An automatic power transfer switch

Abstract

This invention discloses an automatic power transfer switch, belonging to the field of low-voltage electrical technology. The automatic power transfer switch includes multiple actuators and a control unit for controlling the actuators. Each actuator includes a closing drive mechanism and a opening drive mechanism for driving the actuator to close and open, respectively. The opening drive mechanism is a holding-type shunt trip unit, which can prevent the closing drive mechanism from performing a closing operation during the duration of the opening drive signal and during the time t0 from the removal of the opening drive signal to the release of the holding-type shunt trip unit. Compared with the prior art, this invention achieves a safe and reliable interlocking function for the automatic power transfer system without any additional interlocking circuits or interlocking mechanisms, and can minimize the load power outage time during power switching.

Description

Technical Field

[0001] This invention relates to an automatic power transfer switch, belonging to the field of low-voltage electrical technology. Background Technology

[0002] With the rapid development of industrial automation and intelligence, the complexity of industrial electricity consumption is increasing daily, and reliability is attracting more and more attention from electricity customers. Traditional automatic power transfer systems typically combine mechanical and electrical interlocking to ensure that two circuit breakers can only be used in a "two-in-one" configuration simultaneously, or three circuit breakers can only be used in a "three-in-two" configuration simultaneously. Mechanical interlocking is generally divided into lever interlocking, cable interlocking, and key interlocking. Lever or cable interlocking can be used when multiple circuit breakers are close together, but not when they are far apart, and key interlocking cannot be used to achieve automatic transfer. Electrical interlocking is generally divided into logic interlocking and closing coil interlocking. Logic interlocking relies on software logic, while closing coil interlocking requires additional wiring and typically uses series and parallel interlocking of auxiliary switches for each circuit breaker. Neither electrical interlocking method can handle the interlocking problems caused by the operation of the closing button on the circuit breaker panel. In summary, the interlocking implementation methods of existing automatic power conversion systems all have some shortcomings, such as limited distance, limited functionality, or incomplete interlocking. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an automatic power transfer switch that can realize long-distance, multi-functional, and all-round interlocking control of the automatic power transfer system at extremely low cost.

[0004] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0005] An automatic power transfer switch includes multiple actuator switches and a control unit for controlling the actuator switches. Each actuator switch includes a closing drive mechanism and a opening drive mechanism for driving closing and opening operations, respectively. The opening drive mechanism is a holding-type shunt trip unit, which can prevent the closing drive mechanism from performing a closing operation during the duration of the opening drive signal and during the time t0 from the removal of the opening drive signal to the release of the holding-type shunt trip unit. For any actuator switch in the open position, the control unit interlocks it according to the following method:

[0006] If there is no need to close the circuit, the control unit always applies a tripping drive signal to the holding-type shunt trip unit of the actuator switch;

[0007] If there is a closing requirement, when the closing delay is non-zero, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at time t0 before the closing delay time of the execution switch arrives, and sends a closing drive signal to the closing drive mechanism of the execution switch at the time when the closing delay time arrives; when the closing delay is zero, if the pre-execution switch in the operation logic has not yet completed the opening, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at the same time as sending the opening drive signal to the pre-execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled; if there is no pre-execution switch in the operation logic or the pre-execution switch has completed the opening operation, the control unit first cancels the opening drive signal of the holding shunt trip unit of the execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled.

[0008] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0009] This invention uses a holding-type shunt trip unit as the tripping drive mechanism for each actuator switch in an automatic power conversion system. Utilizing the characteristic of the holding-type shunt trip unit that it can prevent the actuator switch from closing during the duration of the tripping drive signal and before the release is completed, combined with ingenious timing control logic, it can achieve safe and reliable interlocking functions in an automatic power conversion system without any additional interlocking circuits or interlocking mechanisms, and can minimize the load power outage time during power switching. Attached Figure Description

[0010] Figure 1 This is a timing diagram of the interlocking control when the closing delay of the automatic power transfer switch in standby automatic transfer mode is non-zero, according to a specific embodiment.

[0011] Figure 2 This is a timing diagram of the interlocking control for the automatic power transfer switch in standby mode with zero closing delay, as shown in a specific embodiment.

[0012] Figure 3 This is a timing diagram of the interlocking control when the closing delay of the automatic power transfer switch in forced mode is non-zero, as shown in a specific embodiment.

