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Writer： Hengfeng you electric Time：2026-09-25 views：times
Common rated voltages for power DC systems include DC220V and DC110V. The appropriate voltage level should be determined according to the project scale, circuit breaker operating mechanism, relay protection and control systems, and other project-specific requirements.
A complete DC panel system typically includes:
During normal operation, the charging modules supply power to DC loads such as relay protection, monitoring and control, signaling, and control equipment, while maintaining the battery bank in float-charging mode. When the AC input power fails, the battery automatically takes over the DC loads and provides continuous power for protection operations and circuit breaker opening and closing.
Depending on the application, DC panels are mainly used in:
For batteries, valve-regulated lead-acid batteries (VRLA) remain a common solution for many industrial power DC systems. For projects with limited space or special weight requirements, dedicated lithium battery systems and corresponding battery management systems can also be selected according to the project technical specifications.
Battery capacity is generally expressed in Ah (ampere-hours). Capacity selection should not simply be based on the number of high-voltage switchgear panels or conventional configurations. Instead, it should be calculated based on the DC load and battery discharge conditions.
DC panel battery capacity calculations mainly consider:
① Continuous Load
This includes relay protection, monitoring and control, communication, signaling, and other DC loads that operate continuously.
② Emergency Load
DC equipment that must remain operational after the AC power supply fails.
③ Emergency Power Supply Duration
The required backup duration should be determined according to the project category, system design requirements, and operating conditions. A single fixed duration should not be applied to all projects.
④ Circuit Breaker Operating Load
Circuit breaker opening and closing operations can generate relatively high instantaneous currents. The battery terminal voltage under this operating condition should therefore be checked to prevent excessive voltage drop during operation.
⑤ Battery Discharge Characteristics and Ambient Temperature
The actual usable battery capacity is affected by factors such as discharge rate, end-of-discharge voltage, and ambient temperature. Capacity correction is particularly important in low-temperature environments.
Therefore, DC panel battery capacity should not be determined simply by looking at the nominal Ah rating. It should be calculated according to the actual DC loads and project design conditions.
DC loads vary significantly between projects. The following values are provided only as references for common engineering configurations and do not represent fixed standard capacities:
| Typical Application | Common Capacity Reference | Main Selection Basis |
|---|---|---|
| Small high-voltage distribution room | 65Ah, 100Ah, etc. | Continuous load, emergency duration and circuit breaker operating load |
| Industrial substation | 100Ah, 200Ah, etc. | Secondary loads and circuit breaker operating current |
| PV step-up substation / GIS substation | 200Ah or above is common | Number of feeders/bays, protection and operating loads |
| Large or special industrial projects | Determined by calculation | System load and project technical requirements |
The above capacities are provided only as engineering references. The final battery capacity should be determined through calculation based on the actual DC load, emergency power supply duration, discharge characteristics, and project design conditions.
Suppose a distribution room in a chemical industrial park is equipped with eight high-voltage switchgear panels. If the DC panel is configured with a relatively small battery capacity based only on conventional experience, without accounting for all continuous and emergency secondary loads, the battery may not be able to provide the required backup duration when the external AC power supply fails.
As the battery terminal voltage continues to decline, relay protection, control systems, and circuit breaker operation may also be affected.
Therefore, when designing a DC system, all DC loads should first be identified and calculated. The required emergency operating duration and battery capacity should then be determined instead of simply applying a fixed battery capacity based on the number of high-voltage switchgear panels.
After determining the battery capacity, the charging modules should also be properly configured.
The charging system needs to simultaneously meet the DC load demand during normal operation and the battery charging requirements. A certain capacity margin should also be considered according to project requirements.
The number of charging modules should take the required redundancy into account. For example, under an N+1 configuration, if one charging module is out of service, the remaining modules should still be capable of meeting the specified DC load and battery charging requirements.
Therefore, the number of charging modules should not be determined only according to the "total load current." The following factors should be considered together:
The DC monitoring unit is an important part of the DC panel and typically monitors:
For important substations and industrial projects, communication interfaces can also be configured according to the requirements of the project automation system, allowing DC system operating status and alarm information to be transmitted to the station control level or power distribution monitoring system.
If a positive or negative ground fault occurs in a DC system and is not detected and addressed promptly, it may further affect protection and control circuits.
Therefore, the DC system should be equipped with an insulation monitoring and ground fault alarm function compatible with the system design to identify insulation abnormalities in a timely manner.
