General technical requirements for low-voltage automatic transfer devices in low-voltage switchgear

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This post was last edited by jennifer12580 on 2016-9-20 at 17:13. 1. Scope of application: These technical specifications are applicable to the general bidding and ordering processes for low-voltage automatic transfer devices, and they constitute the technical terms in the relevant equipment bidding documents/ordering contracts. 2. Adoption of standards: The supplier shall use the latest **standards, industry standards, and IEC standards; other standards with higher performance may be used with the user’s consent. The industry standards contain provisions regarding the grading of product quality, and the performance of the products supplied by the vendor must meet the standards for top-quality products. When the provisions in the above standards differ from these technical specifications, these technical specifications shall prevail. 3. Equipment Specifications 3.1 Equipment Name: 0.4kV Low-Voltage Automatic Transfer Switch 3.2 Equipment Dimensions: Door opening size: 324 (width) × 135 (height) 3.3 Operating Environment Conditions 3.3.1 Altitude: ≤1000m 3.3.2 Ambient temperature: -25℃ to +55℃ 3.3.3 Relative humidity: 30% to 95%, without condensation 3.3.4 Seismic resistance: Horizontal ground acceleration: 0.3g; Vertical ground acceleration: 0.15g. Three sine waves acting simultaneously; safety factor: 1.67 3.3.5 Maximum daily temperature difference: 25℃ 3.3.6 Installation location: Indoor 3.4 Operating Conditions 3.4.1 Rated voltage: AC 100–240V, DC 24V 3.4.2 Maximum transient current: 40A 3.4.3 Protection rating: IP20 3.4.4 Impact resistance: 147 (15gn) m/s2 for 11ms 3.4.5 Processing time: 1ms for 1000 logical instructions 3.4.6 Communication: (1) Port type: RS485; serial port adapters can be added. (2) Communication protocol: Mod Bus master/slave RTU, ASCII character mode 3.4.7 DC input characteristics: (1) Number of input channels: 14. (2) Rated input voltage: 24VDC (20.4–28.8V). (3) Rated input current: 11mA for IO.0 and IO.1; 7mA for other inputs. (4) Input impedance: 2.1kΩ for IO.0 and IO.1; 3.4kΩ for other inputs. 3.4.8 Output characteristics: (1) Number of outputs: 10. (2) Output current: 2A per channel; 8A per common terminal. (3) Load (resistive, inductive): 2A/AC 220V or 2A/DC 30V (maximum operating frequency: 1800 times per hour) ； ⑷ Terminal insulation voltage: 1500V AC, 1 minute. 3.4.9 Service life: Electrical life: Minimum 100,000 operations ； Mechanical life: Minimum 20 *106 operations ； 4. Equipment Performance and Functional Requirements 4.1 Layout of Components on the Device Panel A total of 5 components are installed on the device panel, namely: 4.1.1 Function conversion switch The function conversion switch has five settings: \"Auto-start and auto-restart,\" \"Auto-start and manual restart,\" \"Manual,\" \"Closing the circuit,\" and \"Remote control.\" 4.1.2 For ring closing, a selector switch is used – in order to save space on the panel, no dedicated selection switch is provided; instead, a selector switch is utilized for this purpose. The toggle switch has three positions: “Select 381 off”, “Select 382 off”, “Select 345 off”. 4.1.3 Device operation indicator light (or LCD screen) 4.1.4 Fault alarm indicator light and reset button 4.1.5 Current setting adjustment device Reliable measures should be taken on the panel of the current setting adjustment device to prevent accidental operations. There is no adjustment mechanism for the set time value, but it must be adjustable within the program. 4.2 Function Implementation 4.2.1 The automatic switching control device is mainly composed of a programmable controller, circuit boards, and ring-closing current protection relays. Based on the acquired digital signals, it carries out logical judgments related to automatic switching through pre-programmed instructions, and issues commands for opening and closing operations. It enables functions such as electrical interlocking between two feeders and the busbar circuit breaker, locking during fault conditions, and adjustable delay times for opening and closing operations. 4.2.2 The self-tap control device shall remain stable and reliable regardless of the power supply condition. If power is lost in both incoming lines, the automatic switching control device shall maintain the open or closed state of the circuit breakers for the lines without power and those for the busbar ； After power is restored, the automatic restart control device should automatically return to its operating state prior to the power loss. 4.2.3 When either of the incoming line circuit breakers or the busbar coupling circuit breaker fails and trips, the device sends a signal to lock those circuit breakers, preventing them from being closed. 