Standby power plant

Operational Behavior Demonstrated in a Standby Power Plant. The plant consists of a diesel engine, the attached generator, and a number of auxiliary systems. Figure 5.25 shows the general plan of the installation. Important auxiliary systems of the plant are the fuel supply system, the lubrication system, the coolant circuits, the generator excitation system, the starter system, the air supply, and the circuitry. 

Diesel plants are used in small power plants for the continuous generation of electricity and in standby power plants for the temporary generation of electric power. In the latter case, they must be able to supply, mostly at short notice, important users with power until the temporary breakdown of the regular power supply has been remedied. These plants are located as standby units in airports, radio and TV stations, hospitals, nuclear power plants, large-scale elevator systems, etc. 

The following is a general survey of standby power plants. Due to the usually very reliable power supply from the public network, diesel plants in standby power units are very rarely called upon to perform. During blackouts (failure of the power supply), however, the standby power plant is expected to bridge the blackout reliably and with minimal loss of time during startup. Also, this must be achieved automatically. The deenergized or dead period between network failure (blackout) and emergency power supply must be as short as possible. Thus the question... 

First, a fault tree of the standby power plant is established. This fault tree should be quantitatively evaluated by means of the failure rates, the duration of operation, inspection intervals, and repair times. The result will be a statistically safe statement of the failure probability of the standby power plant. 

Power plants in both peaking and standby modes aehieved 30,000 hours between major overhauls. It was during these operations that the deposit problem on the turbine nozzles beeame apparent. Also, deposits developed on the fuel nozzles, a situation that eould eause deviation in the fuel spray angle and related eombustion problems. Therefore, both turbine and fuel nozzles needed frequent eleaning. 

All process plants require both steam and electric power in their operations. Power is cither purchased from local utility companies or generated at the plant site. Even if power is generated by the process plant, arrangements for standby power from the local utility must be made for emergency purposes. Steam is rarely purchased but is generated at the plant for use in the process and as a driving medium for pumps and compressors. 

Diesels are used in many industrial applications (for example, for base-load generation in mines, cement plants and in remote regions of the world). In addition, they are often utilized to provide standby power for hospitals, telecommunications, banks, computer centers and office complexes that must have full independent power capability. The diesel can be started rapidly, making it ideal for peak lopping duties to meet maximum load demands, or for emergency use in cases of power supply interruptions. 

The supply system for the power plant auxiliaries, including the provision of supplies to any important drives and the provision of standby supply systems. The protection and synchronizing schemes applicable to the generator circuit. 

A power failure exceeding the time limit is most critical during MD. In this case a standby power generator with a start up time of e. g. 1 min either for the operation of the whole plant or at least for the critical components is the only answer. The sequence of importance for the components can be ... 

Fig. 5.14 Standby power high performance Plante cell. The container is fabricated from transparent styrene acrylonitrile which enables the electolyte level and cell condition to be easily monitored. (By courtesy of Chloride Industrial Batteries,)...

The power required for pumping is relatively small as compared to the proposed helium plant, and aside from the unusual importance of adequate and reliable standby power, capable of being brought into service in fractional minutes, no new problems are involved. 

Ms. Swindle manages eight employees at a Georgia power plant. The plant is a "peaking plant," which means it runs only when the weather is really hot or really cold and the power grid needs a boost. "We always say we re on hot standby," she says. "It s almost like a last resort. We can run the units within 30 minutes so people will be able to flip their switch and have power."... 

Harunuzzaman, M. Aldemir, T. 1996. Optimization of standby safety system maintenance schedules in nuclear power plants. Nuclear Technology 1996 113 354-67. 

Lead-acid batteries are also used for emergency power in uninterruptible power systems (UPS), telecommunications back-up systems, and safety equipment in critical applications such as hospitals and nuclear power plants. Stationary or standby battery designs and recharge profiles vary according to the specific system requirements. Large battery strings are connected in series to deliver up to several hundred volts. 

Even though it may generally be considered safe to maintain a reactor in a hot-standby condition for a long time, experience has shown that there have been abnormal occurrences that required long-term cooling until the reactor coolant system was cold enough to perform inspection and repairs. For this reason, the ability to transfer heat from the reactor to the environment, after a shutdown resulting from an accident or abnormal occurrence, is an important safety function. It is essential that a power plant be able to go from hot-standby to cold-shutdown conditions subsequent to any accident or abnormal occurrence condition. 

The literature ([5-27], [5-28], [5-29]) provides failure rates for diesel standby plants which differ by several magnitudes. However, since the question posed can only be answered with the help of quantitative analysis, a statistical analysis of the operational behavior of diesel plants is indispensable for the determination of reliable failure rates. Figure 5.26 shows how many influence factors may lead to the failure of a diesel plant. This, in turn, requires that the failure rates for standby diesel power plants be determined as to type and mode of application. For this purpose, voluminous data on the operational behavior of standby diesel plants is required. This data can never be collected from the behavior of standby diesel plants under blackout conditions alone, since these blackouts, as mentioned above, are very rare. However, there is another avenue which leads to the acquisition of failure data, namely via monthly trial runs while the public power supply is in full and normal operation. 

Figure 5.26 Causes of failures in standby diesel power plants.

The main plant components (vessels, reactor installation, turbine generator plant, control consoles and systems, electric system, auxiliary and standby power supplies) are mounted, tested and commissioned at an interior shipyard. 

Node-oriented PTU In computer architecture nodes normally operate independently for their associated application. In a node-oriented FTU, there is replication of the node(s). In case of failure of the primary node, the designated replicas of the primary nodes will take over with a necessary mechanism to allow just one replicated unit to take over to avoid collisions or contention [9]. There are a number of hoiler controls in a power plant, namely, a closed loop control such as a superheater temperature control, furnace safeguard and supervisory system, high pressure bypass, etc., each with different apparently independent applications. In node-based architecture, there may be FTUs for each of these control systems acting as one node. In a particular node, when one of the main units fails any one of the standby controllers takes over irrespective of the application. Here the major concern is the size and capacity, and also the changeover mechanism. 

Nuclear power plants include engineered safety features (ESF) that initiate automatically to perform required safety functions. These safety systems allow also for operator intervention and control during operating events. Once the operator intervenes and takes manual control, many ESFs will not automatically re-initiate until the ESF is restored to a standby configuration with the actuation logic reset or rearmed. 

Two onsite standby diesel generator units, each furnished with its own support subsystems, provide power to the selected plant ac loads. Power supplies to each diesel generator subsystem components are provided from separate sources to maintain reliability and operability of the onsite standby power system. 

Working hours vary according to the area of the industry. Design, research and development roles generally work from nine to five, Mon- day to Friday. However, in power plant operatiorts, hours may be based arotmd a seven-day rolling shift system to provide cover 24 hours a day, seven days a week. Some staff may be on standby for call-out in case of emergencies. 

Traditionally, in the Probabilistic Safety Analysis (PSA) in Nuclear Power Plants (NPPs) it is assumed a constant standby failure rate, Mt)=... 

In case of emergency, the incineration plant has available a 258 kVA standby power generator and, for further safety, an accumulator station with a capacity of 7(X) Ah. 

Table 50.6 High-performance Plante-typelead-acid standby power batteries availablefrom Chloride Industrial Batteries... 

The small noncondensing turbine also occupies a large and important field in power plants and marine installations because it is particularly well adapted to drive variable-speed auxiliaries and because its exhaust steam can be used to supply heat to the feedwater. A further advantage of the auxiliary turbine is its availability and convenience as a standby unit in case of interruptions to the power supply of motor-driven auxiliaries. 

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