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The rated short time withstand current (I _K), the peak‐withstand current (I _p), and the duration of the short circuit (t _K) are basic dimensioning parameters for GIS design (see Table 1.7).

These values have a great impact on the electromechanical forces to the insulators and conductors, and on the thermal rise, mainly of the contact system. These values are also tested by specific type tests to confirm the satisfactory function of the different devices of a GIS, such as the circuit breaker, disconnect, ground switch, and bus bars.

Table 1.6 Typical current ratings of GIS related to voltage classes

5000–8000 A				×	×	×
4000–5000 A				×	×	×
3150–4000 A			×	×	×
2500–3150 A	×	×	×	×
1250–2500 A	×	×
	52–72.5 kV	100–170 kV	245–300 kV	362–550 kV	800 kV	1100 kV

Table 1.7 Typical short‐circuit current ratings of GIS related to voltage classes

63–100 kA				×	×	×
50–63 kA		×	×	×	×	×
31.5–50 kA		×	×	×
25–31.5 kA		×	×
16–25 kA	×
	52–72.5 kV	100–170 kV	245–300 kV	362–550 kV	800 kV	1100 kV

Table 1.8 Typical factors to calculate rated peak withstand currents (I _p)

Networks	Factor to calculate I p	DC constant (ms)
50 Hz up to 500 kV	2,5	45
60 Hz up to 500 kV	2,6	45
50/60 Hz 800 kV and above	2,7	60, 75, 120

Table 1.9 Rated duration of short circuit (t _K)

	Rated duration of short circuit (t K) (s)
Short	0.5
Standard	1.0
Long	2.0
Very long	3.0

Table 1.10 Rated supply voltages

	Rated supply voltages
DC	48, 110, and 125 V
AC	208/120 V three‐phase, 400/230 V three‐phase and 230/115 V single‐phase