Transformator overdrukapparaat: Functie, Soorten, en werkingsprincipe (2025 Gids)

What Is a Transformer Pressure Relief Device?

A transformer pressure relief device is a mechanical safety valve (or membrane) installed on the transformer tank—typically
on the top cover—to vent gas and oil mist when internal pressure exceeds a preset threshold. By doing so,
it prevents catastrophic tank deformation or explosion and provides a visible and/or electrical signal to trigger protection
actions. PRDs are widely used on oil-immersed power and distribution transformers, including those in
renewable, industrieel, and utility environments.

• Primary purpose: relieve overpressure to protect the tank and personnel.
• Typical set pressure: engineered per transformer design (manufacturer-specified range).
• Reset behavior: spring-loaded valves auto-reset; rupture discs are single-use.
• Interface: mounting flange on tank; optional microswitch for alarm/trip signals.

Transformer Pressure Relief Device Key Takeaways

• Prevents catastrophic failures: releases excess internal pressure before tank rupture.
• Two major designs: reusable spring-loaded valves vs single-use rupture (burst) discs.
• Safety signaling: many PRDs include a microswitch for remote alarm/trip.
• Standards-driven: selection and installation should align with IEC/IEEE/GB standards and utility specs.
• Maintenance matters: periodic inspection of seals, reset integrity, and signal wiring is essential.

Why Pressure Relief Matters in Transformers

Internal transformer pressure can spike due to thermal expansion of oil, fault-generated gases,
overloads, of isolatie defect. Without a proper relief path, the tank can bulge,
welds may fail, and flammable oil mist could ignite—posing severe safety, milieu, and downtime risks.
A properly specified PRD is the transformer’s first line of defense against these scenarios.

• Risicoreductie: mitigates fire/explosion hazards and protects adjacent equipment.
• Asset integrity: preserves tank structure and bushings by avoiding extreme mechanical stress.
• Operational continuity: fast venting + signaling supports protection schemes to isolate faults.

Components of a Transformer Pressure Relief Device

While designs vary by manufacturer and rating, most PRDs include the following key parts:

Housing / Body

Metal construction (often stainless steel or aluminum alloy) compatible with transformer oil; provides mechanical strength
and corrosion resistance for outdoor service.

Diaphragm / Valve Disc

Pressure-sensitive element that lifts when internal pressure exceeds the set point, opening a flow path for rapid venting.

Spring Mechanism (for spring-loaded types)

Defines the opening pressure and enables automatic reseating after pressure returns to normal.

Sealing Gasket & Seats

Oil-resistant elastomers or composites ensuring tight sealing under normal operation; prevent seepage and vapor loss.

Indicator & Microswitch (optioneel)

Mechanical flag and/or electrical contacts that change state upon operation, enabling alarm or breaker trip.

Mounting Flange / Interface

Bolt-on connection to the transformer tank (per drawing/spec). Must maintain planarity, gasket compression, and clear vent path.

How a Transformer Pressure Relief Device Works

De operating principle of a transformer pressure relief device is based on detecting and releasing excess internal
druk caused by abnormal conditions inside the transformer. These include internal short circuits, isolatie defect,
overload heating, or oil expansion. When pressure rises beyond a defined limit, the PRD activates instantly to
discharge the excess gas and restore equilibrium.

1. Pressure build-up: Faults or overheating cause gases and vaporized oil to expand rapidly, increasing tank pressure.
2. Activation: Once the pressure exceeds the calibrated limit (bijv., 0.3–0.7 MPa depending on design), the diaphragm or valve disc lifts.
3. Venting process: Gas and oil mist are expelled through the outlet port in a controlled direction, preventing violent rupture.
4. Signaling: For units with microswitches, contact change triggers an alarm or circuit-breaker trip to isolate the transformer.
5. Reset: Spring-loaded types reseat automatically; rupture discs require replacement after operation.

Proper sizing ensures that venting capacity is sufficient to relieve the maximum credible overpressure without excessive oil loss.
A well-designed PRD not only safeguards the transformer but also provides early warning of internal faults before catastrophic failure.

Types of Transformer Pressure Relief Devices

Different transformer designs and capacities require specific PRD configurations. Below are the most common types used in
modern power and distribution transformers:

1. Spring-Loaded Pressure Relief Valve (PRV)

This reusable valve type uses a spring mechanism to maintain closure under normal operation.
When pressure exceeds the spring’s threshold, the valve opens and vents the excess gas.
Once the pressure drops, the valve reseats automatically, minimizing maintenance downtime.
It is widely applied in large vermogenstransformatoren waarbij snelle respons en herbruikbaarheid van cruciaal belang zijn.

2. Barsten (Scheuren) Schijf

Eenmalig gebruik metalen of composietmembraan gekalibreerd om te scheuren bij een specifieke druk.
Wanneer het breekt, de interne gassen ontsnappen onmiddellijk, biedt snelle bescherming voor kleine of gesloten distributietransformatoren.
Na activering, de schijf moet worden vervangen om de bescherming te herstellen.

