KR20110061191A - Management system on underground city-gas facility - Google Patents

Abstract

PURPOSE: A system for managing an underground gas facility is provided to previously prevent the occurrence of gas accidents and rapidly respond to the gas accidents in case of occurrence. CONSTITUTION: A sensor monitors the situation information of an underground a gas facility. A transmitter(100) transmits detected data to a converter(200) using first protocol with first frequency. The converter converts the transmitted data into second protocol with second frequency and transmits the converted data to a collector(400). The collector transmits received data to a remote server(500).

Description

Management system on underground city-gas facility}

The present invention relates to an underground city gas facility management system, and in particular, by constructing a sensor network in an underground city gas facility to enable real-time remote monitoring of the situation of an underground city gas facility, improving safety and streamlining maintenance and improving gas accidents. It is about underground city gas facility management system that prevents the accident and prevents gas accidents.

With the introduction of ubiquitous technology, radio frequency identification (RFID) and ubiquitous sensor network (USN) are introduced through various media. RFID is an advanced form of automatic recognition system. Automatic recognition systems have developed into a focus of increasing data capacity and recognition distance from barcode systems to RFID systems by attaching identification information to objects and reading them by a reader. Bar code system is a binary code that has been used successfully for over 20 years, but it does not overcome the limitation of being recognized only by touch.OCR is highly readable because both humans and objects can identify it, Due to complex reader problems, public use is not possible. Recently, smart cards with subsidiary computer capacity have been widely applied and applied in various fields, but they are vulnerable to wear, corrosion, and dirt. The RFID system is developed from smart cards. The recognition speed and distance are improved by improving directionality and wearability. The network connection and software platform between RFID systems are adopted to provide a foundation for medium / long distance communication.

USN, which aims to provide optimal functions to humans through automatic recognition of environment and situation by providing computer and network functions to all things, can be classified into information resource layer, BCN backbone layer, middleware layer, and application service layer. The information resource layer may include a sensor node measuring a situation factor in a target facility, and a base station (collector) that collects information from the sensor node and delivers the information to the server. Devices used in the information resource layer have key requirements such as low power consumption technology in hardware, flexible I / O, miniaturization, resource efficiency in software, reusability, ad-hoc network support, and bottleneck avoidance. . In addition, the following design criteria are required to form a network between devices.

Functionality: ensuring correct functionality and minimizing side effects from other events

Scalability: maintains functionality and performance regardless of sensor node growth / decrease

Fault tolerance: Self-configuration allows information to be sent to the destination base station even if some sensor nodes stop working due to faults or errors

Cost: Network configuration with minimum cost while satisfying required function

Domestic and foreign cases applied to industrial facilities are shown in Table 1 below.

Case name Explanation Gas station sensor network The gas sensor network solution using Zigbee technology was introduced to the gas station point-of-sale information management system, enabling network configuration using short-range wireless communication without expensive wired network design equipment. Digital home network SK Telecom installs a gateway in every home and installs a small sensor node in windows, lighting fixtures, gas valves, etc. so that the home uses a remote control with a built-in Zigbee chip. Agricultural product cultivation environment monitoring As a pilot project of the Ministry of Information and Communication, the USN sensor and RFID installed in horticultural facilities participated by Dongbu Information Technology, UCT Korea and Dongbu Hannong Chemical to conduct data collection, field control, field temperature and humidity verification, and data analysis for crop growth. Jeju Coastal Marine Environment Information Collection System Performed a pilot project involving five companies including Jeju Knowledge Industry Promotion Agency for the purpose of collecting and analyzing data such as dissolved oxygen and seawater temperature through USN sensors installed off the coast of Jeju. Free Mobility Auxiliary Project Japan's Ministry of Land, Infrastructure, Transport and Tourism can measure the location of moving objects using photovoltaic networks so that users can acquire the necessary information anytime, anywhere by installing a simple wireless sensor. Industrial remote surveillance systems The US Department of Energy pursues a project to track energy loss and monitor gas use in production using Zigbee sensors to reduce energy costs by up to 15% in steel, aluminum and six other industries. Industrial plant monitoring MITSIBISHI electric research lab (MERL) develops service profiles for industrial plant monitoring and prototypes monitoring systems based on Zigbee technology Gas sensor network A project at the University of Maryland that aims to prevent accidents or terrorism in public places using chemical sensor networks. GASNET project Implement and develop a gas pipeline network sensor system in the US National Energy Technology Laboratory (NETL) to optimize the function of the national natural gas distribution facility structure

