Technology for handling lightning protection measures in telecommunications center data centers
Most telecommunications network systems are high-precision electronic devices with poor ability to withstand lightning currents, resulting in a high probability of lightning accidents; Moreover, the telecommunications network system requires smooth operation 24 hours a day ago, with workstations and servers connected through twisted pair cables. Once struck by lightning, it will seriously affect the normal operation of the network, as well as hardware damage and data loss. Therefore, it is necessary to take lightning protection measures for the telecommunications system center computer room.
The main focus of lightning protection for the telecommunications system center computer room is diversion and voltage equalization. Diversion is to allow lightning current to enter the ground through various channels outside the computer room, with minimal or no entry into the computer room; Equal voltage is to maintain the equipotential between various devices as much as possible, and to maintain the equipotential of the power supply ground, protection ground, and lightning protection ground. According to the relevant standards of IEC, VDE, and GB. We mainly carry out lightning protection measures for the telecommunications system center computer room from the following aspects.
1, The protection of weak current equipment in power systems is mainly based on the strategy of cutting off the induction source and focusing on protection, which suppresses instantaneous overvoltage and current to the computer, communication, and instrument equipment to withstand a high safety state due to its low operating voltage (a few volts or more), small current (milliampere level), and high frequency. Its ability to defend against overvoltage in power lines is much lower than that of power equipment and power lines. The principle of graded protection of lightning arresters: The International Electrotechnical Commission (IEC) defines the protection zones for lightning protection. According to the requirements of the protection zones, corresponding lightning arresters need to be installed at the junction of each zone, that is, the first level is a B-level lightning arrester, the second level is a C-level lightning arrester, and the third level is a D-level lightning arrester. Its working principle is to use graded lightning arresters to release the energy induced by lightning in layers, gradually reducing the surge voltage and protecting user terminal equipment.
A. The first level (B level) lightning protection is installed with three sets of power SPDs at the low-voltage power output terminal of the transformer (i.e. at the main distribution box of the machine room's mains power input), with a maximum current capacity of 50KA (10/350) μ s) The protection level is less than 4KV. If the switch type SPD and voltage limiting SPD are cascaded and the spacing is too small, a series decoupling device should be considered.
B. The second level (Level C) lightning protection is installed with a power SPD at the input end of the three-phase AC power supply in the computer room, with a nominal discharge current of 40KA and a maximum discharge current of 80KA. The voltage protection level is less than 2.5KV.
C. The third level (D-level) lightning protection is installed at the power input end of important equipment in the computer room (such as programmable switches, servers, transceivers, etc.) with a single-phase SPD power supply. The nominal discharge current is 20KA, the maximum discharge current is 40KA, and the voltage protection level is less than 1.8KV.
2, Lightning protection for signal lines. LEMP enters external signal lines through electrostatic induction, high potential counterattacks, direct strikes, and other methods before entering the equipment, causing serious damage to the interface and equipment. This is because information lines are numerous and long, easy to sense, and generally adopt protective measures such as shielding, grounding, and installing lightning arresters.
3, The equipotential laying and grounding system is laid under the anti-static floor of the computer room, and 30 * 3 purple copper strips are laid along the cement floor around the computer room to form an equipotential connection ring busbar. As the grounding device of the entire computer room, the equipotential connection ring busbar and the grounding terminal must be connected in both directions. The metal shells of all equipment in the computer room must be connected to the nearby grounding system. At the same time, connect the protective ground of the equipment, power PE line, anti-static floor bracket, shielding groove for power and network lines, doors, windows, ceiling suspended ceiling, exchange cabinet, power lightning arrester, signal lightning arrester, ground wire, etc. to the nearest equipotential connection ring busbar. The grounding wire adopts the Φ 6-10 square meters of stranded copper wire, forming an equipotential system for all equipment in the computer room. For computer rooms without anti-static flooring, copper strips should be laid around the walls inside the computer room. Then, connect the protective ground wire of each device to the equipotential strip nearby. Thus achieving comprehensive equipotential, eliminating lightning counterattacks, and protecting the safety of workers.
4, Shielding measures. The impact of lightning electromagnetic pulses on equipment is mainly coupled in the form of fields and circuits. The basic measure to reduce electromagnetic interference is shielding. In order to reduce the lightning induction effect, external shielding, laying of lines in appropriate circuits, and line shielding slots should be jointly adopted; Therefore, it is inevitable to use metal shielding materials to absorb or reflect electromagnetic interference and overvoltage energy in order to attenuate them.
(1) For the shielding laying of the line, a 50 * 50 * 0.5 white iron wire slot is used to set up along the line. The signal cable is placed in the slot for protection, and the two ends of the slot are firmly connected to the grounding grid to ensure good grounding; This can reduce the high-frequency interference voltage generated by lightning electromagnetic pulses on the circuit by two orders of magnitude.
(2) The shielding treatment for the walls of the computer room generally adopts the method of metal woven mesh shielding grounding or aluminum alloy plastic plate decoration grounding for protection. At the same time, the process is required to be beautiful, and there should be no less than 4 reliable connections between the metal woven mesh or aluminum alloy plastic plate and the grounding device.
5, Other handling measures. The correct location of the computer room and the appropriate distance between equipment placement are equally important in lightning protection treatment. According to the requirements of IEC lightning protection standards, it is generally safer to choose a floor below the top four floors in the computer room, because the higher the lightning current diversion coefficient, the stronger the magnetic field strength generated, and the greater the degree of equipment damage.
