Cat.6_A cable, together with the field-configurable X-coded M12 data connector, ensures this function. Data rates of up to 10 Gbit/s are possible for high-resolution cameras in moving applications. Industrial Ethernet assemblies comprising robust, resilient cables with M12 connectors, also ensure a reliable connection in areas where contamination and damp must be taken into account. This extensive networking paves the way for new possibilities in maintenance and storage, as well as in production. With this in mind, Lapp is planning on attaching RFID chips to its cables, among other innovations. If a replacement were required, a service technician would be able to scan the exact data directly from the cable and then immediately initiate an order for the required part from the e-shop.

The "fourth industrial revolution" has many challenges in store for machinery and plant construction firms, hardware and software suppliers and, last but not least, manufacturers of connection technology. To achieve the flexible and customized vision of production that lies at the heart of the futuristic intelligent factory concept, companies are going to need innovative solutions that allow the vertical and horizontal integration of their value creation processes. Developments that facilitate the processing of large data volumes and communication between the various components are spurring this revolution on.

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