[0013] Figure 4 The diagram shows the interlocking control timing of the automatic power transfer switch in forced mode when the closing delay is zero, as shown in a specific embodiment. Implementation

[0014] To address the shortcomings of existing technologies, the present invention addresses this issue by using a holding-type shunt trip unit as the tripping drive mechanism for each actuator switch in an automatic power conversion system. Utilizing the characteristic of the holding-type shunt trip unit that it can prevent the actuator switch from closing during the duration of the tripping drive signal and before the signal is released, combined with ingenious timing control logic, the automatic power conversion system can achieve safe and reliable interlocking functions without any additional interlocking circuits or mechanisms, and can minimize the load power outage time during power switching.

[0015] Compared to traditional pulse-type shunt trip units, the holding-type shunt trip unit can prevent the circuit breaker from performing a closing operation during the duration of the drive signal and from the removal of the drive signal until the release is complete, thereby preventing malfunction of the circuit breaker. To meet the requirements of miniaturization, the electromagnet coil used in existing holding-type shunt trip units typically adopts a single-coil structure and uses PWM control, with high current pull-in and low current sustaining to achieve low power consumption. Currently, holding-type shunt trip units with a dual-coil structure employing a start-up coil and a sustaining coil have also emerged.

[0016] Specifically, the automatic power transfer switch proposed in this invention includes multiple actuator switches and a control unit for controlling the actuator switches. Each actuator switch includes a closing drive mechanism and a opening drive mechanism for driving the actuator switch to close and open operations, respectively. The opening drive mechanism is a holding-type shunt trip unit, which can prevent the closing drive mechanism from performing a closing operation during the duration of the opening drive signal and during the time t0 from the removal of the opening drive signal to the release of the holding-type shunt trip unit. For any actuator switch in the open position, the control unit interlocks it according to the following method:

[0017] If there is no need to close the circuit, the control unit always applies a tripping drive signal to the holding-type shunt trip unit of the actuator switch;

[0018] If there is a closing requirement, when the closing delay is non-zero, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at time t0 before the closing delay time of the execution switch arrives, and sends a closing drive signal to the closing drive mechanism of the execution switch at the time when the closing delay time arrives; when the closing delay is zero, if the pre-execution switch in the operation logic has not yet completed the opening, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at the same time as sending the opening drive signal to the pre-execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled; if there is no pre-execution switch in the operation logic or the pre-execution switch has completed the opening operation, the control unit first cancels the opening drive signal of the holding shunt trip unit of the execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled.

[0019] To facilitate public understanding, the technical solution of this invention will be described in detail below using an automatic power conversion system with a two-input-one-bus tie structure as an example, in conjunction with the accompanying drawings:

[0020] The automatic power transfer switch with a two-input-one-bus tie structure includes a control unit and three actuator switches: a normal switch and a standby switch connecting the normal power supply and the standby power supply respectively, and a bus tie switch connecting the normal power supply bus and the standby power supply bus. The normal switch, standby switch and bus tie switch all use a holding-type shunt trip unit as their respective tripping drive mechanism. In this embodiment, the holding-type shunt trip units used in the normal switch, standby switch and bus tie switch are the same, and the time required for their drive signal to be withdrawn and released to the final position is t0 (this parameter is the rated parameter of the holding-type shunt trip unit). Let the tripping delays of the normal switch, standby switch and bus tie switch be t1, t3 and t5 respectively, and the closing delays of the normal switch, standby switch and bus tie switch be t2, t4 and t6 respectively.

[0021] Assuming that the normal and standby power supplies are normal, the normal switch is closed, the bus tie switch is open, and the standby switch is closed. The control unit obtains the position feedback signals of the normal switch, standby switch and bus tie switch in real time. The control unit applies the opening drive signal to the bus tie switch which is currently in the open state, so as to prevent the bus tie switch from closing.

[0022] When the closing delay is non-zero in automatic transfer switch mode, if the main power supply fails, the system will switch to supply power to both the main and backup busbars from the backup power supply. The interlocking control sequence of the control unit is as follows: Figure 1As shown, the specific steps are as follows: When the control unit determines that the main power supply is abnormal, after a main power supply tripping delay t1, the control unit continuously applies a tripping drive signal to the holding shunt trip of the main power supply to trip the main power supply, thus tripping the main power supply and preventing it from closing. After the main power supply is tripped, after a bus tie switch closing delay t6, the tripping drive signal of the holding shunt trip of the bus tie switch is removed before the t0 time period, allowing the bus tie switch to close. After the bus tie switch closing delay t6 is reached, the control unit applies a closing drive signal to the closing drive mechanism (closing electromagnet) of the bus tie switch to close the bus tie switch. At this time, since the holding shunt trip of the bus tie switch has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch is closed, the system status is: main power supply tripped, bus tie closed, standby closed. At this time, since a tripping drive signal is continuously applied to the holding shunt trip of the main power supply, the closing of the main power supply is prohibited.

