Phase-to-neutral

The voltage across the healthy phases is now times or 73% more than the phase to neutral voltage under healthy conditions. 

This is measured between phase to phase or phase to neutral, depending upon the availability of the neutral. The test current is kept at the rated value for the equipment or the system under test. For the system shown in Figure 20.9(a). 

L1, L2, L3 phase conductors 1/1, 1/2, 1/3 voltages phase to neutral C1, C2, C3 capacitances phase to earth PE protective earthed conductor RF earth fault resistance UN, PE voltage between neutral N and PE in case of an earth fault... 

Much deeper insights into the water sorption properties of polyelectrolytes can be provided by evaluating the (nNa)p term directly. By the use of the activity coefficient of Na+ ions in the PA A polyelectrolyte phase, (yNa)p, (aNa)p can be expressed as (aNa)p = (yNa)P [Na]p. Two concentration terms, i.e., (1) Na+ ions present in the polyelectrolyte phase to neutralize free car-boxylate groups and (2) Na+ ions imbibed in the polyelectrolyte phase in the form of NaCl, contribute the [Na]p term. Escape of Na+ ions from the polyelectrolyte phase due to their thermal motion, which produces a site vacancy of the polyion, should also be taken into consideration. The fraction of site vacancy of polyelectrolytes is available as a practical osmotic coefficient, c/>p-Na, which can simply be related to the linear charge separation of the PAA polyion. It has been revealed that PiNa is not affected by the change in the polyion concentration nor Cs, which is known as an additivity rule [16,17]. Thus the (aNa)p term can finally be expressed as... 

Assume that the secondary phase-to-neutral emf of the snpply transformer is E and the fnn-damental reactance of each phase winding is X/, and the DC load current is Ij, then for Mode 1 operation the DC output voltage is. 

Assume the inverter equivalent output phase-to-neutral voltage consists of a 180° rectangle waveform plus a 60° rectangle waveform. The complete waveform has a harmonic content of,... 

The rms value of the fundamental phase-to-neutral voltage is 415/.y3 = 239.6 volts. Therefore its peak value is 239.6 2 = 338.85 volts which corresponds to bi having a value of 2.0085. The peak values of the first 17 harmonic components of the phase-to-neutral voltage are given below in Table 15.3. 

This voltage increase is not a problem for electrical equipments due to it is considered in design. The problem turns pessimistic due to short circuit current of ground fault phase to neutral, affecting the waveform of un-faulted phases, which stay with a no sinusoidal waveform. As a result of the interaction between fault phase and the others phases, it is obtained a waveform, as shown in Fig. 3.3.4. 

Loop impedance tests are carried out to determine the loop impedance between the power source(s) and the point in the installation where the test is done. The device employed measures the current which passes through a resistor and displays the result in ohms. It is used to determine the loop impedance between phases, phase to neutral or any phase to earth. Some instruments incorporate a transformer to enable the neutral/earth loop impedance to be measured. From Ohm s law these readings can then be expressed in prospective short circuit fault currents. 

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