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Instructions on the Technical Modernization of Rural Hydro in China
Ministry of Water Resources of the People¡¯s Republic of China
    In April 2003, the ¡°Instructions on the Technical Modernization of Rural Hydro¡± was issued by the Ministry of Water Resources, which clarified the technical direction for the development of the rural hydropower sector in the years to come in order to quicken the pace of modernization for China's rural hydropower. The document pointed out the direction for standardizing and guiding the rural hydropower sector for technical advancement. The overall objectives are, prior to year 2010, 50% of rural hydropower plants and their power grids should be modernized, and in 2015 the rural hydropower sector should be all modernized. Through scientific and technical innovation and management improvement, the competitiveness of the rural hydropower market should be noticeably improved.

    The ¡°Instructions on the Technical Modernization of Rural Hydro¡± bring out some objectives and requirements as follows:

    (1) Rural hydropower plants

    --- Much attention should be paid to the cascade and rolling development of a certain basin, and the cascade hydropower station should be designed and built according to the comprehensive programming of this basin. Priority should be given to develop those hydropower stations with at least seasonal regulation capability, and pumped storage power plants should be developed as appropriate.

    --- New hydropower plants should be designed and constructed according to the requirements of unmanned control and operation (or with a few operators on duty). Those stations built before the 1990s should be programmed for renovation or upgrading in line with the overall objectives. Generating units past their service life and that cannot meet the requirements even if technically upgraded should be discarded for rebuilding or forcibly put out of service.

    --- Integrated planning and design should be carried out for the renovation of hydropower plants. The output and efficiency of units can be improved, and service life extended through improvements to the hydraulic structures, adopting a high efficient anti-cavitation and abrasion-resistant runner, upgrading the generator insulation, bettering its cooling conditions, applying SCR or brushless excitation technology, gravity butterfly valve and plastic tiles. Meanwhile, the automation of hydropower plants can be improved by renewing or renovating the supervision and control devices and the automation components.

    --- New high-efficiency turbine-generator units should be applied. The suitable type of unit should be selected according to different water heads and discharges. For the detailed selection method and principles refer to ¡°The Runner Type Series of Medium and Small-scale Kaplan and Francis Turbines¡± (JB/T6310-92), and ¡°The Type Series of Cross-flow Turbines¡± (JB/T7640-94), and also consider the existing proven runners of manufacturers.

    --- Hydropower plants with total installed capacity of 5 MW and above should use open and distributed computer-based supervision and control system. The governor, excitation device, and the oil, water, air and D.C. systems inside the plant, and gates should adopt microcomputer-based systems for their supervision and control. The digital communications between the computer-based supervision and control system and the control units of devices can be carried out through the main communication line at site, serial communication or I/O modes.

    --- For hydropower stations with total installed capacity of 5 MW or less, the centralized and decentralized computer-based supervision and control system should be combined together. The DC system should communicate with the computer-based supervision & control system. The governor can adopt microcomputer-based type or oil-pressure actuator. The supervision and control for the in-plant oil, water, air and other systems can adopt simple-structured automatic relay control devices.

    --- Inside hydropower plants with a generator voltage of 400 V, the simpler integral compact supervision and control system should be adopted. Energy-storage for the turbine¡¯s actuator can be chosen to be in the form of high-pressure nitrogen cylinder or high-pressure oil. Standardized hydraulic components should be adopted to reduce the maintenance cost and the space occupied.

    --- The oil, water, air systems and other auxiliary devices inside the plant should be integrated with the main machine for their control, so non-maintained of easily maintained devices or equipment are preferred.

    --- Inside a power plant, the automation components will play a key role in the unmanned operation of this station, so mature, qualified products which also reach national standards and are fit to be operated in a humid environment should be selected for application. Meanwhile, much attention should be paid to improving the working environment, which must meet the requirements specified in the operation manual. For the oil-water mixture sensor, the liquid-level transducer, the flow transducer, the pressure transducer and the position transducer, those products with 4-20mA modular output or serial communication interface should be selected. For hydropower stations with a relatively large capacity, a gear type and/or the residual voltage should be adopted for speed measuring. The pressure and the liquid-level transducer should adopt a kind of integral structure in which the capacitor type or the diffusive-silicon piezo-resistor is combined with a special signal amplification circuit. The 4-pass ball valve is recommended as the multi-passage electromagnetic valve, and the electromagnetic valve for cooling water should be of the active thermal diffusion type. Cu50 or Pt100 should be used for the temperature sensor, and the temperature data logging devices should be equipped with RS485 or RS232 communication interface.

    --- In rural hydropower plants, the main electrical connection should be as simple and reliable as possible. Products with high reliability, low fault occurrence, low maintaince requirement, or even non-maintaince properties should be selected for use as the main electrical devices. Examples are the new type energy-saving transformer used as the main transformer, the dry type transformer adopted as the excitation transformer or the plant-service transformer, the vacuum circuit breaker or the SF6 circuit breaker and the zinc oxide lightning arrester. In summer there is serious condensation inside the power plant, so a generator with F or above insulation grade should be adopted. For those rural hydropower plants located in the hilly areas, there are many occasions for them to be attacked by lightning, so much attention should be paid to mitigating lightning attacks, and earthing design and construction.

