Abstract : This article analyzes the problems of line congestion, signal interference, and poor operational reliability caused by the lack of uniformity in the design and installation of various low-voltage electronic systems in intelligent buildings. It focuses on issues such as power supply and AC/DC isolation, grounding, and signal line interference prevention. Furthermore, it proposes a reference model for integrated power distribution design of low-voltage equipment rooms and a design concept for combined movable interference prevention cabinets. Keywords: Intelligent building, Building Automation (BA), Integrated power distribution model, Interference prevention cabinet, Modular power socket. In recent years, building intelligence technology has developed rapidly, especially network communication technology. Many high-rise buildings are now competing to introduce various integrated low-voltage systems to improve the building's intelligent management level and achieve Building Automation (BA), Communication Automation (CA), and Office Automation (OA). This is the trend of modern high-rise building development, but in the current implementation process, many problems still need to be improved and solved. For example, in many high-rise buildings, the design and construction of power distribution and cabling in the core computer rooms of various low-voltage electronic systems present numerous problems. The latest national standard atlases, such as "Design and Construction Atlas of Low-Voltage Electrical Engineering for Intelligent Buildings" (atlas number 97X700) and "Atlas of Electrical Installation Engineering for Buildings" (Volume 4), while providing relatively detailed standard practices for power distribution and cabling in fire protection, security monitoring, telephone stations, and electronic equipment rooms, lack detailed and comprehensive descriptions of standard practices for power distribution and cabling in other areas such as computer rooms, building control equipment rooms, and closed-circuit television rooms. Some descriptions are too vague. Recent publications of intelligent building design technical manuals (such as those compiled by the East China Architectural Design & Research Institute and the Northeast Architectural Design & Research Institute) and building low-voltage electrical design engineering technical manuals (such as those compiled by Liu Guolin, Liang Hua, and Chen Yicai) also fail to address this issue in detail and depth. The current "Code for Electrical Design of Civil Buildings" (JGJ/T16-92) also lacks sufficient detail and clarity in its provisions on this issue. Therefore, most architectural design institutes and professional low-voltage electrical design and installation companies currently produce rather rough designs for low-voltage electrical rooms, with drawings resembling schematic diagrams rather than construction drawings. There are very few construction and installation companies with the technical expertise and capabilities to install both strong and low-voltage systems. Furthermore, it is neither possible nor realistic for a single electrical installation company to undertake the installation of all strong and low-voltage equipment systems in a smart building. Even low-voltage system integration cannot be completed by any single installation company alone, because there are many types of low-voltage equipment, and each product installation company has its own product and technical advantages. After comprehensively considering factors such as quality, price, and after-sales service, the smart building developer will inevitably divide the low-voltage system integration project according to system function, into several low-voltage electrical system projects: large low-voltage installation companies can contract for the entire building control and automation system project, such as the Chinese agents of Honeywell and Johnson in the US, and Satchwell in the UK; smaller low-voltage installation companies can contract for projects such as closed-circuit television monitoring and electronic security systems, and such installation companies are numerous. This has resulted in a situation where, during the actual integration of low-voltage electrical systems in intelligent buildings, the power installation companies and the low-voltage electrical system installation companies each perform their respective duties, installing equipment and pipelines relatively independently. Furthermore, due to a lack of technical safety regulations, cooperation and coordination between the various equipment systems are poor (leading to ineffective management by relevant construction supervision departments). Therefore, the low-voltage equipment rooms in several intelligent buildings that I visited and investigated almost invariably exhibited the following problems: signal lines of different voltage levels and frequencies were crisscrossed within the room and intertwined at the back interfaces of the equipment; power supply configurations were unreasonable; and potential hazards included electrical fires, leakage, and signal interference. System reliability was also poor, and equipment maintenance and management inconvenient. Therefore, I propose a comprehensive power distribution and cabling model for low-voltage electrical rooms in intelligent buildings. Low-voltage electrical rooms in intelligent buildings can be broadly categorized by nature and function as: computer rooms, building control equipment management rooms, program-controlled exchange rooms, fire alarm and control rooms, closed-circuit television rooms, and security monitoring rooms. Considering that most of these low-voltage electrical rooms contain computer equipment, this article focuses on rooms with computer equipment for the reference of colleagues and experts. 