Electrical power disturbance

Long, A. B., and Kanazava, R. M., Summary and Evaluation of Scoping and Feasibility Studies for Disturbance Analysis and Surveillance Systems, EPRI Report NP-1684. Electr. Power Res. Inst., Palo Alto, CA, 1980. 

A control system requires a mechanism to change the state of the process when a disturbance causes the control variable to move fi"om the desired value. This control mechanism is most often a control valve although it can be a motor, a set of louvers, an electrical power supply, a fan on an aircooled condenser, etc. Control which is achieved by changing the area of the valve body opening is a direct energy expense to the operating unit. 

Energy in chemical production sites comprises two main sources electric power and heat. Electric power is distributed via a cable network. Either a local power plant exists or the production site is supplied by an external partner. At a production site often a backup system exists to overcome short-falls of the primary source of electric power (at least for some time). Hence, disturbances due to a power short-fall occur quite seldom at chemical production sites. 

Infrastructure systems are also vulnerable to myriad stresses and failures as a result of everyday interdependencies, insufficiencies, and inefficiencies. Cascading power blackouts in the United States in July and August 1996 cost an estimated 1.5 billion, including related infrasttucture and environmental impacts (Amin, 2000). On a grander scale, recent estimates of the annual cost to the U.S. economy from non-cyber power disturbances exceed 119 billion, most of which is related to disruptions to discrete manufacturing and electricity-dependent utilities... 

The pervasive use of ICT within other Infrastructures, as e.g. the electric power grid, provides many benefits which become indispensable for the operation of today s interconnected systems, mainly with respect to efficiencies, automation and availabihty of information. This dependency, however, increases the vulnerability of the analyzed systems to disturbances of the ICT infrastructure. These topics are at an early stage of development (Carreras et al. 2005). 

Cooling of the reactor core when the plant is in the shutdown condition or following the occurrence of abnormal events is reliably assured by making use of the natural force of gravity. Provision of a large water inventory inside the reactor pressure vessel as well as of a large source of water inside the containment makes active, fast-response safety equipment, pumps and electric power unnecessary in the event of disturbances in the reactor coolant system. 

All safety systems in the VVER-440 concept are divided into three, or in certain sections four, separate and independent redundant subsystems, each of which meets the requirements caused by loss-of-coolant accidents or other disturbances. The various circuits of the redundancy subsystems are located in physically separate areas and supplied with electrical power from separate diesel—backed sources. This separation principle provides reliable protection against external and internal influences, such as earthquakes, airplane crashes, explosions, flooding and fire, etc. 

Core damage should be excluded without personnel action in any initiating event with a heat removal disturbance or uncontrolled reactivity addition followed by the failure of control and active safety systems requiring electric power, through the use of passive systems and natural heat dissipation ... 

From Whitaker, J.C., Power system protection alternatives, in AC Power Systems Handbook, 2nd ed., CRC Press, Boca Raton, FL, 1999, p. 267. After Key, Lt. Thomas, The Effects of Power Disturbances on Computer Operation, IEEE Industrial and Commercial Power Systems Conference, Cincinnati, June 7,1978, and Federal Information Processing Standards Publication No. 94, Guideline on Electrical Power for ADP Installations, U.S. Department of Commerce, National Bureau of Standards, Washington, D.C., 1983. 

Powerscope Performance, Productivity and Practicality for Power Disturbance Analysis, 1993. Electric Power Analyzers Tools for Measuring Electric Power Quality, Power Plow, Disturbances, and Demand, 1993. 

In the case of disturbances, the protection of the auxiliary power supply of the NPPs is given top priority. The necessary measures are fixed. In addition, there are specifications for the electrical power suppliers in Germany as well as in Europe for the control and limitation of grid disturbances and the restoration of the grid following a grid breakdown. 

This subsection should provide information relevant to the plant on the off-site electrical power systems. It should include a description of the off-site power systems, with emphasis on features for control and protection (breaker arrangements, manual and automatic disconnect switches) at the interconnection to the on-site power system. Special emphasis should be put on all design provisions used to protect the plant from off-site electrical disturbances and to maintain power supply to in-plant auxiliaries. Information on grid reliability should also be provided and any design specific provisions necessary to cope with frequent grid failures should also be described. 

Power quality. Some industries, for instance chip manufacturers, are very sensitive to disturbances in the electric power quality. One way to solve this problem is to generate high quality, on-site power using fuel cells. 

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