China is a country with a high incidence of lightning disasters, and the frequency and intensity of lightning are high. In order to detect potential safety hazards in a timely manner and reduce the impact of lightning disasters on traffic safety and transportation efficiency, a set of lightning protection system power supply departments has been studied and designed.

The mileage of China's high-speed railways has reached 20,000 km, making it the longest-running and largest-scale high-speed railway network in the world. China is a vast country with a high incidence of lightning. The frequency and intensity of lightning are much higher than those in continental Europe and Japan. The railway signal system is responsible for the collection, processing, and control of all kinds of information related to railway traffic. It is an important infrastructure for ensuring traffic safety, improving transportation efficiency, and improving management level. In order to discover potential safety hazards in time and reduce the impact of lightning disasters on traffic safety and transportation efficiency, a set of intelligent lightning protection systems was studied and designed.

1 System Composition
The intelligent lightning protection system of railway signal equipment has been intelligently transformed on the basis of traditional lightning protection. The combination of a new smart lightning protection module and various sensors has provided new functions such as parameter display, comprehensive early warning, and data query to the system. .
Through the establishment of a traceable intelligent platform, the original passive lightning protection can be promoted as an automatic intelligent lightning protection system integrating remote monitoring, historical data viewing, and comprehensive early warning functions. The intelligent lightning protection system consists of an intelligent protection unit, a sensor acquisition unit, a data center, and a monitoring platform, as shown in the figure.
The intelligent lightning protection system shall support the setting of privilege and realize the three-tier management of the railway bureau, electricity operation section and workshop. The system capacity can be configured according to the actual situation on the site.

Smart Protection Unit. It is composed of a power surge protector, a circuit breaker, a status indicator, a power status acquisition module, a surge protector status acquisition module, and an integrated acquisition system that implements thermal trip and overcurrent protection tripping functions. The intelligent protection unit has independent input and output one-input two-output terminal blocks, and the cabinet circuit and the surge protector in series with the circuit breaker for reasonable wiring, to ensure that the intelligent protection unit and the protected circuit wiring meet the "iron mark" is less than The 0.5m requirement suppresses surge overvoltage and overcurrent caused by lightning or other causes in the power supply network and information system, so that the protected equipment is always in a safe state. In the structural design, the intelligent protection unit separates the power distribution part from the lightning protection device and realizes an integral compartment structure to meet the requirements of fault-safety and fire and explosion protection.

Sensor acquisition unit. The high-precision lightning current sensor, chassis temperature sensor and non-contact grounding resistance sensor can be used to monitor in real-time the number of lightning protection surge surge surges, peak lightning current, operating temperature inside the chassis, grounding resistance status, etc. The integrated acquisition system in the intelligent protection unit collects, summarizes, and preprocesses sensor data, and forms a unified format for uploading to the data center.

data center. It is composed of data server, application server and system server software to realize the analysis, processing and storage of monitoring data of each intelligent protection unit, and generate alarm data and forward it to relevant responsible persons. The data center should satisfy functions such as information exchange, resource sharing, fault location, and performance analysis; the communication interface with the upper-level department management information system should be reserved for transmitting the alarm information of the state of the intelligent protection unit.

Monitoring platform. It is composed of monitoring software of intelligent lightning protection system. The railway bureau, electricity service section and shop floor users can configure the right to check the real-time status data of the intelligent protection unit within their jurisdiction. System software can be used on mobile platforms such as PDAs and smart phones according to user requirements.

2 System Functions
The intelligent lightning protection system can monitor the lightning protection status of the signal equipment in real time and alert the maintenance unit so that the hidden dangers caused by the lightning disaster can be eliminated in time and effectively protect the safety of the vehicle. Therefore, the system should have the following functions.