3. Gecombineerde klep met microschakelaar

Integreert een mechanisch overdrukventiel met een elektrische microschakelaar dat een alarm- of uitschakelsignaal op afstand geeft.
Deze configuratie maakt gecoördineerd mogelijk bescherming door de transformator te isoleren tijdens een storing evenementen.

4. Dome-type PRD met hoog debiet

Ontworpen met een grote uitlaatkoepel voor ontluchting met hoog volume, deze units zijn gebruikelijk op extra hoogspanning stroomtransformatoren.
Ze laten snel grote hoeveelheden gas vrij om de tankintegriteit tijdens ernstige storingen te behouden.

Vergelijkingstabel

Function of a Transformer Pressure Relief Device

Beyond releasing pressure, a PRD performs several important functions that contribute to the safe and reliable operation
van electrical networks:

• Explosion prevention: releases gas before the tank reaches rupture pressure, preventing fire or blast.
• System protection: limits mechanical and thermal stress on the transformer tank and components.
• Alarm signaling: integrated contacts provide early warnings to the protection system.
• Operational continuity: enables quick return to service after minor faults (for automatic-reset valves).
• Environmental safety: minimizes oil spillage and environmental contamination during fault venting.

Samen, these functions make the PRD one of the simplest yet most crucial passive protection devices in transformer ontwerp.

Safety Features and Standards

Because pressure relief devices are directly related to transformer safety and public protection, they must meet
stringent international and regional standards. Compliance ensures proper design, material integrity,
and operational reliability throughout the product’s life cycle.

Key Safety Features

• Corrosion-resistant housing: usually stainless steel, brass, or aluminum alloy, suitable for outdoor substations.
• Oil-resistant gaskets: made from nitrile or fluororubber to prevent leaks under thermal cycling.
• Weather protection: rated IP55–IP65 for dust and rain resistance.
• Reset assurance: spring tension and sealing tests verify reliable reseating after relief.
• Electrical signaling: microswitch contacts isolated for safe low-voltage control circuits.

Applicable Standards

• IEC 60076-22-1 / IEC 60076-7: transformer accessories and temperatuur stijging limits.
• IEEE C57.12.34 / C57.12.00: U.S. requirements for liquid-immersed distribution and power transformers.
• GB/T 1094 & GB/T 7225: Chinese national standards for transformer safety devices.
• IS 2099 / IS 10028: Indian standards for transformer accessories and maintenance.
• UL & CE-markering: confirm product conformity and export acceptance.

Manufacturers must also perform type tests and routine tests including pressure calibration,
leak test, En electrical insulation test for signaling circuits to ensure consistent performance.

Installation and Maintenance Guide

Correct installation is essential to guarantee effective pressure relief and long-term reliability.
Follow these best practices when fitting and maintaining transformer drukontlastingsapparaten:

Installatiestappen

1. Mount the PRD vertically on the top cover of the transformer tank to ensure unrestricted venting.
2. Check gasket alignment and apply even torque to flange bolts to prevent oil seepage.
3. Ensure the vent outlet is unobstructed and directed away from personnel and sensitive equipment.
4. Connect microswitch leads to the designated alarm or trip circuit, verifying continuity before energizing.
5. Label the PRD with set pressure, type, and last inspection date for easy reference.

Maintenance Recommendations

• Perform a visual inspection every six months to detect corrosion, olie lekt, or dirt buildup.
• Test the microswitch circuit annually to confirm alarm and trip functionality.
• For spring-loaded types, check the spring tension and reseating capability during scheduled overhauls.
• Replace sealing gaskets if swelling or cracking is observed.
• After any PRD operation, document the event and, indien van toepassing, replace burst discs immediately.

Maintenance should always be performed with the transformer de-energized and pressure-free.
Neglecting these procedures can compromise relief accuracy and transformer safety.

How to Choose the Right Pressure Relief Device

Selecting the right PRD depends on transformer design, oil volume, en omgevingsomstandigheden.
The goal is to achieve sufficient venting capacity while maintaining mechanical compatibility and minimal oil loss.

Selectiecriteria

• Rated transformer volume (L): defines the required venting area and flow rate.
• Operating pressure range (MPa): choose a set pressure ≈ 10–20% above normal operating pressure.
• Reset type: decide between automatic spring return or replaceable burst disc.
• Outlet capacity: ensure sufficient gas-release rate to avoid tank deformation.
• Mounting standard: flange dimensions per DIN or ANSI to match existing openings.
• Electrical features: microswitch contact rating compatible with control circuits (bijv., 250 V AC, 5 A).
• Environmental rating: IP and material selectie for outdoor, kust, or corrosive sites.

Example Comparison

When in doubt, consult the transformer manufacturer for the exact venting requirement and flange compatibility.
Oversized devices are safer than undersized ones but must still meet tank design limitations.

