A Cable Tunnel Intelligent Integrated Monitoring System

1. Preface

With the increase of power grid capacity and the improvement of intelligence and automation level, the amount of cables used is increasing. The scale of cable trenches in substations, distribution rooms, switch stations, and switch stations is also becoming larger and more complex. Due to their location underground, they often become safety blind spots. Cable failures in underground trenches usually occur in a concealed and gradual manner. Once accident symptoms are discovered, the losses are usually difficult to recover, and in severe cases, they can also affect the safe operation of the power grid.

In order to help power inspection personnel manage safely, conveniently, and quickly, a modern intelligent monitoring system that integrates visualization, intelligence, and unmanned technology has gradually adopted the traditional management mode, realizing online real-time monitoring of the environment and operating status inside cable tunnels, and providing guarantees for the safe operation of power.

The comprehensive online monitoring system for tunnels mainly consists of toxic and harmful gas monitoring, distributed fiber optic temperature measurement, environmental monitoring, fire system monitoring, video monitoring, high-voltage cable sheath circulation monitoring, cable partial discharge and central platform. It uses modern high-tech electronic technology, sensor technology, computer network technology, communication technology, and embedded technology to monitor and analyze data on the environment, equipment and facilities inside the cable tunnel, achieve remote monitoring of cable tunnel equipment, and ensure the safe operation of the power grid.

IIA Cable Tunnel Intelligent Integrated Monitoring SystemDesign Basis

2.1 Technical Guidelines for Monitoring and Communication System Design of Power Cable Tunnels (Q/GDW 12080-2021)

2.2 "Eighteen Major Anti accident Measures for Power Grid of State Grid Corporation of China (Revised Edition)" (State Grid Equipment [2018] No. 979)

Guiding Opinions on Selection and Construction of Power Cable Channels (State Grid Equipment [2014] No. 354)

2.4 "Principles for the Configuration of Cable Bodies and Environmental Monitoring in Tunnels" (Yunjian II [2017] No. 105)

2.5 "Code for Design of Cables in Electric Power Engineering" GB50217-2007

2.6 "Code for Construction and Acceptance of Electrical Equipment Installation Engineering" GBJ232-92

2.7 Technical Specification for Security and Prevention Engineering GB50348-2014

2.8 Design Code for Automatic Fire Alarm System (GB 50116-2013)

2.9 Technical Specification for Distributed Fiber Optic Temperature Measurement System for Power Cables (DL/T 1573-2016)

2.10 "Design Specification for Video Security Monitoring System Engineering" GB50395-2007

2.11 General Technical Conditions for Anti theft Alarm Controllers GB12663-2001

2.12 "Design Code for Entrance and Exit Control System Engineering" GB50396-2007

2.13 Design Specification for Video Security Monitoring System Engineering (GB 50395-2007)

2.14 Electrical Equipment for Combustible Gas Detection (GB 20936-2009)

2.15 "Management Specification for Cable Channels of State Grid Corporation of China"

IIIA Cable Tunnel Intelligent Integrated Monitoring SystemSystem Composition

3.1 System Architecture

3.1 System Description

The comprehensive monitoring system for cable tunnels consists of a front-end online monitoring system, a communication network, and a comprehensive monitoring platform.

Ø Application layer: Summarize real-time data information of the entire station, evaluate the operation status of the entire station, and schedule and control the monitoring layer based on relevant data information.

Data layer: The process of storing, parsing, distributing, and applying collected data through a unified database read-write interface.

Ø Access layer: The equipment responsible for data communication transmission, including network switches, servers, communication fibers or cables, in order to transmit data collected by monitoring layer devices to servers.

Ø Monitoring layer: Directly perform online detection and statistics of the status parameters of each monitoring point, including various sensors, signal acquisition integration units, professional data processing devices, and other equipment.

4、 Technical solution

Project Introduction

The total length of this project is XXX meters. A comprehensive monitoring system for cable tunnels is designed, including cable body status monitoring, online monitoring of cable tunnel environment, etc. A comprehensive monitoring platform is set up at the nearest substation or user designated location to be responsible for the daily management, equipment monitoring, and safety prevention of cable tunnels. The design is as follows:

4.1 Distributed Fiber Optic Temperature Measurement System

Advanced distributed fiber optic temperature measurement technology is used for online monitoring of cable temperature. By laying a temperature measuring optical cable on the surface of the cable, the temperature of the cable is monitored to ensure the safety of the entire cable line operation. Real time temperature measurement, alarm, and early prediction are achieved to prevent problems before they occur.