On the other hand, city gas facilities (equipment) can be largely classified into piping, constant pressure, valves, T / B (test box), meter, and other, and the environmental factors for this facility are largely environmental, such as earthquake, ground subsidence It can be divided into management factors such as factor, electric method, pressure and gas leak. At present, the city gas facility has introduced a remote monitoring system that measures the operating conditions of the main supply facilities and supply pressure of the pipe network, such as SCADA (Supervisory Control and Data Acquisition) system, to perform data analysis, storage and monitoring functions. .

However, systems that have remote monitoring and control / control functions for city gas facilities exposed to the environment for large-scale excavation construction sites and facilities installed in special sections are insufficient, and provide services by applying wireless-centric ubiquitous technology. There are very few systems. In particular, underground city gas facilities, i.e. buried piping, gas valve rooms, etc., due to the bad condition of the underground closure environment, communication is difficult to apply to the situation has been made only by manual management by people.

The present invention has been made to solve the above problems, and provides an underground city gas facility management system that can remotely monitor the situation of underground city gas facilities to prevent gas accidents in advance and to quickly cope with gas accidents. There is a purpose.

In order to achieve the above object, the underground city gas facility management system of the present invention includes a sensor for outputting sensing data sensing the situation information of the underground city gas facility to the transmitter; A transmitter installed in an underground section and transmitting sensing data input from the sensor to a converter installed in a ground structure using a first protocol having a first frequency; A converter for converting the data transmitted from the transmitter into a second protocol having a second frequency and transmitting the data to a collector; And a collector for transmitting the data transmitted from the converter to a remote server. In addition, it may further comprise a repeater consisting of at least one or more hops to deliver data transmitted from the converter to the collector by relaying using the second protocol having the second frequency.

Specifically, the converter performs a repeater function that connects the ground (transmitter) and the ground (repeater and collector). In other words, the converter is intended to facilitate the communication between the ground / ground.

According to the applicant's test, the transmitter and the relay node were able to communicate over 80m in the 800MHz band, that is, the RF communication protocol. Therefore, it is preferable that the communication frequency band between the transmitter and the converter is 800 MHz or less, and the converter is installed on a ground structure (eg, a power pole or a roof of a building) located within 80m away from the underground city gas facility where the transmitter is installed. Do.

In addition, according to the present applicant's testing, Zigbee (Zigbee) of the short-range communication protocol can be self-configured, and the communication distance is longer than other short-range communication protocol (for example, Bluetooth), the underground city of the present invention It has been found to be most suitable for application to gas facility management systems. Therefore, it is preferable that the communication scheme between the converter, the repeater and the collector is Zigbee.

In addition, if the communication method between the converter, repeater and collector is 2.4GHz ZigBee is applied, it is preferable that the converter converts the frequency band of the signal received from the transmitter to a high frequency (eg, 424.7 MHz-> 2.4 GHz).

On the other hand, a pressure regulator which is a device for stepping down or boosting the pressure of city gas is installed in various places around the road, and generally has a dedicated communication facility for communication with a remote server. Therefore, it is preferable that the collector is installed in the pressure regulator and communicates with the remote server using the communication facility of the pressure regulator.

As described above, the present invention is to build a sensor network in the city gas facilities to monitor the situation of the city gas facilities in real time, to improve the safety and efficiency of maintenance to prevent gas accidents in advance and to respond quickly in the event of a gas accident. To provide.

Hereinafter, with reference to the accompanying drawings will be described in detail for the underground city gas facility management system according to a preferred embodiment of the present invention.

