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To further improve the design work for the connection of large-scale hydroelectric and thermal power plants to the power system, our bureau assigned the Northwest Electric Power Design Institute to draft the \"Detailed Requirements for the Design of Connection Systems for Large-Scale Hydroelectric and Thermal Power Plants (Draft for Comment)\). After extensive consultation, a version ready for review was finalized. On this basis, our department organized units such as planning, production scheduling, infrastructure construction, hydropower planning and design, and power engineering design to conduct reviews, making the necessary revisions and additions to the draft submitted for review. The approved \"Detailed Requirements for the Design of Grid Connection Systems for Large Water and Thermal Power Plants\" SDGJ84—88 (Trial) is now issued for trial implementation. If any issues are encountered during its application, please inform the Planning Department of our bureau. June 16, 1986 Chapter 1 General Provisions Article 1.0.1 The system development for large-scale water and thermal power plants includes preliminary feasibility studies, feasibility studies, and system integration design. The preliminary feasibility study and the system portion of the feasibility study are carried out in accordance with the detailed requirements regarding the preliminary work ； The access system design is carried out in accordance with the details specified in these regulations. These regulations apply to the system connection design of large hydropower and thermal power plants with a voltage level of 220 kV and above. Article 1.0.2 The design of the connection system for large-scale water and thermal power plants should generally begin after the project management authority submits the project design assignment, and it must be completed before the preliminary design of the project is finished. If necessary, it can also be carried out in accordance with the schedule requirements assigned by the project’s main supervising department. Article 1.0.3 The design for the connection of large-scale water and thermal power plants to the power system involves a more in-depth examination of the relationship between such plants and the power system, once the feasibility study for the project has been completed. It entails determining and specifying the scope of power supply provided by the plant, the voltage levels of the output circuits, the number of such circuits, the electrical main wiring scheme, as well as the parameters of related electrical equipment. This is done to meet the system-related requirements of the plant’s preliminary design, and to provide a basis for preparing the design specifications for the plant’s power transmission facilities. Article 1.0.4 The design for integrating the power plant into the system shall be based on the reviewed medium- to long-term electricity plan or the approved power system design. It is necessary to implement the relevant guidelines and policies, as well as the applicable design codes and regulations. Article 1.0.5 The design of the power plant’s connection to the system should be based on practical considerations. Work is carried out in a targeted manner based on the design scale of the power plant or the different characteristics of hydroelectric and thermal power plants. For example, in the case of large regional power plants, special attention should be paid to studying the issues related to those plants and the larger power system ； For regional power plants, it is appropriate to focus on studying the issues related to that plant and the regional system ； For hydropower plants, it is important to focus on research into expanding the grid’s capabilities to provide peak-shaving or compensatory regulation services. Article 1.0.6 Design of power plant connection to the system. Attention should be paid to combining near and far perspectives, and conducting technical and economic comparisons of multiple options from near to far. Its recommended solutions should be technologically advanced, make efficient use of energy, simplify system wiring, facilitate transition, allow for flexible operation, and provide power to the system in a practical, reliable, and cost-effective manner. Sensitivity analysis should be conducted regarding the uncertain and variable factors in the power system. Chapter 2: Design Basis and General Design Principles Article 2.0.1 explains the basis for this design task. Article 2.0.2 States the superior authorities’ review comments on the relevant parts of the feasibility study for this power plant ； Main principles of the design task order submitted by the department in charge of the project or approved by the Planning Commission ； Principled issues related to the design of the power plant’s connection to the grid, such as approved power system designs or feasibility studies for major power projects. Article 2.0.3 The design base year shall be reasonably selected based on factors such as the scale of the power plant and the construction progress. And looking ahead to the time when the plant reaches its final scale. Article 2.0.4 The geographical scope of the system to which the power plant is connected shall be determined after analyzing the plant’s designed capacity, the distribution of system loads, and the requirements of the power system operation mode. Chapter 3: Current Status of the Power System and Overview of the Designed Power Plant 3.0.1: Overview of the existing systems related to this power plant. Article 3.0.2 The general overview of the designed power plant shall specify the location of the plant, as well as the planned capacity and the breakdown of capacities for different design phases. If it is a thermal power plant, the fuel source and site conditions should also be described ； For hydroelectric power plants, information such as guaranteed output, annual electricity generation, monthly average output across different hydrological years, and reservoir regulation capacity should also be provided. The compensatory role of those large reservoirs with excellent regulation capabilities should also be explained. Chapter 4 Load Development and Analysis Article 4.0.1 Based on the load data for corresponding base years provided in the power system planning and design, or by the electricity administration authorities and the provincial, regional, and municipal electricity bureaus for the design of integrating this power plant into the system, the annual growth rate of electricity generation across the entire system or a specific region, as well as the loads on substations at 220 kV and higher voltage levels, are listed; meanwhile, the factors contributing to this load growth are briefly described. A special explanation should be provided regarding the load growth in the vicinity of this power plant. Article 4.0.2 To study the system operation mode and the requirements for peak shaving in this power plant, the load characteristics shall be analyzed. Article 4.0.3 When changes in load have a significant impact on the installed capacity, construction schedule of power plants designed to be connected to the system, as well as on the backbone