4 | Technical data
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8DJH • Installation and Operating Instructions • Version 11 • 500-8384.9
Altitude correction factor
For site altitudes above 1000 m, the altitude correction factor K
a
must be considered.
Curve m = 1 for rated short-duration power-frequency withstand voltage and rated lightning
impulse withstand voltage according to IEC 62271‑1 / VDE 0671‑1.
m
1000
1,00
1,10
1,20
1,30
1,40
1,50
1500
2000
2500
3000
3500
m=1
K
a
Fig. 20:
Correction factor K
a
as a function of the site altitude in m above sea level
Tab. 34:
Dielectric strength
Rated voltage (r.m.s. value)
kV
7.2
12
15
17.5
24
Rated short-duration power-frequency withstand voltage (r.m.s. value)
– Across isolating distances
kV
23
32
39
45
60
– Between phases and to earth
kV
20
28
36
38
50
Rated lightning impulse withstand voltage (peak value)
– Across isolating distances
kV
70
85
105
110
145
– Between phases and to earth
kV
60
75
95
95
125
Calculation example:
3000 m site altitude above NN (K
a
= 1.28)
17.5 kV rated voltage of the power grid
95 kV rated lightning impulse withstand voltage (see "Dielectric strength" table, rated voltage 17.5 kV)
Necessary rated lightning impulse withstand voltage:
95 kV * 1.28 = 122 kV
Result
:
According to the above "Dielectric strength" table, switchgear for a rated voltage of 24 kV with a rated lightning
impulse withstand voltage of 125 kV is to be selected.
4.12 Selection of HV HRC fuse-links
According to IEC 60282-1 (2009) Clause 6.6, the breaking capacity of HV HRC fuse-links is tested
within the scope of the type test at 87% of their rated voltage.
In three-phase systems with resonance-earthed or isolated neutral, under double earth fault and
other conditions, the full phase-to-phase voltage may be available at the HV HRC fuse-link during
breaking. Depending on the size of the operating voltage of such a system, this applied voltage
may then exceed 87% of the rated voltage.
To be observed during configuration of switching devices and selection of HV HRC fuse-links:
▪ Use only fuse-links satisfying the stated operating conditions.
▪ Use only fuse-links whose breaking capacity was tested at least with the maximum system
voltage.
In case of doubt, select a suitable HV HRC fuse-link together with the manufacturer.
Summary of Contents for 8DJH
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