1. Power Supply The equipment in the low-voltage electrical room is a Class I load and should be supplied by two dedicated trunk lines with two independent power sources interconnected at the end. For smaller power capacities, power can be sourced from the nearest Class I lighting load trunk line. When the power failure rate is high, consider installing a backup generator near the computer room or increasing the battery capacity. Computer equipment has high power quality requirements, requiring not only an uninterruptible power supply system but also voltage fluctuations within ±10% for normal operation. Some network data transmission equipment even requires voltage fluctuations within ±5%. However, the integration of the low-voltage electrical system in intelligent buildings typically occurs during the building's final finishing stage, with frequent use of various building equipment, making it difficult for the power supply voltage to meet these requirements. After the intelligent building's technicians started using it, the power supply voltage frequently exceeded the ±10% fluctuation range during commuting hours. Extensive field measurement data confirms this. Therefore, when designing and selecting an uninterruptible power supply (UPS): (1) Its output power should be 1.3 to 1.5 times greater than the sum of the rated power of the electrical equipment, and the rated discharge time should be 10 to 30 minutes. (2) It should meet the voltage fluctuation resistance index; otherwise, a power regulator should be installed before the UPS. (3) When the rectifier load in the electrical equipment is large, a harmonic absorber should be installed on the distribution circuit before the UPS to absorb high-order harmonics, so that the distortion of the output voltage and total waveform does not exceed 5% (10% is allowed for single-phase output). In areas with poor power grid quality, a frequency deviation protector should be installed before the UPS. (4) According to the requirements of the electrical equipment for power supply reliability and continuity, select the UPS power supply working mode: single type, parallel type, redundant type and parallel redundant type. Its bypass power supply should meet the load capacity and characteristic requirements. A filter should be installed on the bypass, and the self-provided generator should not be used as a bypass power supply to directly supply the load. Design and construction companies must gather as much information as they do about the power supply environment when designing and installing a substation to ensure proper power supply design and layout, thus reasonably meeting the power needs of the low-voltage equipment room. The low-voltage equipment room should have a separate power management room, isolated from the low-voltage equipment by firewalls to prevent noise, battery acid/alkali leakage, and electrical fires from spreading to the equipment room. A single-leaf door opening towards the power management room should connect the equipment room and the power management room; a glass observation window may be considered between them. The power management room should have a concrete floor, and a 0.3-0.5m high concrete platform can be built to support the UPS power supply for moisture protection. For computer rooms and building control equipment management rooms with heavy data signal transmission and reception tasks and many network servers, intelligent UPS power supplies should be selected. The UPS should send a message to the system monitoring host of the computer room indicating that the power storage capacity is insufficient due to main power failure, self-charging failure or other reasons and the power supply cannot be supplied normally. The system monitoring host should have the corresponding hardware interface and power monitoring processing software to set the order of each data processor and server in the system, force the storage of their current data information, backup files, enter sleep state and perform shutdown operations, etc., to avoid data transmission disorder and computer control system misoperation. After the intelligent UPS power supply is troubleshooted and power is restored, it should send a signal to the system monitoring host to restart it, and then activate and restart the dynamic real-time working equipment such as each data processor and server in the system. 