    --- Microcomputer-based auto quasi-synchronizing device or the microcomputer-based relay protection device should be adopted.

    --- Digital or impulse type electrical energy meters are recommended for metering the electrical energy of the hydropower plant.

    --- For hydropower pants with a large capacity, the fibre-optic digital instrument transformer and its new automation technology with a low volume and strong anti-interference capacity should be actively recommended.

    --- As for hydropower stations equipped with a computer-based supervision and control system, the database structure should be of open type, and through reserving communication interfaces and using standard communication protocol, the requirements of dispatching automation can be met, and remote terminal unit (RTU) are not necessary.

    --- The computer-based supervision and control system inside the hydropower plant should gradually lead to economical operation of the whole station, and cascade power stations can realize optimum dispatching among different cascades. At the same time, communication interfaces should be reserved for connections with other systems (such as water regime forecast, dam safety detection, visual supervision and control, fault diagnosis and status inspection), so that data sharing and information management inside the whole plant can be achieved.

    --- The structural design of the powerhouse should gradually move towards standard modules, and the building style, form and internal and external decoration must be compatible with the surrounding environment, and aim to beautify the environment and develop tourism. The power plant should be sealed against dust, pests and small animals. During the construction period, the gate in the powerhouse for equipment access should have a framework structure and adopt lightweight removable materials. A permanent large gate should then not be designed any more, and all these gates can be blocked after construction. The arrangement of secondary panels and cubicles is a challenge to the traditional design mode, and a transparent closed equipment corridor can be built. When renovating old plants, attention should be paid to adopt the same panel shape and same color.

    (2) Dispatching automation system

    ---The plan for the dispatching automation system should be formulated according to the development program of the local power grid, and for the master station, communication channel and remote terminal unit (RTU) of the dispatching automation system, the function requirements, technical norms, equipment (hardware/software) programming and the step execution plan should be drawn up.

    --- The basic functions of a dispatching automation system include the system control and data logging (SCADA), and the management and application functions for the dispatching operation should be taken as a selection. When selecting these functions, the actual demands on management should be taken into account. Status estimation, current calculation, line loss analysis, load forecast, fault analysis, safety analysis and reactive power optimum operation and management and other high-level applied software should be configured where relevant, and also put into practice.

    --- When selecting the system platform, the operation conditions of the system platform which has been put into use in that area should be examined, so as to meet the demand of inter-communication among systems. Hardware equipment with superior properties and low price should be selected, to ensure the system is highly safe, reliable, practical, open-structured, extendable, easily-applicable and flexible.

    --- The dispatching automation system should adopt a standard communication protocol, and it is suggested to adopt the professional standards of China¡¯s power industry, ¡°Standard of Basic remote control Tasks¡± DL/T634-1997 (equivalent to IEC-60870-5-103 protocol), the ¡°Circulating Remote Protocol¡± (DL451-91) and the ¡°Application-level Protocol on the Real-time Digital Communication of Power System¡± (DL476-92).

    --- For some counties which plan to construct a distribution automation system at the same time, the scheme for the integration of dispatching and distribution should be considered, and for others which plan to set up a distribution automation system in the next few years, consideration should be given to including capacity in the dispatching automation system for extension to the distribution automation system.

    --- The dispatching automation system should be able to interface with the dispatching information management system and the distribution automation Master station, and meanwhile, it can be connected to the management information system (MIS), the water-regime measuring and forecast system, and the dam safety monitoring system, and its interface safety should meet the requirements of the ¡°Safety of the Computer-based Supervision and Control System and the Data-dispatching Network in Power grids and Powerplant¡±, to ensure the safe operation of the power grid.

    (3) Other matching power grids

    --- Building a high-voltage power grid mainly based on 110 kV network, with reasonable structure and simple and reliable arrangement, and which is also flexibly operated with adequate power supply capacity is suitable for meeting the long-term demands of load increase and rural hydro development.

    --- In cities the arrangement of 10 kV dispatching power grid should adopt a looped network structure with double power sources, which can be operated under open loop. The distribution network located in rural areas will still mainly adopt a radiative structure. A main line or a sub-line which is relatively long should be equipped with a tap changer or branch switch, and other switching and control devices should be actively applied such as the intelligent looped network cabinet (RMV), the automatic recloser, the automatic sectionalizer, the feeder remote terminal unit (FTU) and the transformer mesure and control unit (TTU), so as to realize feeder automation.

    --- The trend for rural substation is to develop as a small outdoor structure, and in cities, a containerized compact substation can be adopted.

    --- New substations to be built should be designed in line with the requirements of unmanned operation, and the aged ones should be gradually refurbished with automation systems to achieve unmanned control (or fewer operators on duty). Priority should be given to the use of a comprehensive automation system with hierarchical structure to meet the measurement, protection, control, regulation and communication demands of substations. Standard communication protocols should be applied among the units themselves, and between the substation and the dispatching unit. (For any special communication protocol, the detailed text should be provided). Additionally, attention should be paid to the compatibility, expandability and the upgrading capability of the software and hardware.

