Principal 7 Falhas comuns do relé Buchholz e como solucioná-las

Em oil-immersed power transformers, o relé Buchholz é um dos dispositivos de proteção mais importantes usados ​​para detectar falhas internas do transformador em um estágio inicial. Installed between the transformer main tank and conservator, this gas-operated relay continuously monitors gas accumulation and abnormal oil flow caused by insulation failures, superaquecimento, or electrical faults.

A properly functioning Buchholz relay can provide an early warning before serious damage occurs, helping utilities, subestações, and industrial facilities avoid costly transformer failures and unplanned outages.

No entanto, even the most reliable transformer protection relay can experience operational problems. Understanding common Buchholz relay faults and troubleshooting methods is essential for transformer maintenance engineers and asset managers.

Neste guia, we examine the seven most common Buchholz relay faults, their causes, warning signs, and practical solutions.

What Is a Buchholz Relay and How Does It Work?

A Buchholz relay is a gas-actuated protection device used exclusively on oil-filled transformers equipped with conservator tanks.

Its primary functions include:

• Detecting gas generated by internal transformer faults
• Monitoring sudden oil movement caused by severe faults
• Triggering alarm signals for developing problems
• Initiating trip signals during major internal faults

When insulation materials or transformer oil decompose due to overheating, descarga parcial, or arcing, gas bubbles form and accumulate inside the relay chamber. The relay then activates an alarm or trip circuit depending on fault severity.

Because of its ability to detect developing faults long before catastrophic failure occurs, the Buchholz relay remains one of the most effective transformer protection devices used today.

Principal 7 Common Buchholz Relay Faults

1. Frequent False Alarm Signals

Symptoms

• Buchholz relay alarm activates unexpectedly
• No confirmed transformer fault exists
• Minimal gas volume detected

Possible Causes

• Air trapped during transformer commissioning
• Improper oil filling procedures
• Loose flange connections
• Low conservator oil level
• Maintenance-related air ingress

Troubleshooting

1. Verify transformer oil level.
2. Inspect all pipe and flange connections.
3. Release trapped air using the relay vent valve.
4. Confirm proper oil filling procedures.
5. Monitor alarm recurrence after corrective action.

Prevention

Proper vacuum oil filling and commissioning practices significantly reduce false Buchholz relay alarms.

2. Excessive Gas Accumulation

Symptoms

• Repeated Buchholz relay alarm operation
• Visible gas collection inside relay
• Rising transformer temperature

Possible Causes

• Insulation overheating
• Localized hot spots
• Core insulation defects
• Loose electrical connections
• Minor winding faults

Troubleshooting

1. Collect gas samples from the relay.
2. Perform Dissolved Gas Analysis (DGA).
3. Compare gas data with historical trends.
4. Conduct infrared thermal inspections.
5. Investigate internal overheating sources.

Why It Matters

Persistent gas accumulation is often the earliest warning sign of an internal transformer fault.

3. Sudden Buchholz Relay Trip

Symptoms

• Immediate transformer shutdown
• No previous alarm indication
• Protection system records trip event

Possible Causes

• Internal short circuits
• Winding-to-winding faults
• Severe insulation failure
• Internal flashover

Troubleshooting

1. Keep transformer isolated.
2. Review relay event records.
3. Perform insulation resistance testing.
4. Check winding resistance values.
5. Conduct comprehensive transformer diagnostics.

Important

Never reset a Buchholz relay trip without identifying the root cause.

4. Oil Leakage Around the Buchholz Relay

Symptoms

• Visible oil leakage
• Falling conservator oil level
• Oil stains near relay flanges

Possible Causes

• Juntas danificadas
• Loose bolts
• Corrosion
• Mechanical damage during maintenance

Troubleshooting

1. Locate the exact leakage point.
2. Tighten flange connections.
3. Replace worn seals and gaskets.
4. Inspect relay housing for cracks.
5. Restore transformer oil level if necessary.

Risk

Oil leakage can allow moisture and air contamination, accelerating transformer insulation aging.