2 Grounding There are three types of electrical grounding in the weak current equipment room: (1) DC ground (including the grounding of logic quantity and analog signal system) (2) AC working ground (3) safety protection ground. The grounding resistance values ​​for all three grounding methods mentioned above are required to be no greater than 4Ω. For intelligent buildings, a reliable and economical grounding method is to use a common grounding system, sharing a grounding device with lightning protection grounding, and adopting a TN-S grounding system. The AC working ground and safety protection ground are taken from the N line and PE line of the power supply line, respectively. The resistance of the unified grounding body in intelligent buildings is generally less than 1Ω. The author has investigated and researched some high-rise building projects in Beijing, Shanghai, Chongqing, Shenzhen, and Hainan, and their unified grounding resistance is mostly 0.2 to 0.5Ω, with the maximum grounding resistance value at individual test points in some high-rise buildings not exceeding 0.8Ω. Of course, the requirement that the unified grounding resistance should not exceed 1Ω is a minimum limit. In specific projects, the lower the better. If the requirement cannot be met, the number of grounding bodies should be increased or artificial resistance reduction measures should be taken to meet the actual measurement requirements (it is advisable to choose a high-efficiency resistance-reducing agent that does not significantly corrode the grounding body). It should be emphasized here that when introducing two power supplies to the UPS power management room of a low-voltage electrical room, the main power supply should use a three-phase five-core (3L+N+PE) insulated fireproof cable, and the backup power supply should use a four-core (3L+N) insulated fireproof cable. The PE wire of the main power cable should be used as an auxiliary equipotential grounding terminal block in the power management room's transfer switch box. Low-voltage electrical rooms requiring DC grounding (such as program-controlled exchange rooms and computer network equipment rooms) should be located adjacent to the computer room. The AC working ground and safety protection ground should be taken from the computer room's power management room, and two insulated fireproof cables with a cross-sectional area of ​​not less than 16mm² (e.g., single-core 16mm², three-core 6mm², and four-core 4mm²) should be separately connected from the main equipotential grounding busbar of the building's substation. A dedicated metal junction box should be installed in the low-voltage electrical room with DC grounding to connect these cables, forming a DC grounding terminal block for DC grounding equipment termination. The main equipotential grounding busbar in the building's substation should be equipped with protective devices such as surge arresters, discharge gaps, or surge suppressors to prevent the grounding device potential from rising during lightning strikes, causing backflashover to electrical equipment and resulting in large fluctuations in DC ground potential, which could lead to malfunctions of electronic equipment. The anti-static raised floor in the low-voltage equipment room should be 0.3m above the ground. Along the four walls of the equipment room, use 20x4mm flat steel or 6mm steel bars to repeatedly ground the metal support pipes of the raised floor at multiple points. On the side near the power management room, use copper core insulated wire of 6mm² or larger, threaded through steel or PVC pipes, to connect to the auxiliary equipotential grounding busbar in the power management room. This ensures that the floor surface of the low-voltage equipment room becomes a safe and reliable equipotential plane, shields and protects various signal lines under the floor from electromagnetic interference, and isolates mutual interference between signal lines of different voltages and frequencies above and below the floor. 3. Power Distribution and Wiring The power supply line to the power management room of the low-voltage equipment room should be protected against lightning strikes. Armored cables should not be used; otherwise, the metal sheath of the cable should be connected to the grounding device. Before armored signal cables and shielded signal lines from outside the building enter the low-voltage electrical room, lightning protection measures should be taken to avoid laying them along the building's exterior walls or near lightning protection down conductors to prevent lightning strikes and to avoid high-frequency electromagnetic interference from lightning protection devices in the event of a lightning strike. After entering the low-voltage electrical room, a metal junction box should be installed to connect the cable's metal (shielded) outer sheath to a surge arrester or surge suppressor. Then, it should be connected to the auxiliary equipotential grounding busbar of the low-voltage electrical room using copper core insulated wire with a cross-sectional area of ​​not less than 6mm², and laid under steel conduit for protection. This also suppresses high-frequency electromagnetic interference signals received by the cables from other nearby interference sources along the transmission path, thus effectively and reliably ensuring the quality of signal transmission. Signal lines exiting the low-voltage electrical room should be laid along the walls and within the ceiling using metal cable trays, avoiding parallel or close contact with other electrical conduits. They should be kept away from air conditioning, fire protection, heating, and