接地变压器简称接地变，根据填充介质，接地变可分为油式和干式；根据相数，接地变可分接地变压器为三相接地变和单相接地变。
Grounding transformer is short for grounding transformer. According to filling medium, grounding transformer can be divided into oil type and dry type. According to phase number, grounding transformer can be divided into three-phase grounding transformer and single-phase grounding transformer.
三相接地变：接地变压器的作用是在系统为△型接线或Y型接线中性点无法引出时，引出中性点用于加接消弧线圈或电阻，此类变压器采用Z型接线，与普通变压器的区别是，每相线圈分成两组分别反向绕在该相磁柱上，这样连接的好处是零序磁通可沿磁柱流通，而普通变压器的零序磁通是沿着漏磁磁路流通，所以Z型接地变压器的零序阻抗很小（10Ω左右），而普通变压器要大得多。按规程规定，用普通变压器带消弧线圈时，其容量不得超过变压器容量的20%。Z型变压器则可带90%～100%容量的消弧线圈，接地变除可带消弧圈外，也可带二次负载，可代替所用变，从而节省投资费用。
Three-phase grounding transformer: The function of grounding transformer is to introduce neutral point for arc suppression coil or resistor when the neutral point of Delta connection or Y connection can not be drawn out. This kind of transformer adopts Z connection, which is different from ordinary transformer. Each phase coil is divided into two groups and winded on the phase magnetic column in reverse, so that connection can be made. The advantage is that the zero-sequence flux can flow along the magnetic column, while the zero-sequence flux of ordinary transformer flows along the magnetic leakage circuit, so the zero-sequence impedance of Z-grounded transformer is very small (about 10), while that of ordinary transformer is much larger. According to the regulations, the capacity of ordinary transformer with arc suppression coil shall not exceed 20% of the transformer capacity. Z-type transformer can be equipped with arc suppression coils of 90%-100% capacity, and grounding transformer can be equipped with arc suppression coils as well as secondary loads, which can replace the used transformers, thus saving investment costs.
单相接地变：单相接地变主要用于有中性点的发电机、变压器的中性点接地电阻柜，以降低电阻柜的造价和体积。
Single-phase grounding transformer: Single-phase grounding transformer is mainly used for neutral point grounding resistance cabinet of generator and transformer, in order to reduce the cost and volume of resistance cabinet.
1）单相接地电弧发生间歇性的熄灭与重燃，会产生弧光接地过电压，其幅值可达4U（U为正常相电压峰值）或者更高，持续时间长，会对电气设备的绝缘造成极大的危害，在绝缘薄弱处形成击穿；造成重大损失。
1) Intermittent extinguishing and reburning of single-phase grounding arc will result in arc grounding overvoltage, whose amplitude can reach 4U (U is the peak value of normal phase voltage) or higher, and its duration is long, which will cause great harm to the insulation of electrical equipment, breakdown in the weak insulation and cause great losses.
2）由于持续电弧造成空气的离解，破坏了周围空气的绝缘，容易发生相间短路。
2) Because of the dissociation of air caused by continuous arc, the insulation of surrounding air is destroyed and the short circuit between phases is prone to occur.
3）产生铁磁谐振过电压，容易烧坏电压互感器并引起避雷器的损坏甚至可能使避雷器爆炸。这些后果将严重威胁电网设备的绝缘，危及电网的安全运行。
3) Ferromagnetic resonance overvoltage can easily burn the voltage transformer and cause the damage of the arrester, and may even cause the arrester to explode. These consequences will seriously threaten the insulation of power grid equipment and endanger the safe operation of power grid.
为了防止上述事故的发生，为系统提供足够的零序电流和零序电压，使接地保护可靠动作，需人为建立一个中性点，以便在中性点接入接地电阻。接地变压器（简称接地变）就在这样的情况下产生了。接地变就是人为制造了一个中性点接地电阻，它的接地电阻一般很小（一般要求小于5欧）。另外接地变有电磁特性，对正序负序电流呈高阻抗，绕组中只流过很小的励磁电流。由于每个铁心柱上两段绕组绕向相反，同心柱上两绕组流过相等的零序电流呈现低阻抗，零序电流在绕组上的压降很小。即当系统发生接地故障时，在绕组中将流过正序、负序和零序电流，该绕组对正序和负序电流呈现高阻抗，而对零序电流来说，由于在同一相的两绕组反极性串联，其感应电动势大小相等，方向相反，正好相互抵消，因此呈低阻抗。
In order to prevent the above accidents, provide enough zero sequence current and voltage for the system, and make the grounding protection operate reliably, it is necessary to establish a neutral point artificially to connect the grounding resistance at the neutral point. Grounding transformer (referred to as grounding transformer) is generated under such circumstances. Grounding transformer is the artificial manufacture of a neutral grounding resistance, its grounding resistance is generally very small (generally less than 5 Euros). In addition, the grounding transformer has electromagnetic characteristics. It has a high impedance to positive and negative sequence current, and only a small excitation current flows through the winding. Because the two windings on each core pole have opposite directions, the zero-sequence current flowing through the same two windings on the concentric pole presents low impedance, and the voltage drop of the zero-sequence current on the winding is very small. That is to say, when the grounding fault occurs in the system, the positive sequence, negative sequence and zero sequence currents will flow through the windings, which present high impedance to the positive sequence and negative sequence currents, while for the zero sequence currents, due to the reverse polarity of the two windings in series in the same phase, their induced electromotive force is equal in magnitude, opposite in direction, and exactly offset each other, so it is low. Impedance.
由于很多接地变只提供中性点接地小电阻，而不需带负载，所以很多接地变就是属于无二次的。接地变在电网正常运行时，接地变相当于空载状态。但是，当电网发生故障时，只在短时间内通过故障电流。中性点经小电阻接地电网发生单相接地故障时，高灵敏度的零序保护判断并短时切除故障线路，接地变只在接地故障至故障线路零序保护动作切除故障线路这段时间内起作用，中性点接地电阻和接地变才会通过零序电流。
Because many grounding transformers only provide neutral grounding resistance without load, many grounding transformers are non-secondary. When grounding is changed to normal operation of power grid, grounding will be equivalent to no load state. However, when the power grid fails, it only passes the fault current in a short time. When single-phase grounding fault occurs in neutral grounding grid with small resistance, high sensitivity zero-sequence protection judges and removes the fault line for a short time. Grounding transformer only works during the period from grounding fault to zero-sequence protection action removing the fault line, and the neutral grounding resistance and grounding transformer will pass through zero-sequence current.
接地变是人为的制造一个中性点，用来连接接地电阻。当系统发生接地故障时，对正序负序电流呈高阻抗，对零序电流呈低阻抗性使接地保护可靠动作。
Grounding is man-made to create a neutral point to connect grounding resistance. When the grounding fault occurs in the system, the positive sequence negative sequence current has a high impedance and the zero sequence current has a low impedance, which makes the grounding protection operate reliably.