小电流接地选线装置进过一代又一代的更新，不断融合现代技术，系统已经十分成熟，在现场使用时，需要注意几点：

Small current grounding line selection device has gone through generations of updates, continuous integration of modern technology, the system has been very mature, in the field of use, we need to pay attention to several points:

(1) 接入选线装置的线路数量问题。一般来说，线路路数至少不少于3路才能保证正确判断，一般变电所都能满足此要求。当出线路数少，母线有防止电压互感器铁磁谐振或防止过电压的接地电容时，接地选线判断比较准确。另外，凡是接在母线上的各馈电线路包括补偿无功功率的电容器等的电缆都必须经过零序电流互感器接入选线装置，否则未接入选线装置的线路接地时采用幅值比较法的装置可能误判断，采用方向比较法的则可能判为母线接地。

(1) the number of lines connected to the line selection device. In general, the line number at least 3 way to ensure the correct judgment, general substation can meet this requirement. When the output line is small, the bus bar has the ability to prevent the ferroresonance of the voltage transformer or to prevent the grounding capacitance of the overvoltage, the grounding line selection is more accurate. In addition, all connected to the bus cable on the feeder circuit including reactive power compensation capacitors must be access through the zero sequence current transformer line selection device, device or no access line grounding line selection device with amplitude comparison method may malfunction by comparative law may be sentenced to for the bus grounding.

(2) 某些线路出线为双电缆时。为保证线路零序电流的准确测量，每条出线电缆应尽可能采用一根电缆，对负荷较大的线路可采用大截面铜心电缆，不得不采用双电缆并列时，应尽可能选用内径较大的零序电流互感器，将两根电缆同时穿入零序互感器。

(2) when some lines are double cables. In order to ensure the accurate measurement of zero sequence current, each outlet cable should be used on a cable line, larger load can be used for large section copper core cable, to double cable tied, should choose a larger inner diameter of the zero sequence current transformer as far as possible, the two cables at the same time penetration of zero sequence transformer.

(3) 零序电流互感器型号统一问题。幅值比较的前提是变电所各出线的零序电流互感器的特性必须一致，否则可能因特性不一致而造成误判断，这一点，尤其在变电所扩容新增加配电线路时一定要注意。新增线路的零序电流互感器必须与原有其它线路的零序电流互感器型号、生产厂家保持一致。对于开合式零序电流互感器，开合接触面应无灰尘，确保面接触。对有架空出线的线路，虽然可以用三只测量用电流互感器滤出零序电流，但由于与电缆出线零序电流互感器特性不一致，架空出线也应改为一段电缆出线，以便于用同型号零序互感器。

(3) unified model of zero sequence current transformer. The premise of amplitude comparison is that the characteristics of zero sequence current transformer must be consistent with each other, otherwise it may be mistaken because of inconsistent characteristics, especially when the substation expansion and new distribution lines are increased. The zero sequence current transformer of the newly added line must be consistent with the zero sequence current transformer model and manufacturer of the other lines. For open close zero sequence current transformer, there should be no dust in the opening and closing contact surface, so as to ensure the surface contact. For the line with overhead lines, although the zero sequence current can be filtered by three measuring current transformers, the overhead line should be changed into a cable outlet because the characteristics of the zero sequence current transformer are not consistent with the cable outlet, so as to use the same type zero sequence transformer.