Page 1011 - Industrial Power Engineering and Applications Handbook

Nominal system Rated maximum One-minute power frequency voltage Standard lightning impulse One-minute d.c.
volrage system voltage withstand at afrequency not less than (I.2/50 p) voltage withstand i voltage withstand
the rated, 60 Hz (phase to ground) (phase to ground) I (phase to ground)
I -7-
I
kV (rm S 1 kV (rm.s.) ~ :(r.m s ) Dew ~ kV (peak)

(1 minute) (I 0 seconds)
kV
~
0.6 0.635 2.2 - 3.1
4.16 4.76 19.0 15.0 60 27.0
13.8 15.00 36.0 24 i 95 50.0
38.00 1
14.4 15.50 50.0 30 70.0
23.0 25.80 60.0 40 I25
34.5 80.0 70 ' 150
69.0 72.50 160.0 140 ~ 350
For application of isolated phase bus to generator, the following voltage ratings will apply.
14.4 to 242 - 50.0 50.0 i 110 70
_.

Table 32.3 Hottest spot temperature rise limits for metal-enclosed bus systems

Component Limit of hottest spot temperature rise over an ambient of
40°C - in "C
As in IEEEX37.20 As in IEC-60439-2
(Tuble 28.2) (Table 14.5)
1 Bus conductors
(i) Bolted plain jnints 30' 50
(ii) Bolted joints silver plated 65b 65b
(iii) Aluminium welded joints 65b 65b
2 Enclosure and support structures
(i) Easily accessible 30'
(ii) Not accessible 50
3 Bus conductors in contact with insulating materials 50*
(or higher, as limited by insulation class, Table 14.6e)

equivalent connections