The necessity of special design, special construction and special acceptance of the dam monitoring system for hydropower stations

The dam is the most important hydraulic structure of the hydropower station. Like other engineering structures, there is also a possibility of failure. The nineteenth article of the "Regulations on safety management of reservoirs and dams" promulgated by the State Council clearly stipulates that the dam management units must carry out safety monitoring and inspection for the dams according to the relevant technical standards, and timely monitor and analyze the monitoring data, so as to grasp the operation status of the dams at any time. When abnormal phenomena and unsafe factors are found, the dam management unit should report to the Department of the Dam immediately and take measures in time. Dam safety monitoring system is basically built in large and medium sized hydropower stations in China. However, there are still some problems such as poor observation facilities, outdated equipment and low observation accuracy, which do not play a good role in monitoring the working performance of dams. The reasons for these problems are directly related to the lack of strict quality control in the design, construction and operation of each link and the lack of management. Therefore, the provisions of the "dam safety management of hydropower station operation" (hereinafter referred to as the "Regulations") in the construction of new dam monitoring system or in the complex, low dam, special design requirements, special examination, special inspection of the monitoring system; monitoring facilities built hydropower station is not complete or can not meet the safety monitoring project power station dam, should be the deadline for rectification, and special design, special examination of reconstruction scheme, special inspection is completed.

1 problems existing in the dam safety monitoring system

Regular inspections of the first 96 hydropower stations showed that the monitoring facilities of the 80% hydropower stations were not perfect. The main problems were: incomplete monitoring items, low monitoring instruments, low accuracy of monitoring instruments, unstable measurement values and poor durability.

In view of the problems found in the first round of inspection, many hydropower plants have renovated the dam monitoring system. According to rough statistics, some or all of the monitoring projects of the 50% hydropower stations have been automatically monitored. Although the situation has improved after the renovation, some of the automation projects are not very successful. The accuracy and long-term stability of some transformed systems are even less than those of the original system. Individual millions of automated transformation projects are almost paralyzed, which can not replace manual observation or manual test. The dam safety monitoring system is not as satisfactory as the hydropower station built after the 90s of last century. Some systems are too complex, the project set everything, the key is not outstanding, many kinds of instruments, uneven quality, operation and management of the later caused a lot of inconvenience; some of the dam monitoring system and the project settings are too simple, and the measuring accuracy is far from standardized regulations, can not effectively monitor the safe operation of the dam in some hydropower station; the date of completion of the project or even the transformation of the monitoring system.

In addition, the monitoring project is not universal enough, the key points of monitoring are not outstanding, the purpose of monitoring is not clear, and the monitoring data is not timely analyzed.

Some effects.

2.2.2 design aspects

The design is the head of the whole work, the design plan is reasonable or not directly determines the quality of the monitoring system. A good design plan first requires the designer to master the structural characteristics and geological conditions of the project, and understand the vulnerable parts, key problems, important design assumptions, main parameters and other factors that may affect the safety of the dam. The setting of projects and measuring points should be clear about the purpose of monitoring, combine closely with engineering practice, emphasize the key points and take account of the whole situation. The selection of instruments and equipment should be durable, reliable, practical, effective and convenient for operation and maintenance. But in actual work, often the designer not in-depth understanding of the specific circumstances of the project, according to the requirements of general layout of measurement points, what is more, even the basic requirements and the system put into operation after the actual effect is disregarded, copy the design history of other engineering, adversely affect days after operation the dam safety monitoring period. Therefore, the design unit should attach importance to the design of the dam monitoring system, and we should set up professionals who are proficient in the structure of the dam, and understand the monitoring technology, the characteristics of the instrument and the operation of the dam. They are devoted to the special design of the dam monitoring system of the hydropower station, and the design plan should be carefully optimized.

2.2.3 review

The review of the design scheme is also an important part of the whole work. Dam safety monitoring system is an important part of dam design. Its review is often included in the design review of dam. Besides some super large projects, it is generally not examined separately. Because the hydropower station involves a wide range of fields and major problems, most experts from immigration, planning, hydrogeology, geology and electromechanical engineering are invited to the actual inspection. On the one hand, experts do not necessarily know well about dam monitoring technology; on the other hand, compared with other professions, the technical problems of monitoring seem to be too small. Most of the concerns in the review are some major problems, which will easily lead to missed trial or rough trial. On the contrary, the project that carried out special inspection on monitoring design ensured quality and control investment. Practice has proved that such special review is effective. During the technical design review of the Three Gorges project, the dam safety monitoring is one of the 8 themes that are parallel to the dam, hydropower plant and permanent shiplock. A special expert group has been set up to organize the review separately, and achieved good results. The final plan after the review is much better than the original design, which highlights the focus of monitoring and improves the pertinence of the monitoring. After the optimization of instrument and equipment greatly reduced in numbers, according to statistics, the deformation monitoring by 1061 points, and sets and reduced to 550 points, and sets the most points, the seepage monitoring was reduced from 2081 to 926, the stress and strain monitoring reduce by 12257 and to 3682 sets, and Taiwan support and set, and Taiwan, hydraulics, power monitoring and reduction of approximately 1 / 2.