The collection and monitoring of the dual-channel power state, when there is an equal failure, can automatically activate the comprehensive acquisition system to send out sound and light alarms, and transmit alarm information to the data center.
The surge protector adopts an independent SPD monitoring device. When the lightning protection module is struck by lightning, the lightning protection module turns red card, sound and light alarm is issued, and alarm information is transmitted to the data center.
When the operating temperature in the chassis exceeds 80°C, an audible and visual alarm is issued and the alarm information is transmitted to the data center.
The use of high-precision lightning current sensors can not only monitor the number of times the smart lightning protection box is exposed to lightning or surge overvoltage, but also provide lightning current peak recording function according to user requirements to retain detailed data for the site.
The non-contact grounding resistance tester is used to monitor the grounding resistance status in real time. When the grounding resistance is abnormal, an audible and visual alarm is issued and the alarm information is transmitted to the data center.
O&M monitoring function. The system shall have a self-test function. When the smart protection unit and the sensor acquisition unit work abnormally, the system operation and maintenance personnel shall be promptly notified of the fault.

3 System Benefits
The railway signal equipment intelligent lightning protection system conforms to the industrialized Modbus protocol, and can be easily networked through RS-485 and Ethernet. It can remotely and real-timely monitor the operating status of the equipment under its supervision on the monitoring platform, and can analyze and browse historical data. . This system has the following advantages over non-intelligent devices.

Change the original passive equipment maintenance. The original lightning protection system can only find problems in the regular inspection of equipment after a fault occurs. If the problem is not found in time, it will bring great security risks to the normal operation of signal equipment. The intelligent lightning protection system can warn the fault point when the fault has not occurred or just occurred, and promptly notify the maintenance personnel to repair the fault.
Ground resistance can be monitored in real time. The use of non-contact grounding resistance tester real-time monitoring of grounding resistance status, timely warning to the maintenance personnel, can effectively avoid the failure of the grounding device caused by failure to discharge the discharge current, counterattack surge lightning strike accident.
Fire protection function. Lightning protection devices containing varistors deteriorated due to multiple lightning or overvoltage shocks and generated heat, causing secondary accidents that caused fire. A temperature sensor is installed in the intelligent monitoring unit to monitor the working temperature in real time. When the working temperature exceeds the preset threshold, the system will send corresponding alarm information to remind the maintenance personnel to check it in time to eliminate the fire hazard.
Accurately locate the point of failure. The number of surge protectors is large and the installation is scattered. It is impossible to detect whether the function is intact during normal operation. The intelligent lightning protection system can monitor the working status of each SPD in real time. If the device fails to red card, it will accurately locate the fault point and save the troubleshooting time.
Historical data can be traced. The intelligent lightning protection system records all the data of its life cycle, including working temperature, number of lightning strikes, lightning current intensity, lightning strike time, and SPD module status, which facilitates future data browsing and analysis, and provides effective protection for replacing equipment. Data support.

4 Technical Requirements
The surge protector should realize the function of thermal trip and overcurrent protection tripping, and the outer package should all adopt flame retardant materials.
The maximum continuous operating voltage Uc: single 275V, three 275/420V.
Nominal and maximum discharge current In (8/20μs): 20kA.
Basic limit voltage UB (3kA): ≤3300V single-phase series ≤ 700V).
Acquisition frequency: The maximum acquisition frequency of the intelligent protection unit should not be less than 1/s; the acquisition frequency of the sensor acquisition unit should not be less than 1/min.
Ground insulation: In addition to the discharge status of the power surge protector connected to ground, the insulation resistance to ground shall not be less than 1000MΩ.
The system false alarm rate is less than 0.1 ‰.
The system complies with the relevant regulations of electromagnetic compatibility.

5 Summary
To eliminate hidden dangers caused by thunder and lightning disasters on railway traffic safety, to avoid delays in trains and traffic accidents caused by lightning strikes on signal equipment, and to provide timely and effective information for electric maintenance operations and reduce waste of manpower and material resources, and apply intelligent lightning protection systems. Significant. Railway administration departments at all levels should pay sufficient attention. All research and development units should actively carry out systematic research and development and upgrades in accordance with the actual needs of current railway communications work, and provide scientific guarantees for the safe operation of railways.
references [1] People's Republic of China Ministry of Railways. TB/T3074-2003. Railway signal equipment lightning electromagnetic pulse protection technology conditions [S]. 2003.
[2] People's Republic of China Ministry of Railways. Railway Transport [2006] No. 26. Railway Signal Equipment Lightning Comprehensive Protection Implementation Guidance [S]. 2006.
[3] Fu Maojin, Study on Risk Assessment of High-speed Railway Signaling System [J]. China Railway, 2015(11):34-36.