1 10 kV substation access system mode optimization and improvement abstract: through the analysis of the original access system mode of 1 10 kV substation, the improvement scheme is put forward. The implementation of the improved scheme can enhance the reliability of power supply in the internal power grid of enterprises. Keywords: substation; Systematic way; Improvement 0 Foreword Nanchang Changli Iron and Steel Co., Ltd. (hereinafter referred to as Nangang Company) has 2 1 10 kV substations with a total capacity of 22 1? 6? MVA 15. One is 90 MVA and the other is 13 1? 6? MVA 15. The two substations are connected to 1 10 kV Changgang I line and 1 0 kV Changgang II line by double T, and are connected to the 220 kV Changdong Substation of Nanchang Power Supply Company through these two lines (Figure1). During normal production in Nangang Company, the total power load of primary and secondary transformers is 130~ 150MVA. 11/defects existing in the original access system of kloc-0/0 kv substation * * The same characteristic of power supply in iron and steel enterprises is large power consumption, which requires high reliability of power supply, and Nangang Company is no exception. Due to the limitation of objective conditions, the first transformer and the second transformer can only be connected to the power grid by double-circuit lines, which brings great inconvenience to the operation and management of the internal power grid of Nangang Company. 1) Nanchang Power Supply Company's 220 kV Changdong Substation is the only power supply of Nangang Company. Whether the substation can run stably and rely on power supply is very important to Nangang Company. If the substation 1 10 kV bus fails, Nangang Company will inevitably suffer huge power outage losses. 2) 1 10kV The maximum designed carrying capacity of Changgang Line 1 and Line 2 is 80MVA and 100MVA respectively. These two lines can't bear all the electricity load of normal production of Nangang Company alone (that is, they don't meet the operating conditions of n- 1). If any line fails or a power outage is scheduled for maintenance, the first and second transformers will be forced to operate under reduced load. 3) Due to the limitation of line carrying capacity, the operation mode of 1 10 kV system must be changed by load limitation under normal conditions or accident conditions. This will not only cause some users to cut off power supply for a short time, but also extend the power outage time of users and expand the impact of accidents in the accident state. 4) Nangang needs to add 120~ 150MVA during the 11th Five-Year Plan period. Due to the problems that cannot be solved by itself, such as few power supply points and power receiving channels, and weak transmission capacity of power receiving channels, the original access system mode of 1 10 kV substation does not have the conditions for power expansion and cannot meet the new power demand of Nangang Company during the Eleventh Five-Year Development. Maintaining the original access system of Nangang Company 1 10 kV substation is not conducive to the stable and smooth operation of the company's internal power grid, nor to the company's sustainable development. We must seize the appropriate opportunity to optimize and improve it. 2 1 10 kV Substation Access System Optimization and Improvement Scheme According to the technical transformation project plan of Nangang Company in 2007, the third transformer project of Nangang started construction in June 2007. The purpose of building three substations is not only to solve the problem of new electricity consumption during the Eleventh Five-Year Plan period, but also to solve the problem of poor reliability of the original access system of 1 10 kV substation. After repeated communication with the provincial electric power design institute and the municipal power supply company, Nangang Company finally reached the design of the access system of the three-transformer project (including the first transformer and the second transformer) according to the following requirements: 1) The newly built double-circuit line of the three-transformer is connected to the 220 kV Guantian substation of Nanchang Power Supply Company, and the line meets the operating conditions of n- 1; 2) The newly-built double-circuit line of the Second Transformer is connected to the 220 kV Guantian Substation of Nanchang Power Supply Company, and the line meets the operating conditions of n- 1; 3) The original double-circuit lines (1 10 kV Changgang I line and10kV Changgang II line) are connected to the 220 kV Changdong Substation of Nanchang Power Supply Company, and the lines meet the operating conditions of n- 1. 4) Build a new 35 kV tie line between the first transformer, the second transformer and the third transformer to form the interconnection between substations. 3 The effect after the implementation of the improvement scheme At present, the third substation project has entered the final stage of the project. After it is completed and put into operation, the wiring system mode of Nangang Company 1 100 kV substation will be formed: three 1 100 kV substations will be powered by two 220 kV substations of Nanchang Power Supply Company respectively; Each 1 10 kV substation has a double-circuit power receiving line that meets the operating conditions of n- 1; Three 1 10 kV substations are newly built with 35 kV tie lines to guarantee each other's power supply. From the point of view of Nangang, the design of this access system is reasonable, which can significantly improve the comfort and reliability of power receiving. 1) reduces the influence range of electrical faults. Power failure of one 220kV substation will not cause power failure of three110kV substations at the same time; A power outage of a 1 10 kV line will not cause a power outage of the corresponding 1 10 kV substation; Even if 1 10 kV substation is out of power, the security load can be transmitted to the substation through the 35 kV tie line. At the same time, the number of emergency plans for power outages has also increased accordingly. Through the implementation of different emergency plans for power outage accidents, the impact of power outage on the company's production of a 1 10 kV line or a 220 kV substation is limited to the smallest possible range. 