This document provides an in-depth analysis of the construction techniques for electrical engineering in substations, combining practical case studies to detail seven key steps: Equipment Installation, Busbar Installation, Panel and Cabinet Layout, Grounding Device Construction, Cable Laying, Fireproof Sealing Measures, and Secondary Circuit Wiring. These steps are crucial for ensuring the overall quality of a substation project.
1. Equipment Installation
In substation electrical engineering construction, equipment installation is the first and a critical step of substation construction. It involves multiple technical requirements, including whether the equipment itself complies with specifications and manufacturer's requirements, whether the moving parts can operate flexibly and correctly, and the reliability of electrical and mechanical interlocks. Simultaneously, it is essential to ensure all sealing components have good sealing performance, porcelain parts are free from damage and cracks, and the equipment's exterior remains intact and uncontaminated.
Furthermore, special attention is needed for the linkage performance of circuit breakers and their operating mechanisms to ensure no jamming occurs, with accurate and clear indications for opening and closing, and reliable and correct operation of auxiliary switches. Meanwhile, the alarm and lockout settings of density relays must meet relevant regulations, and the operation of electrical circuits must be verified as correct. Additionally, parameters such as the pressure, leakage rate, and moisture content of SF6 gas are critical indicators that need strict control during the equipment installation process.
To achieve the goal of requiring no adjustment shims during installation, the primary task is to ensure the accuracy of civil engineering construction, keeping the elevation error of foundation embedded parts within the allowable range specified by design codes. Moreover, during the equipment selection phase, priority should be given to equipment with bolt adjustment functions to facilitate flexible on-site adjustments.
2. Busbar Installation
Following the installation of circuit breaker supports, the next critical step is busbar installation. Busbar installation includes flexible busbars and tubular busbars. This step similarly requires meticulous operation and strict adherence to specifications to ensure the normal operation of the power system and the safety and stability of the equipment.
2.1 Key Points for Flexible Busbar Installation
Ensure the conductor wires are free from looseness, broken strands, or damage, and check for dents or deformations in expanded-diameter conductors. Between equipment, flexible conductors should bend naturally and smoothly, with consistent curvature and orderly arrangement. Furthermore, the sag of flexible busbar connections to equipment must be consistent, with appropriate tightness and overall aesthetic appeal. The layout of jumpers should be smooth, and the sag of three-phase jumpers must be balanced.
2.2 Overview of Key Points for Tubular Busbar Installation
The three-phase busbar tube sections must maintain parallel axes and uniform elevation, while the deflection must strictly comply with design and specifications. The appearance should be smooth and clean, welding techniques must be excellent, ensuring weld seams are at least 50mm away from the edges of supports. Additionally, phase color markings must be complete and accurate.
3. Panel and Cabinet Installation
During panel and cabinet installation, strict adherence to technical requirements is mandatory. Panel and cabinet installation emphasizes flat panel surfaces, secure fastening, clear naming/identification, and reliable grounding connections. This includes the surface flatness of control, protection, automation, and DC panels arranged in rows; the flatness error between two adjacent panels should be controlled within 1.5mm, and bolts should be used for secure fastening. Moreover, both the front and back of panels and cabinets should clearly display naming/identification numbers. Components inside panels and cabinets (including terminal boxes and local cabinets) must have complete and easily identifiable labels. Additionally, the panel/cabinet body must be reliably connected to the earth ground for safety. For doors that can be opened, a flexible copper braid should be used for reliable grounding connection.
4. Grounding Device Construction
During the construction of grounding devices, it is essential to follow strict welding and marking requirements to ensure the burial depth of grounding bodies, lap lengths comply with regulations, and avoid safety risks.
4.1 Burial and Welding of Grounding Bodies
The burial depth of grounding bodies should follow design specifications. If not specified, it should not be less than 0.6 meters. Steel grounding bodies should be joined using lap welding, ensuring both the lap length and welding method meet code requirements. After welding, anti-corrosion treatment must be applied promptly, especially to cut sections of steel and areas where the galvanized layer is damaged during welding on galvanized steel.
4.2 Standardized Welding of Grounding Bodies
Lap welding is preferred for welding grounding bodies (conductors), and the lap length must meet the following requirements:
For flat steel, the lap length is twice its width (and at least three edges should be welded).
For round steel, the lap length is six times its diameter.
When connecting round steel to flat steel, the lap length is six times the diameter of the round steel.
In welding flat steel to steel pipes or flat steel to angle steel, to ensure connection reliability, besides welding on both sides of the contact area, an additional curved (or right-angled) clamp made from steel strip should be added, or the steel strip itself can be bent into a curve (or right angle) and welded to the steel pipe (or angle steel).
4.3 Connection of Lightning Rods and Down Conductors
During the installation of grounding devices, the choice of connection method between lightning rods (strips) and down conductors is crucial. To ensure safety and stability of the connection, welding or thermite (exothermic) welding should be used.
In practice, it has been observed that some installations of independent lightning rods do not adhere to this requirement, resulting in connections to down conductors not using welding. This practice may affect the overall performance and safety of the grounding device. Therefore, it is imperative to ensure the correct welding method is selected and lap lengths are strictly controlled according to code requirements to guarantee the grounding device functions stably and effectively.