PLC-based short-time parallel operation control device for low-voltage double-incoming-bus tie

Abstract

This utility model discloses a PLC-based low-voltage dual-incoming-line bus tie short-time parallel operation control device, relating to the field of industrial automation control. It includes a first incoming line circuit breaker (1QF), a second incoming line circuit breaker (2QF), and a bus tie circuit breaker (3QF). Synchronous relays are installed in the bus tie cabinet. A PLC controller is also installed in the bus tie cabinet, with its signal input terminal electrically connected to the synchronous relays and voltage monitoring relays installed on the two incoming power supply sides. This PLC-based low-voltage dual-incoming-line bus tie short-time parallel operation control device, through a PLC controller, synchronous relays, voltage monitoring relays, a changeover switch, and operation buttons, connects the signal input terminal of the PLC controller to the synchronous relays and voltage monitoring relays, and connects the control output terminal to the electrical operation circuit of each circuit breaker. Simultaneously, a three-in-one electrical interlocking program and a backup automatic transfer logic program are pre-stored in the PLC controller's memory, constructing a highly integrated and logically rigorous intelligent control system.

Description

Technical Field

[0001] This utility model relates to industrial automation control technology, specifically to a PLC-based low-voltage dual-incoming-bus short-time parallel operation control device. Background Technology

[0002] In the field of industrial automation control, the reliability and flexibility of low-voltage power distribution systems have always been key research and application directions. With the continuous growth of electricity demand and the increasing complexity of power grid structure, low-voltage dual-incoming-line bus tie systems are widely used in data centers, hospitals, large factories and other occasions with extremely high requirements for power supply quality as an important means to ensure power supply continuity. This system achieves automatic switching in the event of a single power supply failure through the coordinated control of two independent power sources and the bus tie circuit breaker, thereby ensuring uninterrupted power supply to the load.

[0003] Existing low-voltage dual-incoming-bus tie systems have significant shortcomings in the integration and intelligence of control logic. In traditional solutions, functions such as electrical interlocking, automatic transfer switching, and synchronization discrimination are often implemented through distributed relays. There is a lack of effective information interaction and collaborative working mechanisms between functional modules, resulting in slow overall system response speed and low control accuracy. Moreover, it is difficult to quickly adapt to and make optimal decisions when facing complex and ever-changing field conditions. In the critical safety control link of preventing three circuit breakers from closing simultaneously, existing technologies mostly rely on mechanical interlocking or simple electrical interlocking between relays. These methods not only increase the complexity of secondary wiring and reduce the reliability and maintainability of the system, but also fail to provide absolutely reliable protection in the face of extreme operating conditions or human error. There is a risk of equipment damage or even power grid accidents caused by asynchronous closing. Therefore, improvements are needed. Utility Model Content

[0004] The purpose of this invention is to provide a PLC-based short-time parallel operation control device for low-voltage dual-incoming-bus tie systems, in order to solve the problems of low integration of control logic, insufficient safety and reliability in existing low-voltage dual-incoming-bus tie systems, especially the lack of efficient and reliable means to prevent the simultaneous closing of three circuit breakers.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a PLC-based low-voltage dual-incoming-bus tie short-time parallel operation control device, comprising:

[0006] First incoming line circuit breaker (1QF), second incoming line circuit breaker (2QF), and bus tie circuit breaker (3QF);

[0007] The synchronous relay is installed in the bus tie cabinet;

[0008] The PLC controller is located in the bus tie cabinet. Its signal input terminal is electrically connected to the synchronous relay and the voltage monitoring relay located on the two incoming power supply sides. Its control output terminal is connected to the electrical operating circuit of the first incoming circuit breaker (1QF), the second incoming circuit breaker (2QF) and the bus tie circuit breaker (3QF).

[0009] The selector switch is located on the panel of the bus tie cabinet, and its output terminal is connected to the signal input terminal of the PLC controller to send a selection signal for manual or automatic mode to the PLC controller.

