Common application scenarios and operating logic of low-voltage automatic transfer switches

Thread Content

The DCM-631 series of low-voltage automatic transfer devices are primarily used in distribution systems below 690V to enable rapid and reliable switching between the main and backup power sources, ensuring consistent power supply for production processes. It features an embedded PLC module with a variety of logical function options, allowing for the adjustment of various parameters based on operational conditions to meet the needs of different applications. The following describes how the DCM-631 series of low-voltage automatic transfer switches are applied in several different power distribution systems. 1. The operation logic of the low-voltage automatic transfer switch in a single-bus sectionalized system is as follows: 1) Under normal conditions, Line 1 supplies power to Section 1, while Line 2 supplies power to Section 2, with the busbar switch in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. 1. The operation logic of the low-voltage automatic transfer switch in a dual-power supply system is as follows: Mode 1 (Automatic transfer): 1) Under normal conditions, Line 1 carries the load while Line 2 is in standby mode. 2) When Line 1 loses power, the automatic transfer switch opens the switch for Line 1 and then closes the switch for Line 2. Mode 2 (Automatic restoration): 1) Under normal conditions, Line 1 carries the load while Line 2 is in standby mode. 2) When Line 1 loses power, the automatic transfer switch opens the switch for Line 1 and then closes the switch for Line 2. 3) When power is restored to Line 1, the automatic transfer switch opens the switch for Line 2 and then closes the switch for Line 1. Mode 3 (Mutual transfer): 1) Line 1 carries the load while Line 2 is in standby mode. When the 1st incoming line loses power, the switch for the 1st incoming line is tripped, and then the switch for the 2nd incoming line is closed. 2) The 2nd incoming line is under load, while the 1st incoming line is in standby mode. When the 2nd incoming line loses power, the switch for that line is opened, and then the switch for the 1st incoming line is closed. The low-voltage automatic transfer logic for the single mains supply plus generator system is as follows: 1) Under normal conditions, the main incoming line carries the load while the generator is in a stopped state. 2) When the main incoming line loses power, the automatic transfer device opens the switch for the 1st incoming line (or it operates due to voltage loss), and then sends a command to start the generator; once the generator’s voltage reaches the required level, the automatic transfer device closes the switch for the generator. 3) When power is supplied from the main feed line, the automatic transfer device opens the generator switch and shuts down the generator, then closes the main feed line switch. 1. Operation logic of the low-voltage automatic backup switching system in a single-bus sectionalized system (automatic restoration of the incoming line, mutual switching of incoming lines): Mode 1 (Automatic switching): 1) Under normal conditions, Line 1 supplies power to Section 1, while Line 2 supplies power to Section 2; the busbar switch is in the open position. 2) When Line 1 loses power, the automatic backup system shuts off the switch for Line 1 and then closes the busbar switch. 3) When Line 2 loses power, the automatic backup system shuts off the switch for Line 2 and then closes the busbar switch. Mode 2 (Automatic restoration): 1) Under normal conditions, Line 1 supplies power to Section 1, while Line 2 supplies power to Section 2; the busbar switch is in the open position. 2) When Line 1 loses power, the automatic backup system shuts off the switch for Line 1 and then closes the busbar switch. When power comes in from line 1, the automatic transfer device opens the busbar switch and then closes the switch for line 1. 3) When power is lost on line 2, the automatic transfer device opens the switch for line 2 and then closes the busbar switch. When power comes in from line 2, the automatic transfer device opens the busbar switch, and then closes the switch for line 2 in mode 3 (mutual transfer). 1) Under normal conditions, line 1 supplies power to one section of the load, while line 2 supplies power to another section; the busbar switch remains open. 2) When line 1 loses power, the automatic transfer device opens the switch for line 1, and then closes the busbar switch. 3) When the 2nd feed line loses power, the automatic backup system opens the switch connected to the 2nd feed line and then closes the switch connected to the 1st feed line. When the 2nd feed line has power while the 1st feed line is without power, the automatic backup switching device closes the switch of the 1st feed line and then opens the switch of the 2nd feed line. 1. In a single-bus sectionalization system (automatic switching on of feed lines, automatic restoration of feed lines, mutual switching between feed lines), the logic for low-voltage automatic backup switching is as follows: when the entire facility loses power, if either feed line gains power, the automatic backup switching device closes the switch of that feed line; after a delay, it checks whether the other feed line has also gained power – if so, it closes its switch; otherwise, it closes the busbar switch. Working mode 1 (self-fed): 1) Under normal conditions, Line 1 supplies power to one load, while Line 2 supplies power to another load; the busbar switch is in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. 