Dual-power Switchgear

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 The dual-power switchgear is an important electrical device used in the power system, mainly used to achieve the switching and distribution of two

 power supplies, ensuring the reliability and continuity of power supply. The following is a detailed introduction to the dual-power switchgear:

### Working Principle

- **Common Modes**

    - **Automatic Transfer and Restoration**: Under normal circumstances, one power supply (the main power supply) supplies power, and the other

 power supply (the standby power supply) is in a hot standby state. When the main power supply fails or the voltage is abnormal, the dual-power 

switchgear will automatically switch the load to the standby power supply to ensure the continuity of power supply. When the main power supply

 returns to normal, the switchgear will automatically switch the load back to the main power supply.

    - **Automatic Transfer without Restoration**: When the main power supply fails, it will automatically switch to the standby power supply. However, 

when the main power supply returns to normal, it will not automatically switch back, and manual operation is required to restore the main power 

supply for powering.

    - **Mutual Standby**: There is no primary or secondary distinction between the two power supplies. According to actual needs or the power 

supply status, either power supply can be flexibly selected for powering. When the power supply in use fails, it will automatically switch to the

 other power supply.

- **Switching Methods**

    - **Mechanical Interlock Switching**: The interlock between the two power supply switches is achieved through a mechanical device to ensure 

that only one power supply switch can be closed at any time, preventing the parallel operation of the two power supplies. This method has high

 reliability, but the switching speed is relatively slow.

    - **Electrical Interlock Switching**: The interlock and switching of the two power supply switches are realized by using electrical signals and

 control circuits. It has the advantages of fast switching speed and flexible control, but it has high requirements for the reliability of the control circuit.

### Structural Composition

- **Incoming Line Unit**: It is used to connect the two power supply incoming lines and usually includes equipment such as circuit breakers, 

disconnectors, and current transformers, which are used for the control, protection, and measurement of the power supply.

- **Switching Unit**: It is the core part of the dual-power switchgear, mainly composed of a dual-power transfer switch, a controller, etc. The 

dual-power transfer switch is responsible for realizing the switching between the two power supplies, and the controller controls the action 

of the transfer switch according to the power supply status and the preset switching logic.

- **Metering Unit**: It is used to measure the electricity of the two power supplies and usually includes equipment such as electricity meters, 

voltage transformers, and current transformers.

- **Outgoing Line Unit**: It is used to connect the load and distribute the switched power supply to various electrical equipment or lines. It 

usually includes equipment such as circuit breakers, contactors, and thermal relays, which are used for the control and protection of the load.

- **Control and Protection Unit**: It includes various control circuits, relays, fuses, etc., which are used to achieve functions such as operation 

control, signal indication, and fault protection of the dual-power switchgear.

### Application Scenarios

- **Hospitals**: Important medical equipment such as operating rooms and intensive care units require a reliable power supply. The dual-power 

switchgear can quickly switch to the other power supply when one power supply fails, ensuring the normal operation of the medical equipment 

and safeguarding the lives of patients.

- **Banks**: Data centers, business outlets, etc., have extremely high requirements for the reliability of power supply. The dual-power switchgear 

can ensure that when the utility power fails, it can be promptly switched to the standby power supply to avoid data loss and business interruption.

- **Airports**: Equipment such as runway lights, communication and navigation equipment, and baggage handling systems all require uninterrupted 

power supply. The dual-power switchgear can provide a reliable power supply guarantee for these devices, ensuring the normal operation of the airport.

- **Industrial Enterprises**: For some industrial enterprises with continuous production, such as the chemical industry and steel industry, a power

 outage may cause huge economic losses and safety accidents. The dual-power switchgear can quickly switch when the power supply fails, ensure 

the continuous operation of production equipment, and reduce power outage losses.

### Selection Key Points

- **Rated Voltage and Current**: Select a dual-power switchgear with appropriate rated voltage and current according to the actual power supply 

voltage level and the magnitude of the load current.

- **Short-circuit Withstand Current**: Consider the possible short-circuit fault current of the system and select a switchgear with sufficient short-circuit

 withstand current capability to ensure the safe and reliable operation of the equipment during a short-circuit fault.

- **Switching Time**: Select a dual-power switchgear with an appropriate switching time according to the requirements of the load for the power outage

 time. For example, for some electronic devices with strict requirements for the power outage time, a switchgear with a switching time in the millisecond

 range may need to be selected.

- **Type of Transfer Switch**: Select an appropriate type of dual-power transfer switch, such as PC class (special type) or CB class (circuit breaker type), 

according to the application scenario and actual needs. The PC class transfer switch has the characteristics of fast switching speed and high reliability 

and is suitable for occasions with high requirements for the switching time; the CB class transfer switch has overload and short-circuit protection 

functions and is suitable for occasions with high requirements for protection.