Although the present invention primarily deals with urgent buried pipes, exposed pipes, specific pressure monitoring sections and gas valve rooms, the following Table 2 shows the environmental characteristics and monitorable situation factors of important city gas facilities.

object Classification Usage Definition Environmental characteristics Context Factor pipe Buried piping City gas transport media Piping material
Underground soil conditions
Installation ground state Corrosion state, stress (ground subsidence), earthquake Special section piping Exposed plumbing Piping installed in facilities exposed to bridges Plumbing material
Installation facility state
Traffic condition such as vehicle Temperature, stress, vibration, earthquake Howol plumbing Piping under the target for traversing rivers, railways, etc. Plumbing material
Protective material status
Installation facility state
Power supply status Corrosion state, stress, earthquake, power supply (AC / DC) Other construction exposure piping Piping that has been buried for a long time due to the construction of other facilities Piping material
Protective material status
Construction site situation Shock / vibration (other construction equipment), stress, temperature (fire), earthquake A pressure regulator Earth pressure regulator Supply by reducing the high pressure to medium pressure City Gas Supply Status
Pressure regulator type
Facility installation state
Facility installation ground state
Surrounding Facilities Pressure, flow rate, gas leak, stress, earthquake
Local pressure regulator Decompression at low pressure Valve (Seal) Facility installed for the purpose of blocking gas for emergency or supply reasons Valve type
Facility installation status
Facility installation ground state
Surrounding Facilities
Traffic condition such as vehicle Pressure, gas leakage, stress, earthquake, water level, anticorrosive current Test box Facility installed to measure the electrical condition of metal piping
Consists of piping, anode wire Plumbing material
Underground soil conditions
Facility installation state Corrosion state meter Facility to measure city gas usage Facility installation status Pressure, flow rate, gas leak, temperature Etc rectifier Electric method (external power) DC
Power supply Power supply status Corrosion state, power supply (AC / DC) RTU Pressure regulator facility monitoring / control unit Communication status Communication status, power supply (AC / DC) CNG charging station Compressed Natural Gas Vehicle Charging Station Facility installation state
Facility operation situation Vibration, stress

Table 3 below shows the range and characteristics of situational factors depending on the target facility. In particular, corrosion status may be affected by corrosion resistance, polarization potential, soil resistivity, and interference with other facilities (cross piping, indentation pipe), but it is a useful judgment factor for monitoring the corrosion of pipes due to the number of measurements, inspection and quantification. Is assumed to be anticorrosive.

Measurement factor sensor Input signal Output signal Data type Measure
unit range pressure Digital pressure gauge V.A V.A static Mpa
(kg / cm ² ) Minimum Low Pressure Supply Pressure Regulation
Medium pressure light only has a range regulation Stress Strain gauge V V static Pa
(kg / cm ² ) Safety range: Within 30% of piping material strength
Alarm range: 30 ~ 70% of piping material strength
Warning range: More than 70% of piping material strength corrosion Saturated Copper Sulphate Reference Electrode V V static V National Association of Corrosion Engineer (NACE) standard RP-0169: -85 V cse or less Gas leak Gas sensor V V static ppm 10ppm or more detection and warning 1/5 over LEL vibration Vibration sensor V V dynamic cm / s Safety range: within 0.2cm / s
Warning range: 0.2 ~ 0.4cm / s

There are many different ways to send context information. Communication methods that can be applied to city gas facilities can be classified into short-range and medium- and long-range.

Near field communication includes RF communication, IEEE 802.15 based Bluetooth (802.15.1), UWB (802.15.3), Zigbee (802.15.4). RF communications require 10mW of power and currently have a maximum reach of 500m to 1Km. Zigbee is a near field communication operating at 868MHz, 902-928MHz and 2.4GHz, capable of data transmission at speeds up to 250Kbps and handling up to 255 peripherals. Zigbee's greatest advantage is its self-configurable mesh network configuration. Bluetooth is the industry standard for personal area networks (PANs). Bluetooth allows various devices to communicate with each other using radio frequencies at a safe and low cost. The response angle is wide, and even if there are obstacles in the transmission, it can be transmitted without any problem. UWB was developed by the US Department of Defense for military purposes in the 1950s and has long been banned from commercial use. Since it is remarkably superior in speed and power consumption compared to the existing WLAN, it is very useful for mass multimedia transmission between devices. A wireless local area network (WLAN) is currently used mainly as a communication network between a computer and a peripheral device, and communication is performed through an access point.