[0010] Multiple operation buttons are located on the cabinet panel, and their output terminals are connected to the signal input terminals of the PLC controller.

[0011] The PLC controller's memory contains a three-in-one electrical interlock program and an automatic switch logic program.

[0012] Furthermore, the logic of the three-in-one electrical interlocking procedure is configured to output a control signal that prohibits the simultaneous closing of the first incoming circuit breaker (1QF), the second incoming circuit breaker (2QF), and the bus tie circuit breaker (3QF).

[0013] Furthermore, the closing permission output contact of the synchronous relay can be connected to the manual closing circuit of the bus tie circuit breaker (3QF).

[0014] Furthermore, the automatic transfer switch logic program of the PLC controller is configured to output a control signal to the closing circuit of the bus tie circuit breaker (3QF) when receiving an undervoltage signal from any voltage monitoring relay.

[0015] Furthermore, the device also includes a human-machine interface (HMI) whose communication port is connected to the communication port of the PLC controller.

[0016] Furthermore, the PLC controller receives signals from the changeover switch, operation button, and voltage monitoring relay through the digital input module, and outputs control signals to the operation circuits of each circuit breaker through the digital output module.

[0017] Compared with existing technologies, the low-voltage dual-incoming-bus tie short-time parallel operation control device based on PLC provided by this utility model, by setting up a PLC controller, synchronous relays, voltage monitoring relays, changeover switches and operation buttons, and electrically connecting the signal input terminal of the PLC controller to the synchronous relays and voltage monitoring relays, and connecting the control output terminal to the electrical operation circuit of each circuit breaker, and pre-storing the three-in-one electrical interlocking program and the backup automatic transfer logic program in the PLC controller's memory, a highly integrated and logically rigorous intelligent control system is constructed. This device integrates the complex logic of dispersed electrical interlocking, backup automatic transfer, and synchronization discrimination into the PLC program, and forms a linkage with the circuit breaker operation circuit through hardware wiring, thereby achieving the effect of highly integrating and intelligentizing the complex control circuit that traditionally relies on a large number of independent relays. It greatly simplifies the secondary wiring of the system, improves the reliability and maintainability of the system, and can flexibly adapt to the customized requirements of switching logic in different sites.

[0018] By directly connecting the closing permission output contact of the synchronous relay in series to the manual closing circuit of the bus tie circuit breaker, a hardware parallel interlocking channel independent of the PLC software logic is formed. When performing a manual closing operation, the closing command must simultaneously obtain the "software permission" (no interlocking in the PLC internal program) and the "hardware permission" (hardware permission) of the synchronous relay before it can be turned on. This achieves the effect of forcibly and reliably preventing asynchronous closing in a purely hardware manner, providing double safety protection for parallel operation in manual mode and greatly enhancing the safety of critical system operations.

[0019] By coordinating the automatic transfer switch logic program with manual and automatic transfer switches, the system can operate in two modes: fully automatic fault response and semi-automatic maintenance. In automatic mode, the system can monitor the power supply status in real time and automatically execute the "break first, then make back" logic operation when a voltage loss fault is detected to quickly restore power supply. In manual mode, maintenance personnel are allowed to execute the "make first, then break" operation when synchronization conditions are met, achieving uninterrupted switching. This achieves a balance between power supply continuity and maintenance flexibility, minimizing power outage time during faults and enabling zero-second switching during planned maintenance, thus comprehensively improving the power supply reliability of the distribution network. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1Circuit control diagram provided for embodiments of this utility model;

[0022] Figure 2 The overall flowchart provided for the embodiments of this utility model. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings.

[0024] As attached Figure 1 As shown:

[0025] Example 1:

[0026] This utility model provides a PLC-based low-voltage dual-incoming-bus tie short-time parallel operation control device, the hardware of which mainly includes:

[0027] Primary equipment: First incoming line circuit breaker 1QF, second incoming line circuit breaker 2QF, and bus tie circuit breaker 3QF. These circuit breakers are installed in their respective incoming line cabinets and bus tie cabinets.