water supply/drainage pipes, maintaining a distance of more than 0.3m from them. The UPS power supply output lines in the low-voltage equipment room should be installed in a metal distribution box, recessed 1.4m from the ground. If this is difficult, it can be wall-mounted or surface-mounted. Single-phase and three-phase circuits should be provided according to the load capacity and distribution of the equipment in the low-voltage equipment room, using miniature vacuum circuit breakers such as C45N or DZ47 for line protection. An auxiliary equipotential grounding busbar should be installed inside the box. For load imbalance in the single-phase output, the difference between the fundamental root-mean-square current of the largest and smallest phase loads should not exceed 25% of the UPS power supply's rated current, and the maximum line current should not exceed the rated value. Lighting and air conditioning loads in the low-voltage equipment room should not be powered by the UPS. They should be powered by a lighting power supply circuit and a fan coil unit or split air conditioner distribution circuit with a total rated power of less than 2kW, provided the power supply and management room transfer switch box is used. Lighting switch boxes or switch panels should be concealed in convenient locations on the walls near the entrance and exit of the computer room. Air conditioning sockets should be installed on the walls inside the suspended ceiling of the computer room or on the walls 1.8m above the ground. Air conditioning loads with a total rated power greater than 2kW should be powered by the power or lighting distribution box near the floor where the low-voltage equipment room is located. The wiring for both lighting and air conditioning loads should be laid along the ceiling or walls, avoiding passage under the raised floor in the low-voltage equipment room. A single-phase maintenance power circuit should be configured in the power management room via this interoperability switching box. Maintenance power sockets should be installed on each wall of the power management room 0.3m above the ground. The use of high-power inductive power tools exceeding 2kW is prohibited. If such tools or three-phase maintenance equipment are necessary, a mobile distribution panel should be used to draw power from the power or lighting distribution box near the floor where the low-voltage equipment room is located. Equipment tables, cabinets, and patch panels can be arranged in the low-voltage equipment room. This example uses the power management room on the right side of the computer room; similar arrangements can be made for other situations. As shown in Figure 2, the power distribution lines from the UPS power distribution box are laid through thin-insulated steel pipes or flame-retardant PVC pipes from under the raised floor of the low-voltage equipment room to the back of each row of equipment tables, cabinets, and patch panels. The lines are then run through protective conduits from the raised floor with cable management holes (this type of raised floor is optional or custom-made; the cable management holes are generally φ20～φ32mm) and connected to metal rail-mounted cable trays, cabinets, or patch panels. The metal rail-mounted cable trays are bolted to the back of the equipment table, preferably 0.1～0.3m from the raised floor. The power cords of general power connectors are 1.0～2.0m long, while the height of the equipment table is generally less than 1.0m, which fully meets the power connection distance requirements. It should be noted that the equipment on the equipment table is generally a single-phase load; if there is three-phase equipment, it should be placed on the floor with a dedicated power circuit using a ground-mounted socket box (junction box). Modular power sockets are installed within metal rail-type cable trays. Uninstalled sockets are secured with metal covers (ideally 0.2m long each) for safety and electromagnetic shielding. Modular power sockets come in two types: termination connectors and center connectors. The socket holes (as shown in Figure 3, front) are compatible with both two- and three-pole external device plugs. Switches or protective covers can be added as needed for easy expansion and disassembly. The sockets are securely, reliably, and safely installed within the metal rail-type cable trays. Modular power sockets are grouped according to the location and quantity of equipment on the equipment table. Groups are connected using wires of the same type as the power supply cord. The power plugs of the equipment on the table should ideally cross the edge of the table vertically before entering the modular power sockets, resulting in neat, safe, aesthetically pleasing, and easily accessible power wiring on the back of the equipment table for maintenance. Signal cables should be laid horizontally and vertically along the equipment table or main plane of the computer room from the cabinets and patch panels under the raised floor. They should be connected to the equipment through the raised floor cable trays on the back of the equipment table (note that they must not share raised floor cable trays with power lines, and the spacing between them should be greater than 0.1m). Signal cables should not be laid along the walls of the computer room to prevent crossing with power conduits. For signal connections between devices on the table, short cables (less than 3m) should be laid openly along the back of the device on the tabletop, but should not be suspended in the air behind the equipment table; long cables (more than 3m) should be run down (or up) through the raised floor cable trays and laid under the raised floor in thin-insulated steel conduits. This approach scientifically ensures the reliability and safety of power supply to the low-voltage equipment room, and provides safe, well-isolated, neat, and aesthetically pleasing installation of signal cables of different voltages and frequencies, facilitating maintenance and management. 