Medium / long range methods include Wibro, WiMax, code division multiple access (CDMA), and 6LoPan. CDMA is currently the most widely used digital mobile communication technology in the world. CDMA has the advantage of being communicated nationwide, but there are disadvantages of high power consumption and high cost. Wimax is a long-range wireless communication that supports a wider access area and faster data transmission speed than existing WLAN technology, and it can provide 100Mbps broadband Internet access service in a large area of about 70km radius of a base station. Wibro is a word that refers to the mobile Internet, and it means a data transmission standard technology that is equipped with the most efficient structure for high-speed data transmission without considering voice service. However, Wibro's focus on interactive services centered on urban areas also makes it difficult to apply to industrial facilities.

In view of the above, the characteristics of the site for applying the examined communication methods to the city gas facilities are shown in Table 4 below.

object Characteristic Application method pipe Buried piping for corrosion monitoring Medium / Low Pressure Buried Piping
Normal power supply difficulty
Consider only communication methods on the ground Near
Medium / Long Distance Special section (exposure piping) Average piping length: less than 50m
Open environment
Normal power supply difficulty Other construction exposure piping Semi-closed environment (central road underground)
Constant power supply Gas valve chamber Closed environment
Normal power supply difficulty
Difficult to send radio waves due to concrete / steel lid Near
Medium / Long Distance

On the other hand, the sensor network that can be applied to the city gas facility includes a pressure monitoring sensor network for measuring pressure in a specific pressure section, a vibration / stress monitoring sensor network for monitoring stress / vibration of an exposed pipe, and a gas leak in a gas valve chamber. It can be classified into a gas valve chamber monitoring sensor network and a potential monitoring sensor network for monitoring the corrosion state of the buried pipe.

Among the various pressure ranges, the gas valve chamber was selected for the pressure monitoring sensor network. This is because it is considered as the most difficult point of communication in the pressure monitoring section. In addition, an environment in which a pressure regulator (generally equipped with a dedicated communication facility) exists in a radius of 1 km in the gas valve chamber was selected for pressure monitoring. As a result, it is considered that near-communication communication is appropriate for this environment. In particular, since the gas valve chamber is covered with concrete and steel lids, the communication between the equipment in the gas valve chamber and the equipment in the open area (exterior flat) and the short-range network configuration that enables communication between the devices in the open area should be considered in depth. To this end, the Applicant performed the performance / function experiment in the outdoor laboratory for Zigbee and Bluetooth method that can be configured Star or Mesh network. Specifically, the maximum communication distance between the devices in the open area was measured without installing the antenna, and then the transmitter and the maximum communication distance between the open area receivers were measured by installing a transmitter in the valve chamber (depth of 30 cm). The Zigbee module used for the test is Radio Pluse's LM2400 (Lime). As a result of experiments using the basic functions provided by this device, the maximum output strength is + 8dbm and the minimum input strength is -98dbm. there was. At this time, no separate antenna was used. The Bluetooth module is SENA's ESD 110, which was also tested as a basic function. As a result, the maximum output strength was + 18dbm, the minimum input strength was -88dbm, and no separate antenna was used. 1 is a photograph showing a test site for pressure monitoring, the experiment was carried out in a number of such sites.

Communication method ZigBee Bluetooth standard IEEE 802.15.4 IEEE 802.15.1 Specifications manufacturer Radio pulse SENA product name MG2450 Lime ESD 110 Output
Signal strength +8 dbm +18 dbm Input strength
century -98dbm -88dbm Etc Use default antenna Test
result Open Area Communication Distance About 200m or more 98 m Valve chamber
~
Open area Valve box
OPEN About 150m or more 40m Valve box
CLOSE 7m 5 m

Table 5 above shows the communication distance between the transmitter in the valve room and the receiver of the open area and the distance between the open and open areas when using the basic functions of each communication module. The accuracy of the data transfer is the same in both methods, and the transmission speed is not significant in the current pressure monitoring environment. Emphasis was placed on the communication distance and the possibility of a self-configuring network between nodes when there were multiple nodes. As a result, it was confirmed that Zigbee communication technology is more suitable than Bluetooth environment in this pressure monitoring environment. The reason for this is that although the maximum output signal strength is about 10 times higher than that of Zigbee, it shows shorter transmission distance. On the other hand, even when comparing in terms of minimum input strength, the absolute value of Zigbee is large, which shows that communication can be performed even at weaker signal strength than Bluetooth. In the network configuration, since Zigbee is a self-configurable network configuration among nodes such as multi-hop (mesh) communication, communication is performed from the valve room to the open area, and Zigbee communication is performed in the pressure monitoring environment where multiple nodes should be available. It is considered to be suitable.

