1. Dual Power Supply 

A dual power supply system refers to an arrangement where two independent power sources—fundamentally distinct in origin—are used to ensure uninterrupted power delivery. Typically, one acts as the primary source while the other remains on standby, ready to take over should the main source fail. The defining characteristic of dual power supply is not the number of feeders but the autonomy and independence of the power sources themselves.

This configuration is not casually deployed. Approval for dual power supply is generally reserved for critical applications where power outages can lead to significant societal, economic, or safety consequences. According to standard practice, such situations include:

• National Security and Administration: Key government, military, and defense research institutions, where an interruption could disrupt sensitive operations or compromise safety.

• Emergency and Public Utilities: Broadcast centers, transportation hubs, emergency call centers, and healthcare facilities where service continuity is essential.

• Industrial and Strategic Enterprises: Factories dealing with hazardous materials or precision manufacturing, where power loss could lead to equipment damage, raw material wastage, or irreversible production loss.

• Public Spaces of Critical Importance: High-density commercial centers or landmarks with strict uptime requirements.

• Specialized Production Needs: Facilities with continuous or batch processes requiring unbroken electrical input.

In all these scenarios, the fundamental idea behind dual power supply is resilience through source diversification. The incoming lines must stem from independent substations or separate sections of the utility grid to qualify as true dual-source feeds.

2. Dual Circuit Power Supply 

Dual circuit power supply, by contrast, refers to a scenario where two feeder circuits—usually of equal voltage—are employed to serve a single load or facility. These circuits might originate from either the same substation (but different switchgear sections) or two adjacent substations. The core objective is operational flexibility and fault tolerance rather than true source redundancy.

In practical terms, this means that if one feeder suffers a fault, the other circuit can be instantly switched in to maintain continuity. The system is frequently deployed in campuses, corporate compounds, or transit infrastructure.

Example: Wuhan’s light rail network operates on a dual circuit model. Two independent substations transmit power to the system. Even if one line goes down, the alternate route ensures that operations continue seamlessly.

It’s essential to clarify a frequent misconception: when both feeders come from the same primary source—i.e., the same substation or transformer yard—they do not qualify as dual power supply, even if physically separate. This is because the source remains singular; the circuits, though redundant, are tied to a common risk domain.

In other words:

• Dual circuit → May share the same source.

• Dual power → Must originate from independent sources.

3. Core Differences Between Dual Power and Dual Circuit Systems

The distinction between the two systems lies in their architectural logic and protective scope. Below is a technical breakdown:

Definition & Source Independence

• Dual Power Supply: Two genuinely independent sources (e.g., different substations, or a substation plus an on-site generator). Loss of one does not compromise the other. This ensures true power autonomy.

• Dual Circuit Supply: Two feeders, typically from the same substation or transformer yard. May be physically isolated but logically coupled through a common power source.

Compliance and Standardization

• Standard Terminology (per GB50052-2009): What is colloquially called "dual power" is formally defined as "dual-source power." It requires that two circuits be functionally and electrically independent, ensuring safe, redundant power supply even under grid failure conditions.

• Transformer Requirements: Dual power mandates feeders from separate busbars or different transformers. Systems using transformers from the same busbar cannot be categorized as dual power, regardless of internal separation.

• Dual Circuit Flexibility: Dual circuit setups are more forgiving. They may stem from the same transformer, the same busbar, or even ring main units, so long as the switching logic allows alternate supply routing during failure events.

Reliability and Application Scenarios

• Dual Power Supply: Suited for first-tier (一级) loads—critical systems with zero tolerance for outages. These include data centers, emergency rooms, air traffic control systems, etc.

• Dual Circuit Supply: Generally meets the needs of second-tier (二级) loads—such as hospitals, banks, or educational institutions—where momentary outages are tolerable, but backup must kick in quickly.

Failure Response Mechanism

• Dual Power: If one power source fails due to regional blackout or transformer damage, the second, isolated source remains unaffected and continues supplying power.

• Dual Circuit: If the fault lies within the shared source (e.g., a transformer fault), both circuits may be compromised, leaving the load without power.

Conclusion: A Structural and Strategic Distinction

Though outwardly similar—both often utilizing two physical incoming lines—dual power supply and dual circuit configurations serve different strategic purposes in electrical design:

• Dual Power Supply is about source diversity. It is a premium-grade solution for uninterrupted operation in critical infrastructure.

• Dual Circuit Supply is about path redundancy. It is a practical compromise where reliability is required but full independence is not essential.

In China's evolving electrical landscape, both architectures are vital. Dual circuit systems serve the majority of medium-critical applications, providing resilience with economic feasibility. Dual power configurations, while costlier, are indispensable in high-stakes environments where any interruption is unacceptable.

Understanding the nuanced difference between these two systems ensures more appropriate design selection, enhanced power security, and optimized resource allocation across urban and industrial projects.