Prescribing Faults

Inappropriate prescribing and irrational prescribing are self-explanatory additional information on them is available in Ref. [12]. 

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MaintainabiUty is a characteristic of design, installation, and operation, usually expressed as the probabiUty that a system can be restored to specified operable conditions within a specified interval of time when maintenance is performed in accordance with prescribed procedures. The ease of fault detection, isolation, and repair are all influenced by system design and are principal factors contributing to maintainabiUty. Also contributing is the supply of spare parts, the supporting repair organization, and preventative maintenance practices. MaintainabiUty must be designed into the equipment. Some factors to consider foUow. 

The prescribed system standard fault level nearest to if, as per Table 13.7 = 35 kA... 

I Shunt reactors These are provided as shown in Figure 24.23 to compensate for the distributed lumped capacitances, C , on EHV networks and also to limit temporary overvoltages caused during a load rejection, followed by a ground fault or a phase fault within the prescribed steady-state voltage limits, as noted in Table 24.3. They ab.sorb reactive power to offset the charging power demand of EHV lines (Table 24.2, column 9). The selection of a reactor can be made on the basis of the duty it has to perform and the compensation required. Some of the different types of reactors and their characteristics are described in Chapter 27. 

The peak value is a function of fault level Section 13.4.1 (7), Table 13.1 1. Which in turn, is a function of size and impedance of the feeding source, such as a transformer or a generator, Section 13.4.1 (5). Table 13.7. The values prescribed in the above table are thus based on these parameters. 

Intrinsically Safe Circuits A circuit which any spark or thermal effect, produced either normally or in specified fault conditions, is incapable, under the test conditions prescribed in this standard, of causing ignition of a mixture of flammable or combustible material in air in its most easily ignited concentration."(3)... 

The second doctor, insisted on prescribing 300 milligrams of trazodone to help me sleep. Yet she would tell me if you can t sleep after taking 300, after twenty minutes take a fourth [pill]. So at the end of the month, inevitably I d have to call her up and say I need another few more pills, So then after a while she starts barking at me because I m requesting more pills. And it s not my fault, I mean, I need them, And [finally] I told her I didn t want her as my doctor anymore.. .. She was out. She was definitely out. (unemployed female, aged 58)... 

Type of protection (Sch)dz indicates that this flameproof enclosure has passed successfully a special type test to avoid the propagation of an explosion inside the enclosure initiated by high current fault arcs to the surrounding atmosphere. This test has been prescribed by a decree of the Supreme Authority in Mines. 

Inspection is an examination of a product, process, service, or installation or their design and determination of its conformity with specific requirements or, on the basis of professional judgment, with general requirements. (DIN EN ISO/IEC 17020). The process of inspection includes determining whether or not a part, product, or batch is free from faults or ""nonconformity" as it is called in DIN EN ISO 9000. A fault in this notion is a departure from prescribed textures, tolerances, sizes, behavior, or other dimensions of quality. The level of quality which should be accomplished is written down in specifications or generally accepted standards. 

The example system was modelled using the Monte Carlo simulation algorithm described. The faults that are considered in order to prescribe the dispatch criteria for the system are the components Ai, Ai, B, Bi and C. At maintenance, the minimum amoimt of repair possible is implemented. Referring back to the example in Fig. 4, this would equate to repairing only... 

ARR residuals as fault indicators should be distinctly sensible to true faults and robust with regard to parameter uncertainties. That is, if parameters varies, the time evolution of ARR residuals should be within prescribed bounds. For real systems described by a hybrid model bounds should be adapted to system modes as the dynamic behaviour can be quite different in different system modes. 

The AP 1000 systems, structures, and components are designed to maintain the plant within prescribed safety limits for postulated fault conditions. 

This claim has been addressed by postulated fault conditions being defined in a fault schedule, and the engineering safety features have being demonstrated to maintain the potential for core damage and release of radioactive material within the defined prescribed safety limits. 

If the earth loop impedance is too high for overcurrent protection to operate within the prescribed time, Regulation 413-02-04(i) permits this time to be exceeded provided local supplementary equipotential bonding is used to meet the requirements of Regulations 413-02-27 and 28 and the fault persistence does not cause damage. Again, the intention is to minimise the potential differences between touchable metalwork items on the occurrence of an earth fault. As an alternative. Regulation 413-02-04(ii) allows the use of RCD protection. 

Regulation 542-0 l-07(i) means that the connections to earth must be effective and the earth loop impedance low enough for the protective devices to operate within the prescribed time in the event of an earth fault. Regulations 542-01-08 and 542-02-03 deal with electrolysis and corrosion. The electrolysis in Regulation 542-01-08 is probably that which occurs in d.c. supply systems where earth leakage can cause corrosion from electrolysis at the positions where the current enters or leaves metallic parts. This problem occurs in d.c. traction systems and certain types of electrochemical plants, and is often associated with cathodic protection systems which impress d.c. currents in the ground. 

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