The method potential sensor network collects corrosion-related information from the data logger in buried pipelines, and then transmits data to a relay point, eg, a pressure regulator, in a near field communication via an antenna on the ground, and the CDMA of the collector (sink node) at the relay point. The communication method may be a method of transmitting data to a server in a medium / long distance. FIG. 2 illustrates an anticorrosive measurement environment. As shown in FIG. 2, when a rectifier generates an electric current through an anode to allow an anticorrosive current to flow in a buried pipe, the data logger of the test box (TB BOX) is a reference. Measure the potential between the electrode and the buried pipe. Applicant measured the maximum transmission distance and communication success rate by short range communication method in open area using Bluetooth Class 1 and 2, RF and dipole antenna and patch antenna.

Specifically, Bluetooth Class 1 has a frequency of 2.4 GHz, and the output is 63.095 mW (18 dbM). The product used for this test is ESD 100, with a recommended distance of about 300m. In the case of using the patch antenna, it was confirmed that there is a slight directivity because a change in sensitivity occurs depending on the direction of the antenna, communication was good up to about 1.12km when there is no obstacle on the straight line distance. The communication status was impossible when the building was an obstacle, and the communication success rate was about 50% when there were no obstacles such as trees or hills. The same test was performed using a dipole antenna, which showed 80% communication success rate for the patch antenna.

Bluetooth Class 2 is a communication method that has a smaller output than Bluetooth Class 1. The frequency is the same but the output is 2.51mW, which is about 4dbM. The module used for the test is an ESD 200 product with a recommended communication distance of about 100m. The test was carried out in the same manner as Bluetooth Class 1, and the communication was good up to 100 ~ 200m in the straight distance, but the communication itself was not made when the distance was over 500m. When there is an obstacle, the communication success rate is about 50% when there is no obstacle, and when the dipole antenna is used, the communication success rate is about 80% of the patch antenna.

RF testing was performed using a Linkwiser 400 product. The output is 10mW and the frequency is 427MHz. In the straight distance without obstacles, the communication success distance is within 100m. When there is an obstacle such as a building between the RF modules, communication was not possible with Bluetooth, but the RF module showed a 50% improvement in communication success compared to the 2.4 GHz communication. The specifications of the equipment used for the Bluetooth and RF test are shown in Table 6, and the summary of the test results is shown in Table 7.

Communication method Product used Print
(mW) (dBM) frequency
(GHz) Recommended distance
(m) Communication speed
(KHz) Power source
(V) Bluetooth
class1 ESD100 63.095 18 2.4 300 115.200 3.6 Bluetooth
class2 ESD200 2.51 4 2.4 100 115.200 3.6 General RF Linkwiser 400 10 0.427 1.024 5

Communication method Patch type Dipole
type Communication success distance
(Km) Communication failure distance
(Km) obstacle
(building) obstacle
(Trees, hills) Bluetooth
class1 1.12 2 No communication
(When fully blocked) 50% without obstacles 80% communication success rate of patch type Bluetooth
class2 0.1-0.2 0.5 No communication
(When fully blocked) 50% without obstacles 80% communication success rate of patch type General RF 0.1 or less 0.3 Bluetooth contrast
50% improvement - -

The gas valve chamber monitoring sensor network measures the gas leakage, level and current in the gas valve chamber and sends status information to the server. In the vicinity of the valve chamber, a constant pressure may or may not be present depending on city gas company and environment. The present applicant has designed a configuration for transmitting data to the server system using a medium / long distance method in an environment in which the pressure regulator is not in a radius of 1 KM. Thirteen gas valve rooms in the Seoul city gas area that meets these circumstances were selected and tested using CDMA and WiBro which can be used for medium / long distance communication at this time. In addition, since the gas valve chamber is sealed with a steel cover and a single cover and a double cover are used depending on the city gas company and the site, the gas valve chamber is classified into a steel cover enclosed, a single cover sealed, a double cover sealed, etc. Was analyzed.

