In recent years, with the rapid advancement of urbanization in our country and the higher standards and requirements for infrastructure development, constructing underground comprehensive pipe galleries has become a crucial measure for achieving the flexibility, intensification, and sustainable development of urban infrastructure. As a result, the state has successively issued a series of opinions and regulations to promote the construction of these pipe galleries, and an increasing number of cities are accelerating the planning and construction of such galleries.
The function of the utility tunnel is relatively clear and single. As the main artery of the city, its importance is self-evident. The power supply and distribution system, as the main auxiliary project of the utility tunnel, ensures electricity for systems such as fire protection, ventilation, drainage, lighting, surveillance, security, and communication within the tunnel. Therefore, guaranteeing the safe operation of the tunnel is the primary goal of the power supply and distribution system design.
Through analysis of multiple comprehensive utility corridor projects and combining with the author's own involvement, a brief introduction to the design of power supply and distribution systems for comprehensive utility corridors is provided.
Section II: Project Overview
The South-North No. 3 Road Integrated Utility Tunnel in a new district of Xi'an City is one of the first tunnels to be constructed in the area, situated beneath the non-motorized bike lane and pedestrian walkway, with a total length of approximately 1.1km. The tunnel accommodates pipelines for electricity, telecommunications, potable water, reclaimed water, wastewater, rainwater, and natural gas. It features a comprehensive compartment, cable compartment, natural gas compartment, and rainwater compartment, constructed with reinforced concrete. See Figure 1 for details.
III. Load Classification
The comprehensive utility tunnel, as one of the key urban infrastructure components, poses significant safety risks if the power supply is interrupted. Therefore, it is designated as a second-level load power supply. It is powered by two independent sources to ensure reliability, with each circuit capable of carrying 100% of the second-level load. The load classification is detailed in Table 1.
Four: Power Supply
The selection of the power supply scheme for the comprehensive utility tunnel is primarily determined by a comprehensive assessment of the construction scale of the tunnel, the short-term and long-term planning, the surrounding power supply conditions, and the operational model of the tunnel.
The South-North No.3 Road Integrated Pipeline Corridor is one of the pipelines initially launched for construction in the new district. The pipeline planning in this area is dense, with pipelines interconnected, forming a networked and extensive layout. Consequently, the selection of the power supply source should be considered comprehensively (see Figure 2).
Due to the fact that all electrical equipment within the comprehensive pipeline is 0.4kV low-voltage equipment, the power supply can be implemented using either a 10kV or a 0.4kV power supply solution.
In alignment with the comprehensive pipeline corridor planning characteristics of the Changning New Area, considering the voltage loss associated with a 0.4kV power supply solution, each pipeline corridor would need to frequently draw power from nearby substations. Given that the Changning New Area is predominantly undeveloped land, difficulties in power connection are expected, along with numerous inconveniences for later pipeline management and maintenance. Therefore, it has been decided to adopt a 10kV power supply solution for this project. Additionally, a comprehensive pipeline corridor monitoring center is being planned and constructed in the Changning New Area. The design proposes to use this monitoring center as a 10kV distribution center, which will provide unified operational, monitoring, and distribution management for the pipeline corridors within the region.
Power Supply Solution
The comprehensive pipeline utilizes a 10kV power supply and 0.38kV distribution system. Along the pipeline, a 10/0.4kV substation (or an enclosed substation, hereinafter referred to as the box substation) is set up to provide low-voltage power distribution for the auxiliary facilities within the pipeline.
In response to the secondary load power supply requirements of the comprehensive utility tunnel, two 10kV power cables need to be laid by the power supply center to supply power to the transformer substations along the tunnel. Due to the need to increase the spacing of outgoing lines, the power supply center has expanded its scale. Additionally, an extra 10kV cable, which is costly, needs to be laid for a small amount of secondary load. Furthermore, this type of power supply often involves the installation of two transformers within the transformer substation at the tunnel site, operating simultaneously with each other as backups. This indicates that the initial investment for this power supply scheme is substantial, the power distribution system design is complex, and the operation of the dual transformers also adds to the cost of later maintenance and operations.