For example, if insulation deterioration occurs in secondary cables inside a photovoltaic prefabricated power cabin after long-term operation, a DC system with an effective insulation monitoring function can detect the ground fault and issue an alarm. Maintenance personnel can then identify the faulty circuit based on the alarm information.
Therefore, when selecting a DC panel, buyers should not compare only battery capacity and charging module prices. Monitoring and insulation monitoring functions should also be included in the technical evaluation.
Outgoing circuits distribute DC power to different loads, including protection, control, measurement, and circuit breaker operating circuits.
The number of outgoing circuits should be determined according to the number of high-voltage switchgear panels, GIS bays, and actual DC loads.
Control Circuits
These provide DC power to relay protection, monitoring and control devices, and related control equipment.
Closing Circuits
These provide power to circuit breaker closing circuits. Since circuit breaker operation can generate relatively high instantaneous current, the circuit breaker operating mechanism parameters should be checked during system design.
Opening and Protection Circuits
These should be independently configured according to project design requirements to ensure reliable DC power for protection and circuit breaker operation under fault conditions.
In addition to battery capacity, charging modules, and outgoing circuits, the following parameters can also affect the actual operating reliability of a DC panel.
| Selection Parameter | Main Considerations |
|---|---|
| DC system voltage | DC110V or DC220V, determined according to project requirements |
| Battery type | VRLA batteries, dedicated power lithium batteries, etc. |
| Battery capacity | Continuous load, emergency load, backup duration and discharge characteristics |
| Charging modules | Load current, charging requirements and redundancy configuration |
| Outgoing circuits | Number of high-voltage switchgear panels/GIS bays and load classification |
| Closing current | Circuit breaker operating mechanism parameters |
| Monitoring functions | AC, DC, battery, module and insulation status |
| Communication functions | Modbus, IEC 104, etc., according to project requirements |
| Environmental conditions | Temperature, humidity, altitude and heat dissipation conditions of prefabricated cabins |
For indoor industrial distribution rooms, VRLA batteries can generally be selected according to project requirements.
For prefabricated power cabins or other applications where space is limited or equipment weight is a concern, dedicated power lithium battery systems may be considered according to the technical specifications.
It should be noted that when lithium batteries are used in power DC systems, the batteries and battery management systems should meet the requirements for power system applications. Ordinary consumer-grade lithium batteries should not be directly used as substitutes.
Battery performance is affected by ambient temperature.
High-temperature or enclosed distribution rooms and prefabricated power cabins require adequate ventilation and heat dissipation. In low-temperature environments, battery discharge performance should be considered when determining the required capacity.
For projects in extremely cold, hot, or high-altitude environments, the DC panel and battery system should be specifically designed according to local environmental conditions.
For projects that require connection to a station control system or energy management system, communication interfaces such as Modbus and IEC 104 can be configured according to the site automation requirements, enabling remote monitoring of DC system operating status, faults, and alarms.
Configuring the battery only according to "how many Ah are required for a certain number of high-voltage switchgear panels" without calculating the actual secondary loads may result in insufficient backup duration after AC power failure.
If too few charging modules are installed, the failure of one module may affect the system's power supply or battery charging capability. Appropriate module redundancy should therefore be designed according to project requirements.
If a DC ground fault is not detected and alarmed in time, the risk of affecting protection and control systems may increase.
If many high-voltage switchgear panels or critical secondary loads share a single outgoing circuit, a fault on that circuit may expand the affected area of the DC power supply system.
For special environments such as prefabricated power cabins, extremely cold regions, and high-temperature regions, insufficient consideration of battery temperature and heat dissipation may affect actual battery performance and service life.
A DC panel is not simply a combination of a cabinet and batteries. Its core function is to provide a reliable DC power system designed according to the project's actual DC load requirements.
Hengfengyou Electric provides DC220V and DC110V power DC panels, as well as AC/DC integrated power supply systems. Based on the number of high-voltage switchgear panels and GIS bays and the characteristics of secondary loads, we can assist customers in determining battery capacity, charging module configuration, outgoing circuits, and monitoring solutions.
Our products can be supplied together with complete high- and low-voltage electrical equipment according to project requirements and are suitable for:
For projects requiring DC panels, we recommend providing the following information during the quotation stage: DC system voltage, DC load, emergency power supply duration, number of high-voltage switchgear panels/GIS bays, circuit breaker operating parameters, and project environmental conditions. This allows for more accurate system configuration and technical proposals.
Hengfengyou Electric — A power transmission and distribution equipment supplier, providing transformers, switchgear, DC panels, and complete electrical equipment for industrial and power projects.
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