First of all, in order to analyze whether medium / long distance communication is possible from the inside of the valve chamber, a CDMA transmitter was installed inside the valve chamber, and the current intensity value was investigated using a spectrum analyzer. Figure 3 is a graph showing the results of the current intensity test. As shown in Figure 3, based on the CDMA minimum power strength of -130dbM as a reference, -55 in the full opening, and -67 when the cover in the seal is closed, the last time when the double cover is closed -77 The degree is shown. Theoretically, this shows that CDMA wireless communication is possible in a valve chamber buried underground, and considering that the depth of the valve chamber is about 2m, the possibility of communication is not a problem.

The experiment was conducted using a real commercial network for full-scale mid / long-range communication experiments in the gas valve room monitoring environment. The equipment used for the test was a transmission / reception program, a CDMA modem and a Wibro terminal developed for the gas valve chamber monitoring environmental test. The test procedure confirmed the communication success rate by connecting two wireless modems to two laptops to control data transmission and reception, one experimental set to the valve chamber, and the other experimental set to transmit and receive data from the vehicle. WiBro also performed the experiment in the same way.

As a result of conducting medium / long distance communication tests at 13 locations, CDMA method has all areas and transmitters except when the transmitter is installed at the bottom in the Duckdong door valve room that uses a large outer cover and fastening steel cover. The communication was good at the location. Due to the deeper depth than other valve chambers, Deok-dong door valve chambers are considered to have poor communication.However, in this environment, the installation location is not based on the characteristics of the situation factors (gas leakage, water level, anticorrosive current measurement). Therefore, there will be no problem with communication since it will be the middle point or the top of the valve chamber. The WiBro method was able to communicate in the central Seoul area, and the communication was not possible because the Wibro commercial network did not spread elsewhere.

The vibration / stress monitoring sensor network is applied to one of the major city gas facilities, special zones (bridges, exposed pipes for large-scale excavation works, etc.). For example, the method may be a method of monitoring vibration (vehicle vibration, etc.) and transmitting each data directly to a final data collection device (sink node) or a server using a wireless communication method. Bridge pipes in special sections are always exposed to unexpected external loads due to their characteristics, and their safety is often determined by the status of suspended bridges. In particular, in the area where subway construction is carried out, city gas pipes, water pipes, etc., which are installed in the corresponding construction section, are exposed for a long time. Accordingly, subway construction involves many harmful environments such as ground subsidence, damage during construction, and shock generation, and damages existing buried facilities network, or stops the supply of environmental pollution, electricity, gas, and water supply. There are also a number of cases that spread to three damages. Therefore, in order to reduce and prevent accidents and losses caused by gas piping and facilities, accurate diagnosis of city gas piping and supply facilities in large-scale excavation works (road infrastructure, infrastructure projects such as railroads, subway construction and extension works, etc.) Oversight is required. In order to acquire stress and vibration in the exposed piping, a stress sensor and a vibration sensor are required. Here, a suitable sensor for measuring the stress on the gas pipe is a strain gauge. Strain gauges are generally general-purpose sensors used to measure mechanical strength (stress). On the other hand, the vibration / stress monitoring sensor network 120 is a special section that is usually the target, since it is located at 1km or more with the constant pressure, the medium / long distance method will be applied.

As described above, the city gas facility may be short-range based communication when the location is close to the dedicated communication facility (constant pressure), otherwise the medium / long distance based communication may be applied. Here, the classification reference distance is, for example, 1km, but this can be extended according to the cost reduction and technology improvement.

