Derating for Cable Crossings – ELEK Software program
Determine 3 exhibits the de-rated present ranking of the cable because of crossing of the steam pipe between the angles of 60° and 90° (comparatively flat) is healthier than at 45° or 30°.
B. Instance 2 – Single core 10 kV cables circuit crossing a three-phase multicore 145 kV cable
This instance is predicated on the instance calculation in Appendix A of IEC Normal 60287-3-3. Determine 1 exhibits the set up entails three-phase circuits comprising single core cables (Circuit 1) crossing with a three-phase multicore cable (Circuit 2). The one core cables are buried at 1.2 m whereas the multi-core cable is buried at 0.9 m. The conductor space for the multicore cable is 400 mm2 and that of the only core cable is 300 mm2. The present carrying capability of the remoted circuits are 665 A and 585 A, respectively, at a soil thermal resistivity of 0.8 Cm/W and an ambient soil temperature of 25 °C.
For the reason that cables in circuit 1 are symmetrical and the losses are similar, the place the place the utmost temperature happen would be the similar as the most well liked cable place. But when any of the above elements corresponding to symmetry or losses are totally different, then the software program makes use of a weighted common technique to search out the purpose of most temperature. The derating elements and de-rated currents have been calculated for various crossing angles (proven in Fig.4 and Fig. 5). The derating elements converged after 4 iterations.
The calculations of the mutual thermal resistance of the appropriate cable within the single core cable circuit (web page 16, Desk A3) in Normal IEC 60287 3-3 [1] is inaccurate. The worth in the usual is 0.174, and the worth we receive is 0.156.