3) When the 2nd incoming line loses power, the automatic transfer device shuts off the switch of the 2nd incoming line and then closes the busbar switch; operation mode 2 (self-restoration): 1) Under normal conditions, the 1st incoming line carries one section of the load, the 2nd incoming line carries another section of the load, and the busbar switch is in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. When power comes in from line 1, the automatic transfer device opens the busbar switch, and then closes the switch for line 1. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. When power comes in from line 2, the automatic transfer device opens the busbar switch, and then closes the switch for line 2 in mode 3 (mutual transfer). 1) Under normal conditions, line 1 carries one section of the load, while line 2 carries another section of the load, with the busbar switch in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. When the 1st feed line has power and the 2nd feed line is without power, the automatic transfer device shuts off the switch of the 2nd feed line and then closes the switch of the 1st feed line. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. When the 2nd feed has power and the 1st feed is without power, the automatic transfer device shuts off the switch of the 1st feed and then closes the switch of the 2nd feed. 1. The logic for the low-voltage automatic transfer to the backup power supply in a dual-power supply with generator system is as follows: 1) Under normal conditions, the main power line carries the load, the backup power line is in standby mode, and the generator is shut down. 2) When the main feed loses power, the automatic backup switching device shuts off the main feed switch, and then closes the backup feed switch. 3) When power is supplied from the main feed line, the automatic backup switching device closes the switch for the backup feed line, and then closes the switch for the main feed line. 4) When both incoming lines lose power, the automatic backup system starts the generator, and after a delay, the generator switch is closed. 5) When power arrives from either incoming line, the automatic transfer device shuts down the generator, opens the generator switch, and then closes the switch of the incoming line. 1. Single-bus sectionalization system with a backup power source; the operation logic of the low-voltage automatic transfer switch is as follows: 1) Under normal conditions, Line 1 supplies power to Section 1, while Line 2 supplies power to Section 2. The busbar switch is in the open position, and the backup line is in hot standby mode, with its switch also in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. 4) When power is restored to the feeder that was out of service, the automatic transfer device opens the busbar connection switch, and then closes the switch for the feeder that has now received power. 5) When both main feeders lose power, the automatic transfer device shuts off the switches of those two main feeders, then closes the switch of the backup feeder, and subsequently closes the busbar switch (if it is in the open position). 6) When power arrives at either of the main feeders, the automatic transfer device closes the switch for the alternate feeder, then closes the switch for the feeder from which power is arriving, and finally closes the busbar switch (if it is in the open position). 1. The low-voltage automatic transfer switch operation logic for a single-bus sectionalized system with a generator is as follows: 1) Under normal conditions, Line 1 supplies power to Section 1, while Line 2 supplies power to Section 2; the busbar switch is in the open position and the generator is shut down. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. 4) When power is restored to the feeder that was out of service, the automatic transfer device opens the busbar connection switch, and then closes the switch for the feeder that has now received power. 5) When both main feeders lose power, the automatic backup system shuts off the switches for those two main feeders, then starts the generator. Once the generator’s voltage is normal, the generator switch is closed; subsequently, the busbar switch can be closed as well (it is necessary to specify whether the busbar switch should be closed at the time of ordering), thereby completing the automatic startup of the generator. 6) When power arrives from either main feed line, the automatic transfer device shuts down the generator and opens its switch; it then closes the switch for the incoming feed line, and subsequently closes the busbar switch (if it is in the open position). 1. The operation logic of the low-voltage automatic transfer switch system with single-phase and single-bus configuration is as follows: (Automatic transfer): 1) Under normal conditions, Line 1 supplies power to one load section, while Line 2 supplies power to another load section; the busbar switch is in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. (Self-recovery): 1) Under normal conditions, Line 1 carries one load, while Line 2 carries two loads; the busbar switch is in the open position. 2) When the 1st incoming line loses power, the automatic transfer device shuts off the switch of the 1st incoming line and then closes the busbar connection switch. When power comes in from line 1, the automatic transfer device opens the busbar switch, and then closes the switch for line 1. 3) When the 2nd incoming line loses power, the automatic transfer device opens the switch of the 2nd incoming line and then closes the busbar connection switch. When power comes in from line 2, the automatic transfer device opens the busbar switch, and then closes the switch for line 2.