Near-field communications require devices that can be self-organized and low power consumption in ground facilities and sectors. The purpose of self-configuration is to redirect data transmission paths to their destinations by rescanning adjacent nodes when a particular device is not operating. IEEE 802.15.4 mesh network method and star network method exist as a basis for the self-organization of transmission paths. Devices can be divided into full function devices (FFDs) and reduce function devices (RFDs), depending on their hardware capabilities. In the mesh method, all the devices participating in the network are composed of FFDs that can act as the lower network coordinators. It is not relayed between other devices. The devices included in the network must find a way to use energy efficiently. When the device is running or an event occurs, the device may participate in the network in the wake-up mode, which is active and in the sleep mode, which is inactive. Can be managed. When near field communication is applied to a city gas underground enclosed environmental facility, communication between the underground and the ground should be possible. In particular, since the city gas pipeline is constructed along the road, the data transmitted wirelessly from the buried city gas facility in the vicinity of the road must be able to reach the upper part of the surrounding ground structure (building, power pole) and the like. Normally, since the city gas valve box exists along the road, there is a ground structure within 80 meters of the straight line distance from the city gas valve box.

Medium- and long-range based communication is currently the most popular and safe application of the method, and it should be possible to transmit situational information in both underground and ground. In addition, it should be able to transmit to the middleware server according to the policy or to the collector of the dedicated communication facility.

As a result, the applicable transmission method for each target facility is as follows.

-Special pressure section (eg gas valve chamber) (pressure)

ㆍ Application Method: Near field communication, dedicated communication facility within 1km radius

ㆍ Feature: Low power, ground (self-organizing, multi-hop network), underground (transfer confirmation over 80m in radius)

-Gas valve chamber (gas leak, water level, current)

ㆍ Application Method: Medium / Long Distance Communication, Dedicated Communication Facility with Radius 1km or more

ㆍ Feature: Low power (sleep mode, acquisition mode, communication mode), adjust device attachment position according to purpose

-Buried piping (anticorrosive potential)

ㆍ Application Method: Medium / Long Distance Communication, Short-range Communication, Dedicated Communication Facility within 1km / within radius

ㆍ Feature: Same as valve and gas valve chamber

-Exposed piping for other construction (vibration, stress)

ㆍ Application Method: Medium / Long Distance Communication, Dedicated Communication Facility with Radius 1km or more

ㆍ Feature: No need for low power mode (electricity)

Figure 4 is a block diagram of an underground city gas facility management system according to an embodiment of the present invention.

As shown in FIG. 4, the underground city gas facility management system according to the present invention includes a sensor, a transmitter 100, a converter 200, a repeater 300, a collector 400, and a remote server 500. Can be.

The transmitter 100 is installed in an underground city gas facility (eg, installed in a purge rod close to a gas valve), and wirelessly transmits various situation information of the underground city gas facility input from a gas pressure sensor or the like.

Applicant conducted a test to transmit the measured pressure information to the ground in the underground environment proved to be the worst condition. The test used 2.4GHz Zigbee, Bluetooth, 800MHz CDMA and 424.7MHz frequency bands. In general, the higher the frequency bandwidth, the lower the maximum transmission distance, and the lower the frequency bandwidth, the better the transmission distance. Specifically, in the case of the 2.4 GHz band, the communication distance was short when the steel cover of the valve box was covered (see Table 5), but it was confirmed that the communication was possible over 80 m in the 800 MHz band or less.

As already mentioned, city gas pipelines are generally constructed along roads, with ground structures within 80 meters of the road. Therefore, the transmitter 100 preferably transmits data in an 800 MHz band or less, for example, a 424.7 MHz frequency band, based on the underground closed environment test result.

In addition, the transmitter 100 is operated in a normal mode and a test mode. In normal mode, data is sent from a pressure sensor. When the power is turned on, it is basically set to normal mode. The test mode is a mode for checking the state of a wireless network. In this mode, test specific data is transmitted.

The transducer 200 is installed on the ground and relays radio communication between the transmitter and the collector. In particular, it is preferable to be installed in a ground structure (for example, a power pole or a roof of a building, etc.) located within 80 m at a straight line distance from an underground city gas facility where the transmitter 100 is installed.

In detail, the converter 200 receives information transmitted from the transmitter 100 in the low frequency band (424.7 MHz), changes the information to the high frequency band (2.45 Hz), and retransmits the information. In other words, it participates in the mesh network of IEEE 802.15.4a and serves as a bridge connecting the transmitter using 424.7 MHz and the network using 2.4 GHz. Upon initial power up, the converter 200 requests that other relay nodes or collectors in the vicinity be added to the mesh network. In response to this request, the collector reconfigures the wireless network.

