IS200ISBBG2A
在存在接地故障的情况下，会像通常的TN系统一样发生短路，但大电流装置无法检测到这种电流，因为光伏发电厂的特点是产生的故障电流值不高于额定电流。因此，关于此故障的危险性，前第4段中关于IT系统第二个故障的考虑是有效的。5.4接地和间接接触防护图4 4标准IEC 60364-7建议直流侧的整个装置（配电盘、电缆和端子板）通过使用II类设备或等效绝缘安装。5.4.1.2变压器供电侧的外露导电部件应考虑TT型网络用户系统。属于用户设备的外露导电部件由位于用户设备开始处的剩余电流断路器保护（图4），从而对网络和光伏发电机进行保护B Rn Id Re IdPV Idr负载电网平行点A-B和网络之间不得有外露导电部分，因为在这种情况下，TT系统中用户设备的所有外露导电部分必须由剩余电流断路器保护的规范要求。

In the presence of an earth fault, a short-circuit occurs as in the usual TN systems, but such current cannot be detected by the maximum current devices since the characteristic of the PV plants is the generation of fault currents with values not much higher than the rated current. Therefore, as regards the dangerousness of this fault, the considerations made in the previous paragraph4 on the second fault for an IT system are valid. 5.4 Earthing and protection against indirect contact Figure 4 4 The Std. IEC 60364-7 recommends that the whole installation on the DC side (switchboards, cables, and terminal boards) is erected by use of class II devices or equivalent insulation. 5.4.1.2 Exposed conductive parts on the supply side of the transformer Take into consideration the network-consumer system of TT type. The exposed conductive parts belonging to the consumer’s plant protected by a residual current circuit-breakers positioned at the beginning of the consumer’s plant (Figure 4), result protected both towards the network as well as towards the PV generator. + - B A Rn Id Re IdPV Idr Load Grid There must not be an exposed conductive part between the parallel point A-B and the network because in such case the normative requirement that all the exposed conductive parts of a consumer’s plant in a TT system must be protected by a residual current circuit-breaker.