Power transformers are among the most critical assets in electrical distribution and transmission systems. To ensure safe operation, long service life, and reduced downtime, transformers are equipped with a variety of protection and monitoring accessories. These devices help detect faults early, prevent catastrophic failures, and improve operational reliability.

In this article, we explore the Top 10 most important transformer protection accessories widely used in modern oil-immersed transformers.

1. Buchholz Relay

The Buchholz Relay is one of the most important protection devices for oil-filled transformers with conservator tanks.

It detects:

• Internal faults
• Gas generation
• Oil movement caused by short circuits

When gas accumulates slowly, the relay sends an alarm signal. In case of severe faults causing rapid oil flow, it triggers a trip signal to disconnect the transformer.

Main Benefits

• Early fault detection
• Prevents major transformer damage
• Reliable mechanical protection

Buchholz Relay

2. DGPT2 Relay

The DGPT2 relay is a multi-function protection device commonly used on hermetically sealed distribution transformers.

It combines:

• Gas detection
• Pressure protection
• Oil temperature monitoring

DGPT2 provides both alarm and trip functions, making it a compact and effective protection solution.

Applications

• Distribution transformers
• Compact substations
• Renewable energy projects

DGPT2-relay

3. Pressure Relief Device (PRD)

A Pressure Relief Device protects the transformer tank from excessive internal pressure caused by internal faults or arcing.

When pressure rises beyond safe limits, the PRD opens automatically to release pressure and avoid tank rupture or explosion.

Advantages

• Improves personnel safety
• Prevents tank deformation
• Essential for medium and large transformers

4. Oil Temperature Indicator (OTI)

The Oil Temperature Indicator (OTI) monitors top oil temperature inside the transformer tank.

If the temperature exceeds preset values:

• Alarm contacts activate
• Cooling systems start automatically
• Trip signals can be generated

OTI helps prevent overheating and insulation aging.

5. Winding Temperature Indicator (WTI)

The WTI measures simulated winding hot-spot temperature, which is often higher than oil temperature.

This accessory protects transformer windings from:

• Overloading
• Thermal stress
• Insulation deterioration

WTI is especially important for transformers operating under variable loads.

6. Magnetic Oil Level Gauge (MOG)

The Magnetic Oil Gauge monitors oil level in the conservator tank.

Low oil level may indicate:

• Oil leakage
• Internal problems
• Temperature abnormalities

MOG devices often include alarm contacts for remote monitoring.

7. Silica Gel Breather

A Silica Gel Breather prevents moisture from entering the transformer conservator during oil expansion and contraction.

The silica gel absorbs humidity from incoming air, helping maintain oil dielectric strength and insulation quality.

Why It Matters

• Prevents moisture contamination
• Extends transformer life
• Reduces oil degradation

8. Sudden Pressure Relay (SPR)

The Sudden Pressure Relay detects rapid pressure increases caused by severe internal faults.

Unlike PRD, which releases pressure mechanically, SPR sends electrical alarm/trip signals to protection systems.

Common Applications

• Large power transformers
• Transmission substations
• Critical industrial installations

9. Transformer Bushing

Bushings provide insulated electrical connections between transformer windings and external power systems.

High-quality bushings improve:

• Electrical insulation
• Mechanical strength
• Long-term reliability

Poor bushing conditions are a common cause of transformer failures.

10. Cooling Fans & Monitoring System

Cooling systems help maintain transformer operating temperature within safe limits.

Modern transformers use:

• Cooling fans
• Oil pumps
• Smart monitoring systems
• SCADA integration

These systems improve efficiency and support predictive maintenance strategies.

Why Transformer Protection Accessories Matter

Transformer protection accessories are essential because they:

• Prevent catastrophic failures
• Improve system reliability
• Extend transformer service life
• Reduce maintenance costs
• Enhance operational safety

Without proper protection devices, even minor transformer faults can lead to major outages and expensive repairs.

MBT Transformer Protection Solutions

MBT provides transformers equipped with advanced protection accessories designed according to IEC standards. Our solutions support:

• Industrial power systems
• Renewable energy projects
• Utility distribution networks
• Oil & Gas applications

MBT integrates reliable transformer protection systems to ensure safe and efficient operation under demanding environments.

Conclusion

Modern transformers require more than just high-quality core and winding design. Protection accessories such as Buchholz Relays, DGPT2, OTI, WTI, PRD, and Breathers play a critical role in maintaining transformer safety and reliability.

Selecting the right transformer protection system helps operators reduce downtime, improve safety, and maximize transformer lifespan.