Understanding the relationship between TNCS, TNS and TT. Similarly, expanding the first item of the right side in equation (6) as series of () and considering the effect of elastic elongation, adopting the first two items, we getEquation (10) is called the improved cable length formula considering the effect of elastic elongation. Comparison of length adjustment results for datum strand in midspan with different sag-span ratios. Minimum cable size can be calculated based on cable length, voltage, amperage, and acceptable loss. (3) All information is provided in good faith. ISO 9001:2008 / AS9120 / 2009 Ignore above comment. (2) Cable sizes should only be used as a guideline and if not using HO7RNF cable, all figures should in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net, Reply to Calculating Maximum permitted cable length with maximum Zs value? From Tables 2 and 3, the following can be found:(1)The applicable range of sag to span ratio for four solutions based on parabola theory is different. The formula Vd= mV/A/m x Ib x L and divide by 1000 will give you the actual volt drop and the figures again can be selected from Appendix 4. The actual voltage drop can vary depending on the condition of the wire, the conduit / raceway being used the temperature the connector the frequency etc. It is well known that cables cannot behave as structural members until large tensioning forces are induced. Alternatively to compute the voltage drop and cable size, you require the following data. How do l calculate the maximum cable length for a maximum Zs value? Calculate Cable Length from Sag, Span Cable or conductor length is a measure of one tenth of a nautical mile or approximately 100 fathoms. Corresponding current for that particular load. = 1.155 x ( Number of Conductors ) x. Resources for electrical engineering professionals. Once you get all the above data, the voltage drop can be calculated as follows. The authors declare that they have no conflicts of interest. The calculation formula of cable length adjustment based on quasi-catenary theory (adopt inextensible catenary elements) can represent explicitly by the ratio (c) of applied distribution load to the horizontal component of cable force, but the solution of c also need to use a complicated iterative method. Minimum cable size can be calculated based on cable length, voltage, amperage, and acceptable loss. Voltage drop in accordance with CENELEC CLC/TR 50480. The calculation error of length adjustment for datum strand in the middle span using traditional and improved simplified formula was compared in this example. (1)The improved simplified formulas considering the influence of elastic elongation on the cable unstressed length was derived for a suspension cable with small sag to develop parabola theory of cable analysis. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Voltage drop Ampere/Meter which you will get from the cable supplier (in mV). Finally, numerical examples are presented and discussed to illustrate the accuracy and efficiency of the proposed analytical method. The simplicity of Ernst’s formula has made it widely used not only in the research field but also for practical designs of cable-supported structures such as suspension bridges. LV and MV cables up to 33 kV with current capacity in accordance with BS 7671, ERA 69-30 and IEC 60502. Custom cable and custom heat shrink shapes are another of our specialties. This paper starts from the basic principle of parabolic theory, considering the influence of elastic elongation on the unstressed cable length, and establishes a simplified and direct calculation method which can apply for datum strand of the main cable and catwalk bearing rope with a small sag. (2) Source: NFPA 70, National Electrical Code, Chapter 9, Table 8. Cable analysis can be separated into two categories: parabolic approach and catenary approach. The calculated results indicate that the cable length adjustment can quickly reach the goal with high accuracy using the improved simplified formula II. The upper limit for the perfect solution of parabola theory is the highest for all four solutions; the upper limit for other three simplified formula is about 1/8, since those three methods ignore the effect of high-order items of expansion series. Standard Wire & Cable Company can supply you with the right sizes, types, and quantities of product you need to keep you on schedule and your management happy.