4. Design Concept of Anti-interference Cabinets For low-voltage electrical rooms, proper cabling of cabinets and single-sided active patch panels (with terminal blocks on one side and shelves on the upper part of the cabinet for active devices such as routers and hubs) is essential to ensure electrical safety, good isolation, and convenient maintenance. Currently, most pre-fabricated cabinets and single-sided active patch panels have electrical hazards: strong and weak current lines cross significantly at the back of the cabinet, and there are no unified standards for power distribution within the cabinet. Current practices often involve arbitrarily placing protective switches and power strips on the back, bottom, or top of the cabinet, sometimes even suspending power strips in the air (this can sometimes be unintentionally caused during cabinet operation and management). This can easily lead to poor contact or leakage, causing power outages and even electrical fires. To address this, the author developed a design concept for an anti-interference cabinet (i.e., modifying existing cabinets and patch panels with the aforementioned problems): Firstly, in terms of appearance, the cabinet width should be greater than 0.5m to allow it to span the two support crossbeams of the raised floor (raised floor panels are typically 0.4x0.4m² and 0.5x0.5m² square panels), ensuring robust support and convenient cable entry/exit through the raised floor. The cabinet height should not exceed 2m for ease of operation and maintenance. The depth can be designed based on the maximum internal equipment depth width + 0.3m. The bottom support feet should use casters to make the cabinet movable, facilitating installation, adjustment, and maintenance. The front door should be a single-leaf sliding door with an acrylic glass panel and metal frame for easy observation and monitoring. Secondly, one to four embedded cooling exhaust fans (power below 100W) should be installed on the top or side of the cabinet to ensure that the internal temperature rise meets electrical operating standards, preventing the internal equipment from being affected by electrical heat and maintaining normal operation. Third, design layered shelves according to the number and size of built-in equipment, and design terminal blocks, cable trays, and splitters according to the number and type of incoming and outgoing cable pairs. Generally, the upper part of the cabinet houses active equipment, while the lower part contains patch panels and cable interfaces. A metal partition is installed on the back side of the active equipment in the upper part of the cabinet, dividing the cabinet into front and rear sections from the top to the bottom layer of active equipment. Holes (preferably φ40～φ60) are drilled at the power interfaces of the active equipment. Low-voltage signal cables, cable pairs, various jumpers, and signal connections between devices are laid in front of the metal partition. Power cables for active equipment are laid behind the metal partition after passing through the holes. Metal rail-mounted cable trays and modular power sockets are installed on the rear side wall of the metal partition for single-phase equipment (including the cabinet cooling fan). Unsecured sections of the cable trays are secured with metal covers. A three-phase five-pole (compatible with four-pole plug-in) socket or three-phase protective switch is installed on the rear wall of the metal partition for three-phase equipment to be plugged in or terminated. The cabinet back door adopts a single-leaf outward-opening metal door. The cabinet shell and metal components are painted to prevent paint peeling and rusting. 5 Conclusion With the rapid development of intelligent buildings, the diversification of low-voltage systems and their integration technologies have brought many new problems and challenges to existing electrical systems and technical models. Based on some problems existing in the current design and installation of intelligent buildings, this paper proposes a comprehensive power distribution mode for low-voltage equipment rooms and a design concept for anti-interference cabinets. It strives to solve problems such as power configuration, AC/DC isolation, grounding, and signal line anti-interference, thereby optimizing the layout and wiring of low-voltage equipment rooms, ensuring reliable power supply, electrical safety, and the transmission quality of various signal lines, and eliminating hazards such as power failure, leakage, crosstalk, and fire.