2.2.4 acceptance

In addition to the excellent monitoring design scheme, the implementation of the design scheme is also the key link of the whole monitoring work. The quality of the monitoring system depends on the quality of the construction team. The quality assurance system of the monitoring system and the technicians who are experienced in the installation of the instrument are required. In addition, as with other construction projects, supervision of the implementation of the monitoring system must be carried out. The construction of the monitoring system is a high technical requirement, which requires the employees to have high technical level and responsibility. But in practical work, it is found that some construction units have no professionals, and they are responsible for the embedment of precision instruments by outsiders or even temporary workers. Although some of the engineering supervision units are equipped with special monitoring technicians, construction supervision for monitoring systems is often a mere formality.

In order to make the dam safety monitoring system play a role, in addition to strengthening the management of monitoring system construction and supervision, acceptance is the last pass of monitoring system. In practical work, in the completion of the project acceptance and tend to focus on finance, immigration, finishing and so on, and the dam monitoring system can meet the requirements of monitoring the safe operation of the dam is little attention. Therefore, in the acceptance of the project, it is necessary to organize the experts to carry out special inspection and acceptance of the monitoring system.

3 construction dam monitoring system

3.1 provisions of the twelfth articles

The reinforcement and renovation of the dam of a hydropower station should be reviewed in the design. For construction projects involving dam foundation and concealment projects of hydropower stations, special acceptance should be carried out in accordance with the requirements of concealed projects. After the completion of the construction, the completion and acceptance of the construction shall be carried out.

The renewal and transformation of the dam monitoring system of hydropower station shall be organized by the operation unit of the hydropower station, and the special inspection and acceptance shall be submitted to the dam center when the project is completed and accepted.

3.2 the necessity of special design, special examination and special acceptance

The reasons for the 3.2.1 problem

After the first round inspection and two rounds of fixed inspection, the majority of the monitoring system has such problems. Many hydropower plants have updated the shortcomings of the dam monitoring system. After the renovation, the situation has improved, but the result is not satisfactory. The reasons are as follows: the design scheme is unreasonable, the scheme is not censored or censored strictly, and the selection of equipment and installation and commissioning unit is not careful.

3.2.2 design aspects

The built dam monitoring system renovation, must first conduct a detailed examination and evaluation test and appraisal of existing monitoring system, clarify the specific problems existing in the current system; then all monitoring data of the dam, and combined with the design and construction data to conduct a comprehensive analysis, grasp the actual working state of the dam, especially to deal with the impact of the dam safety and weak parts of the important parts of a clear understanding; then according to the principle of comprehensive focus, from the perspective of monitoring dam safety operation, specific issues of effective monitoring measures, monitoring project layout and the corresponding measuring points, proposed the system operation and management requirements. However, in practical work, some hydropower plants do not work according to the above principles. Please only some power plant equipment manufacturers do a simple scheme, design idea is not clear, the focus of the monitoring is not prominent, monitoring items and arrangement of measuring points excessive, even more a few manufacturers to sell their equipment in the design of blending is obviously unreasonable composition; although some power plant please design the unit to do the design, but some of the design units to its own level, design is only a general scheme for No. Therefore, in order to ensure the quality of monitoring and updating, a high-level design plan should be put forward by senior designers of professional design institutes on the basis of comprehensive understanding and in-depth research.

3.2.3 review of the design scheme is an important link to ensure the quality of the design. A high level of experts in hydraulic and monitoring should be invited to participate in the review. Experts should understand the actual working state of the dam and the key points of safe operation. The emphasis should be on the design principles of the scheme, the layout of the measurement points and the selection of the instruments. In actual work, individual power plants had hired experts is not strong sense of responsibility, low level of business involved in the review, did not play a gatekeeper role; there are individual power plants even appeared some experts for personal or departmental interests, influence, interference design situation. Therefore, the operation unit of the hydropower station should attach importance to the review of the design scheme so as to ensure the optimization of the design scheme.

3.2.4 implementation

The implementation of the monitoring system is generally adopted by the contractor in the way of bidding. The contractor should have rich practical experience and good reputation. Because the dam monitoring instruments are installed at the scene, some parts are humid, and some parts are electromagnetic waves. When selecting the instruments and equipment, we must pay attention to selecting suitable equipment for the on-site working environment of the dam. Equipment procurement should be excluded from non - Technical interference, and the most suitable products should be selected according to the actual situation of the hydropower plant. The key monitoring facilities for the automation system should be fixed on the spot and through a long time test in the high humidity environment. Power plant technical personnel should be in the installation and debugging of the system. The whole process of operation, master the basic skills of maintenance. In actual work, have found that individual power plants in the purchase of equipment is too hasty, listen to the instrument manufacturer's version, the system after the transformation and change the original intention is not the same, not up to the design requirements.

3.2.5 acceptance

Like other engineering projects, after the change of monitoring system is completed, in order to check whether the quality of civil construction and instrument installation and commissioning meets the contract requirements, we should check the completed system. Because the dam monitoring system is an important project related to dam safety, its transformation effect is directly related to the safe operation of the dam. Therefore, the dam safety supervision department must check and accept the transformation results. For the monitoring automation reform project, the new system after the change is required to achieve the degree of practicality, otherwise the corresponding manual monitoring can not stop. Found in the actual work, some power plants in the realization of automation of dam monitoring, although the situation has improved, but the effect is not ideal, the accuracy and long-term stability of some automation system is even lower than that of manual monitoring, the automation system at the same time, manual monitoring still can not stop, resulting in a great waste of manpower, material and financial resources. This situation not only for the work and dam safety monitoring will also spend a lot of energy, monitoring personnel, interfere with the normal work of dam safety monitoring. Therefore, the renewal and transformation of the monitoring system must ensure the quality and work in the work.