Overvoltages computation

Consider Example 25.1 for 7200 kVAr units arranged in a single star and 14 400 kVAr units arranged in a double star. The computation of overvoltages and fault currents in the event of failure of a single unit in the two configurations is in a tabulated form as follows ... 

The elimination of this rapid energetic surge requires special devices and can not be prevented by crowbars, gas diodes, or overvoltage protectors commonly found in computers and power supplies. Considerable problems exist with filtering devices, unless they are especially made with much higher than expected insulation requirements and are used in conjunction with fast, specifically designed overvoltage protectors. 

Unfortunately, the protector provided in many OEM computers and power supplies is for overvoltage or overcurrent protection for failing components, and its response time is fa,r too long for the rapidly rising surges and transients entering the system. 

When the E-value for (i) is computed as 0.82 V for pH 7.0, as in (a), oxygen evolution takes precedence. [In practice, overvoltage or polarization is more difficult to avoid in the case of reactions involving gases (O2) as compared with liquids and dissolved solutes, so that electrolysis of NiBr2 at most electrodes would probably lead to Br2 formation.]... 

There are other reasons for grounding not implicit in the IEEE definition. Overvoltage control has long been a benefit of proper power system grounding, and is described in IEEE Standard 142, also known as the Green Book [3]. With the increasing use of electronic computer systems, noise control has become associated with the subject of grounding, and is described in IEEE Standard 1100, the Emerald Book [4]. 

The EMTP has been widely used all over the world as a standard simulation tool for transient analysis not only in a power system, but also in an electronic circuit. The BPA of the U.S. Department of the Interior (later U.S. Department of Energy) started to develop a computer software for analyzing power system transients, especially switching overvoltage from the... 

The increase of Ch with overvoltage rj was found to agree well with that computed according to Nernst s equation from the measured... 

Step was relatively simple. In addition to the above conditions, a change of the concentration of the ionic species in the film was taken into account by IczKOWSKi [58] and Bennion and Tobias [34]. Finally Iczkowski [63] computed the total current density of the H2 oxidation on porous nickel electrodes as the sum of the currents which would be produced at the given overvoltage by each of the individual pores in 1 cm of electrode material... 

Flight control computers must be particularly robust. They are protected against overvoltage, under-voltage, electromagnetic attacks, the indirect effects of lightning, various vibrations, shocks, etc. The computers are cooled by a ventilation system, but can operate correctly even in case of loss of ventilation. 

Fig. 10.6 Total currents with relevant cathodic and anodic components, i.e., forward and backward currents, respectively, as a function of the overvoltage for two different reversibility degrees, as simply computed by the Butler-Volmer expression in Eq. (10.27) in plot (b) the total current coincides with the anodic (red line) or cathodic (blue line) component, for positive and negative values of q, respectively...

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