1、The status of foreign electric tunnel monitoring
In the field of electric tunnel construction and its operation monitoring, Western Europe and Japan are the world leaders. They have succeeded in constructing large cross-section, long-distance, high-voltage level electric cable tunnel that can be used under special circumstances (such as the seabed, bridge, etc.) (such as the Britain France Dover Strait tunnel, length of 48.5km, laying 220kV multi-parallel lines cable; Japan Tokyo Bay tunnel, length of 9.4km, laying 77kV cable, and set aside 500kV cable channel). What’s more, they have done innovative works in the conventional monitoring of urban cable tunnel (Southport firepower 3.4km long range transmission cable lines of the Kansai electric Power Company, using indirect water cooling system).
Take the downtown electricity tunnel in London for example, the tunnel length is 10km, located in the underground of the busy commercial district. In the 1990s, it was built in accordance with the grid upgrade of the city center and the construction of underground substations. Until now, it has been laying 132kV 4 parallel lines cable and 66kV six parallel lines cable; in terms of electric tunnel monitoring, this tunnel deployed distributed optical fiber temperature measurement system and gas sensing system, which can not only improve its capability of fire warning, but also preliminary achieve the real time monitoring of cable current carrying capability through the real-time online temperature measurements of the cable.
2、The status of domestic electric tunnel monitoring
Since the first domestic power tunnel was completed, its monitoring methods has undergone stages of artificial monitoring, semi-artificial monitoring and simple linkage control monitoring. Currently, it is making a big step forward towards integrated intelligent control stage.
Ever since the 1980s, the State Grid had been tried to construct electric tunnel, but most electric tunnel didn’t have monitoring devices at that time, the status monitoring of the tunnel and cable can only be done by manual inspection (inspection contents include that if there are external damages or potential dangers, whether the tunnel entrance is intact and there are no obstacles, inside the tunnel what is concerned about is whether the cable location is normal, the cable sheath, armored and sheathed with or without corrosion, with or without injury and mouse biten phenomenon, whether cable terminal insulating sleeve is intact, clean, with or without signs of flashover discharge, cable wire, lead white and ground distance comply with the requirements, the ground wire is intact, whether oil-filled cable, especially the cable connector is leakage, whether the cable color is obvious, temperature and humidity inside the tunnel is normal or not, if there is water or debris, cable bracket is solid or not, with or without corrosion and loosening, fire-proof、ventilation、drainage and other facilities are perfect or not, etc.).
In the 1990s, there were fire accidents occurred in the electric tunnel (especially tunnels laid with oil-filled cables), so the State Grid used the development of the cable tunnel monitoring in domestic and foreign countries for reference and gradually set up the necessary fire alarm facilities in the new power tunnels. In addition, the State Grid made certain renovations to the original cable tunnel and supplemented with periodic manual inspections.
Nowadays, all kinds of functional devices for the main purpose of fire warning and fire control (such as various types of temperature fire alarm systems, fire and ventilation linkage systems, and communication systems linkage, etc.) have been gradually used in the cable tunnels of the State Grid. To further ensure the safe operation of electric tunnel, the State Grid has gradually started to experimentally coordinate and integrate all the separated devices. However, as there has not yet been formed a systematic network of tunnels, the electric tunnel in different regions are constructed solely according to their own needs and characteristics, adopting one or more monitoring or control devices. These monitoring devices independently complete their specific functions, while lack of necessary inter-connections and effective coordinations, as a result, they can not achieve information sharing.
3、Solutions
Beijing Oriental RayZer Technology Ltd.’s electric tunnel integrated monitoring system is an integrated monitoring platform, which is in the leading domestic level. The system is constructed according to the characteristics of the electric tunnel and it organically integrated all of the monitored objects in the electric tunnel. The system uses advanced industrial field bus and data service bus, has the function of layed downgrade. It can be seamlessly attached to the power distribution and production control management systems. Currently the system includes five subsystems ----cable multi-state on-line monitoring, tunnel environment online monitoring, online monitoring of tunnel safety, intelligent video surveillance and tunnel traffic monitoring.
Through high-precision current transformer, cable Multi-state online monitoring subsystem realize the acquisition of the cable ground current; by DTS distributed temperature measurement, the host make the entire real-time monitoring on the skin temperature of cable inside the power tunnel ; at the same time, according to the measured skin temperature and cable characteristics , uses advanced dynamic current capacity calculation module, then calculates the real-time conductor temperature and dynamic current capacity of the cable, thus provide accurate information for the scheduling of power management sector.
Tunnel environment online monitoring subsystem measure the ambient temperature of the cable tunnel by DTS measurement host, meanwhile comprehensively monitoring the equipment states, like the combustible gases inside the tunnel, harmful gases, oxygen concentration, fans, smoke, humidity, water level, water pumps, fire doors and so on. When an alarm occurs, the subsystem will make the remote linkage with relevant equipments in real-time.
Tunnel safety online monitoring subsystem mainly make real-time status monitoring for covers and entrances, making infrared intrusion monitoring and alarm for key monitoring cites.
Intelligent video surveillance subsystem is mainly focused on the tunnel video, capture and playback of the key parts of tunnel.
Tunnel traffic monitoring subsystem is applied for the tunnel wired intercom and regional broadcasting.
Subsystems can be switched by the system-oriented interface.