Due to the distinctive characteristics of the power supply and distribution system in the comprehensive utility tunnel, such as load dispersion, long power supply distance, and a relatively low simultaneous operating coefficient for all electrical equipment, the secondary load has a smaller capacity and requires a shorter power supply time compared to the entire distribution system. Based on these features, installing one transformer and one EPS unit at the tunnel site in a power distribution arrangement can meet the secondary load's power requirements. The transformer serves as the power source for the normal operation of the tunnel, while the EPS acts as a backup power source for times when the normal supply is not available.
The lOkV power supply system utilizes a ring network configuration, with each transformer box equipped with one entry and two exits, forming a total of three sides of 10kV ring network cabinets. One output line is connected to a self-use transformer, while another output line connects to transformers in adjacent and intersecting road tunnels within the area, composing the ring network power supply system. Both ends of the 10kV lines are supplied from different bus sections of the monitoring center (which employs dual-circuit power supply for incoming lines), enhancing the reliability of power supply.
During normal operations, the 10kV ring network lines are disconnected at the midpoint, with the two sections of 10kV power lines operating independently. In the event of a fault in a substation within the ring network or when the 10kV busbar at the monitoring center requires maintenance, the 10kV circuit breakers within the ring network system can be adjusted to switch the power lines.
The South-North No.3 Road Comprehensive Utility Tunnel is powered by a 10kV ring main supply, with the power originating from the 10kV power distribution room of the monitoring center within the area. A transformer is set up at the site's box transformer, providing low-voltage power distribution for the project. Additionally, an EPS power cabinet is installed in the distribution room within the tunnel, serving as a backup power supply for the secondary load of the project.
Six: Power Supply and Distribution System
The integrated utility tunnel is powered by a 10kV supply system and distributed at 0.38kV. The 10kV power distribution lines are laid within the tunnel. Considering the lower power load density, smaller total capacity, and other characteristics of the tunnel, along with factors such as the monitoring center's service radius and cable voltage loss, it is determined that the 10kV power supply lines should be controlled at 6km intervals, with each 10kV line operating normally with a controlled number of transformers at 5 units (or 1000kVA).
The monitoring center's 10kV power distribution system utilizes a segmented single busbar wiring method, where the busbars are not segmented for operation. It features two 10kV main power sources, equipped with a closing lock device in the incoming cabinet, strictly prohibiting simultaneous closing.
The electrical equipment capacity within the comprehensive utility tunnel is relatively small, with a high number and scattered distribution along the tunnel alignment. Considering the rationality of the power distribution system, the shorter the power supply distance, the smaller the voltage loss. From the perspective of investment cost, the fewer the number of transformer cabinets, the lower the investment. Combining with the experience in municipal road power supply and distribution design and the characteristics of fire compartmentation in the tunnel, the distribution radius is controlled at 600m to 700m (approximately 3 to 4 fire compartments), with an ultimate limit not exceeding 1km (5 fire compartments).
The 0.38kV distribution in the pipeline is divided into separate units based on fire partitions, with each section equipped with a main power distribution box and a dual-power distribution box. The main power box is responsible for distributing the three-level loads within the distribution unit, utilizing a single power source input directly from the transformer substation. The dual-power box handles the distribution of the two-level loads within the distribution unit, employing dual power source inputs—one from the transformer substation and the other from EPS. Considering the long power supply distance, scattered loads, and lower usage frequency within the pipeline, a pre-branch cable trunk distribution system is adopted from the transformer substation to each distribution unit. This solution effectively reduces the use of main distribution cables, saves investment, and improves utilization.
Section 7: Lighting System
The lighting in the integrated utility tunnel is divided into normal lighting and emergency lighting. Control switches should be installed at each section entrance, emergency exit, and personnel entrance to facilitate access to the fire-resistant sections. Emergency lighting must be interconnected with the fire alarm controller and has a higher priority than manual and automatic controls.
AcrelEMS-UT Integrated Pipeline Energy Management Platform
1. Platform Overview
The AcrelEMS-UT Integrated Pipeline Energy Management Platform integrates power monitoring, energy management, electrical safety, lighting control, and environmental monitoring into one comprehensive system. It provides data support for establishing a reliable and secure pipeline management system. Through the design of data collection, communication networks, system architecture, linkage control, and comprehensive data services, it addresses the fundamental issues of strong internal interference, numerous users, and complex coordination within the integrated pipeline. This significantly enhances the reliability and manageability of the system operations, as well as improves the efficiency of the use and recovery of pipeline infrastructure, environment, and equipment.
