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Analysis of cable anti-theft technology and application requirements in different fields

Analysis of cable anti-theft technology and application requirements in different fields

  • Time of issue:2021-12-21

Analysis of cable anti-theft technology and application requirements in different fields

  • Time of issue:2021-12-21

The perimeter alarm system uses technologies such as microwave, active infrared, electronic fence, etc. to form a visible or invisible "protective wall" at the protected boundary. When a wall-crossing behavior occurs, the detector in the corresponding defense zone will send an alarm. The signal is sent to the alarm control host of the control center, which displays the alarm location while giving out sound and light warnings. It can also be linked to the perimeter analog electronic screen, and even linked to the camera monitoring system, access control system, strong electric lighting system, etc.
In recent years, the perimeter defense system has become a basic and indispensable security subsystem of the security system. It is not only visible in high-end fields such as military factories, military camps, airports, ports, and government agencies, but also widely used in residential communities. , And maintain a very high application growth rate in these areas. Cable anti-theft is a common technical application.
   Several common cable anti-theft technologies
   1. Power line carrier communication monitoring system anti-theft
   Power carrier is a concept derived from the interdisciplinary of power and communication. The power carrier communication method (as shown in Figure 1) uses signal transmission in the wire and cable anti-theft system to load the detection carrier signal on the cable within the detection range, and the alarm of the monitoring center is connected to the carrier signal on the monitored cable. The cable outlet section causes the signal transmission to be interrupted. If the alarm fails to receive the signal, it will automatically alarm and play a warning role. The power line carrier communication method is currently the most widely used anti-theft method, because it transmits the carrier signal on the monitored cable and does not require additional lines. Therefore, the power line carrier communication method has the advantages of easy installation, concealed detection, and wide monitoring range ( Up to several kilometers) and other advantages. However, because the cable can only be stolen by alarm but cannot deter criminals, and video image forensics cannot be obtained, a single power carrier communication is facing the challenge of integration and systemization.
   2. Capacitance detection and monitoring system anti-theft
The principle of the capacitance detection method is to first use a pair of vacant cables to short-circuit the cable terminal, and connect the other end to the multi-resonance of the alarm. When the cable is working normally, the oscillator of the alarm does not vibrate; when the cable goes out of the section, it is vacant. The cable becomes a simple capacitor, the oscillator will output a signal, causing an alarm, and the frequency of the oscillator's output signal varies with the position where the cable is cut. Figure 2 shows the basic model of the capacitance detection method.
  3, current detection type monitoring system anti-theft
   The system judges the integrity of the cable system by detecting whether there is transmission current in the cable loop on-line. That is to say, when the cable is working normally, the detection system has no response; when there is no current transmission in the cable, the detection system will activate the alarm system. The current detection system cannot be used in cable anti-theft systems with voltage but no current, such as subway tunnels or highway tunnel blower power cables. In addition, the system can only alarm when all the branch cables of the circuit system are cut off (because the total current of the cable loop is zero when all the cable branches are disconnected). Therefore, the current detection type monitoring system has the hidden danger of "not reporting when there is an alarm".
   Cable anti-theft technology application requirements analysis in different fields
   1. Underground cable for street lamp anti-theft alarm
   With the rapid development of the national urban-rural integration, the rapid development of municipal construction has been accelerated. Street lamps are the main body of urban night landscape lighting, and they carry an important role. The cables for street lamps have now basically turned from overhead laying to buried laying. The buried laying of street lamp cables mainly includes: direct buried laying, pipeline laying, and cable trench laying. No matter what kind of installation, there is a hidden danger of being stolen, which will lead to serious consequences such as economic loss and public security disorder.
An ideal anti-theft system with buried cables for street lights. The most important requirement is that the alarm and anti-theft system requires no power supply at the end during the time when the lights are turned off; when the lights are turned on, the alarm and anti-theft system should be Etc.) No direct relationship. Use as many lines as possible to communicate with the control room through a main control device through communication equipment.
  2, highway power cable anti-theft alarm
  The expressway mainly uses power cables, and one of the core problems in the research and development of the expressway cable anti-theft alarm system is the signal detection when the cable is abnormal. In view of highway cable requirements, the main requirements of the anti-theft system are: availability, reliability (low false alarm rate), advancement (alarm differentiation), scalability (networking with high-speed traffic police system), etc. At present, the power line carrier communication method is mainly used, but there are still the following problems to be solved:
  The transformer of the distribution system has a blocking effect on the power carrier communication information;
  The three-phase power system in the circuit has a signal loss of 10-20dB. When the communication distance is relatively short, the general carrier signal can only be transmitted on a single-phase line;
   The power line has its own pulse interference. The frequency of AC power in our country is 50Hz. If there is a secondary peak in a single cycle of the sinusoid, then secondary pulse interference will occur, that is, there is 100Hz pulse interference on the power line, which is its inherent property;
  Different signal coupling methods correspond to different power carrier communication signal losses;
  The power line can cause the data signal to be deformed.
In summary, the points mentioned above are the directions worthy of research and development of the power carrier communication method in the cable anti-theft system. This also shows that the technology of the power carrier cable anti-theft system in my country is not fully mature. The best cable anti-theft system in China is a certain An enterprise producing anti-theft cable systems in Hangzhou.

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