Thread Content
The power grid is a network for the exchange of electrical energy; it refers to all the facilities and equipment that connect the power generation side with the power consumption side. Generally, the integrated system that links power generation and consumption, consisting of transmission, transformation, and distribution equipment along with the corresponding auxiliary systems, is called the power grid, or simply the grid. It should be specifically noted that the power grid of the refining enterprises mentioned here includes generator systems and load systems, while the main grid structure refers to the connection pattern of the power grid at distribution voltage levels (35 kV, 6 kV) and above. The relationship between the main electrical network structure and the main electrical wiring is as follows: The main electrical wiring, also known as the primary wiring in power plants and substations, consists of primary equipment that is used directly for generating, collecting, converting, transmitting, and distributing electrical energy. It represents the core structural element of the electrical part of a power plant (substation) and is an important component of the power system network structure. The main grid structure refers to the wiring scheme of the primary equipment in a local power grid, including the main wiring of all power plants and substations within the grid as well as their connection methods, along with the power interconnection lines. Therefore, the main grid structure of the power grid includes the electrical main connections of all power plants and substations within the grid. The main electrical wiring is a key component of the wiring scheme in power systems. It shows the number of electrical equipment such as generators, transformers, lines, and circuit breakers, as well as their connection methods and possible operating modes, thereby enabling the tasks of power generation, transformation, transmission, distribution, and consumption. Its determination is directly related to the selection of electrical equipment throughout the plant, the layout of power distribution systems, as well as the implementation methods for relay protection and automatic control devices. It also affects the safe, reliable, stable, flexible, and economical operation of the power system. Most of the large-scale oil refining and chemical enterprises in our country have been formed through the gradual expansion and transformation of medium and small-sized enterprises. The terminal loads mainly consist of fans, compressors, and pump sets driven by large asynchronous motors, along with a small number of synchronous motors and other loads such as lighting. It is common for refining and petrochemical companies to add new units or carry out expansion and renovation projects; there are also some large or very large projects that are built from scratch. For various reasons, some companies, during the phase of expanding their main facilities and experiencing a significant increase in power demand, do not upgrade their grid systems simultaneously. Instead, they opt for a \"brick-by-brick\" approach, constructing several new 110kV step-down and distribution systems to handle the additional load. As a result, there is no unified grid within the company; this decentralized power supply approach makes it difficult to maintain load balance, reduces the ability to withstand external disturbances, increases the incidence of system failures, and requires higher costs related to the basic capacity of the main transformers. Therefore, where possible, integration and upgrading should be carried out to strengthen the enterprise’s main network structure and create a unified internal power grid. Basic requirements for the main network structure: reliability, flexibility, cost-effectiveness