Configuration Description: It is estimated that X groups of 3 cables will need to be monitored in this phase of the project, with a total of X sets of 10km temperature measurement hosts for X channels. The temperature measurement hosts will be installed in the substation or at a nearby installation location. The temperature measuring optical cable is laid on the surface of the cable, and appropriate allowance is considered.

Fiber optic host temperature sensing fiber

4.1.1 System Characteristics

1) Continuous distributed measurement
Distributed fiber optic sensors are truly distributed measurements that can continuously obtain measurement information along several tens of kilometers of temperature sensing fibers, greatly reducing false alarm and missed alarm rates. Simultaneously achieve real-time monitoring.

2) Anti electromagnetic interference, can work normally in high electromagnetic environment
The optical fiber itself is composed of quartz material, which provides complete electrical insulation; At the same time, the signal of the fiber optic sensor is carried by fiber optic, which is inherently safe and not affected by any external electromagnetic environment interference.

3) Intrinsic lightning protection
Lightning often damages a large number of electrical sensors. Fiber optic sensors, due to their complete electrical insulation, can resist the impact of high voltage and high current.

4) Long measurement distance, suitable for remote monitoring
The two prominent advantages of optical fiber are the large amount of transmitted data and low loss, which can achieve remote monitoring for tens of kilometers without the need for relays.

5) High sensitivity and measurement accuracy
In theory, the sensitivity and measurement accuracy of most fiber optic sensors are superior to general sensors, and this has been proven by mature products in practice.

6) Long lifespan, low cost, and simple system
The material of optical fiber is quartz glass, which has the characteristics of non corrosion, fire resistance, water resistance, and long service life. It can usually serve for 30 years. Taking into account the cost of the sensor itself and future maintenance expenses, using fiber optic sensors can greatly reduce the final operating cost of the entire project.

4.1.2 Technical Parameters

4.2 Cable sheath current monitoring system

This system monitors the grounding current in real time by installing a protective layer current monitoring device. When the grounding current of the metal protective layer is abnormal, the system will automatically alarm and the signal will be transmitted to the monitoring platform, which can real-time grasp the operation status of the cable metal protective layer grounding system.

Configuration Description: The protective layer grounding current monitoring device is installed at the position where the cable metal sheath is grounded. Each protective layer current monitoring device includes one protective layer current collector and three clamp current transformers.

Data acquisition host current transformer

4.2.1 System Functions

1) Protective layer current monitoring function: Real time monitoring of the grounding current of power cables, which can detect abnormal grounding current of cables early and take measures to deal with cable faults;

2) Expandable collection of cable line current, sheath voltage, cable joint temperature, environmental temperature and humidity, etc;

3) The front-end equipment adopts low-power design, with a power not exceeding 3W; except for the current transformer, it is installed as a whole in the collection device inside the tunnel, with a high protection level (IP68), suitable for the humid environment inside the tunnel;

4) Multiple levels of alarms are available, including normal, prompt, warning, alarm, and fault;

5) Implement grounding current change rate alarm, which includes 1-minute, 15 minute, and 1-hour monitoring of grounding current changes;

6) Real time storage of information, capable of querying historical data, printing alarm information, etc; Publish relevant data such as cable sheath current through WEB;

7) Self checking function: The system has a self checking function, which can conduct regular or real-time inspections of lower level machines, on-site equipment, etc., and detect communication or device abnormalities in the first time.

4.2.2 Technical Parameters

4.3 Cable Partial Discharge Monitoring System

This system adopts wideband pulse current measurement method. By installing partial discharge monitoring devices at cable joints, the partial discharge signals on the cable body are detected and collected. The collected data is transmitted to the backend analysis system through optical fibers for data analysis and processing, and the insulation defect status of the cable is evaluated.

Configuration instructions: The partial discharge monitoring device should be arranged at the cable terminal grounding or intermediate joint. Each set of partial discharge monitoring device includes one partial discharge monitoring host and three partial discharge sensors.