[0028] Secondary equipment: All secondary control equipment is centrally installed in the bus tie cabinet, including:

[0029] A PLC controller serves as the control core.

[0030] A synchronous relay is used to detect the voltage, frequency, and phase difference of the two incoming power supplies.

[0031] Two voltage monitoring relays are installed in the secondary circuits of the two incoming power supplies to monitor the power status (voltage present / voltage absent) of the I and II busbars.

[0032] A changeover switch (SA) is installed on the bus tie panel and has two positions: "manual" and "automatic".

[0033] A set of operating buttons (SB) is installed on the bus tie cabinet panel, including "1QF Close", "1QF Open", "2QF Close", "2QF Open", "3QF Close", and "3QF Open" buttons, for operation in manual mode.

[0034] A human-machine interface (HMI) (such as a touch screen) is installed on the cabinet panel to display system status, fault alarm information, and operation instructions.

[0035] Electrical connection relationships:

[0036] The PLC controller receives signals from the following components via its digital input (DI) module:

[0037] Manual / automatic position signal of the selector switch (SA);

[0038] Command signals for all operation buttons (SB);

[0039] The passive dry contact signals of the two voltage monitoring relays;

[0040] The synchronous relay outputs a "closing permission" contact signal;

[0041] Auxiliary contacts of the three circuit breakers (used to provide feedback on the closing and opening status).

[0042] The PLC controller outputs control signals to:

[0043] The closing and opening coil circuits of the first incoming circuit breaker 1QF;

[0044] The closing and opening coil circuits of the second incoming circuit breaker 2QF;

[0045] The closing and opening coil circuits of the bus tie circuit breaker 3QF.

[0046] In addition, the "closing permission" output contact of the synchronous relay is directly connected in series to the manual closing circuit of the bus tie circuit breaker 3QF, forming an independent hardware permission channel.

[0047] Implementation of control logic:

[0048] The PLC controller's memory contains a pre-stored control program, which includes the following logic:

[0049] Three-in-two electrical interlocking logic: This logic is configured to continuously monitor the status of 1QF, 2QF, and 3QF. Under any circumstances, as long as two of the circuit breakers are detected to be in the closed state, the PLC will output an interlocking signal to the closing circuit of the third circuit breaker, fundamentally preventing all three switches from closing simultaneously.

[0050] Automatic transfer switch logic (automatic mode):

[0051] This logic is activated when the selector switch is in the "automatic" position and the PLC detects through the voltage monitoring relay that either incoming power line (e.g., line #1) is undervoltage while the other (line #2) is normal.

[0052] The PLC first outputs a trip signal to disconnect the incoming circuit breaker (1QF) on the undervoltage side.

[0053] After confirming that 1QF has been tripped, the PLC outputs a closing signal to close the bus tie circuit breaker (3QF), thus supplying power to the entire load from the normal No. 2 power supply.

[0054] When the lost power supply #1 is restored to normal, the PLC will not automatically switch back to its original state; the system will remain powered by power supply #2 via the bus tie. The operator must manually switch the selector switch to "manual" mode to perform a manual reset.

[0055] Parallel operation logic in manual mode:

[0056] When the operator selects "manual" mode and closes the bus tie circuit breaker 3QF via the button, the closing command must meet two conditions simultaneously to be executed:

[0057] The PLC internal program has no interlock signal;

[0058] The "closing permission" hardware contact of the synchronous relay must be closed (i.e., the two power supplies meet the synchronization conditions).

[0059] Only when both of the above conditions are met can the closing signal sent by the operation button pass through the contact channel of the synchronous relay and finally close the 3QF, thereby realizing short-term parallel operation of closing first and then opening.

[0060] If they are not synchronized, the contacts of the synchronizing relay will open, and the manual closing operation cannot be performed. In this case, the "open first, close later" operation sequence must be adopted.

[0061] Fault blocking function: The PLC program is configured such that when the system detects that any incoming circuit breaker has tripped due to a fault (such as relay protection operation), the PLC will immediately output a continuous blocking signal to prevent the bus tie circuit breaker 3QF from closing, in order to prevent the fault from spreading or closing out of sync.

