Research on 5G+ horizontal balance monitoring system to improve the operation safety of vehicle-mounted mobile substation

0 Introduction

A mobile substation is a small mobile substation with a compact structure, convenient transportation and quick installation. The electrical equipment mainly consists of high-voltage switches, current transformers, pressure transformers, isolating switches, grounding transformers, main transformers, station transformers, low-voltage switch cabinets, AC and DC systems, secondary protection, and monitoring systems. The whole is mounted on a mobile flatbed truck. It has a wide range of applications and can greatly improve power supply reliability, shorten the power outage time of key power users, and effectively reduce their economic losses [1]. In the power system, the operation safety of substations is very important. The equipment in the substation also has very high requirements for foundation balance, especially the main transformer, the most important equipment in the substation. The horizontal balance of its operating environment directly affects the operation stability of the main transformer body and the gas relays, gas relays and other equipment configured in the decomposition switch. The vehicle-mounted mobile substation equipment is mainly configured on a flatbed truck, relying on multiple hydraulic support rods configured on the flatbed truck to maintain the horizontality of the equipment operating foundation surface, so that the electrical equipment can operate stably on the same horizontal plane.

1 Problem Analysis

1.1 Structure of vehicle-mounted mobile substation

The equipment configuration diagram of the mobile substation is shown in Figure 1 and Figure 2. The high-voltage part generally adopts the line-to-line connection form, with a high-voltage incoming line connected to a double-coil three-phase non-excited step-down transformer; the low-voltage part adopts a single busbar connection method, and the equipment adopts a metal-clad fixed central switch cabinet, with low-voltage feeder intervals, transformer intervals, used transformer intervals, and main transformer low-voltage switch intervals.

Figure 1 Layout of transformer car

Figure 2 Distribution car layout

The main transformer is equipped with PCS978 power protection, which mainly includes differential protection, compound voltage blocking, overcurrent, etc. At the same time, it is equipped with non-power protection, including main body heavy gas, main body light gas, loaded heavy gas and light gas, main body and loaded pressure release, etc. All kinds of protection can realize the rapid judgment and elimination of faults when the vehicle-mounted mobile substation is in operation.

1.2 High requirements for levelness

The distribution car is equipped with main transformer protection and control, telecontrol host and various outgoing line equipment protection and control devices. These devices are microcomputer-based devices with high requirements for the operating environment. Once a balance problem occurs, it will bring risks to the operating stability of these devices.

Since the main transformer is an oil-insulated device, its non-electrical quantity protection realizes real-time protection through the internal oil flow rate, gas volume in the oil, and internal oil pressure. If the transformer car is unbalanced or tilted, it will cause changes in the internal oil level, oil pressure, and oil speed, and there is a risk of misoperation of the protection. Once the non-electrical quantity protection misoperates, the switches on both sides of the main transformer will be tripped, causing a large-scale power outage.

1.3 Solution

Prevention is the priority, real-time monitoring. A wireless horizontal balance monitoring device is developed to achieve real-time monitoring and rapid alarm of the balance of each equipment configuration area of ​​the vehicle-mounted mobile substation. A central controller is configured to realize information aggregation and status evaluation of the monitoring device, and timely send local and remote alarm signals to prevent abnormal levelness. At the same time, it can also provide a level verification value when the vehicle-mounted mobile substation adjusts each hydraulic support structure, helping the mobile substation operation and maintenance personnel to adjust the horizontal inclination of the vehicle-mounted mobile substation equipment operating surface.

2 Solution Exploration

2.1 Device function design

The vehicle-mounted mobile substation equipment is mainly configured on a flatbed truck, and relies on multiple hydraulic support rods configured on the flatbed truck to maintain the horizontality of the equipment's operating base surface. Each hydraulic support rod should be electrically adjustable and form an integrated linkage with the horizontal balance monitor to ensure that the horizontal inclination of the operating surface of the vehicle-mounted mobile substation equipment meets the operating requirements. The mobile flatbed truck horizontality monitoring device consists of two parts: a horizontal inclination monitoring module and a core control module. Among them, the monitoring module supports up to 6, which can be configured at the support rod position of each device and on the operating interface of important equipment to achieve real-time monitoring of the horizontal inclination. The core control module is responsible for receiving the monitoring data of each monitoring module, making intelligent judgments and outputting judgment conclusions.

