What is a DC screen? What is the use of a DC screen?


Release time:

2023-04-19

DC screen is one of the indispensable electrical equipment in the power system, often produced by Derun ElectricHigh voltage switchgearCompanionship. Provide DC power supply for high-voltage switch in normal operation and accident state of split closing, relay protection, automatic control, switch signal indication, accident lighting, etc. The reliability of DC screen is irreplaceable by other power supply devices, which can meet the high reliability requirements of power supply in substations and power plants.

Wanzheng DC screen

DC screen is one of the indispensable electrical equipment in the power system, often produced by Derun ElectricHigh voltage switchgearCompanionship. Provide DC power supply for high-voltage switch in normal operation and accident state of split closing, relay protection, automatic control, switch signal indication, accident lighting, etc. The reliability of DC screen is irreplaceable by other power supply devices, which can meet the high reliability requirements of power supply in substations and power plants.

Why should comprehensive protection relays and control circuits use DC instead of AC 

First, alternating current is alternating and used in control loops, single-phase control, just in the case of split closing or accident tripping, that point is exactly at the potential 0 position, then it can't jump or close

Second, if the alternating current control loop is short-circuited to the ground, it will not be used immediately, and the control switch must be jumped off, or the control loop or control cable electrical appliances will be burned out 

And using direct current:

First, direct current is guaranteed by the DC charger charging module, and at the same time, parallel batteries ensure that there is still direct current in the event of an accident, and ensure that there is still electric energy to jump off all the switches of the fault in the event of a failure, and play a certain protective role  

Second, the direct current potential is stable, but the zero point, in use, no matter when the opening and closing, can ensure that there is a rated voltage and can be reliably opened  

Third, the use of direct current is generally 220V (positive and negative poles to ground are +110V -110V) At this time, even if the control loop has a little grounding phenomenon, the loop voltage is still rated and can still ensure reliable opening and closing, and DC ground faults can be found without affecting equipment operation under the condition of ensuring operation 

System energy flow diagram

DC screen flow diagram

The composition of the DC screen

DC screen components

As can be seen from the above figure, the DC screen is mainly composed of AC power input unit, rectifier unit, battery charge and discharge control unit, battery pack, DC feed, bus monitoring (voltage measurement, isolation, flash) and other parts. The DC screen with microcomputer control adds a central monitoring unit, making the interface of the DC screen more friendly, operation and control simpler.

DC screen check items

DC screen check items

DC screen check items

DC screen check items

DC screen check items

DC screen inspection items