ICS TRIPLEX T3485 DCS工控模块备件
检测（如果使用）。有关2相CT信息，请参见第A-1页附录A.1：2相CT配置。b） 接地电流输入469具有用于接地CT连接的双初级隔离变压器。接地电流输入上没有内部接地连接。如果取出装置，469外壳上的自动机构会使接地CT电路短路。1 A/5 A抽头用于零序/铁芯平衡应用或剩余接地连接，其中三相电流CT的总和通过接地电流输入（见下图）。1 A/5 A抽头的最大接地CT初级电流为5000 A。或者，50:0.025接地CT输入设计用于高电阻接地系统上的灵敏接地电流检测，其中使用GE Multilin 50:0.025芯平衡CT。例如，在必须测量漏电电流以确保人员安全的采矿应用中，GE Multilin 50:0.025 CT可检测到低至0.25 A的一次接地电流。给定装置上只能使用一个接地CT输入抽头。图2-12：剩余接地CT连接如果使用1 A/5 A抽头，469测量的次级电流可达5 A。由于转换范围相对较小，1 A或5 A选项可现场编程。正确选择该设定值可确保正确读取一次接地电流。选择的1 A/5 A接地CT必须能够驱动469接地CT负载（见第1-4页第1.2节：规格）。如果该抽头与GE Multilin铁芯平衡CT一起使用，469可测量高达25 A的一次接地电流。注意：GE Multilin 469电机管理继电器2-11 2安装2.2电气2建议采用零序连接。CT的不均匀饱和、电机的尺寸和位置、电力系统的电阻和电机铁芯饱和密度等可能会导致剩余连接的GF电路中的错误读数。只应连接一个接地输入–另一个输入应未连接。仅检测接地故障电流的零序CT的准确位置如下所示。如果将铁芯平衡CT放置在屏蔽电缆上，则在电机启动期间将相电流电容耦合到电缆屏蔽中，可检测为接地电流，除非屏蔽线也穿过CT窗口。建议在零序CT上使用双绞线。图2-13：堆芯平衡接地CT安装注释：屏蔽电缆无屏蔽电缆2-12 469电机管理继电器GE Multilin 2.2电气2安装2 c）差动电流输入469有三个通道用于差动电流输入，每个通道都有一个隔离变压器。电流输入上没有内部接地连接。如果装置退出，469外壳上的每个差动CT电路都会被自动机构短路。最大差动CT一次电流为5000 A。469测量差动CT输入的二次电流高达5 A。由于转换范围相对较小，1 A或5 A选项可现场编程。正确选择该设定值可确保正确读取初级相位差电流。选择的1 A/5 A差动CT必须为
detection (if used). See Appendix A.1: Two-Phase CT Configuration on page A–1 for 2-phase CT information. b) GROUND CURRENT INPUT The 469 has a dual primary isolating transformer for ground CT connection. There are no internal ground connections on the ground current inputs. The ground CT circuits are shorted by automatic mechanisms on the 469 case if the unit is withdrawn. The 1 A / 5 A tap is used either for zero-sequence/core balance applications or residual ground connections where the summation of the three phase current CTs is passed through the ground current input (see the figure below). The maximum ground CT primary current is 5000 A for the 1 A / 5 A tap. Alternatively, the 50:0.025 ground CT input has been designed for sensitive ground current detection on high resistance grounded systems where the GE Multilin 50:0.025 core balance CT is to be used. For example, in mining applications where earth leakage current must be measured for personnel safety, primary ground current as low as 0.25 A may be detected with the GE Multilin 50:0.025 CT. Only one ground CT input tap should be used on a given unit. Figure 2–12: RESIDUAL GROUND CT CONNECTION The 469 measures up to 5 A secondary current if the 1 A / 5 A tap is used. Since the conversion range is relatively small, the 1 A or 5 A option is field programmable. Proper selection of this setpoint ensures proper reading of primary ground current. The 1 A / 5 A ground CT chosen must be capable of driving the 469 ground CT burden (see Section 1.2: Specifications on page 1–4). The 469 measures up to 25 A of primary ground current if this tap is used in conjunction with the GE Multilin core balance CT. CAUTION GE Multilin 469 Motor Management Relay 2-11 2 INSTALLATION 2.2 ELECTRICAL 2 The zero-sequence connection is recommended. Unequal saturation of CTs, size and location of motor, resistance of power system and motor core saturation density, etc., may cause false readings in the residually connected GF circuit. Only one ground input should be wired – the other input should be unconnected. The exact placement of a zero-sequence CT to detect only ground fault current is shown below. If the core balance CT is placed over shielded cable, capacitive coupling of phase current into the cable shield during motor starts may be detected as ground current unless the shield wire is also passed through the CT window. Twisted pair cabling on the zero-sequence CT is recommended. Figure 2–13: CORE BALANCE GROUND CT INSTALLATION NOTE NOTE SHIELDED CABLE UNSHIELDED CABLE 2-12 469 Motor Management Relay GE Multilin 2.2 ELECTRICAL 2 INSTALLATION 2 c) DIFFERENTIAL CURRENT INPUTS The 469 has three channels for differential current inputs, each with an isolating transformer. There are no internal ground connections on the current inputs. Each differential CT circuit is shorted by automatic mechanisms on the 469 case if the unit is withdrawn. The maximum differential CT primary current is 5000 A. The 469 measures up to 5 A secondary current for the differential CT inputs. Since the conversion range is relatively small, the 1 A or 5 A option is field programmable. Proper selection of this setpoint ensures proper reading of primary phase differential current. The 1 A / 5 A differential CT chosen must be