2.2 Device panel design

The control panel of the horizontal tilt monitoring module is equipped with a communication antenna, a USB interface for programming, a Type-C interface for charging, a power double-position switch and a double-position indicator light, as shown in Figure 3.

Figure 3 Horizontal tilt monitoring module panel effect diagram

The device panel configuration of the core control module is shown in Figure 4. In addition to the antenna based on 5G communication technology, a WLAN transmission antenna is also configured to achieve information interaction with each horizontal tilt monitoring module [2]. Similarly, the conventional configuration also includes a USB interface for programming, a Type-C interface for charging, a two-position power switch, and a two-position indicator light. The sound and light alarm can realize a rapid alarm when the data exceeds the limit, and the high-precision display screen can realize visual display and management.

Figure 4: Core control module panel rendering

2.3 Device principle design

The basic principle of the 5G+ horizontal balance monitoring system is shown in Figure 5. The system is divided into two parts, namely the horizontal tilt monitoring module and the core control module mentioned above. The horizontal tilt monitoring module uses an angle sensor to monitor the horizontal tilt data, and uses the core controller (MCU) to control the sensor to achieve angle measurement 3 times/min, thereby ensuring the monitoring time frequency of the horizontality. After that, the MCU digitizes the monitoring data and transmits it to the core control module through the WLAN network. The core control module obtains the data of each horizontal tilt monitoring module through the WLAN network, and performs data threshold judgment at the same time, and takes corresponding actions according to the threshold comparison result. If the horizontal tilt value exceeds or falls below the threshold, the MCU performs sound and light high-input control, and simultaneously uses the 5G network to send an alarm SMS and detailed information such as the number and value of the over-limit horizontal tilt monitoring module, and notifies the security administrator in the form of SMS, and completes the recording at the same time.

Figure 5 Schematic diagram of 5G+ horizontal balance monitoring system

3 Angle Sensor Research

3.1 Principle design

Based on Newton's second law, the commonly used angle sensor technology adopts the inclination measurement theory; according to relevant physical principles and system theories, within the same system, the velocity V cannot be measured and calculated, but the change in velocity can be calculated, that is, the acceleration can be measured. If the initial velocity of a system is a known quantity, the acceleration polarity integral can be used to calculate the relevant velocity and linear displacement. The principle of the angle sensor is the inclination angle measurement theory, which uses the law of inertia to calculate the acceleration in the system [3]. If the sensor does not tilt, that is, remains stationary, it means that the sensor does not obtain acceleration in all directions (except the direction of gravity). The angle between the vertical axis of the gravity acceleration and the sensitive axis of the angle sensor can be defined as the measured inclination angle, thereby realizing the measurement of the inclination. After obtaining the angle data and signal through the sensor, a high-precision A/D conversion is performed to obtain the digital signal, and then the high-precision instantaneous acceleration is obtained through data processing methods such as filtering, smoothing, and variance estimation, thereby determining the accurate value of the measured inclination angle.

The angle sensor in the horizontal tilt monitoring module is based on the acceleration principle and is configured as a dual-sensitive axis sensor. The dual-sensitive axis sensor is mainly used to accurately calculate and sense the tilt and pitch angles of the horizontal plane. The measurement range is usually -30°~30°, which can meet the operation requirements of vehicle-mounted mobile substation equipment. The internal principle and functional structure of the dual-sensitive axis sensor is shown in Figure 6. In order to complete data processing, the internal configuration includes A/D converters, EEPROM memory, SPI transmission interface, signal conditioning circuits and other devices. The sensing element generally uses a silicon capacitor unit to improve the operating stability of the sensor. In order to further improve the stability of the dual-sensitive axis sensor, a dual-channel configuration is adopted to sense the two sensitive axes respectively, thereby completing the calculation of the tilt and pitch angles of the horizontal plane. This sensor uses two signal output modes, namely, pseudo-voltage signal output and SPI digital signal output. The sensor is also equipped with a temperature sensor to achieve temperature compensation, further reducing the influence of ambient temperature on the measurement accuracy of the angle sensor.