    --- An unmanned control substation may not be equipped with a fixed main computer, but at site there should be some interfaces reserved to connect to the main computer for commissioning. If necessary, a perimeter alarm system and a visual surveillance system can be installed.

    --- As for substations with voltage of 35 kV and above, the energy-saving on-load regulation transformer should be extensively applied. The distribution transformer should be of the low energy-consuming type with superior technical properties, or a completely sealed transformer or an amorphous alloy transformer. The high-energy-consuming transformers that the government has ordered to be put out of service should be replaced in the next few years.

    --- For newly built substations, the vacuum circuit breaker, SF6 circuit breaker or other advanced switch equipment should be adopted in line with the voltage grade, and oil switches should no longer be adopted. 35 kV and 10 kV voltage and current transformers should be of resin type. For the voltage levels of 110kV and above, gas-insulated switchgear (GIS) can be selected for use. The oil switch devices used in early times should be discarded gradually.

    --- According to the system requirements, a reactive compensator with suitable capacity should be reasonably installed, and a reactive auto voltage control device should be erected.

    --- The use of microcomputer-based protection devices and microcomputer-based auto safety devices should be popularised.

    --- The use of zinc oxide lightning arrestors should be popularised.

    --- The distribution cubicle integrating functions such as protection, control, metering, reactive compensation and lightning protection should be adopted for the distribution system in cities.and towns.

    --- Optical-fibre digital instrumental transformers, optical-fibre digital substations and other new technologies should be popularised.

    (4) Distribution automation

    --- Pilot projects of distribution automation should be actively tried out, and then applied extensively. The distribution automation scheme and its equipment should be selected according to the local economic development, load type and its requirements on dependability. Priority should be given to the SCADA system, the distribution automation (DA) of feeders, automatic mapping/feeder management/geographical information system (Am/FM/GIS) and the remote meter reading system.

    --- In the distribution automation system developed at the initial stage, attention should be paid to the selection of the operating system, the database management system and the network system with excellent open characteristics, and in design, some principles should be noted, such as standardization, openness, integration and expandability. Equipment with modularized design should be adopted as far as possible, and the demand for standard interfaces to expand and upgrade functions should be met.

    --- The design for the master station of the distribution system should abide by the national or professional standards, and it should be endowed with superior properties such as safety, reliability, practicality, expandability, openness, fault-tolerance, and meeting the requirements of the power system for real-time performance. In principle, it should be designed integrally with the dispatching automation system, and interfaced with the management information system. The data exchange among various systems should observe a unified interface norm, so as to use the same information sources, mutually share the information and simultaneously renew the figures and data. Before the dispatching automation system has been set up, the distribution automation system should not be implemented in advance.

    --- The remote meter reading system should be initially carried out, and then gradually popularized if practical. The communication channels of the remote meter reading system should be considered as a whole when planning the communication channels of the power grids, so as to try to realize their mutual sharing, and additionally a certain development in the future should be considered.

    (5) Information management

    --- The management information system (MIS) consists of production, finance, manpower resources, power sales, office automation and other sub information management systems, and much attention should be paid to practicality and compatibility when developing the software of such systems. Therefore, it is suggested to adopt object-oriented technology, so that the software can adapt to changes in organization structure, management mode and operation flow, and extend the life span of the software system.

    --- Enterprise resources planning (ERP) should be popularized, and the ERP platform should be set up with the full use of the information from MIS and SCADA systems. The technical support system of the power market could be initially adopted, so as to meet the requirements of ¡°price competition for selling to the power grid¡±, reduce the operation costs of enterprises and improve the economic benefits.

    (6) Communication system

    --- The communication system should meet the demands of the power system for its safe and economical operation, and surplus capacity should be suitably set aside to meet the requirements for expanding new communication businesses.

    --- The design of the communication system should stick to the principles of being advanced, openness, safety, expandability and practicality. This system should adopt the mainstream technology and mature products, and can be suitably state-of ¨Cthe -art. The network and equipment should support the standard interfaces, and extensively applied standard protocols should be selected so as to realize reliable interconnections with other systems concerned. The key parts of the system should have redundancy. The communication devices and the power source should be highly reliable, and be able to support the smooth upgrading of the system, and meanwhile, it must be guaranteed that business will not be affected during network expansion. The system should be simple to operate, easy to maintain and convenient to manage. For the sake of meeting business demands, the optimum performance-cost ratio should be reached.

    --- Key networks should adopt optical fibre for communication as a first priority, and the branch communication network should mainly adopt power line carrier technology. When the cost-performance ratio is very good, then the wireless spectrum-spreading device is recommended, with the telephone channel taken as standby.

    --- Inside the communication network, the exchange, transmission and interfaces should all conform to the national standard, ITU-T norms or other related professional standards.

    --- During the construction of the communication network, safety measures should be adopted accordingly, so as to meet the requirements specified in ¡°The Safety of the Computer-based Supervision and Control System of Power Grid and Power Plant, and the Data-dispatching Network¡±.


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