2) The problem that the internal power grid of Nangang Company can't continue to increase the power capacity has been well solved. If the variable capacity factor of the superior 220 kV substation is not considered, only the design carrying capacity of two transformers and three transformer power lines is estimated, and the two substations * * * have the ability to continue to increase the power capacity 100 MVA, which can basically meet the new power demand of Nangang Company in the five-year planning period. After the third transformer is put into operation, it can also be considered to switch an eccentric boiler transformer with long-term power supply on the 35 kV Luogang line of Nanchang Power Supply Company to the third transformer. This can not only improve the load rate of the three transformers and the main transformer, but also reduce the power consumption cost of the company. 3) If local improvement and transformation are continued in the first transformer and the second transformer, it can be realized as follows: ① transform the 1 10 kV bus coupler switch of the second transformer (the bus coupler disconnector is replaced by a bus coupler circuit breaker). After the transformation, all three 1 10 kV substations can flexibly change the operation mode of 1 10 kV system without affecting the normal power consumption of users. (2)110 kv standby automatic switching device is located in one or two transformers. After completion, the emergency response speed of three 1 10 kV substations can be improved synchronously. 4 Problems that must be paid attention to when adopting the new access system mode and countermeasures 1) How to prevent the formation of ring network (refers to the operation problem that two 220 kV substations in the power system form an electrical ring network in the internal power grid of Nangang Company). Whether the power grid can run around the network must meet two conditions. First, it must ensure that it has no impact on the stable operation of the power system; Second, monitoring is required to be in place and technical measures are complete. As the end user of the power grid, Nangang Company does not have the ability to control the operation of the ring network. If the ring network is operated blindly, unpredictable and serious consequences may occur. To this end, the company must strengthen the operation management of 35 kV security lines and important users with two independent power supplies at 35 kV and 6 kV (such as improving the schedule, implementing the system, and assisting in installing electrical and mechanical locking devices at possible loops). ) to prevent the ring network from running. 2) How to prevent the internal power grid and the system power grid from being unsynchronized and juxtaposed? According to the requirements of national industrial policy and energy law, two small generators (1 gas-fired cogeneration generator and 1 TRT generator) were built and put into operation in Nangang company. In the future, according to the needs, we will continue to build a number of generators for comprehensive energy utilization. Under normal circumstances, small generator sets in internal power grid can't be juxtaposed with system power grid, but they may be juxtaposed under special circumstances (such as 1 10 kV power line tripping, small generator sets in internal power grid failing to follow emergency shutdown, and automatic reclosing of superior substation without pressure detection). In order to prevent the above problems, the following technical measures must be taken: ① The line reclosing device (1 10 kV standby automatic switching device for the first, second and third transformers) of the superior substation must be put into pressure test locking. If the above conditions are not met, the line reclosing device (one, two, three transformers 1 10 kV standby automatic switching device) must be put into operation. (2) Small generator sets in the internal power grid must be equipped with low-voltage and low-frequency cutting devices. 3) How to adjust the power load of transformers 1, 2 and 3 in Nangang Company. After the third substation is completed and put into operation, the power load of three 1 10 kV substations in Nangang Company must be adjusted. There are two main purposes of load adjustment: one is to enable important users to obtain two independent power supplies, so as to improve the reliability of power reception and the flexibility of operation of important users; Secondly, according to the actual carrying capacity of each 1 10 kV substation and the future load growth trend of the substation, the reasonable load distribution is beneficial to the economic operation and safe power supply of the substation. When carrying out load adjustment, we must fully consider the structure and power supply of the company's internal power grid, and implement this work step by step according to the implementation principles of new projects, such as power supply by three transformers, load transfer nearby (load transfer between two transformers and three transformers), load transfer by using existing lines, etc., which is convenient for implementation and saves investment. Conclusion The optimization and improvement of the access system mode of Nangang Company make the fragile power receiving channel strong and smooth. This has played a powerful role in improving the operation quality of the company's internal power grid and enhancing the power supply capacity. How to adapt to the change of access system mode, further sort out the internal power grid structure of the company, and make the power grid operation more stable and power supply more reliable still needs further research and exploration in the future work.