power transmission network of these plants, it is necessary to conduct investigations and analyses of such important loads. Article 4.0.4 During the design horizon of the plant’s connection system design, if there are approved feasibility study reports for expanded interconnection projects within the system, the power transmission and reception relationships as well as the load characteristics after interconnection shall be specified. Chapter 5 Electricity: Power Balance Article 5.0.1 Overview: The scale and power generation capacity of other hydropower and thermal power plants that are likely to come online during the design base year and the forecast period. Article 5.0.2: If the design of the connected system requires an examination of the operation modes of thermal and hydroelectric power plants, it is advisable to provide a list showing the output parameters of such power plants within the entire system or regional system. These include: the compensation calculation conditions for various hydropower plants, guaranteed output, monthly average output for different years, expected output, and forced output ； The minimum output allowed for thermal power plants. Article 5.0.3 The following shall be determined through power and energy balance analysis: First, conduct a year-by-year power balance analysis for the entire system or regional system, from one year prior to the commissioning of the first unit in the power plant up to the design level year, as well as for future years; prepare corresponding power balance tables, and determine the total operating capacity of hydropower and thermal power plants along with their respective reserve capacities. II. Analyze the system peak-shaving situation and the requirements for this power plant. III. Based on the operating capacity of the power plant calculated from the power balance, as well as the system’s peak-shaving needs and backup requirements, the appropriate installed capacity and construction schedule for the designed power plant are determined. Furthermore, the power delivery area covered by this power plant and its role within the power system are discussed in detail. IV. Perform electricity balance or analysis for different hydrological years on a monthly or decadal basis. If it is a hydropower plant, it is also necessary to analyze whether there is seasonal electricity and its utilization methods ； If it is a thermal power plant, the designed annual operating hours of that plant should be determined. Chapter 6: System Access Solutions Article 6.0.1: Analysis and description – Provides an overview of the network structure of the relevant systems in the power plant one year prior to the commissioning of its first unit. Article 6.0.2 Conduct analysis for different seasons (for thermal power plants, only the season with the highest annual output of the plant is analyzed) ； Hydropower plants should analyze the typical operating patterns on representative days in different seasons, such as those of high and low water levels, in order to determine the power exchange between the designed plant and the power delivery area. Article 6.0.3 Based on the results of operation mode analysis, the characteristics of the system voltage levels, the features of the existing network, and the load distribution, proposed comparison options for the system voltage to which the power plant will be connected and the corresponding network structure for such connection. Article 6.0.4 For scheme comparison, the following partial or full verification electrical calculations and analyses shall be carried out as necessary: 1. Power flow calculation analysis to determine whether the compared schemes meet the requirements for normal and fault conditions in terms of power transmission capacity as well as the corresponding reactive power compensation capacity. II. Verify the stability level and propose measures to improve it. III. For power plants that require connection to the system via ultra-high-voltage long lines, issues such as power-frequency overvoltage, stray supply current, and self-excitation are considered, and restriction measures are proposed in light of the plant’s reactive power output capacity. IV. Impact of short-circuit current on relevant systems after the power plant is put into operation. V. Conduct research on transition years, and propose transitional measures where necessary. Article 6.0.5 Regarding the route selection for lines in access system designs, when corridors are limited, there are long spans involved, or the routes pass through areas with harsh environments, thorough investigations and research should be conducted to identify solutions. Article 6.0.6 Conduct a comprehensive technical and economic comparison of the access system solutions, and propose a recommended solution. Chapter 7 Requirements for the Electrical Main Wiring of Power Plants and Parameters of Related Electrical Equipment Article 7.0.1 Based on the planned capacity of the power plant, the phased design approach, the power supply area, the load conditions in the nearby area, the line voltage and the number of output circuits, as well as the requirements for the safe operation of the system, requirements for the main wiring of the power plant are established through technical and economic analysis and comparison. Article 7.0.2 Further electrical calculations are carried out on the recommended solutions for connecting to the system, to serve as a basis for selecting the parameters of relevant electrical equipment. Article 7.0.3 Based on the electrical calculation results, determine whether parallel reactors and electrical braking devices should be installed in the designed power plant. Article 7.0.4 sets requirements for the following parameters of major electrical equipment: 1. Whether the hydro-turbine generator set operates in phase-regulating or leading-phase mode. II. The excitation method of the generator, the power factor of the hydro-generator, the transient reactance, and the cooling method, etc. III. Turbogenerator sets are required to provide peak-shaving capacity and fast control capabilities. IV. Specifications for main transformers and tie transformers and neutral point grounding methods. Chapter 8 Conclusions, Recommendations, and Appendices Article 8.0.1 The main issues addressed in this design study and the recommended recommendations. Section 8.0.2 Major issues in the design and recommendations for future work. Article 8.0.3: Propose the power transmission and distribution projects (the high-voltage output section of the power plant), reactive power compensation measures, scale, estimated investment, and approximate commissioning time that need to be constructed to implement the recommended system connection plan for this power plant. Article 8.0.4 Content of the attached drawings: 1. Current geographical wiring diagram of the power system. II. Geographical connection diagram of the surrounding areas before and after the construction of the power plant. III. Comparison diagram of power plant connection system schemes (with necessary power flow indications). IV. Flow diagram of the recommended scheme for power plant connection to the system. V. Stabilize the calculation of the swing curve graph.