Page 1010 - Industrial Power Engineering and Applications Handbook

Testing a metal-enclosed bus system 32/955
Table 32.1(A) For series I voltage systems: Insulation levels, power frequency and impulse withstand voltages for metal-enclosed
bus systems
Nominal system Rated max. system One-minute power frequency voltage withstand Standard lightning impulse,
voltage voltage at a frequency between 45 and 65 Hz for LT and 1.2/50 p voltage withstand
25 and 100 Hz for HT systems (phase to ground)
1 2 3 4 5
For a switchgear For the tap-offs in a (a) We consider here only
assembly and a bus power-generating station, List 11, which is more
system connecting a UAT through prevalent. For List I,
(phase to ground) the main bus section between refer to Table 13.2.
the generator and the (b) For impulse voltage
generator transformer withstand across the contact
(Figure 31.1) (phase to gaps of an interrupting
ground) device refer to
IEC 60694
kV (r.m.s.) kV (r.m.s.) kV (r.m.s.) kV (rms.) kV (peak)
0.415 0.44 2.5 - -
0.6 0.66 2.5 - -
3.3 3.6 10 21 40
6.6 7.2 20 27 60
11 12 28 35 75
15 17.5 38 - 95
22 24 50 55 125
33 36 70 75 170
Based on IEC 60439-2 LT, IEC 60694 for HT and IS 8084 for tap-offs.
Notes
1 Generally, there is no application of a bus system beyond a maximum system voltage of 36 kV.
2 Field tests (power frequency voltage withstand) after erection at site, if required, may be conducted at 85% of the values indicated above
in LT and 80% in HT systems.

Table 32.1(8) For series I voltage systems: Power frequency voltage withstand levels for metal-enclosed bus systems
Nominal system Rated maximum One-minute power frequency Field test after erection at site (phase to ground)
voltage system voltage withstand voltage at any
v, frequency between 25 and A.C. test lfor one minute at any D. C tesP
100 Hz (phase to ground) frequency between 25 and 100 Hz)
I 2 3 4 5
kV (mu.) kV (r.m.s.) kV (r.m.s.) kV (rms.) kV

0.415 0.44 2.0 2.0 3.0
0.6 0.66 2.0 2.0 3.0
3.3 3.6 9.5 8.6 5.0
6.6 7.2 17.0 15.2 10.5
11 12 27.0 24.0 18.0
15 17.5 36.0 32.0 25.0
22 24 52.0 46.0 37.5
33 36 76.0 68.0 60.0
(2V, + 2) for HT systems

Based on BS 159
* In the absence of a.c. test voltage at site, a d.c. test can also be conducted, the duration of which will be 15 minutes.