Power Transformer Accessories

A power transformer is only as reliable as its accessories. The components mounted on and around the active part handle voltage transition through the tank wall, regulate output voltage, manage cooling, accommodate oil expansion, and provide the protection and monitoring that prevent small faults from becoming catastrophic failures.

Evenson Power offers a comprehensive portfolio of transformer accessories, engineered to integrate seamlessly with oil-immersed and dry type transformers alike. Whether equipping a new build or refurbishing an existing fleet, customers can source matched, standards-compliant components from a single trusted brand.

• Complete portfolio of protection, monitoring and cooling accessories
• For oil-immersed and dry type power transformers
• Engineered for seamless integration and long service life
• Standards-compliant, quality-controlled components

Bushings carry energized conductors through the grounded tank wall while maintaining insulation and controlled electric-field grading. Evenson Power supplies porcelain and polymer (composite) bushings, including oil-impregnated paper (OIP) and resin-impregnated paper (RIP/RIS) condenser types for higher voltage classes, complete with grading rings and creepage-rated surfaces for polluted or coastal environments.

Each bushing is selected for the system voltage class, rated current, and basic insulation level, and is tested for partial discharge, capacitance and tan-delta, and dielectric withstand.

• Porcelain and polymer/composite construction
• OIP and RIP/RIS condenser bushings for HV classes
• Grading rings and high-creepage surfaces
• Tested for PD, capacitance/tan-delta and dielectric withstand

Units are rated for the system current and step voltage, with motor-drive mechanisms, control cabinets, and tap-position indication available for OLTC applications. Robust contacts and proven switching mechanisms ensure a long maintenance interval.

• On-Load Tap Changers (OLTC) with motor drive and control
• De-energized (off-circuit) tap changers
• Tap-position indication and remote signaling
• Rated to system current and step voltage

The Buchholz (gas-actuated) relay, mounted in the pipe between tank and conservator, detects gas accumulation from incipient faults and surges in oil flow from severe faults, providing alarm and trip signals. Evenson Power also supplies pressure-relief devices that rapidly vent dangerous internal overpressure to protect the tank, and sudden-pressure relays for fast fault detection.

These protection accessories are coordinated with the transformer’s ratings to give early warning of developing faults and to limit damage when faults occur.

• Buchholz / gas-actuated relay with alarm and trip stages
• Spring-loaded pressure-relief devices
• Sudden-pressure relays for fast fault detection
• Coordinated with transformer protection scheme

Cooling capacity is matched to the transformer rating and ambient conditions, with corrosion-protected finishes for long outdoor life.

• Pressed-steel panel and tubular radiators
• Detachable cooler banks
• Cooling fans and oil pumps for ONAF/OFAF operation
• Corrosion-protected for outdoor service

The conservator tank accommodates the expansion and contraction of insulating oil with temperature. Evenson Power supplies conservators with rubber-bladder or diaphragm air-cell systems that isolate the oil from the atmosphere, plus silica-gel breathers that dry incoming air to keep moisture out of the oil.

Oil-level gauges (magnetic dial and prismatic types) give clear local indication and remote alarm contacts, completing the oil-preservation system.

• Conservator tanks with bladder/air-cell oil preservation
• Silica-gel breathers (standard and maintenance-free)
• Magnetic and prismatic oil-level gauges
• Local indication plus remote alarm contacts

Accurate temperature monitoring protects insulation life. Evenson Power supplies oil-temperature indicators (OTI) and winding-temperature indicators (WTI) with dial, capillary, and electronic types, providing local readout, multi-stage alarm/trip contacts, and cooling-control outputs.

Advanced electronic monitors and digital relays add remote communication, data logging, and integration with substation control and SCADA systems for condition-based maintenance.

• Oil-temperature indicators (OTI) and winding-temperature indicators (WTI)
• Dial/capillary and electronic monitor types
• Multi-stage alarm, trip and cooling-control contacts
• Digital monitors with SCADA/communication options

All Evenson Power accessories are manufactured and tested to the international standards applicable to each component family, covering bushings, tap changers, gas-actuated relays, cooling equipment, and instrumentation. Components undergo dielectric, mechanical, thermal, and functional testing as appropriate to their type.

Supported compliance and certification marks across the accessory range include IEC, UL, CE, KEMA, and TUV, ensuring compatibility and interchangeability across transformer fleets.

• Each component tested to its applicable standard
• Dielectric, mechanical, thermal and functional testing
• Compliance: IEC, UL, CE, KEMA, TUV

Evenson Power accessories are supplied ready for straightforward mounting on standard transformer fittings, with documentation for correct installation, commissioning, and connection of alarm/control wiring. Correct gasket selection and torque, and verification of relay and gauge function, are part of recommended commissioning.

Routine maintenance includes checking breather silica-gel color, verifying oil levels and temperatures, functionally testing protection relays, inspecting bushings for cleanliness and integrity, and exercising tap changers per the maintenance schedule.

• Standard mountings with full documentation
• Commission protection relays and gauges before energizing
• Check breather, oil level and temperature regularly
• Functionally test relays; inspect bushings; service tap changers

Sourcing accessories from Evenson Power means matched, compatible, standards-compliant components from one supplier, simplifying procurement and spares management. The breadth of the range, from bushings to digital monitors, covers every protection, monitoring, and cooling need.

Backed by rigorous quality control and responsive technical support, Evenson Power accessories help transformers run safely, efficiently, and reliably throughout their service life.

• Single-source, matched and compatible components
• Full coverage of protection, cooling and monitoring needs
• Standards-compliant and quality-controlled
• Backed by responsive technical support

Every Evenson Power transformer accessory is manufactured and tested to the same exacting standard as the transformers they protect and serve. Bushings undergo power-frequency withstand, partial discharge, and capacitance and tan-delta measurement to confirm dielectric integrity, while tap changers are mechanically cycled through their full operating range and verified for contact resistance, sequence, and transition timing before dispatch.

Protective devices receive functional verification appropriate to their duty. Buchholz relays are tested for gas-collection and surge-trip operation, oil-level gauges are calibrated against reference marks, and pressure relief devices are checked for accurate set-point operation and reseal. Radiators and conservators are pressure- and leak-tested to confirm sealing integrity under operating and transient conditions.

Each accessory is supplied with a test or calibration certificate, and components can be matched and pre-fitted to Evenson Power transformers so that interfaces, gaskets, and mounting flanges align perfectly on arrival.

• Bushing tan-delta, capacitance, and partial discharge testing
• Tap changers cycled and verified for contact resistance and timing
• Buchholz and pressure relief functional set-point testing
• Pressure and leak testing of radiators and conservators
• Calibration certificate supplied with each component

Evenson Power maintains a broad inventory of standard bushings, tap changers, Buchholz relays, conservators, radiators, and oil-level gauges, alongside the capability to manufacture to specific ratings, creepage distances, and mounting interfaces. When ordering, clients are encouraged to supply the transformer rating, voltage class, mounting orientation, and existing flange or gasket dimensions so that components can be matched precisely to the installation.

The technical team provides selection guidance, retrofit drawings, and compatibility checks for both new builds and refurbishment of legacy units. Where an exact replacement is unavailable, Evenson Power can reverse-engineer interfaces from sample parts or drawings to ensure a drop-in fit without modification to the transformer tank or cover.

Spare-part kits, gasket sets, and recommended stocking lists are available to support maintenance programmes, minimizing downtime when a component must be replaced in service.