Cable partial discharge monitoring system

4.3.1 System Characteristics

1) The system uses partial discharge sensors and signal processors installed at cable terminals and intermediate joints to effectively remove interference signals from partial discharge signals occurring inside high-voltage cables. The measurement data is transmitted to the station control level monitoring platform through the transmission resources of the on-site industrial control bus in the cable tunnel;

2) The system host analyzes and processes the received monitoring data, evaluates the defect status of the cable, analyzes and judges the type and level of partial discharge through the analysis system, evaluates the impact of partial discharge, determines the insulation status of the equipment, and provides corresponding equipment maintenance guidance plans;

3) Professional chart analysis function: It has functions such as partial discharge amplitude accumulation chart, partial discharge data display, single cycle chart data display, short-term trend display chart, as well as various two-dimensional and three-dimensional charts, and can complete data horizontal comparison and overlay comparison between different icons;

4) Replay function: It can replay historical data, single data, or multiple data. The replay has two-dimensional maps of φ - q, q-t, and n-t, as well as three-dimensional maps of φ - q-n and φ - q-t;

5) Analyze the waveform characteristics of partial discharge pulses, identify the type of partial discharge, and remove noise signals;

6) Extract characteristic values of partial discharge signals, such as time features, frequency features, and discharge time intervals between different types of discharges, and use these features to identify different types of discharges;

7) The sampling frequency band of the system is in the high-frequency band, which has strong on-site anti-interference ability.

4.3.2 Technical Parameters

4.4 Tunnel Environmental Monitoring System

This system provides real-time monitoring and alarm of environmental parameters such as temperature and humidity, concentration of harmful gases such as CO, CH4, H2S, air oxygen content, water level, etc. in cable tunnels, providing comprehensive protection for the reliable operation of cable tunnels and the personal safety of pipeline operation and maintenance personnel, and achieving energy-saving operation.

Configuration Description: (Cable tunnels are temporarily divided into zones every 25 meters):

Ø Universal collection unit: set 1 set in each partition;

Ø Temperature and humidity sensors: set one in each partition;

Oxygen sensor: Install one in each partition;

Ø Hydrogen sulfide sensor: Install one in each partition;

Ø Methane sensor: Install one in each partition;

Ø Carbon monoxide sensor: Install one in each fire compartment;

Ø Water level sensor: Install one in each collection well;

Monitoring of switch status and remote start stop control for ventilation, lighting, and drainage: configured as needed.

Tunnel environment monitoring architecture

4.4.1 System Functions

1) Harmful gas content monitoring function: Real time detection of harmful gas content inside the tunnel to avoid harm to personnel inside the tunnel. The harmful gases that need to be monitored are H2S and CO.

2) Oxygen content monitoring function: Monitor the oxygen (O2) content inside the cable tunnel.

3) Easy to burn gas content monitoring function: Monitor the methane (CH4) gas content inside the cable tunnel.

4) Temperature and humidity monitoring function: Monitor the temperature and humidity inside the cable tunnel.

5) Water level monitoring function: Monitor the water level of the collection well in the cable tunnel, achieve automatic monitoring of the water level in the tunnel, remote data upload, abnormal state alarm and other functions, and link with the drainage equipment.

6) Data transmission function: The system can transmit real-time detection of harmful gas content data, oxygen content data, temperature and humidity data to the monitoring center, and store and record them.

7) Linkage control function: The system can monitor the status of ventilation equipment, drainage equipment, and lighting equipment in the tunnel, and control the ventilation equipment, drainage equipment, and lighting equipment in the tunnel through linkage based on environmental conditions or other alarm systems.

8) Alarm function: When the system detects abnormal environmental parameters, an alarm will pop up on the monitoring center software interface, requiring the ability to locate the alarm zone to remind the monitoring center staff to take relevant measures.

4.5 Tunnel video surveillance system

The video surveillance system, by installing high-speed dome cameras in the cable tunnel, allows duty personnel to remotely and timely monitor the operation status of pipelines and ancillary equipment in the cable tunnel from the monitoring room. At the same time, it can also intuitively monitor the activities of personnel in the cable tunnel, thereby ensuring the safe operation of pipelines and ancillary equipment in the cable tunnel.

Configuration instructions: Install a camera every 20 meters in the cable tunnel, and add it as needed in key monitoring areas such as entrances and exits or corners. Set up video storage devices in the monitoring room to store video signals within the corresponding management area, with a storage time of one month.

Video surveillance architecture

4.5.1 System Functions

1) Real time video surveillance function

The system monitors the important nodes and equipment inside the cable tunnel in real time, transmits the monitoring images back to the monitoring center, and displays them in real time on the monitor, so that the on duty personnel of the central monitoring and management center can clearly understand the basic situation of the entire cable tunnel and obtain timely information on unexpected situations.

