5 Differences Between High-Voltage Switchgear And Transformers
This article will compare the differences between high-voltage switchgear and transformers through five core dimensions, making it clear to non-professionals or industry novices a good understanding.
High-Voltage Switchgear Vs Transformer
Core Function Comparison
High-voltage switchgear: Its core function is “control and protection.”
Control: Connects or disconnects circuits as needed, enabling the commissioning and shutdown of power lines.
Protection: Quickly cuts off fault current when overloads, short circuits, or other faults occur in the line, acting like a fuse to protect downstream transformers, lines, and other equipment from damage.
Isolation: Creates a clear disconnect point during equipment maintenance, ensuring personnel safety.
Transformer: Its core function is “energy conversion.”
Voltage transformation: Utilizes the principle of electromagnetic induction to change the voltage level of alternating current. It is mainly divided into “step-down” (reducing transmission high voltage to distribution low voltage) and “step-up” (increasing voltage at the power plant for long-distance transmission).
Energy transfer: Achieves efficient energy transfer while transforming voltage; it does not generate energy itself.
In short: switchgear is the “command and control system” of electricity, and transformer is the “voltage converter” of electricity.
Operating Principle Comparison
High-voltage switchgear: Its core is the combination of mechanics and electrical control. Internally, it contains components such as circuit breakers, disconnectors, and load switches, controlling the on/off state of the circuit through the action of mechanical mechanisms (closing and opening). It is supplemented by relay protection devices and measuring instruments to achieve automated control and protection.
Transformer: Its core is based on the law of electromagnetic induction. When alternating current passes through the primary coil, it generates an alternating magnetic field. This magnetic field is conducted in the iron core and induces an electromotive force in the secondary coil. By changing the turns ratio of the primary and secondary coils, the voltage can be increased or decreased.
Position And Function In The Power System
High-voltage switchgear: Found throughout all parts of the power system.
In substations, it is located on the incoming and outgoing sides of transformers, controlling transformer switching and providing protection.
In distribution lines, it serves as a segment and connection point, improving power supply reliability.
Transformers: Typically located at critical nodes in the power system.
Step-up transformers: Located in power plants, they step up the voltage of electricity generated by generators before sending it to the transmission network.
Step-down transformers: Located in substations (such as 110kV/10kV substations) and at the user end (such as 10kV/0.4kV transformers in community distribution rooms), they gradually reduce the voltage to a usable level for the user.
Within a substation, multiple switchgear units typically surround and control one or more transformers.
Structural Composition Comparison
High-voltage switchgear: A complex assembly. Typical structure includes:
Cabinet: A metal enclosure providing support and protection.
Core components: Circuit breakers, disconnectors, grounding switches, and current/voltage transformers.
Auxiliary equipment: Relay protection devices, instruments, indicator lights, and operating mechanisms.
Insulation medium: Air (air insulation), SF6 gas (gas insulation), or solid insulating materials.
Transformer: Relatively simple and centralized in structure. Main components include:
Core: An iron core made of laminated silicon steel sheets, used for magnetic conduction.
Windings: Primary and secondary coils wound with copper or aluminum wire.
Insulation medium: Transformer oil (oil-immersed), epoxy resin (dry-type), or air.
Auxiliary components: Oil tank, radiator, oil conservator, tap changer, bushings, etc.
Classification Comparison
High-voltage switchgear: Diverse classifications, primarily based on:
Insulation medium: Air-insulated switchgear, SF6 gas-insulated switchgear (GIS), solid-insulated switchgear.
Installation method: Removable (handcart type), fixed type.
Main wiring method: Single busbar, double busbar, line transformer group, etc.
Transformers: Also richly classified, primarily based on:
Application: Power transformers, distribution transformers, rectifier transformers, etc.
Cooling method: Oil-immersed transformers (ONAN, ONAF, etc.), dry-type transformers.
Number of phases: Single-phase transformers, three-phase transformers.
How To Choose Between High-Voltage And Transformers?
In power projects, high-voltage switchgear and transformers are not mutually exclusive but rather complementary. The correct question is: How to select the appropriate switchgear and transformer for a project?
When selecting a transformer, the main considerations are:
Capacity (kVA): Determined based on total load requirements.
Voltage level: Input and output voltages.
Installation environment: Indoor or outdoor? Dry-type transformers are often used in locations with high fire safety requirements (such as indoor buildings).
Energy efficiency rating: Select transformers with higher energy efficiency standards (such as China’s Level 1 energy efficiency rating) to reduce operating losses.
When selecting high-voltage switchgear, the main considerations are:
Rated current and short-circuit breaking capacity: Must meet the system’s maximum operating current and potential short-circuit current.
Reliability requirements: Critical loads require switchgear and protection configurations with higher reliability.
Land area: Gas-insulated switchgear (GIS) saves more space than air-insulated switchgear (AIS).
Automation level: Whether intelligent functions such as remote monitoring and remote operation are required.
FAQ
4.1 What Is The Service Life Of Switchgear And Transformers?
Transformers: Their design life is typically long, generally 20-30 years or even longer. Their lifespan mainly depends on the aging rate of the insulation materials and is closely related to operating temperature and overload conditions.
High-voltage switchgear: Its design life is typically 20-25 years. Its lifespan mainly depends on wear and tear of the mechanical operating mechanisms, the number of short-circuit current interruptions, and the degradation of the performance of the insulation components.
4.2 Why Are There More Switchgear Than Transformers In A Substation?
Because a transformer requires multiple switchgear units to work together, a substation typically has a layout of “many switchgear units and few transformers”.
4.3 Do Ordinary People Come Into Contact With Switchgear And Transformers In Their Daily Lives?
You will “come into contact” with the electricity they provide, but you usually won’t directly touch the equipment itself.
Transformer: That “big box” (distribution transformer) you see next to the green space in your community or in the underground distribution room is the equipment that transforms 10kV voltage into 380V/220V for your home.
Switchgear: Usually installed in a locked distribution room, it’s invisible to the average person. But it works behind the scenes to protect the power supply safety of your community.
4.4 What Are The Differences In Investment And Cost?
Transformers: Especially large-capacity transformers, are among the most valuable single pieces of equipment in a substation, with their cost primarily determined by materials (copper, iron, and oil).
High-voltage switchgear: While the price per unit may be lower than that of transformers, their large number can contribute significantly to the total investment. Their cost depends on the technological sophistication, the breaking capacity of the circuit breakers, and the level of automation.
4.5 How Do Transformers And Switchgear Improve Energy Efficiency?
Transformers: Improving energy efficiency is key. Using high-quality silicon steel sheets and amorphous alloy cores, among other low-loss materials, can significantly reduce no-load and load losses, making them a major contributor to power grid energy conservation.
High-voltage switchgear: Primarily saves energy by reducing its own losses, for example, by using low-resistance contact materials. More importantly, it ensures the efficient and stable operation of the power grid at the system level by quickly clearing faults and optimizing network operation (such as reactive power compensation switching), indirectly improving energy efficiency.
Conclusion
High-voltage switchgear and transformers are two core pieces of equipment in a power system that have very different functions but work closely together. Transformers focus on the voltage conversion and transmission of energy, while switchgear focuses on the control, protection, and distribution of circuits.