[0023] When the main power supply returns to normal, the system will switch back to supplying power to its respective busbars by the main and backup power supplies. The switching and interlocking operations are as follows: When the control unit determines that the main power supply has returned to normal, after a bus tie switch tripping delay t5, the control unit continuously applies a tripping drive signal to the holding-type shunt trip unit of the bus tie switch to trip the bus tie switch and prevent the bus tie switch from closing; after the bus tie switch has tripped, after a main power switch closing delay t2, the holding-type trip unit of the main power switch is deactivated at the moment before the t0 time period. The tripping drive signal of the excitation trip unit enables the closing of the service switch; after the closing delay time of the service switch reaches t2, the control unit applies a closing drive signal to the closing electromagnet of the service switch to close the service switch. At this time, since the holding-type shunt trip unit of the service switch has been released, the service switch can reliably perform the closing operation; after the service switch is closed, the system status is service switch closed, bus tie tripped, and standby closed. At this time, since the tripping drive signal is continuously applied to the holding-type shunt trip unit of the bus tie switch, the closing of the bus tie switch is prohibited.

[0024] When the closing delay is zero in the standby automatic transfer mode (i.e., t2, t4, and t6 are all 0), if the main power supply fails, the system will switch to supply power to both the main and standby busbars from the backup power supply. The interlocking control sequence of the control unit is as follows: Figure 2As shown, the specific steps are as follows: When the control unit determines that the main power supply is abnormal, after a delay t1 for the main power switch to open, the control unit continuously applies a tripping drive signal to the holding shunt trip of the main power switch to open the main power switch and prevents the main power switch from closing. At the same time as applying the tripping drive signal to the shunt trip of the main power switch, the tripping drive signal to the holding shunt trip of the bus tie switch is canceled, and the release timer t of the holding shunt trip of the bus tie switch is started. After the main power switch is opened, if t < t0, the timer continues to wait. When t ≥ t0, the control unit applies a closing drive signal to the closing drive mechanism (closing electromagnet) of the bus tie switch to close the bus tie switch. At this time, since the holding shunt trip of the bus tie switch has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch is closed, the system status is: main power switch open, bus tie switch closed, and standby switch closed. At this time, since the tripping drive signal is continuously applied to the holding shunt trip of the main power switch, the closing of the main power switch is prohibited.

[0025] When the main power supply returns to normal, the system will switch back to supplying power to its respective busbars by the main and backup power supplies. The switching and interlocking operations are as follows: When the control unit determines that the main power supply has returned to normal, after a bus tie switch tripping delay t5, the control unit continuously applies a tripping drive signal to the holding-type shunt trip unit of the bus tie switch to trip the bus tie switch and prevent the bus tie switch from closing. At the same time as applying the tripping drive signal to the bus tie switch shunt trip unit, the drive signal of the holding-type shunt trip unit of the main power supply is removed, and the holding-type shunt trip unit of the main power supply is activated. The timer t is set to release the circuit breaker into position. After the bus tie switch is in position, if t < t0, the timer continues to wait. When t ≥ t0, the control unit applies a closing drive signal to the closing electromagnet of the service switch to close the service switch. At this time, since the holding shunt trip of the service switch has been released, the service switch can reliably perform the closing operation. After the service switch is closed, the system status is service switch closed, bus tie switch open, and standby switch closed. At this time, since the holding shunt trip of the bus tie switch is continuously applied with a closing drive signal, the closing of the bus tie switch is prohibited.

[0026] When the closing delay is non-zero in forced mode, the system switches from being powered by the normal power supply to the normal section bus and the backup power supply to the backup section bus to being powered by the normal power supply to both the normal and backup sections bus. The interlocking control sequence of the control unit is as follows: Figure 3As shown, the specific steps are as follows: After a standby switch tripping delay t3, the control unit continuously applies a tripping drive signal to the standby switch's holding-type shunt trip unit to trip the standby switch and prevents it from closing. After the standby switch is tripped, after a bus tie switch closing delay t6, the drive signal of the bus tie switch's holding-type shunt trip unit is removed at the moment before the bus tie switch closing delay time t6 reaches t0, allowing the bus tie switch to close. After the bus tie switch closing delay time reaches t6, the control unit applies a closing drive signal to the bus tie switch closing electromagnet to close the bus tie switch. At this time, since the bus tie switch's holding-type shunt trip unit has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch is closed, the system status is normal closing, bus tie closing, and standby tripping. At this time, because a tripping drive signal is continuously applied to the standby switch's holding-type shunt trip unit, the standby switch closing is prohibited.

