I. Overview of dual power supply

The dual power supply automatic diverter switch plays a vital role in modern power grid systems. It is a microprocessor-controlled device that can initiate switching between grid power and grid power or grid power and generator power to ensure continuous power supply. This device has a wide range of applications in numerous fields, the most common of which include elevators, fire protection, monitoring, and lighting.
In the elevator field, the importance of dual power supply is self-evident. Once the common power supply fails or stops, the dual power switch can quickly and automatically put into the backup power supply to ensure the normal operation of the elevator and the safety of passengers. In the field of fire fighting, reliable power supply is the key to the normal operation of fire fighting equipment. Dual power supply can provide continuous power for fire fighting facilities in case of emergency, providing strong guarantee for fire fighting and rescue work. The monitoring system is also inseparable from the dual power supply, which ensures the uninterrupted operation of the monitoring equipment and provides stable support for security prevention.
According to the material searched, dual power automatic switching appliances (transfer switch ATS also called ATSE), is composed of one or several transfer switch appliances and other necessary appliances for monitoring power circuits, and one or several load circuits from one power source to another power source automatically. It is referred to in the electrical industry as “dual power automatic transfer switch” or “dual power switch”.
Dual power supply is mainly categorized as contactor type, molded case circuit breaker type / load disconnecting switch type, and one-piece automatic transfer switch appliance type. Different types of dual power supply have their own characteristics and applicable scenarios. For example, the contactor type power switching system uses the contactor as the switching actuator, the disadvantage of which is that the contactor of the main circuit needs to be energized for a long period of time in the secondary circuit, which is prone to temperature heating, contact bonding, coil burning and other faults, and has been gradually replaced by new products. The integrated automatic transfer switch class power conversion system set switch and logic control in one, without the need for additional controllers, the real realization of mechatronics, the product is generally a small conversion time, switching is smooth and reliable, energy-saving significant, no temperature heating, contact bonding, coil burning phenomenon, is the mainstream of the power switching class of products.
In short, dual power supply plays an important role in ensuring the stable operation of the power grid system and the continuous power supply of key equipment.
Second, the dual power supply configuration program

(A) Program 1 Introduction
According to the material searched, dual power supply configuration program one is: two power sources installed in the same place, and share the same low-voltage distribution cabinet, the feeder circuit or dual power switching circuit should be used four-pole switch.
The specific connection is: the front of the power-using equipment to install two three-pole circuit breakers with RCD protection for the dual power supply mutual throw. When a single-phase ground fault or a three-phase unbalance occurs in the power-using equipment, the single-phase ground fault current or the neutral current caused by the three-phase unbalance may flow through the N and PE lines of the circuit breaker circuit in the disconnected state. In order to avoid the magnetic field generated by the neutral current in the informal path from interfering with sensitive information equipment and malfunctioning of the circuit breakers, it is necessary to use four-pole switches for these two circuit breakers to cut off the path of fault current flow.
Applicable scenarios are: applicable to the higher requirements for power supply stability, and the two power sources are installed in the same place and share the same low-voltage distribution cabinets, such as the power supply system for key equipment in some small factories.
(B) Program two introduction
Program two is: dual distribution transformer for each other as a backup power supply, or transformer and diesel generator for each other as a backup power supply, and the neutral point of the transformer and generator are close to direct grounding. If the two sets of power supply shared low-voltage distribution cabinet, the incoming circuit should be used four-pole switch.
It is characterized by the following: the low-voltage distribution network is of TN-S grounding type, the neutral point of the transformer is grounded nearby, and the three-phase, N and PE wires are led from the transformer to the inlet circuit of the low-voltage distribution cabinet. Normal use of the two feeder circuit breakers closed and the busbar open, when the Ⅰ busbar on the power equipment in the event of a single-phase grounding fault, the correct path of the fault current is clear, but due to the uncertainty of the N line and the PE line bonding point, it may produce an informal path of the neutral current, causing the Ⅱ section of the feeder circuit breaker tripped to make the accident expanding. The use of a four-pole switch cuts off the irregular path of the fault current and eliminates the potential for accidents. If one of the transformers is replaced by a generator, the generator inlet circuit breaker must also be a four-pole switch.
Advantages are: it greatly improves the reliability of power supply, ensures that when the main power supply fails, the backup power supply can be put into use quickly and stably, and is suitable for places with very high requirements for power supply continuity, such as hospitals, communication centers and other important units.
(C) program three introduction
The third program is: two sets of power supply in the same room (common ground), but do not share the low-voltage distribution cabinet, then the power conversion switch in the secondary power distribution equipment can be used three-pole switch.
The connection is: transformer and generator are in the same low-voltage distribution house, but they do not share the low-voltage distribution cabinet. When three-phase unbalance occurs in the circuit breaker load of the secondary distribution equipment, three-phase unbalance current will appear in the neutral line of the power-using equipment, and the path of this current is a conventional path. Since ATSE is unidirectional in conversion, only one can be selected in the transformer inlet and generator inlet, and the neutral line current will not appear in the unconventional path.
Application: It is suitable for some places with limited space, but need to ensure certain power supply reliability, such as some important power areas in small shopping centers. In these occasions, it can meet the basic power supply requirements, but also save costs and space.