IEC Standard | Calculation of the continuous current rating of cables ( % load factor). ument IEC the current carrying capabilities of power cables can be mathematically modelled. Current rating of power cables can hence be done without. IEC Electric cables – Calculation of the current rating – Part Current rating equations ( % load factor) and calculation of losses – General.
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The standard gives the following equations for the calculation of the cable current rating for all alternating current voltages and direct current up to 5 kV:. Each of these areas is discussed in more detail in the following posts which together form a comprehensive guide to the standard:.
Introduction to Current Transformers Current transformers CTs are used to convert high level currents to a smaller more reasonable oec for use as inputs to protection relays and metering The IEC publishes a series of documents and rules governing the preparation of documents, drawings and the referencing of equipment.
IEC 60287 Current Capacity of Cables – Introduction
Voltage Drop in Installations – Concepts Problems on achieving maximum voltage drop within an installation come up often. As the current increases, the losses increase and the thermal equilibrium temperature of the cable will increase. View 8 Comments old system. Within the note the IEC have been introduces and the problem of finding the current capacity of a cable boiled down to that of a thermal calculation. Earth Fault Loop Impedance.
The equations give a safe steady state rated current for a cable. I – conductor current, A R’ – d. Insulating materials have dielectric losses, alternating current introduces skin effect, sheath and eddy current losses, several cables are simultaneously producing heat and the surrounding materials are non-homogeneous and have boundary temperature conditions.
At some temperature the rate at which heat is being dissipated to the environment will be the same as the rate at which it is generated due to loses.
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Calculating Cable Performance d. While the standard addresses each of these issues, the resulting equations are more complex do take some effort to solve. Thermal Problem Principle- simple wire in homogeneous material The methodology taken to the sizing of cables is that of treating the issue as a thermal problem. Steven McFadyen Steven has over twenty five years experience working on some of the largest construction projects.
As an example, consider finding the current carrying capacity of a 50 mm 2 conductor, with XPLE insulation directly buried with an insulation thermal resistance of 5.
It is on the Siemens Paul, please feel free to keep pointing out problems. As an overview, the standard looks at the following situations: IECitself does have the correct equation.
One topic per page All topics one page Export Print Email. For cables which have varying or cyclic loads, the current rating could possibly be increased. As an overview, the standard looks at the following situations:.
Symbols – Fault Calculations. The calculation of each element needs some explanation and these have been split across several notes with each note dealing with one topic. Economic Optimisation of Cables.
Derating Factors – cables grouped in air. Having never used it before, I thought I would download a development While software is a great asset, many times Thanks for the feedback. This note looks at how to obtain the necessary loss factors for use within Within the standard this above is used to derive the equations for current rating.
IEC 60287 Current Capacity of Cables – Rated Current
We then looked at one method of applying the standard and identified resources enabling the calculation of all the various parameters involved. However, a step by step working through it approach will enable the current carrying capacity to be calculated. My view is that you should used the equations to select the cable based on your anticipated current rating.
Anyone attempting to apply this method should be working directly from kec copy of the standard. This note will introduce the concepts adopted by the standard, provide some guidance on using the standard and direct the reader to further resources.