[0027] When the closing delay is non-zero in forced mode, the system switches from being powered by the normal power supply to the normal bus section and by the backup power supply to the backup power supply to both the normal and backup bus sections. The switching and interlocking operations are as follows: After the normal switch opening delay t1, the control unit continuously applies a opening drive signal to the holding-type shunt trip unit of the normal switch to open the normal switch and prevent the normal switch from closing; after the normal switch is fully open, after the bus tie switch closing delay t6, the bus tie is removed at the moment before the t0 time period. The tripping drive signal of the shunt trip unit of the switch enables the bus tie switch to close. After the bus tie switch closing delay time reaches t6, the control unit applies a closing drive signal to the closing electromagnet of the bus tie switch to close the bus tie switch. At this time, since the shunt trip unit of the bus tie switch has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch is closed, the system status is normal operating tripped, bus tie closed, and standby closed. At this time, since the tripping drive signal is continuously applied to the shunt trip unit of the normal operating switch, the closing of the normal operating switch is prohibited.

[0028] When the closing delay is zero in forced mode (i.e., t2, t4, and t6 are all 0), the system switches from being powered by the normal power supply to the normal section bus and the backup power supply to the backup section bus to being powered by the normal power supply to both the normal and backup section buses. The interlocking control sequence of the control unit is as follows: Figure 4As shown, the specific steps are as follows: After a delay t3 after the standby switch trips, the control unit continuously applies a tripping drive signal to the shunt trip unit of the standby switch to cause the standby switch to trip and prevents it from closing. Simultaneously with applying the tripping drive signal to the shunt trip unit of the standby switch, the tripping drive signal to the shunt trip unit of the bus tie switch is removed, and a release timer t is started for the shunt trip unit of the bus tie switch. After the standby switch trips, if t < t0, the timer continues to wait. When t ≥ t0, the control unit applies a closing drive signal to the closing electromagnet of the bus tie switch to cause it to close. At this time, since the shunt trip unit of the bus tie switch has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch closes, the system status is: normal closing, bus tie closing, standby tripping. At this time, because a tripping drive signal is continuously applied to the shunt trip unit of the standby switch, closing of the standby switch is prohibited.

[0029] When the closing delay is zero in forced mode, the system switches from being powered by the normal power supply to the normal bus section and by the backup power supply to the backup bus section to being powered by the backup power supply to both the normal and backup bus sections. The switching and interlocking operations are as follows: After the normal switch tripping delay t1, the control unit continuously applies a tripping drive signal to the holding shunt trip unit of the normal switch to trip the normal switch and prevents the normal switch from closing; while applying the tripping drive signal to the shunt trip unit of the normal switch, the tripping drive signal to the holding shunt trip unit of the bus tie switch is removed, and the bus tie switch is started. The timing t is set when the holding shunt trip unit is released. After the main switch is opened, if t < t0, the timing continues. When t ≥ t0, the control unit applies a closing drive signal to the closing electromagnet of the bus tie switch to close the bus tie switch. At this time, since the holding shunt trip unit of the bus tie switch has been released, the bus tie switch can reliably perform the closing operation. After the bus tie switch is closed, the system status is: main switch open, bus tie closed, standby closed. At this time, since the opening drive signal is continuously applied to the holding shunt trip unit of the main switch, the closing of the main switch is prohibited.

Claims

1. An automatic power transfer switch, comprising a plurality of actuator switches and a control unit for controlling the actuator switches; characterized in that, The actuator switch includes a closing drive mechanism and a opening drive mechanism for driving the actuator switch to close and open operations, respectively. The opening drive mechanism is a holding-type shunt trip unit, which can prevent the closing drive mechanism from performing a closing operation during the duration of the opening drive signal and during the time t0 from the removal of the opening drive signal to the release of the holding-type shunt trip unit. For any actuator switch in the open position, the control unit interlocks it according to the following method: If there is no need to close the circuit, the control unit always applies a tripping drive signal to the holding-type shunt trip unit of the actuator switch; If there is a closing requirement, when the closing delay is non-zero, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at time t0 before the closing delay time of the execution switch arrives, and sends a closing drive signal to the closing drive mechanism of the execution switch at the time when the closing delay time arrives; when the closing delay is zero, if the pre-execution switch in the operation logic has not yet completed the opening, the control unit cancels the opening drive signal of the holding shunt trip unit of the execution switch at the same time as sending the opening drive signal to the pre-execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled; if there is no pre-execution switch in the operation logic or the pre-execution switch has completed the opening operation, the control unit first cancels the opening drive signal of the holding shunt trip unit of the execution switch, and sends a closing drive signal to the closing drive mechanism of the execution switch at time t0 after the opening drive signal is canceled.

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