target="_blank" rel="nofollow" href="#ulink_e97c4b22-eda6-58c2-bfe6-ba275080dc8f">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 |
1.4.7 Rated Peak Withstand Current
The rated peak withstand current (I p) is defined by the DC time constant of the network. The rated peak withstand current is defined as a factor of the rated short time withstand current. Typical values in the network are 45 ms in most voltage classes, and up to 120 ms in ultra‐high voltage (UHV) networks. The related factors are shown in Table 1.8.
GIS equipment is designed to fulfill these requirements.
1.4.8 Rated Duration of Short Circuit
The rated duration of a short circuit (t K) depends on the network protection and is symmetrical. Over the decades of network development, this value has typical decrease, because of faster protection relay equipment. A typical value today is 1 s, but also 0.5 s can be used. In some cases, 2 s or 3 s may be required. The duration of a short circuit has a significant impact on the GIS design, and it is recommended to keep this time as short as possible (see Table 1.9).
1.4.9 Rated Supply Voltages
There are many different supply voltages used and covered by the standards. This high variation is costly for substation design and should be reduced. Therefore, the standards give some preferred values. For existing substations, this might not be economical but new substation design should follow these recommendations (see Table 1.10).
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