HEARING EDITION REPORT PHASE 1 CONCLUSIONS SAFETY MEASURES TO PREVENT EXPLOSION AND FIRE LECTRICALPOWER PLANTS 14th January 2002 Page 1 of 3 SEBK PHASE 1 - CONCLUSIONS Oil-filled components in power plants are dangerous, hazardous objects in which serious explosions and fires can occur. In particular large power step-up transformers in underground power plants are a primary area of focus. The SEBK highlights the explosion potential and the consequences of incidents that can be considered as being out of control. Risk means “the rate of probability multiplied by the consequence”. Although comprehensive measures are given increasing priority in the power sector, incidents always occur. Therefore power stations to be designed in order to provide as good sectioning as possible in order to provide both explosion and fire barriers. Directly or indirectly electrical faults are the predominant cause of incidents in power plants. Minor or insignificant failures may develop or may cause serious incidents and they can spill over to more important plant functions and result in a disaster occurring. Failures in high voltage or high-energy circuits or components, such as short circuits, are subject to special attention. Incorrect manual operation may cause the development of a serious incident if no automatic back-up safety functions are provided. Particular high-risk areas are transformers, oil-filled cables, cable connections and other oil-filled components. Primary causes of incidents include mechanical stresses, a lack of maintenance and a lack of inspection. Faults in minor important components or outbreaks of fire may affect high-risk components or areas. Component failures are normally found to result from manufacturing defects/weaknesses, incorrect operation or aging. Hacker and High Power Microwave (HPM) technology represents a worsening of the safety risk. The Internet and the increasing use of automatic and software based systems increase the possibilities of entering power control networks. Cable joints represent a potentially high safety risk as well. The termination of cables into a connection chamber filled with oil represents a substantia l explosion potential. Insulation material defect caused the disaster at Tonstad power station in 1973. Risk levels for personnel and material assets as well as the consequences of these risks are considerable higher in underground electric power plants than in plants located above ground. The establishment of escape routes is a major problem in the design of underground power plants. safety measures. After the de-regulation of the Norwegian power marked, the operational mode has been changed dramatically in the majority of plants. The present level of knowledge that is available concerning the aging processes in power transformers is not satisfactory despite many years of research and operating experience. Both the paper and the oil are the weakest components in the insulating devices inside the transformer. These are obviously the components in the aging process of transformers. The researchers agree that it is no satisfactory way whereby the transformer oil can be replaced in order to improve the condition and increase the remaining lifetime of the transformer since any such improvement seem to be marginal. In spite of a lack of quantitative statements it seems clear that the water content of the paper increases dramatically the decomposition speed of the insulation. Additionally, the operating temperature, the average temperature and the hot-spot temperature inside the transformer and its duration all have a major influence of the decomposition of the paper. The development of gasses caused by decomposition of the insulating oil and its pressure expansion seems to be the most important factor in a fault situation. If an ignition source then occurs as a result of an electrical or HEARING EDITION REPORT PHASE 1 CONCLUSIONS SAFETY MEASURES TO PREVENT EXPLOSION AND FIRE LECTRICALPOWER PLANTS 14th January 2002 Page 2 of 3 other fault then the resulting damage due to combustion and associated danger to personnel will be substantial. In the power sector not enough focus has been placed on acceptable risk as being a steering factor as well as risk evaluations connected to various safety measures despite the fact that acceptable risk has been the subject of lessons and references. Long and dangerous escape routes in a poor environment and in dangerous circumstances. Large fire-loads without the possibility of relieving pressure to the free atmosphere. Much smoke develops during a fire and is difficult to ventilated away from the area. Enormous amounts of energy are released into a confined space The Norwegian Ministry of Defense has defined accept criteria for individual risks and group risks within their areas of responsibility. In the power sector, however, the authorities, represented by the Energy department, have not brought this subject into the arena for discussion and clarification. Everybody makes mistake in their daily work and all systems have to intercept them, automatically and systematically, in order to avoid consequential damages. All mistakes must be reported and included in the maintenance work. If a mistake is not reported or the operator try to hide the mistake, then the mistake will become much more serious. Measures that can warn power station attendants prior to an explosion occurring are very limited. An abnormal operational status, fault signals and noise might be the only early warning prior to an explosion occurring.To reduce risk of explosion is fundamental. The environmental aspects related to the SEBK project are Halon used as extinguishing and suppression remedy and transformer oil pollution A number of accidents have occurred in Norway and abroad where oil mist was the cause of an explosion. Some are reported in this report. Examples of research and work out in the field of safety risk are reported as well. Suppression/quenching of an explosion during it is development and fire extinguishing have an important difference. The status of the extinguishing equipment market at present is fragmented and unstable. There is a multitude of methods, means, products, consultants and suppliers. The market is inundated with opinions and attitudes. However it is necessary to treat this complicated area with a degree of caution and respect and to adopt a practical, down-to-earth approach. Extinguishing a fire in an underground power station presents a number of special challenges where a variety of factors come into play. The fires that occur have different features depending on the fire load supporting the fire and the time that has elapsed since the fire started. Further, it is necessary to have sufficient knowledge with regard to the materials that can burn and how the fire is likely to develop There is no medium available today that has all of those features. However, they provide good guidance when the choice of extinguishing medium is made. There has been a long-term trend towards using water (alone or with additives) as an extinguishing medium for all types of fires. This means that attention has been paid to the use of water in this report. When water mist is considered as an extinguishing medium it is necessary to differentiate between actions against fire and those against explosion. The drop size is important when fire extinguishing and when water damage is to be avoided. HEARING EDITION REPORT PHASE 1 CONCLUSIONS SAFETY MEASURES TO PREVENT EXPLOSION AND FIRE LECTRICALPOWER PLANTS 14th January 2002 Page 3 of 3 According to the partial report by GexCon it is, with a high degree of certainty, likely that in the first phase of an explosion spray systems, especially water spray, create much turbulence thus an uncontrolled development. It is reasonable to be cautious and view the present situation with some scepticism.
Pages to are hidden for
"SAFETY MEASURES TO PREVENT EXPLOSION AND FIRE LECTRICALPOWER PLANTS HEARING"Please download to view full document