Common Applications

Transformer pressure relief devices are widely used in various electrical installaties waar in olie ondergedompelde transformatoren werken
onder veeleisend thermische en mechanische omstandigheden. Het gebruik ervan strekt zich uit van compacte distributietransformatoren tot grote utiliteitstransformatoren
opstapeenheden. Hieronder zijn typisch toepassingsscenario's:

• Distributietransformatoren: klein en middelgrote olie-ondergedompelde units geïnstalleerd in industriële installaties en stedelijke netwerken.
• Stroomtransformatoren: eenheden met grote capaciteit in transmissieonderstations snel vereisen, ontluchtingsvermogen met hoog debiet.
• Generator-opvoertransformatoren: geïnstalleerd stroom opwekkingsinstallaties voor hernieuwbare of thermische centrales.
• Hernieuwbare energietransformatoren: zonne- en windpark installaties die zijn blootgesteld aan grote temperatuurschommelingen.
• Industriële procestransformatoren: gebruikt in de chemie, metallurgie, en olie & gassectoren met strenge veiligheidseisen.

In elke toepassing, selecting the correct PRD ensures safe operation and compliance with national grid and utility standards,
preventing costly equipment damage and extended downtime.

FAQ – Transformer Pressure Relief Device

1. What is the main function of a transformer pressure relief device?

The primary function is to release excessive internal pressure generated inside an oil-filled transformer due
to faults or overheating, preventing tank rupture and fire hazards.

2. How often should the device be tested or replaced?

Perform an inspection every 6–12 months. Spring-loaded types can operate for several years with regular checks; rupture discs must
be replaced immediately after activation or if corrosion is visible.

3. What is the typical opening pressure for PRDs?

Depending on transformer size, the set pressure generally ranges from 0.3 naar 0.7 MPa. Manufacturers calibrate
the exact value according to tank volume and design pressure.

4. Can a PRD be reused after operation?

Spring-loaded valves automatisch gereset en kan opnieuw worden gebruikt nadat de afdichtingsintegriteit is geverifieerd.
Breek schijven, Echter, zijn voor eenmalig gebruik en moeten na elke activering worden vervangen.

5. Wat is het verschil tussen een PRD en een overdrukventiel?

Beide dienen hetzelfde doel, maar de term 'overdrukventiel' verwijst doorgaans naar veerbelaste typen die automatisch kunnen worden gereset,
terwijl “overdrukinrichting” een bredere categorie is, inclusief breekplaten en gecombineerde kleppen.

6. Wat veroorzaakt drukopbouw in een transformator?

Kortsluitingen, oververhitting van de olie, gedeeltelijke ontlading, En Degradatie van isolatie genereert gas en damp die uitzet en de tank omhoog brengt
druk buiten de ontwerpgrenzen.

7. Moeten drukontlastingsapparaten gecertificeerd worden??

Ja. Gerenommeerde producten zijn getest en gecertificeerd volgens IEC, IEEE, GB/T, of UL-normen, het garanderen van de veiligheid en
compatibiliteit met nutsvoorzieningen.

8. Does the PRD affect transformer performance?

Nee, under normal operation it remains sealed and inactive. It only activates under overpressure conditions, without impacting
efficiency or oil circulation.

Conclusie

A transformer pressure relief device is a simple but essential safety component that prevents catastrophic
transformator defect. By releasing internal pressure before it reaches dangerous levels, it protects both the transformer and
surrounding environment. Understanding its types, normen, and maintenance procedures is crucial for safe and reliable
power system operation.

When choosing a PRD, consider your transformer’s design pressure, oil capacity, and site conditions.
Partnering with experienced manufacturers ensures compliance with IEC/IEEE standards and provides betrouwbaarheid op lange termijn.

Technical Summary and Key Specifications

Below is a concise technical overview of transformer pressure relief devices, summarizing design data that users and engineers
typically review before specifying or purchasing units for their systems.

Reviewing these parameters helps engineers confirm compatibility with system design, ensuring the relief device functions
effectively within the transformer’s operational envelope.

Related Topics

• Transformer Buchholz Relay – Function and Working Principle
• Topaccessoires voor olie-ondergedompelde transformatoren
• Hoe transformatorkoelsystemen te onderhouden
• Gids voor filtratie en testen van transformatorolie

Final Thoughts

Investeren in een gecertificeerd transformator overdrukapparaat zorgt voor betrouwbare bescherming tegen interne druk
spanningspieken en apparatuurstoringen. Door aanbevolen normen te volgen, maintenance practices, en correct selectiecriteria,
je beveiligt zowel de infrastructuur als het personeel.

Onze productlijn omvat veerbelaste overdrukventielen, breuk schijven, En
gecombineerde modellen met microschakelaar ontworpen voor midden- en hoogspanningstoepassingen. Alle eenheden worden vervaardigd
met corrosiebestendige materialen en getest per IEC- en IEEE-specificaties voor maximale betrouwbaarheid.

Voor bulkbestellingen, OEM customization, of technische tekeningen, Neem vandaag nog contact op met ons technische team.