BUCHHOLZ RELAY – THE SILENT GUARDIAN OF OIL-IMMERSED TRANSFORMERS
1. Introduction
The Buchholz Relay is one of the most essential protective devices installed on oil-immersed transformers.
Its main function is to detect early-stage internal faults such as arcing, winding short circuits, or insulation failures.
By identifying these problems before they escalate, the relay helps prevent severe damage, ensure system reliability, and enhance operational safety for electrical networks.
2. Structure and Operating Principle
The Buchholz Relay is mounted on the pipe connecting the main transformer tank and the conservator.
Inside the relay are two floats and two mercury switches (or magnetic sensors), performing two main functions:
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Alarm Function: During minor internal faults, gases generated from the fault accumulate inside the relay. This causes the upper float to drop, activating the alarm contact and sending a warning signal.
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Trip Function: In case of severe faults, the sudden oil movement caused by pressure variations tilts the lower float, triggering the trip contact to disconnect the transformer from the power system.
3. Importance and Benefits
The Buchholz Relay plays a vital role in early detection of internal faults, protecting key components such as the windings, magnetic core, and insulating oil.
With its high sensitivity, reliability, and automatic operation, the relay acts as an “early warning system” for large-capacity transformers used in substations, industrial zones, and power plants.
In short, it ensures long-term operational stability, safety, and efficiency for every transformer system.
4. Application at CTC
At Hanoi Electric Equipment and Transformer Manufacturing JSC (CTC), all oil-immersed transformers are equipped with high-quality Buchholz Relays, fully compliant with international standards IEC 60214 and IEC 60076.
This ensures maximum safety, durability, and performance during operation.
In addition, CTC provides inspection, maintenance, and replacement services for Buchholz Relays used in operating transformer systems across Vietnam, helping customers maintain stable and cost-effective performance.
5. Conclusion
The Buchholz Relay is more than just a protective device — it is the “silent guardian” ensuring the safety, reliability, and longevity of every oil-immersed transformer.
Choosing CTC transformers, equipped with international-standard protection systems, is the smartest way to secure your power network with efficiency and peace of mind.