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Uo是標(biāo)稱交流或直流線對(duì)地電壓。綜上所述，很明顯，由于上述關(guān)系中分母處的電流量不同，使用靈敏度不同的剩余電流斷路器，接地布置的電阻RA值會(huì)有所不同。事實(shí)上，通過使用靈敏度為30mA的剩余電流裝置，接地電阻值低于表1：就斷開時(shí)間而言，終電路的大斷開時(shí)間不超過32A，本標(biāo)準(zhǔn)區(qū)分了兩種可能性；•額定電流不超過32A的終電路：在這種情況下，必須在表1所示的時(shí)間內(nèi)滿足上述條件（故障電流值明顯高于剩余電流斷路器的額定剩余電流，通常為5·I?n）履行；•額定電流超過32A的配電電路或終電路：在這種情況下，必須在不超過1s（常規(guī)時(shí)間）的時(shí)間內(nèi)滿足上述條件。在TT系統(tǒng)中，如果通過過電流保護(hù)裝置實(shí)現(xiàn)斷開，并且保護(hù)等電位連接與裝置內(nèi)的所有外部導(dǎo)電部件相連，則可使用適用于TN系統(tǒng)的大斷開時(shí)間。注1：除電擊保護(hù)外，可能需要斷開連接。注2：如果RCD符合上述要求，則根據(jù)上表，斷開時(shí)間與預(yù)期剩余電流相關(guān)，顯著高于RCD的額定剩余工作電流（通常為5·I?n）。RA公司≤ 50=1666.6W 0.03 RA≤ 50=166.6W 0.3，而對(duì)于靈敏度較低的剩余電流裝置（例如300mA靈敏度），接地電阻值低于：
Uo is the nominal a.c. or d.c. line to earth voltage. From the above, it is evident that the value of the resistance RA of the earthing arrangement results to be different by using residual current circuit-breakers with different sensitivity, since the current quantity at the denominator in the above mentioned relationship is different. In fact, by using a residual current device with 30mA sensitivity, an earthing resistance value lower than Table 1: Maximum disconnection times for final circuits not exceeding 32A As regards the disconnection times, the Standard distinguishes two possibilities; • final circuits with rated currents not exceeding 32A: in this case it is necessary that the above mentioned condition with the times shown in Table 1 (values referred to fault currents significantly higher than the rated residual current of the residual current circuit-breakers typically 5·I?n ) is fulfilled; • distribution circuit or final circuit with rated currents exceeding 32A: in this case it is necessary that the above mentioned condition is fulfilled with a time not exceeding 1 s (conventional time). Where in TT systems the disconnection is achivied by an overcurrent protective device and the protective equipotential bonding is connected with all extraneous-conductive-parts within the installation, the maximum disconnection times applicable to TN systems may be used. NOTE 1 Disconnection may be required for reasons other than protection against electric shock. NOTE 2 Where compliance with the above mentioned requirement is provided by an RCD, the disconnecting times in accordance with the table above relate to prospective residual currents significantly higher than the rated residual operating current of the RCD (typically 5·I?n ). RA ≤ 50 = 1666.6W 0.03 RA ≤ 50 = 166.6W 0.3 shall be obtained, whereas with a less sensitive residual current device (for example with 300mA sensitivity) an earthing resistance value lower than:
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