Handbook of Electrical Engineering

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 225 currents. The starting, or run-up, time durations for low voltage motors are ...

226 HANDBOOK OF ELECTRICAL ENGINEERING The base currentIbaseat 11,000 V is, Ibase= Sf× 106 √ 3 ×Vbase = 150 × 106 √ 3 × 11000 = ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 227 The equivalent full-load impedanceZfltis, Zflt= Vos √ 3 Iflt = 460 √ 3 × 3137 ...

228 HANDBOOK OF ELECTRICAL ENGINEERING Figure 9.5 Cut-off and prospective current of fuses. For the selection of fuses the prosp ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 229 Table 9.27. Cable and fuse currents and time data Cable current (kA) Time (se ...

230 HANDBOOK OF ELECTRICAL ENGINEERING transformer for this relay has a primary current rating of 150 amps. Assume only one of t ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 231 Figure 9.7 Fuse and cable time versus current curves. to be no less than 3 at ...

232 HANDBOOK OF ELECTRICAL ENGINEERING Table 9.28. Cable data for the worked example Cable conductor area (mm^2 ) Resistance at ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 233 Again let the cut-off current be 20% ofIfpka, Ico 0. 2 × 87909 =17582 amps A ...

234 HANDBOOK OF ELECTRICAL ENGINEERING Figure 9.8 Earth loop impedance diagram. For TT and IT systems: Zloop=Znez+Zsec+Zc+Za+Zbo ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 235 Vph is the nominal phase-to-neutral voltage of the source. If is the fault cu ...

236 HANDBOOK OF ELECTRICAL ENGINEERING e) Disconnection time: The standard recommends two nominal disconnection times 0.4 and 5. ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 237 Full-load currentItxflof the transformer = Stx √ 3 V = 250000. 0 √ 3 × 415 =3 ...

238 HANDBOOK OF ELECTRICAL ENGINEERING Table 9.30. Cable data for the worked example Nominal Current 3-core conductor GSWB armou ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 239 Vrun= √ 365. 82 ( 0. 2960 × 0. 85 + 0. 0268 × 0. 5268 ) 100 415 = 7 .299%. F ...

240 HANDBOOK OF ELECTRICAL ENGINEERING Table 9.34. Earth loop impedance results for the worked example with braided armouring No ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 241 For a 16 mm^2 cable, Za+Zc= 0. 2960 +j 0. 0268 + 0. 72 = 1. 016 +j 0. 0268 Zl ...

242 HANDBOOK OF ELECTRICAL ENGINEERING If the 50 mm^2 cable and a MCCB rating of 125 amps are chosen then the circuit earth loop ...

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 243 Figure 9.10 Overcurrent protection of a cable and motor. For the circuit show ...

244 HANDBOOK OF ELECTRICAL ENGINEERING which is also satisfactory. Hence the requirements of IEC60364 are satisfied. 9.5 Cables ...