4.2.4 The automatic switching control device is installed in the secondary instrument room of the busbar coupling cabinet; communication serial ports can be added as required to enable communication functions, allowing the transmission of signals related to the activation and deactivation of automatic switching as well as the status of automatic switching operations. 4.2.5 When ring-closing operations are required, a ring-closing current protection device shall be installed in the bus coupler cabinet (comprising a programmable controller within the automatic switching control device, a switch for selecting ring closing, a ring-closing current protection relay, etc.), and it shall have the function of selecting ring closing. The implementation of the ring current protection function is carried out by the programmable controller of the automatic switching control device. 4.2.6 Microcomputer-based protection devices must have a self-check function. When a fault alarm is triggered and it is not possible to determine the cause of the fault (whether it is a problem with the secondary wiring or a fault in the device itself), it is necessary to use the self-check function to examine the device and determine whether there is anything abnormal with it. It is recommended to place the testing port of the self-checking device on the side of the device. 4.2.7 Regarding the criterion for no voltage loss: The relays for detecting no voltage loss in cabinets 381 and 382 have been removed; both the criterion for no voltage loss and its associated functionality are now handled by the device itself. For 381 and 382, the criteria for detecting no voltage have been increased to two; both are taken from the upper port of the main switch, and different criteria are used for different circuits as much as possible to ensure the accuracy of the no-voltage detection. 4.2.8 The device shall be able to transmit fault signals even in the event of a power failure on both circuits. 4.2.9 The device shall have a fault recording function that allows for the logging of previous operations as well as the value of the closing current; this information can be viewed on-site or uploaded via a communication port as needed. 4.2.10 Closing current and time for ring closing: The reference value for the closing current is 400 A, and the reference value for the operating time is 0 seconds. Both the ring current and time should be adjustable, with stepwise and continuous adjustment possible. 4.3. Working condition description: 4.3.1 Automatic switching: Powered by two power sources; when there is no voltage at the low-voltage output of either distribution transformer, its main feed circuit breaker is opened after a delay of t1, and the busbar connection circuit breaker is closed after a delay of t2 ； 4.3.2 Self-recovery: After the auto-switching operation, the low-voltage output voltage of the distribution transformer on the side with lost voltage is restored; the busbar circuit breaker is opened after a delay of t3, and its incoming line circuit breaker is closed after a delay of t4 ； 4.3.3 When the main incoming line circuit breaker trips due to overload or short-circuit faults, the automatic tripping of the bus coupler circuit breaker should be locked out ； 4.3.4 The various delay values (t1, t2, t3, t4) are set through a preset program, and the adjustment of these values is carried out by modifying the program. 4.3.5 Interlock: Under normal operating conditions, an interlock mechanism should be in place between the two low-voltage main incoming circuit breakers and the bus coupler circuit breaker to prevent the power sources from being connected in parallel, and this interlock is implemented by the automatic transfer device ； In the ring-closing operation mode, the interlock program can be disabled by the automatic start control device. When any of the circuit breakers 381, 382, or 345 fails, the system will be in a fault state; under such conditions, any switching operations are prohibited, but disconnection operations can still be performed. At the same time, the red light on the fault reset button lights up, indicating a locked state. After the fault is resolved, first manually reset the circuit breaker, and then use the reset button to reset the system. After pressing the reset button, if there is no fault at that time, the red light will automatically turn off and return to normal. 4.3.6 Ring-closing operation: 1) The automatic switching control device can perform low-voltage ring-closing operation when it is set to the “ring-closing” mode and the circuit is connected by activating the switch for ring closing. At this point, the electrical interlock procedure is released. 2) The self-switching control device shall have ring-closing current protection and selection function during ring-closing operations, which is achieved through a ring-closing selection switch. 3) The auto-closing control device shall have the capability to detect the closing current, and when this current exceeds a preset value (adjustable on-site), it shall disconnect the selected incoming line or busbar circuit breaker after a delay (adjustable via program modification).