In modern industrial age, the use of electric energy has a higher status in the production and operation of enterprises. In order to ensure the safe and stable operation of the power distribution cabinet in the power distribution room, and to improve the repair accuracy of the staff when an error occurs. This paper designs a monitoring system that collects the internal status data of the power distribution cabinet. This design is based on the STM32 of ARM Company, which can control modules to collect various kinds of data such as voltage and current, temperature and humidity, smoke concentration, etc. Then upload the data to the monitoring cloud platform through 4G Cat1 module. The user can monitor the status on the WeChat applet. When the data is abnormal, the terminal automatically alarms and sends a short message to the control personnel, so that the staff can quickly fix the machine and reduce the economic loss of the enterprise.
With the development of society and the progress of human society, the annual electricity
consumption is increasing exponentially. As the tail end of the distribution system of the power grid,
the performance of the distribution cabinet has a crucial impact on the safe and stable operation of the
local power system [
The internal state data acquisition system terminal of the electric cabinet designed in this paper can obtain the electric energy parameters and non-electrical energy parameters inside the electric cabinet in time. When the parameters are abnormal, there will be a voice alarm, which can make the staff aware of the equipment failure at the first time, increase the repair efficiency, reduce the workload of manual inspection on site, and ensure the safety of enterprise production and people's life.
The internal situation monitoring system of the smart electric cabinet designed in this paper is composed of four parts: front-end data acquisition equipment, Internet of Things communication transmission, cloud platform server and user terminal.
The front-end data acquisition equipment is designed to install a data acquisition terminal in each
power distribution cabinet to collect internal electric data and environment data. These data are
transmitted to the cloud platform server using the 4G cat1 communication module with MQTT protocol
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user terminal
Considering the requirement of the high performance, low cost and low power consumption of the
design, the data acquisition equipment of this design selects the STM32F103ZET6 chip of ST
Semiconductor Company as the microprocessor. Its core is an ARM32-bit Cortex-M3 CPU whose
highest operating frequency is 72MHz, and it has abundant I/O ports and communication interfaces [
This system selects SUI-101A AC energy metering module to obtain electrical parameters such as voltage, current, active power, etc. The transmission accuracy of current and voltage measured by SUI101A can reach ultra-high precision of 0.2 class. It is connected with MCU（Microcontroller Unit） through TXD and RXD, as shown in Figure 2.
The module obtains the current and voltage signals from the load line through the built-in current and voltage transformers and sends them to the 24-bit high-precision ADC for processing, and then sends the waveform data to the 8-bit microcontroller to calculate the current, voltage and other parameter values, and finally transmitted to STM32 through the serial port for data analysis.
The monitoring system terminal data standards are as follows:
1. Electric power monitoring standards. At present, most of the power distribution rooms are 220V
or 380V low-voltage power distribution cabinets. The voltage on the primary side can be
directly measured, and the current on the primary side needs to be converted into a secondary
side measurement current of 5A/1A. This paper takes the rated 220V, 5A, and the power factor
of 1.0 as an example to monitor the voltage, current and active power in the power distribution
cabinet in real time, and the accuracy error of the measured value is required to be no less than
0.2%.
2. Air temperature and humidity adjustment standards. According to the national standard for
lowvoltage complete sets of equipment (GB7251.1-2013) [
At the same time, the average temperature difference in one day shall not be higher than +35℃. 3. Smoke concentration standard. The range of detectable combustible gas and smoke of MQ-2 smoke sensor is 100-10000ppm, Therefore, when it is detected that the smoke concentration in the power distribution cabinet exceeds 200ppm, a voice alarm is activated, and a short message is sent to notify the maintenance personnel to check whether the cables and wires wrapped with rubber skin inside the power cabinet are damaged.
In this experiment, the power distribution cabinet in the school laboratory is selected for testing. To ensure the safety of electricity and personnel, the power data collected in this experiment are normal safety data, and will be further tested in a professional and safe environment in the future; Taking the normal environment as a reference, the temperature and humidity changes are changed by the flame of the lighter and the placement of the ice pack, so as to trigger the abnormal temperature and humidity alarm; To detect the status of the wires and cables in the power distribution cabinet, the burning waste rubber skin is used to simulate a fire and trigger the smoke concentration alarm.
