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通過(guò)過(guò)電流保護(hù)裝置進(jìn)行保護(hù)
相間接地保護(hù)自動(dòng)裝置的選擇
故障和間接接觸應(yīng)通過(guò)適當(dāng)協(xié)調(diào)
故障回路阻抗的斷開時(shí)間。
因此，有必要滿足以下條件：
Zs公司
·Ia公司≤ U0
哪里：
ZS是故障回路的阻抗（單位：歐姆），包括
-來(lái)源；
-線路導(dǎo)體至故障點(diǎn)；
-外露導(dǎo)電部分的保護(hù)導(dǎo)體；
-接地導(dǎo)體；
-裝置的接地電極；
-電源的接地電極；
我
a是終電路的斷開電流，時(shí)間如表1所示
配電電路電流不超過(guò)32A或1秒以內(nèi)
對(duì)于電流超過(guò)32A的終電路；
U0是標(biāo)稱交流均方根對(duì)地電壓（V）。
自動(dòng)裝置的選擇應(yīng)通過(guò)適當(dāng)協(xié)調(diào)
故障回路阻抗的斷開時(shí)間。
關(guān)系Zs
·Ia公司≤ U0
可以表示為：
我
一≤ U0=IkL對(duì)地Zs
其中，IkL對(duì)地是相對(duì)地故障電流。因此，可以聲明
當(dāng)跳閘電流Ia時(shí)，驗(yàn)證間接接觸保護(hù)
保護(hù)裝置的電壓（在表1所示的時(shí)間內(nèi)或1s內(nèi)）較低
比ea的相位

Protection by means of overcurrent protective devices The choice of the automatic device for the protection against phase-to-earth faults and indirect contact shall be carried out by coordinating properly the disconnection times with the impedance of the fault loop. As a consequence, it is necessary to fulfill the following condition: Zs · Ia ≤ U0 where: ZS is the impedance (in ohms) of the fault loop comprising - the source; - the line conductor up to the point of the fault; - the protective conductor of the exposed-conductive-parts; - the earthing conductor; - the earth electrode of the installation; - the earth electrode of the source; I a is the disconnection current in the times shown in Table 1 for final circuits with currents not exceeding 32A or within 1 second for distribution circuits and for final circuits with currents exceeding 32A; U0 is the nominal a.c. r.m.s. voltage to earth (V). The choice of the automatic device shall be made by coordinating properly the disconnection times with the impedance of the fault loop. The relationship Zs · Ia ≤ U0 may be expressed as : I a ≤ U0 = IkL-to earth Zs where IkL-to earth is the phase-to-earth fault current. Therefore, it is possible to state that the protection against indirect contact is verified when the tripping current Ia of the protective device (within the times shown in Table 1 or within 1s) is lower than the phase-to-ea