2. Platform Composition
The Ankelei Urban Underground Integrated Pipeline Energy Management System is a deeply integrated automation platform that incorporates a 10KV/O.4KV substation power monitoring system, transformer substation environmental monitoring system, intelligent motor monitoring system, electrical fire monitoring system, fire equipment power supply system, fire door monitoring system, intelligent lighting system, fire emergency lighting and evacuation guidance system. Users can access data through browsers and mobile apps, enabling centralized monitoring, unified management, and unified dispatch of the pipeline's electricity usage and safety from a single platform, while meeting the requirements for reliable, safe, stable, and orderly electricity usage in the pipeline.
3. Platform Topology Diagram
4. Platform Subsystem
4.1 Power Monitoring
Our electrical power monitoring primarily targets 10/0.4kV overhead or underground transformer substations. It protects and monitors the high-voltage circuit configurations of transformer substations with micro-computer protection devices and multifunctional instruments. It also includes the 0.4kV outgoing lines equipped with multifunctional metering instruments, which are used for measuring and controlling the electrical parameters and energy consumption of outgoing lines. It enables real-time monitoring of the switchgear, transformer micro-computer protection and control devices, generator control panels, ATS/STS, and UPS systems, encompassing remote control, remote signaling, remote measurement, remote adjustment, accident alarms, and records.
4.2 Environmental Monitoring
Environmental monitoring encompasses the collection, display, and early warning of temperature and humidity, smoke and heat sensors, waterlogging, flammable gas concentrations, access control, video surveillance, air conditioning, and fire data. Additionally, it can integrate with third-party systems that include equipment such as pumps and ventilation exhaust fans within the pipeline corridor's chambers to achieve comprehensive environmental monitoring.
4.3 Motor Monitoring
Madar Monitoring achieves protection, telemeasurement, telemetering, and remote control functions for tunnel motors, enabling the protection, monitoring, and alarm of abnormal situations such as motor overload, short circuit, missing phase, and leakage. In cases requiring it, linkage control can be set.
4.4 Electrical Safety
AcrelEMS-UT Energy Management System is equipped with electrical fire sensors, temperature sensors, fire equipment power sensors, and fire door status sensors for electrical safety hazards in distribution systems. It connects to the status display of fire evacuation lighting and indicator lights in real-time, and monitors the battery temperature and internal resistance of the UPS in real-time. In case of anomalies, it promptly issues warnings through audio-visual signals, SMS, and the APP.
4.5 Smart Lighting Control
Fire compartments are individually controlled with intelligent control panels and local drivers installed within each compartment. Switch drivers are connected to the fire alarm system, receiving fire alarm information and forcing the opening of the driver circuit.
Intelligent lighting sensors are installed above the corridor, which automatically turn on the lights when personnel enter the tunnel, keeping them constantly lit while inside, and turn off upon departure.
In addition to on-site control methods, centralized control can be achieved through the computer, allowing for real-time remote monitoring of lighting conditions in the current area. Remote control of the area's lighting can be activated as needed.
④ Considering the wide distribution and long distances of the on-site modules, in addition to on-site control methods, centralized control via the computer interface is also available. Real-time remote monitoring of the current area's lighting conditions can be achieved, with the option to remotely control the lighting as needed.
The system supports various control methods such as single control, area control, automatic control, sensor control, timing control, scene control, and dimming control. It also features delayed control to prevent simultaneous lighting loads from impacting the power distribution system. Modules operate independently without relying on the system, each equipped with a time module. They can automatically identify sunrise and sunset times based on latitude and longitude to enable automatic control functions.
Section 9: Hardware Selection List for Platform Deployment
Ten, Conclusion
As an essential municipal infrastructure, the design phase of the comprehensive pipeline corridor should take into account various factors and optimize the design alternatives. The power supply and distribution design, an indispensable component, should further enhance the reliability, safety, and economy of the design while ensuring its functionality.
The comprehensive pipeline adopts a single-box transformer substation and distribution system, with a radius controlled between 600m to 700m. It utilizes a pre-branch cable trunking system for power supply and employs EPS as a backup power source, ensuring both safe and reliable power supply while significantly reducing engineering investment.