The repeater 300 transmits data received from the converter 200 or another repeater to the collector 400 and supports the IEEE 802.15.4a wireless network. The device is installed in the required location by signal strength test according to distance measurement for smooth data transmission in the network. The repeater 300 also finds another repeater or repeater and requests it to be added to the mesh network.

The collector 400 collects the situation information from the transmitter 100 and transmits the situation information to the remote server 500. In other words, it serves as the network coordinator of the highest level of the entire IEEE 802.15.4a network. It also controls the transmission and reception of data between remote servers and lower network devices and the mesh configuration. In addition, it is installed in the pressure regulator, and transmits data to the data converter 200 using a communication facility of the pressure regulator. It can be connected to remote server through various communication methods such as RS-232C and Ethernet (TCP / IP). At initial power up, the mesh network configuration is checked and the mesh network is reconfigured. In addition, an auxiliary storage medium such as an SD card may be provided to store data.

As the MAC protocol of the mesh network according to the present invention, the basic MAC protocol of IEEE 802.15.4 may be applied. On the other hand, since the collector is fixed as the final destination as the routing protocol, the tree routing scheme is modified and applied accordingly. Specifically, in the routing scheme of the present invention, an equal ratio sequence is applied, and accordingly, a layer is configured according to the signal strength strength (RSSI) and the number of n number of child nodes specified when the mesh network is generated. For example, when three child nodes are assigned to a parent node, the second level hierarchy (one hop) has three nodes, and the third level hierarchy (two hops) has nine nodes according to an equality equation.

FIG. 5 illustrates a tree structure construction and data transmission process of a mesh network applicable to the present invention. A converter, a repeater, and a collector except a transmitter participate in the mesh network as shown in FIG. 4.

As shown in Fig. 5, after the tree routing structure is completed, the transmitter delivers data to the parent node in a unicast manner through the constructed tree, and finally transmits context information to the collector. Each node has information about its parent and child nodes, so there is no need to maintain complex path information for multi-hop routing. The collector can periodically check the bottom nodes to determine whether they are up and measuring the strength of the signal, recognizing the relay nodes as they rebuild the mesh and leave the network.

The underground city gas facility management system of the present invention is not limited to the above-described embodiments, and may be modified and implemented in various ways within the scope of the technical idea of the present invention.

1 is a photograph showing a test site for pressure monitoring.

2 shows an anticorrosive measurement environment.

Figure 3 is a graph showing the results of the current intensity test.

Figure 4 is a block diagram of an underground city gas facility management system according to an embodiment of the present invention.

5 illustrates a tree structure construction and data transmission process of a mesh network that can be applied to the present invention.

*** Explanation of symbols for the main parts of the drawing ***

100: transmitter

200: converter

300: repeater

400: collector

500: remote server

Claims (4)

A sensor for outputting sensing data sensing the situation information of the underground city gas facility to the transmitter; A transmitter installed in an underground section and transmitting sensing data input from the sensor to a converter installed in a ground structure using a first protocol having a first frequency; A converter for converting the data transmitted from the transmitter into a second protocol having a second frequency and transmitting the data to a collector; A collector for transmitting the data transmitted from the converter to a remote server; City gas facility management system comprising a. A sensor for outputting sensing data sensing the situation information of the underground city gas facility to the transmitter; A transmitter installed in an underground section and transmitting sensing data input from the sensor to a converter installed in a ground structure using a first protocol having a first frequency; A converter for converting the data transmitted from the transmitter into a second protocol having a second frequency and transmitting the data to a repeater; A repeater comprising at least one hop for delivering data transmitted from the converter to a collector by relaying using the second protocol having the second frequency; A collector for transmitting the data transmitted from the repeater to a remote server; City gas facility management system, including The method according to claim 1 or 2, The first frequency has a value smaller than the second frequency, The first protocol is an RF communication protocol, And said second protocol is a short-range network protocol. The method of claim 3, wherein the collector, City gas facility management system, characterized in that installed in the pressure regulator to step up or down the pressure of the city gas, and transmits a signal to a remote server using the communication facility of the pressure regulator.

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