How smart meters prevent lightning strikes

1. Introduction

Most of the industrial computers, various communication modules, security devices and on-site measuring instruments of the intelligent instrument control system use the combination of electronic device integrated circuits . These microelectronic devices usually have insulating Achilles heels such as low resistance and low surge resistance are often damaged by lightning during stormy seasons, which can partially damage the input and output modules of multiple instrument computers, or cause the whole device control system to be crippled and forced to shut down for maintenance, resulting in huge loss. Therefore, it is very necessary to add lightning protection devices to these control and generation devices.

Secondly, the pathway of lightning intrusion

Lightning intrusion causescomputer and communication failures. When the power surge exceeds the computer\'s ability to withstand, there will be garbled data, chip damage, or even damage to software systems that cause interruptions in data reception/transmission.

The research on intelligent instrument control system lightning protection should start from two aspects: external system lightning protection and internal system lightning protection. External lightning protection measures mainly solve the damage caused by the induced lightning strike on the measuring instrument. The main way of surge intrusion is that the signal cable introduces the induced surge into the circuit of the side measuring instrument to damage the insulation, break down the micro-electrical components, cause the failure of the instrument and strike direct lightning toinduction through the meter body and directly enter the instrument circuit, breaking down the circuit module and causing failure. The solution is to reconsider the overall lightning protection measures of the device and the grounding of the signal communication cable according to the requirements of the lightning protection code, reasonable wiring and the grounding of the metal instrument case. For the key lock signal protection system, surge devices should be installed; the internal lightning protection system mainly refers to the lightning protection of the intelligent instrument control system power supply, the grounding of data processing equipment such as the control display unit , the operating system and the engineer station, and access to and from the computer. Lightning protection of signal and m channelsLightning protection measures for switches, network cards, and other LAN-related signals and power supplies.

3. How to prevent lightning strikes

3.1 Improve the grounding system

(l) Safety protective ground, control cabinet , operating table, engineer station, power supply cabinet, etc. The chassis masses are all connected together by flat steel.

(2) The signal ground of the instrument and the input and output signal ground of the computer are reference points for the measurement of the instrument.

(3) Intrinsically safe grounds, safety barriers, isolation barriers, safety devices and other grounds should also be connected to the signal reference point of the instrument to form an equipotential system.

3.2 Leisure source anti-surge

The power supply of the intelligent instrument control system inbe in the main computer control room from the power distribution system. The power system is used by the power plant instrumentation system through the transformer and the power distribution system. In stormy weather, the power supply is transmitted in the circuit due to the long path, and it is very likely to be struck by lightning. Therefore, the power supply at this time is not 380v or 220v, 50Hz AC. This is a power surge mixed with various encumbrances. If the surge protection system is not installed, the electrical equipment used will cause accidents due to exceeding the withstand voltage limit. A, B, C, and D which come from the main power distribution. The four-phase wires are connected to the A, B, C, and D terminals opposite the surge. During a thunderstorm, the lightning-induced overvoltage is protected by the surge protector pto transfer the overload current to the ground, and the output voltage is clamped in the safe working area to ensure the safe operation of the power supply. The surge suppressor system of the power supply is shown in Figure 1.

3.3 Signal channel surge device

The signal channel surge device shall provide transmission accurate, stable and flexible of all kinds of the instrument\'s detection information under normal conditions, and it can also eliminate power surges in stormy weather. The surge is discharged to the ground, and the output voltage is fixed in a safe area, thus ensuring the safety of signal transmission. From the effect of use, installing a surge protector greatly improves the safety factor of smart meters in storm weather. The signal lightning protection system is shown in Figure 2.

The following factors should beconsidered when applying lightning protection products:

(l) Regular inspection and maintenance of instrument control system engineering power system grounding, busbars , grounding body rust, breakage and other defects, repair it in time to restore it to normal, and regularly check the resistance (resistance should be kept at 1). If it is found that the resistance value is increasing, the reason should be found out and the resistance should be reduced.

(2) Perform annual inspection on the surge device in proportion. Since the surge device is used for a long time, the working voltage of electronic equipment will drop due to aging, resulting in unqualified lightning protection parameters.

(3) Lightning protection grids are generally used inpower distribution systems. There are many products with alarm devices. Once the lightning protection grid overheats, the device will automatically disconnect and send out alarm signals such as photoelectric sound. Its appearance and ground leakage corrosion should be checked regularly. When selecting a surge protector, pay attention to the load size and choose an appropriate surge protector.

3.4 Review example

The SKT-H5 automatic flexible packaging underwrapping machine purchased by Quickstar Viscose Industry Co., Ltd. of Germany Profil-Clip GmbH uses a frequency converter from Siemens The wiring diagram of the company\'s 420 frequency converter is shown in Figure 3. is displayed, indicating that it was due to a power surge. During this period, three frequency converters burned out. The system does not useno lightning protection technology. After adopting the power supply anti-surge system shown in Figure 1, the same kind of failure phenomenon did not occur again.

Four. Conclusion

In order to make the intelligent control system of industrial production instruments safe and reliable, it is imperative to learn and learn advanced lightning protection measures and select products of high quality lightning protection.

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