With the rapid advancement of the country's 5G construction, it is the general trend that 2G and 3G
will withdraw from the stage [
This paper selects ATK-IDM750C module as the communication module. It is a high-performance full Netcom 4G Cat1 DTU product that can hold 4G mobile phone cards. It is applied in occasions with low bandwidth rate requirements with the advantages of low latency and low cost, and can quickly solve the wireless data transmission solution in the application scenario.
It supports connecting to various cloud servers (such as Tencent Cloud, Alibaba Cloud), supports AT commands/SMS, and supports MQTT data transparent transmission. Data transmission is shown in Figure 5. In MQTT transparent transmission mode, serial data can be sent to the MQTT server through DTU.
Serial communication Send serial
data MCU
ATK-IDM750C Cat1 DTU 4G wireless communication DTU packages MQTT data and publishes it to the pub topic
Publish topic: pub
MQTT Server
Server receives data
The overall architecture of the software design is shown in Figure 6. After the system is powered on, the single-chip microcomputer first initializes the sensor module, obtains the environmental data information inside the cabinet, and compares the collected information with the set threshold. If the data parameters are not within the threshold range, a voice alarm will be sounded immediately, the data will be sent to the cloud platform through the communication module, and the management personnel will be notified by SMS to check the abnormality.
Module initialization Electric energy data collection
Temperatureand humidity data collection
Smoke concentration
collection Isthe data within the threshold?
Y
N Trigger alarm and report to cloud platform and send SMS
periodically
The compilation of the hardware control program is written using KEIL5 software, which is the best
development tool for Cortex-M core processors. In order to make the work between each functional
module of the system independent and improve the effective utilization of CPU, the UC/OS-III
embedded system is transplanted into STM32 [
MQTT is a low-overhead, low-bandwidth instant messaging protocol. Its biggest advantage is that it can provide real-time and reliable message services for remote devices with very little code and limited bandwidth. MQTT is widely used in Internet of Things, mobile applications, etc.
The MQTT workflow is shown in Figure 7. First, the subscriber subscribes the topic to the server and waits to receive the message; then, the server receives the message published by the publisher and determines the topic of the message. If the message topic is consistent with the topic subscribed by the subscriber, the message is forwarded to the subscriber to realize the delivery of the message from the publisher to the subscriber.
The MCU communicates with the ATK-IDM750C through AT commands, and the message quality
QoS selects QoS0 that is distributed at most once. The terminal will collect data to the 4G module
through the serial port. The 4G module uploads data every 5 minutes. The PING heartbeat request
interval is 1 minute. When there is no message to send, a heartbeat packet [
Publish topic: pub Message : specific data
Broker
Subscribe to topics: sub
Topic: pub
Message : specific data Publish
Subscribe
The user terminal can view the data through the WeChat applet. The interface during the test is shown in Figure 8. (a) shows the interface when the data is normal. (b) shows the interface when the smoke concentration exceeds the standard. (c) is the SMS reminder interface received when the data is abnormal. (c) Figure 8: (a) Data normal interface, (b) Data exception interface, (c) SMS interface.
This paper introduces a monitoring system based on STM32 for collecting internal status data of
power distribution cabinets. Through the intelligent terminal installed in the power distribution cabinet,
the electric data of the cabinet can be automatically collected and analyzed, and the parameters such as
humidity and temperature of the environment can be automatically identified. When the collected data
exceeds the set limit, the system will trigger an alarm. After receiving the alarm information, the staff
can eliminate potential safety hazards in time, which significantly improves the safety of the power
distribution cabinet. It can also reduce the workload of on-site manual inspections, increase the work
efficiency of staff, ensure the safety of electricity consumption of personnel, and actively respond to
the unattended management direction of the power distribution room advocated by the state [
In the future, this design plans to increase the image acquisition function and realize the network long-distance transmission function of the image, which can enable the staff to view the internal status of the power distribution cabinet more intuitively. It is also planned to connect the system to the network alarm device, and notify the relevant departments for rescue as soon as a fire or other major accident occurs to further improve safety. 6. References