Application of LoRa ultra-long-range 470 module in fault indicator

The power outages we have experienced were not too long, and any power grid failure in the city would be promptly remedied by repairmen. However, if the electricity transmitted across mountains and rivers to counties and towns was cut off, the line inspectors would have to follow the rivers and mountains to investigate. In ancient times, beacon towers have been replaced by radios at border posts. Now, wireless fault indicators have also built new beacon towers in smart grids.

Figure 1 Electric towers among mountains and rivers

my country's suburban and rural areas are vast and the settlements are scattered. The transmission lines covering the central cities are long and the environment is harsh. Manual maintenance is dangerous, inefficient and costly. According to the plan of the State Grid, 120 billion yuan has been invested in grid transformation in the past three years (2017-2015), mainly for Class D and E users (suburbs and rural areas), of which 20 billion yuan has been invested in distribution automation transformation. In the next three years, this trend will continue and deepen.

Figure 2 Fault indicator for overhead cables

Therefore, real-time monitoring of the operating status of large-area power grids, accurate knowledge of fault nodes and fault types, and the formation of a closed-loop automated repair indication system will have a direct impact on the intelligence level of smart grids, and there is a huge market involved.

Grid Fault Indication System Structure

The power grid fault indication system has three layers, namely the fault collection layer, the data transmission layer, and the background monitoring layer. It consists of two parts: the fault collection sensor and the display. The sensor is responsible for detecting the current passing through the cable, and the display is responsible for judging the current information transmitted by the sensor and making fault indication actions. The judgment result is directly transmitted to the background monitoring layer through the data transmission layer, and maintenance personnel are directly dispatched to the fault node for emergency repair. The block diagram of the power grid fault indication system is shown in Figure 3.

Figure 3 Block diagram of power grid fault indication system

Due to the harsh working environment, the fault indicator needs to have the following three characteristics:

1. Low power consumption and long-term online operation

The use of protective coatings and shell materials can adapt to various environmental conditions, such as immersion in water, high salt spray and extreme heat and cold conditions, and can be installed outdoors or in cable branch boxes for a long time, requiring low power consumption of the equipment;

Figure 4 Fault indicator on overhead cable

2. Long and short distance fault indication

The fault information can be transmitted to the gateway through wireless transmission and summarized to the background to assign maintenance personnel. At the same time, it must be equipped with a high-brightness LED. When searching for faults and patrolling the lines at night, the fault alarm location can be accurately found within a range of 300m.

3. Automatic reset of fault indication

After a fault occurs, it will automatically reset at the set time in the absence of current and voltage, and will automatically return to normal state when power is supplied next time. At the same time, the abnormal information and reset state will be transmitted to the background through wireless communication.

Wireless data transmission layer solution:

Figure 5 ZM470SX-L data transmission scheme

Advantages of ZM470SX-L for power grid fault indication system

1. Low power consumption

The module integrates a +12dBm adjustable power amplifier and can achieve a receiving sensitivity of more than -110dBm. The link budget can meet most short-distance communication needs. It integrates the industry-leading power consumption control technology to minimize the power consumption of the module, making it very suitable for low-power applications with high power consumption requirements.

2. Industrial-grade quality, anti-interference

lIndustrial-grade quality can cope with various harsh environments such as high salinity, high temperature and humidity in coastal areas to ensure stable transmission.

3. Transmitting power is adjustable in multiple levels

The module integrates a power amplifier with a maximum power of 12.5dBm and provides multiple adjustable power levels from -8.5 to 12.5@Step 3dB. The signal coverage can be freely adjusted according to the remoteness of the fault indicator placement.

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In addition to being used at the branches of overhead cable feeders, the power grid fault indicator can also be directly installed on box-type transformers, various ring network cabinets, cable branch boxes, and substation inlet and outlet lines.