Abstract: UniMAT has developed a dedicated three-phase AC power and leakage current monitoring module for mining applications, specifically designed for the characteristics of explosion-proof feeder switch control systems. This module measures phase voltage, current, zero-sequence voltage, zero-sequence current, and leakage resistance. Results show that using the UniMAT CPU224+ mining three-phase AC power and leakage current monitoring module not only reduces costs but also meets national standards for leakage protection. It simplifies configuration, optimizes programming, and allows for easy upgrades from the basic KBZ630Z model to more demanding models like the KBZ800Z and KBZ1000Z. This expands the application of the three-phase AC power and leakage current monitoring module to various AC power monitoring systems, enabling it to play a more significant role in diverse applications.
Keywords: Three-phase AC power monitoring, UniMAT PLC, CPU224, EM231, power supply switch
I. System Overview
Mining explosion-proof vacuum feeder switches (hereinafter referred to as feeder switches) are mainly used in underground coal mines. In AC 50Hz lines with voltages up to 1140V and rated currents of 400A, 500A, 630A, and 800A, they serve as main switches or branch switches in the power supply system, or as feeder switches for mining explosion-proof mobile substations (connecting to the mobile substation after opening the rear cover). They can also be used for infrequent starting of large-capacity motors. They feature overload, short circuit, undervoltage, and leakage protection (selective leakage protection) as well as leakage interlocking functions. These products can be applied in coal mine safety power monitoring systems, including mining explosion-proof vacuum feeder switches.
II. System Configuration and Function Implementation
1. Hardware configuration of the KBZ630Z control system
Display screen: One 4-line Chinese text display screen with an IP65 protection rating.
Programmable Logic Controller: One UN200 series CPU224Q UN 214-1AF23-0XB0 CPU224Q CPU224Q UN 214-1AF23-0XB0 programmable logic controller.
Expansion Module: One UN 231-0BH22-0XA0 three-phase AC power and leakage current monitoring module.
(Note: The KBZ800Z model requires two three-phase AC power supplies and a leakage current monitoring module.)
2. System Architecture
The system consists of a control system comprised of a UniMAT PLC and a text display, and an execution system comprised of vacuum circuit breakers, as shown in the figure. The CPU performs some logic control, while the mining module mainly collects signals such as AC voltage, current, and leakage resistance, thereby enabling system monitoring and control, and performing protection functions such as leakage current interlocking, overload, short circuit, phase loss, undervoltage, and overvoltage. It features high intelligence, stable performance, and reliable operation.
3. System Challenges
The system mainly needs to ensure that the leakage current protection action time is less than 50ms and the short circuit protection action time is less than 100ms. Therefore, it is necessary to ensure that the CPU's acquisition and processing speed is very fast. The UniMAT PLC uses a high-frequency microprocessor, and its instruction processing speed is 3-10 times faster than that of ordinary PLCs. The acquisition and control cycle time of the UniMAT UN200 PLC is 12ms, plus the peripheral equipment time of 30ms, for a total of 42ms, which meets the standard requirements of the equipment.
4. Monitoring Function Design
Employing a text display screen in conjunction with the UniMAT UN200 series small PLC, the system displays and memorizes the operating status, parameters, and fault types of the power supply switch. Specific parameters can be modified and adjusted. The user-friendly interface provides excellent human-machine interaction capabilities, greatly improving the efficiency of fault diagnosis and troubleshooting.
All analog signals are processed into digital signals, featuring strong anti-interference ability, simple wiring, large information capacity, and reliable and accurate control.
It has complete self-testing, self-diagnosis and fault simulation test functions, which can conveniently check whether the protection and control system is normal.
5. System Function Implementation
This power supply switch fully considers the working environment in underground coal mines, integrating disciplines such as mechanical manufacturing, automation, measurement and control technology and instrumentation, and computer application science and technology. Its main technical specifications are as follows:
Voltage rating: 1140V/660V; Frequency: 50Hz;
Total rated current: 800A, 1200A, single unit operating current can reach 400A;
Leakage current interlock protection: Additional DC detection, 1140V-40K ohm, 660V-22K ohm;
Leakage protection operation: 1140V-20K ohms, 660V-11K ohms;
Short circuit protection: 3-10 times the rated current;
Overvoltage and undervoltage protection: 0.75Ue
Over-temperature protection and over-limit protection;
The switchgear has leakage test and overcurrent test buttons, which can be used to test the protection function of the power supply switch at any time;
System schematic diagram
Currently, most domestic power feeder switches use a Siemens + transmitter + residual current device (RCD) control scheme. While this scheme meets system requirements, it has significant limitations in control functionality. Replacing this scheme with this new one allows for online monitoring of the entire power feeder switch's process parameters, such as current and voltage. This reduces customer costs, ensures stable process conditions, and improves product response speed. The use of a text display screen allows operators to easily troubleshoot faults based on alarm information displayed on the screen, thus improving production efficiency.
6. System Highlights
A major highlight of this system is the UN 231-0BH22-0XA0 three-phase AC power and leakage current monitoring module. This module, through an AC transformer, can collect AC power information. Combined with CPU processing and control, it can provide overvoltage, undervoltage, overload, short circuit, leakage current, and three-phase imbalance protection functions; it can also monitor the grid insulation resistance; and it has zero-sequence voltage and zero-sequence current acquisition capabilities. This product is an extension module of the UN200 PLC.
See the diagram and wiring diagram below for details:
The technical specifications for this module are as follows:
This module can also be applied to various power monitoring and control products, such as power distribution system monitoring for various electrical controls, monitoring systems for small substations, and other combination switches.
III. Analysis of Usage Effect
This control system achieved its intended purpose in the power supply switch system. Based on the importance of the power supply switch system in practical applications, Shenzhen Yiwei Automation's UN200 series PLC and three-phase AC power and leakage current monitoring modules were selected, improving system stability, meeting system response requirements, simplifying wiring construction, and reducing maintenance difficulty. Since this series of PLCs is fully compatible with Siemens S7-200 PLCs, it reduced the development difficulty for engineers and saved system costs to a certain extent. The system has performed well since its commissioning and has also been applied to the power supply panel monitoring of multiple automated control systems, showing good prospects for industry applications.