The video surveillance camera adopts infrared monitoring technology, which can clearly display the scene in the absence of light, reflecting the entry and exit status of personnel and the operation of equipment.

2) Video image display function

The monitoring images of each video surveillance camera in the cable tunnel can be displayed in real time on the monitor in the monitoring center, and can be manually operated to switch and view. The monitoring images are clear and complete.

3) Data transmission function

The system will transmit the real-time recording stream (4Mbps) of the video surveillance cameras in the cable tunnel back to the monitoring center, with a transmission delay of no more than 300ms.

4) Video storage and playback function

The system transmits high-definition recordings from the front-end video surveillance cameras back to the monitoring center for storage. It uses a network hard disk recorder with a storage time of one month. Operators can browse past recordings and replay them at any time, and can display, store, retrieve, and replay videos from multiple selected cameras simultaneously.

4.6 Tunnel manhole cover monitoring system

This system achieves real-time monitoring and remote opening of the manhole cover by installing a manhole cover monitoring device at the entrance of the tunnel, solving the protection and anti-theft problems of artificial wells. It can effectively combat manhole cover theft and illegal entry into the tunnel to damage power equipment. The electronic manhole cover monitoring system mainly consists of intelligent electronic manhole covers, manhole cover data acquisition and control devices, communication lines, monitoring hosts, and upper monitoring software.

Configuration instructions: Install one set of electronic manhole covers at each wellhead of the tunnel.

Tunnel manhole cover monitoring system

4.6.1 System Functions

1) The system has intelligent monitoring and warning functions such as manhole cover displacement, damage, unauthorized opening alarm, etc. It also has real-time monitoring of the opening and closing status of manhole covers and entrances, effectively preventing theft and illegal intrusion;

2) The system has the functions of automatic collection, processing, and transmission of state variables, and adopts a monitoring method combining timed detection and sudden change wake-up detection;

3) The system has data upload and local storage functions, which can correctly record dynamic data. When the device is abnormal, it can correctly establish dynamic event indicators to ensure the security of recorded data;

4) The system can monitor the opening and closing of manhole covers and external impact events, and the monitored events should be able to be reported to the management platform in real time;

5) The system supports remote opening and closing functions through various methods such as RS485, NB IoT, and switch control;

6) The system manhole cover has a warning light function inside;

7) If the manhole cover is opened or stolen, the monitoring center will issue an alarm message and display the specific number, location, and other information of the manhole cover;

8) The system can quickly query alarm information based on various conditions such as time, location, and equipment number.

4.7 Tunnel access control monitoring system

The tunnel access control monitoring system is mainly used to monitor and manage the opening and closing of the entrance and exit doors of the cable tunnel. It can effectively restrict unauthorized personnel from entering the cable tunnel and give an alarm for violent intrusion and other abnormal situations. At the same time, access control monitoring should be linked with video surveillance. When there is an "illegal intrusion" at the entrance and exit, the video surveillance can be linked to capture real-time footage of the entrance and exit.

Configuration instructions: Install one set of access control monitoring devices at each entrance and exit of the tunnel (excluding manhole covers).

The access control unit consists of an access controller, door switch buttons, card readers, electric locks, etc. Lead control cables from the access control controller to various devices for intelligent control of door access.

access control system

4.7.1 System Functions

1) Can achieve functions such as remote door opening;

2) Multiple permission settings for location and time can be implemented;

3) The fire door monitoring system can be linked with the fire alarm system;

4) Equipped with multiple input and output interfaces, as well as RS232/RS485/RJ45 communication interfaces;

5) Support a capacity of no less than 200 users;

6) It can query self inspection status, fault information, card history information, front-end controller resource usage, etc.

4.8 Tunnel Settlement Monitoring System

This system uses a static level to monitor factors such as displacement and settlement of cable tunnel structures, timely understanding the deformation rate and trend of the tunnel, and providing decision-making basis for judging the effectiveness of reinforcement construction and the service status of the tunnel.