5. Stuck Float Mechanism

Symptoms

• Relay fails to respond during testing
• No alarm despite gas accumulation
• Inconsistent operation

Possible Causes

• Sludge buildup
• Oxidized oil deposits
• Mechanical wear
• Internal corrosion

Troubleshooting

1. Remove relay from service safely.
2. Inspect float movement manually.
3. Clean internal components.
4. Replace worn parts.
5. Perform operational testing before reinstallation.

Maintenance Tip

Annual inspection helps prevent mechanical failures from compromising transformer protection.

6. Faulty Reed Switch or Contact Assembly

Symptoms

• Alarm circuit failure
• False indications
• Intermittent operation

Possible Causes

• Electrical aging
• Contact deterioration
• Entrada de umidade
• Vibration damage

Troubleshooting

1. Check electrical continuity.
2. Verify switch operation.
3. Inspect terminal connections.
4. Replace defective components.
5. Test alarm and trip circuits.

Modern Practice

Many modern Buchholz relays use reed-switch technology for improved reliability and environmental compliance.

7. Relay Operation During External Disturbances

Symptoms

• Alarm or trip occurs during:
  • Transporte
  • Earthquakes
  • System switching
  • Nearby short-circuit events

Possible Causes

• Sudden oil surges
• Excessive vibration
• Incorrect relay sensitivity settings

Troubleshooting

1. Review system disturbance records.
2. Check relay calibration.
3. Verify installation stability.
4. Inspect mounting hardware.
5. Evaluate whether operation was genuine or nuisance triggering.

Warning Signs That Should Never Be Ignored

The following conditions often indicate developing transformer problems:

• Repeated Buchholz relay alarms
• Rapid gas accumulation
• Rising oil temperature
• Abnormal DGA results
• Sudden relay trips
• Frequent protection system events

Ignoring these warning signs can lead to severe transformer damage and costly downtime.

Preventive Maintenance Checklist for Buchholz Relays

A proactive maintenance program significantly improves transformer reliability and extends service life.

Frequently Asked Questions (Perguntas frequentes)

Why does a Buchholz relay give an alarm?

A Buchholz relay alarm is typically caused by gas accumulation inside the relay chamber. Common causes include insulation overheating, oil decomposition, loose electrical connections, or trapped air introduced during maintenance.

What gases are commonly found in a Buchholz relay?

Typical gases include:

• Hydrogen (H₂)
• Methane (CH₄)
• Ethylene (C₂H₄)
• Ethane (C₂H₆)
• Acetylene (C₂H₂)

The gas composition can help identify the type of transformer fault through Dissolved Gas Analysis (DGA).

What causes a Buchholz relay trip?

A Buchholz relay trip usually occurs when a severe internal fault creates a rapid oil surge between the transformer tank and conservator. Common causes include winding short circuits, quebra de isolamento, and internal arcing.

Can a transformer continue operating after a Buchholz alarm?

In some cases, sim. No entanto, the cause of the alarm must be investigated immediately. Gas analysis and transformer diagnostic testing should be performed before determining whether continued operation is safe.

How often should a Buchholz relay be tested?

Most utilities recommend functional testing at least once per year, along with routine visual inspections and alarm/trip circuit verification every six months.

Looking for Reliable Transformer Protection Components?

Effective transformer protection depends on the quality of every component in the system.

At PDDN, we supply a wide range of transformer accessories and protection devices, incluindo:

• Relés Buchholz
• Buchas do transformador
• Indicadores de nível de óleo
• Pressure Relief Devices
• Winding Temperature Indicators
• Conservator Accessories

Our engineering team can help you select the right components for power transformers, distribution transformers, subestações, projetos de energia renovável, e aplicações industriais.

Contact us today for technical support, product specifications, and competitive quotations.

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O que é um relé Buchholz e por que ele é tão importante para a proteção de transformadores?

Author

PDDN – Power Distribution & New Energy Solutions

PDDN specializes in transformers, subestações, power distribution equipment, solar energy systems, soluções de armazenamento de energia, and integrated power infrastructure projects. Our engineering team is committed to providing reliable electrical equipment and technical expertise for utility, industrial, and renewable energy applications worldwide.