Introduction to Electrical Engineering

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Pro: ČEKO IMPORT a.s.
Vydal: České vysoké učení technické Praha Autor: Vladimír Kůla, Michal Kříž

Strana 84 z 112

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5 Automatic disconnection supply The verification the efficacy the measures for protection against indirect contact by automatic disconnection supply effected follows: a) For systems Compliance with the rules for systems shall verified by: 1) measurement the loop impedance. Table 9.c. The testing apparatus shall capable of supplying the test voltage specified Table 9.4 Polarity test Where the rules forbid the installation single pole switching devices the neutral conductor, test polarity shall made verify that all such devices are connected the phase only.5 Above 500 1000 ≥1.VERIFICATION ELECTRICAL EQUIPMENT AND INSTALLATION 85 The insulation resistance, measured with the test voltage values indicated Table 9.1 when loaded with mA. 9. (V) Insulation Resistance (MΩ Ω Ω Ω) SELV and functional extra-loe voltage, when the circuit supplied froma safety transformer and also fulfils other requirements 250 ≥0. When the circuit includes electronic devices, only the measurement between phases and neutral, connected together, earth shall made.25 Up and including 500 with the exception the above cases 500 ≥0.1, is satisfactory each circuit, with the appliances disconnected, has insulation resistance not less than the appropriate value given Table 9.0 Measurement shall carried out with direct current.3 Protection separation circuits (electrical separation) The separation the live parts from those other circuits and from earth shall verified by measurement the insulation resistance. Note: This precaution necessary because carrying out the test without connection between live conductors could cause damage electronic devices.1 Minimum value insulation resistance Nominal circuit voltage (V) Test voltage d.1. 9. 9. alternative compliance may verified by measurement the resistance protective conductors.3. Note: The above measurements are not necessary where the calculations the fault loop impedance the resistance the protective conductors are available and when the arrangement the installation permits measuring .3. The resistance values obtained shall in accordance with Table 9.3.1, with the appliances, far possible, connected