Page 207 - Handbook of Electrical Engineering

CABLES, WIRES AND CABLE INSTALLATION PRACTICES 191

9.3 COMPOSITION OF POWER AND CONTROL CABLES

The composition of a power cable is dependent upon the rated voltage at which it will be expected
to operate continuously without breakdown.
IEC60038 gives the standard voltages for electrical equipment. However, for cables the AC rms
voltages are defined for example in IEC60502, in terms of their line-to-earth and line-to-line values.

See Tables 9.6 and 9.7. Table 9.7 is derived from BS6622.
Note that occasionally u o is quoted as the value obtained by dividing u by 1.732 and rounding
to one decimal place. u o is derived from IEC60038.

IEC60502 covers the construction and factory testing of polymeric solid insulated cables in
the voltage range 1000 to 30,000 volts. IEC60183 gives guidance on the selection of cables for high
voltage systems. BS6622 is similar to IEC60502 but is restricted to cables operating at voltages
between 6600 and 33,000 volts, with screened XLPE or EPR insulation. BS5467 covers unscreened
thermosetting insulated cables that operate between 1000 and 3300 volts; hence the standard is
reasonably applicable to low voltage systems e.g. 380, 400, 415, 440, 600 and 750 volts (line to

Table 9.6. IEC standard rated voltages of power cables
Line-to-earth Line-to-line Maximum value of the highest
voltage voltage system line-to-line voltage
u o u u m
600 1,000 —
1,800 3,000 3,600
3,600 6,000 7,200
6,000 10,000 12,000
8,700 15,000 17,500
12,000 20,000 24,000
18,000 30,000 36,000

Table 9.7. UK standard rated voltages of power cables
Line-to-earth Line-to-line Maximum value of
voltage voltage the highest system
line-to-line voltage
∗
u o u u Note a)
m
600 1,000 —
3,800 6,600 (8,000)
6,350 11,000 (13,200)
8,700 15,000 (17,500)
12,700 22,000 (26,400)
19,000 33,000 (39,600)
Note a) This column is not shown in BS6622 but is included
to be consistent with Table 9.6 where a 20% upward
margin is added to u to obtain u m before rounding
is applied.
Note b) A method of rounding numbers upwards or downwards
is given in Appendix B of IEC60502.