能源供应点的功率（Sknet）值。但是，如果
短路电流Iknet已知，功率值可通过以下方式获得：
对于三相系统，使用以下公式：
你在哪里
是电源点的额定电压。
如果上述数据不可用，则在
下表可作为参考值：
净电压Ur
[kV]短路功率Sknet[MVA]
高达20 500
高达32 750
高达63 1000
发电机
短路功率来自：
其中X*
d%是次瞬态电抗（Xd）的百分比值
”
)或
瞬态电抗（Xd
’
)或同步电抗（Xd），根据
评估短路功率值的瞬间。
通常，电抗用额定阻抗的百分比表示
发电机（Zd）的计算公式如下：
你在哪里
和Sr
是发电机的额定电压和功率。
典型值可以是：
-Xd公司
“从10%到20%；
-Xd’从15%到40%；
-Xd从80%到300%。
通常，考虑坏的情况，即亚瞬态电抗。
下表给出了短路功率的近似值
发电机（Xd
”
= 12.5 %):
Sr公司
[千伏安]50 63 125 160 200 250 320 400 500 630 800 1000 1250 1600 2000 2500 3200 4000
Skgen[MVA]0.4 0.5 1.0 1.3 1.6 2.0 2.6 3.2 4.0 5.0 6.4 8.0 10.0 12.8 16.0 20.0 25.6 32.0

power (Sknet) value at the point of energy supply. However, if the value of the short-circuit current Iknet is known, the value of the power can be obtained by using, for three-phase systems, the following formula: where Ur is the rated voltage at the point of energy supply. If the aforementioned data are not available, the values for Sknet given in the following table can be taken as reference values: Net voltage Ur [kV] Short-circuit power Sknet [MVA] Up to 20 500 Up to 32 750 Up to 63 1000 Generator The short-circuit power is obtained from: where X* d% is the percentage value of the subtransient reactance (Xd ” ) or of the transient reactance (Xd ’ ) or of the synchronous reactance (Xd), according to the instant in which the value of the short-circuit power is to be evaluated. In general, the reactances are expressed in percentages of the rated impedance of the generator (Zd) given by: where Ur and Sr are the rated voltage and power of the generator. Typical values can be: - Xd ” from 10 % to 20 %; - Xd’ from 15 % to 40 %; - Xd from 80 % to 300 %. Normally, the worst case is considered, that being the subtransient reactance. The following table gives the approximate values of the short-circuit power of generators (Xd ” = 12.5 %): Sr [kVA] 50 63 125 160 200 250 320 400 500 630 800 1000 1250 1600 2000 2500 3200 4000 Skgen [MVA] 0.4 0.5 1.0 1.3 1.6 2.0 2.6 3.2 4.0 5.0 6.4 8.0 10.0 12.8 16.0 20.0 25.6 32.0