Configuration instructions: The settlement monitoring device should be installed in key areas with settlement risks, such as deep backfill areas, intersections with other tunnels or underground structures. The focus of this project is to monitor the tunnel joints, and a settlement monitoring point is temporarily set up every 25 meters. Each monitoring point is equipped with 2 static level gauges.

static level

4.8.1 System Functions

1) The system uses high-precision micro pressure static level to measure the changes in settlement of the monitored points, realizing the function of tunnel settlement monitoring, and effectively grasping the relative settlement changes of the tunnel through data analysis, achieving the effect of early risk warning;

2) The system sensor is equipped with a built-in temperature sensor, which can simultaneously monitor the vertical displacement of the measuring point position and the ambient temperature, and perform temperature compensation on the settlement data;

3) One end of the vent pipe is connected to the storage tank, and the vent pipe is connected to the storage tank through a drying pipe to form an internal pressure self balancing system, which can effectively eliminate the influence of atmospheric pressure on the system;

4) The system can display the initial reading, location, and identification number (determined by the user) of each monitoring point sensor;

5) The settlement monitoring data collected on-site by the system should be able to be uploaded to the monitoring platform through a fiber optic transmission network;

6) The system can automatically alert monitoring objects that exceed the safety range, and relevant units can evaluate and analyze them based on the engineering situation and monitoring data, which is conducive to timely elimination of risks and hidden dangers.

4.8.2 Technical Parameters

4.9 Tunnel Fire Alarm System

This system mainly consists of manual alarm buttons, sound and light alarms, smoke detectors, fire alarm controllers, and ultra-fine dry powder fire extinguishing devices. It detects and alarms the fire situation in cable tunnels, reduces fire damage, and avoids property damage to facilities and equipment in cable tunnels caused by fires.

Configuration Description:

Install one fire alarm host in the substation control room;

Install one manual alarm button and one sound and light alarm every 25 meters inside the tunnel;

Install one smoke and fire detector every 10 meters inside the tunnel;

Install ultra-fine dry powder fire extinguishing devices in areas such as cable joint zones and joint concentration zones;

Tunnel fire alarm system

4.9.1 System Functions

1) Automatic fire detection function: The system can timely and accurately detect the location of internal fires in cable tunnels through smoke detectors.

2) Automatic fire alarm function: The system can receive fire detection signals or alarm signals from manual alarm buttons, and sound and light alarms inside the tunnel to alert the staff inside the tunnel. The system can simultaneously sound an alarm in the monitoring center, pop up an alarm in the software interface, and automatically (or manually) switch the main monitor to the location of the fire on the monitoring platform, warning the monitoring center staff to take relevant measures.

3) Manual fire alarm function: When the staff in the tunnel press the fire alarm button, it can immediately sound an alarm in the monitoring center, requiring the ability to locate the fire occurrence point and warn the monitoring center staff to take relevant measures.

4) Automatic fire extinguishing function: Ultra fine dry powder fire extinguishing devices should be installed in areas such as cable joint zones and joint concentration zones. The fire extinguishing devices should support three start-up modes: constant temperature start-up, hot start-up, and electric control start-up.

5) Linkage control with fire-fighting equipment: The system has two states: automatic control and manual control. In automatic control mode, when the fiber optic temperature measurement equipment detects a fire, the fire alarm system can automatically activate the pre prepared fire plan and link relevant fire equipment, such as starting the fan for smoke exhaust, starting the gas fire extinguishing device, etc. In manual control mode, after the staff confirms the fire, the fire plan can be activated and relevant fire equipment can be linked.

4.10 Tunnel Comprehensive Monitoring Platform

The tunnel comprehensive monitoring platform is an integrated, digital, and intelligent security management platform. The tunnel comprehensive online monitoring system platform is an independently developed integrated multi system networking platform based on the SOA system architecture. It adopts advanced software and hardware development technology to solve problems such as centralized system management, multi-level networking, information sharing, interconnection, and multi business integration.

The integrated monitoring platform combines big data technology and intelligent network algorithms. It can analyze and utilize various data sources such as partial discharge, protective layer, temperature measurement, etc., and use high-tech methods such as data trend analysis, artificial intelligence learning, and neural network diagnosis to diagnose and analyze the operating status of cables, and output cable status evaluation results, providing technical assistance and data support for power inspection work, and realizing comprehensive monitoring of smart grids.

Configuration Description: The monitoring platform is set up at the nearest substation or at a location specified by the user. The monitoring platform includes hardware equipment and platform software. The hardware equipment includes main station servers, gigabit switches, LCD displays, UPS power supplies, equipment cabinets, etc; The main functions of the software platform include centralized collection and management of station data, flat display of real-time station status, including equipment operating conditions, real-time detection data curves, historical data curves, and other interfaces, which intuitively describe the on-site environmental status.

Interface Display

Main Interface

Protective layer circulation

Distributed fault location

Device Control