[0062] Application example:

[0063] To ensure the continuity of power supply to critical loads such as servers, network equipment, and cooling systems, large data centers are equipped with two independent mains power supplies. These two power supplies are connected to the data center's dual-bus bus via a low-voltage power distribution system. This power distribution system adopts a classic two-input-one-bus-connection structure, where each mains power supply is connected to one incoming cabinet, and the two incoming cabinets are connected by a bus-connection cabinet.

[0064] In its initial design, the system only had a simple automatic transfer switch function (i.e., after one power source fails, the incoming circuit breaker is disconnected and the bus tie circuit breaker is closed, allowing power to be supplied by another power source), but it could not perform power switching or maintenance operations without power interruption. Any planned power switching (such as power outage maintenance on one mains power source) or unplanned power switching could result in temporary power outages for critical loads, which is unacceptable for data centers requiring 24-hour uninterrupted operation.

[0065] To completely solve this problem and improve power supply reliability and operation and maintenance flexibility, the data center operator decided to carry out intelligent transformation of the control part of the low-voltage power distribution system and introduce the PLC-based low-voltage dual incoming bus short-time parallel operation control device described in this application.

[0066] The core of this renovation is to thoroughly upgrade the secondary control system of the bus tie cabinet without changing the original primary power distribution architecture (i.e., 1QF, 2QF, 3QF circuit breakers and their busbars).

[0067] Phase 1: Hardware Installation and Wiring

[0068] Technicians first installed the core components of this utility model device inside the bus tie cabinet: a PLC controller acting as the control brain, a synchronization relay for detecting the synchronization status of the two mains power lines, and two voltage monitoring relays for monitoring the voltage status of the two mains power lines respectively. On the panel of the bus tie cabinet, a mode conversion switch (labeled "manual" and "automatic"), a set of manual operation closing / opening buttons, and a color touchscreen (HMI) were installed. All cables were laid and connected according to the design drawings: voltage signals were taken from the voltage transformers of the two bus sections; the PLC's digital input module was connected to the conversion switch, operation buttons, relay contacts, and circuit breaker auxiliary contacts; its digital output module was connected to the opening and closing coil circuits of each circuit breaker; the "closing permission" output contact of the synchronization relay was cleverly connected in series in the circuit of the 3QF circuit breaker's manual closing button, forming a hardware redundancy protection. The HMI was connected to the PLC via a communication cable for status monitoring and human-machine interaction.

[0069] Phase Two: Software Programming and Logic Configuration

[0070] Engineers use specialized programming software to download the pre-designed control logic program into the PLC. The core of this program consists of two parts:

[0071] The three-in-one electrical interlocking program continuously scans the status of the three circuit breakers. At any time, if the program logic determines that two circuit breakers are in the closed state, it will immediately generate an interlocking signal internally and physically disconnect the closing circuit of the third circuit breaker through the output module, ensuring from both software and hardware perspectives that the extreme situation of "three switches closing at the same time" will never occur.

[0072] Automatic transfer switch logic program: This program is activated in "automatic" mode. It analyzes the signals from the two voltage monitoring relays in real time.

[0073] Phase 3: System Debugging and Function Verification

[0074] After the system was powered on, the technicians conducted a comprehensive functional test.

[0075] Automatic mode test: Simulate a power outage on one mains line (e.g., incoming line #1). The PLC quickly detects this change, and the control program automatically starts. Following the logical sequence, it first disconnects circuit breaker 1QF. After confirming its reliable tripping, it issues a closing command to close circuit breaker 3QF. The entire process is smooth and rapid, with power supply #2 handling all loads, achieving seamless switching. Subsequently, power supply #1 voltage is restored. As designed, the system maintains its current operating state without any automatic operations. A prompt message is displayed on the touchscreen, instructing operators to switch to manual mode if they wish to restore the original operating mode, verifying the "automatic transfer without automatic reset" function.

