ICS TRIPLEX T3485 DCS工控模塊備件
檢測（如果使用）。有關(guān)2相CT信息，請參見第A-1頁附錄A.1：2相CT配置。b） 接地電流輸入469具有用于接地CT連接的雙初級隔離變壓器。接地電流輸入上沒有內(nèi)部接地連接。如果取出裝置，469外殼上的自動機構(gòu)會使接地CT電路短路。1 A/5 A抽頭用于零序/鐵芯平衡應(yīng)用或剩余接地連接，其中三相電流CT的總和通過接地電流輸入（見下圖）。1 A/5 A抽頭的最大接地CT初級電流為5000 A。或者，50:0.025接地CT輸入設(shè)計用于高電阻接地系統(tǒng)上的靈敏接地電流檢測，其中使用GE Multilin 50:0.025芯平衡CT。例如，在必須測量漏電電流以確保人員安全的采礦應(yīng)用中，GE Multilin 50:0.025 CT可檢測到低至0.25 A的一次接地電流。給定裝置上只能使用一個接地CT輸入抽頭。圖2-12：剩余接地CT連接如果使用1 A/5 A抽頭，469測量的次級電流可達(dá)5 A。由于轉(zhuǎn)換范圍相對較小，1 A或5 A選項可現(xiàn)場編程。正確選擇該設(shè)定值可確保正確讀取一次接地電流。選擇的1 A/5 A接地CT必須能夠驅(qū)動469接地CT負(fù)載（見第1-4頁第1.2節(jié)：規(guī)格）。如果該抽頭與GE Multilin鐵芯平衡CT一起使用，469可測量高達(dá)25 A的一次接地電流。注意：GE Multilin 469電機管理繼電器2-11 2安裝2.2電氣2建議采用零序連接。CT的不均勻飽和、電機的尺寸和位置、電力系統(tǒng)的電阻和電機鐵芯飽和密度等可能會導(dǎo)致剩余連接的GF電路中的錯誤讀數(shù)。只應(yīng)連接一個接地輸入–另一個輸入應(yīng)未連接。僅檢測接地故障電流的零序CT的準(zhǔn)確位置如下所示。如果將鐵芯平衡CT放置在屏蔽電纜上，則在電機啟動期間將相電流電容耦合到電纜屏蔽中，可檢測為接地電流，除非屏蔽線也穿過CT窗口。建議在零序CT上使用雙絞線。圖2-13：堆芯平衡接地CT安裝注釋：屏蔽電纜無屏蔽電纜2-12 469電機管理繼電器GE Multilin 2.2電氣2安裝2 c）差動電流輸入469有三個通道用于差動電流輸入，每個通道都有一個隔離變壓器。電流輸入上沒有內(nèi)部接地連接。如果裝置退出，469外殼上的每個差動CT電路都會被自動機構(gòu)短路。最大差動CT一次電流為5000 A。469測量差動CT輸入的二次電流高達(dá)5 A。由于轉(zhuǎn)換范圍相對較小，1 A或5 A選項可現(xiàn)場編程。正確選擇該設(shè)定值可確保正確讀取初級相位差電流。選擇的1 A/5 A差動CT必須為
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 The ground CT circuits are shorted by automatic mechanisms on the 469 case if the unit is withdrawn.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
