什么是发电机的直轴超瞬变电抗Xd"与发电机结构有什么关系，Xd"的大小对系统有什么影响 What is the direct axis transient reactance Xd of a generator? What is the relationship between Xd and the structure of the generator? What impact does the size of Xd have on the system

Xd"是代表发电机运行中三相突然短路，最初一瞬问的过渡电抗。发电机组突铁短路时，转子励磁绕组和阻尼绕组为保持磁链不变，感应出对电枢反应磁通起去磁作用的电流，将电枢反应磁通挤到励磁绕组和阻尼绕组的漏磁通的路径上，这个路径的磁阻很大即磁导很小，故其相对应的直轴电抗也很小，这个等效电抗称为直轴超瞬变电抗Xd”,也即有阻尼绕组的发电机突然短路时，定子电流的周期分量由Xd"来限制。

结构上Xd"主要由发电机定子绕组和阻尼绕组的漏抗值决定。

对于无阻尼绕组的发电机则Xd"=Xd'。

由于xd"的大小影响电力系统突然短路时短路电流的大小，故Xd"值的大小也影响到系统中高压输变电设备特别是高压断路器的选择，如动稳定电流等参数。从电气设备选择来说希望Xd"大些,这样短路电流小一些。

Xd "represents the transient reactance at the beginning of a sudden three-phase short circuit during generator operation. When a generator experiences a sudden iron short circuit, the rotor excitation winding and damping winding induce a current that demagnetizes the armature reaction magnetic flux to maintain the magnetic flux constant. This current squeezes the armature reaction magnetic flux onto the path of the leakage magnetic flux of the excitation winding and damping winding, which has a high magnetic resistance and low magnetic conductivity. Therefore, the corresponding direct axis reactance is also very small. This equivalent reactance is called the direct axis transient reactance Xd ", which means that when a generator with damping winding suddenly experiences a short circuit, the periodic component of the stator current is limited by Xd".

Structurally, Xd is mainly determined by the leakage reactance values of the generator stator winding and damping winding.

For generators without damping windings, Xd "=Xd '.

Due to the influence of the magnitude of xd on the short-circuit current in the power system during sudden short circuits, the magnitude of Xd also affects the selection of high-voltage transmission and transformation equipment, especially high-voltage circuit breakers, such as dynamic stability current and other parameters in the system. In terms of electrical equipment selection, I hope Xd can be larger so that the short-circuit current is smaller.