[0076] Manual Mode and Parallel Operation Test: The selector switch was turned to the "Manual" position. An attempt was made to manually close the 3QF circuit breaker when there was a phase difference between the two mains power supplies. Because the "closing permission" contact of the synchronizing relay was not closed, the hardware circuit was not open, and the closing operation was prohibited, ensuring safety. Subsequently, the two power supplies were adjusted to achieve synchronization, at which point the synchronizing relay contacts closed. The operator pressed the 3QF closing button, and the closing command successfully passed through the closed synchronizing relay contact channel, successfully closing the 3QF circuit breaker. The two power supplies achieved short-term parallel operation. Subsequently, the operator sequentially disconnected the original incoming line circuit breakers, completing the "close first, then disconnect" uninterruptible power supply switching operation. Throughout the process, the HMI clearly displayed the system status, mode, circuit breaker position, and synchronization status, providing the operator with sufficient decision-making information.

[0077] Fault Interlock Test: Simulates an incoming switchgear tripping due to overcurrent protection. The PLC program immediately recognizes this as a fault trip rather than a normal trip, and triggers the fault interlock logic, continuously blocking the closing circuit of 3QF. At this time, any attempt to automatically or manually close 3QF is prohibited, effectively preventing the power supply to the fault point and protecting the equipment and system safety.

[0078] Through the above applications, the device successfully endowed the data center with secure, flexible, and reliable power management capabilities, significantly reducing the risk of business interruption due to power switching and meeting its highest level of operational continuity requirements.

[0079] The foregoing description only illustrates certain exemplary embodiments of the present invention. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A short-time parallel operation control device for a low-voltage double-inlet bus coupler based on a PLC, characterized by, include: First incoming line circuit breaker (1QF), second incoming line circuit breaker (2QF), and bus tie circuit breaker (3QF); The synchronous relay is installed in the bus tie cabinet; The PLC controller is located in the bus tie cabinet. Its signal input terminal is electrically connected to the synchronous relay and the voltage monitoring relay located on the two incoming power supply sides. Its control output terminal is connected to the electrical operating circuit of the first incoming circuit breaker (1QF), the second incoming circuit breaker (2QF) and the bus tie circuit breaker (3QF). The selector switch is located on the panel of the bus tie cabinet, and its output terminal is connected to the signal input terminal of the PLC controller to send a selection signal for manual or automatic mode to the PLC controller. Multiple operation buttons are located on the cabinet panel, and their output terminals are connected to the signal input terminals of the PLC controller. The PLC controller's memory contains a three-in-one electrical interlock program and an automatic switch logic program.

2. The PLC-based low-voltage dual-feeder bus coupler short-time parallel operation control device according to claim 1, characterized in that, The logic of the three-in-one electrical interlocking program is configured to output a control signal that prohibits the simultaneous closing of the first incoming circuit breaker (1QF), the second incoming circuit breaker (2QF), and the bus tie circuit breaker (3QF).

3. The PLC-based low-voltage dual-feeder bus coupler short-time parallel operation control device according to claim 1, characterized in that, The closing permission output contact of the synchronous relay can be connected to the manual closing circuit of the bus tie circuit breaker (3QF).

4. The PLC-based low-voltage dual-feeder bus coupler short-time parallel operation control device according to claim 1, characterized in that, The automatic transfer switch logic program of the PLC controller is configured to output a control signal to the closing circuit of the bus tie circuit breaker (3QF) when receiving an undervoltage signal from any voltage monitoring relay.

5. The PLC-based low-voltage dual-feeder bus coupler short-time parallel operation control device according to claim 1, characterized in that, The device also includes a human-machine interface (HMI) whose communication port is connected to the communication port of the PLC controller.

6. The PLC-based low-voltage dual-feeder bus coupler short-time parallel operation control device according to claim 1, characterized in that, The PLC controller receives signals from the changeover switch, operation button and voltage monitoring relay through the digital input module, and outputs control signals to the operation circuit of each circuit breaker through the digital output module.

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