Power Transformers

Power & Distribution Transformers

Perfect Solution Contracting provides integrated power and distribution transformer solutions for commercial, industrial, infrastructure, utility, data center, and critical-facility electrical systems.

Transformers form a key interface between different voltage levels within an electrical distribution network. In typical building and infrastructure applications, transformers can be used to step medium voltage down to the low-voltage level required by the facility's electrical distribution system.

Our scope can include engineering coordination, technical and material submittals, transformer supply, transportation and positioning coordination, installation, MV and LV connections, earthing, protection interfaces, monitoring interfaces, inspection, testing, commissioning, and final handover according to approved project requirements.

Transformer selection is based on factors such as primary and secondary voltage, rated power, system frequency, load characteristics, impedance, vector group, insulation requirements, installation environment, cooling method, losses, temperature rise, short-circuit conditions, and the approved electrical design.

Transformer capacity can be specified in kVA or MVA depending on the size of the electrical system. Selection should consider the calculated demand, diversity, future requirements where specified, operating conditions, and the overall distribution philosophy.

Transformer loading should be coordinated with the actual project load study rather than selected solely from the total connected load. Diversity, demand, operating profile, future expansion, redundancy, and environmental conditions can affect the required transformer capacity.

Transformer solutions can include oil-immersed transformers and dry-type transformers depending on the application, installation environment, project specification, fire-safety requirements, maintenance philosophy, and approved electrical design.

Oil-Immersed Transformers

Oil-immersed transformers use insulating liquid as part of the electrical insulation and cooling system. Their construction, cooling arrangement, fluid type, protection accessories, installation requirements, and containment provisions depend on the selected transformer design and project requirements.

Oil-filled transformer installations require coordination with the transformer room or outdoor installation arrangement, ventilation, access, fire-safety provisions, oil containment or bunding where required, cable routing, earthing, and maintenance clearances.

Dry-Type Transformers

Dry-type transformers can be used in applications where their construction and installation characteristics are appropriate for the project. Cast-resin and other dry-type designs can be selected according to voltage, capacity, environmental conditions, enclosure, insulation system, and project requirements.

Dry-type transformer installations require adequate ventilation and heat dissipation. Transformer room temperature, airflow, clearances, enclosure configuration, and manufacturer requirements are coordinated during installation.

Voltage Ratio & Vector Group

The transformer primary and secondary voltage ratings are selected to match the upstream and downstream electrical networks. Typical project arrangements can include medium-voltage primary systems supplying low-voltage distribution networks.

The transformer vector group defines the winding connection and phase displacement between the primary and secondary sides. The required vector group is selected according to the electrical system design, grounding arrangement, parallel operation requirements, and project specification.

Transformer Impedance

Transformer percentage impedance is an important parameter affecting fault current, voltage regulation, and coordination with the downstream electrical distribution system.

Transformer impedance is considered as part of the project short-circuit study to determine the prospective fault level at the low-voltage side and support the selection and coordination of downstream switchgear and protective devices.

Tap Changers

Transformers can incorporate tap-changing arrangements to adjust the transformation ratio within the range provided by the selected design.

Distribution transformers commonly use an off-circuit or de-energized tap changer where specified, while other transformer applications can require an On-Load Tap Changer (OLTC). The required arrangement depends on the system design and transformer application.

Tap positions and operating procedures should follow the approved transformer data and manufacturer's instructions. De-energized tap changers should not be operated while the transformer is energized.

Transformer Protection

Transformer protection is coordinated with the transformer capacity, construction, upstream medium-voltage system, downstream low-voltage system, grounding arrangement, and approved protection philosophy.

Electrical protection can include overcurrent, earth-fault, differential, restricted earth-fault, thermal, and other functions where applicable to the transformer size, system arrangement, and project protection study.

Protection functions are coordinated with the associated MV switchgear, LV switchgear, circuit breakers, protection relays, and other protective devices to achieve the required protection and selectivity.

Oil-immersed transformers can include protection and monitoring accessories such as oil and winding temperature indicators, pressure devices, oil-level indication, and gas-actuated protection where applicable to the transformer construction.

The exact protection accessories depend on transformer type, rating, tank arrangement, manufacturer design, and approved project specification and should not be assumed to be identical for every transformer.

Dry-type transformers can incorporate temperature sensors within the windings and temperature monitoring or control devices for alarm, fan control, and trip functions where these features are included in the approved transformer design.

Temperature Monitoring

Transformer temperature monitoring supports operating supervision and protection. The monitoring method depends on whether the transformer is oil-immersed, dry-type, or another approved construction.

Where specified, transformer alarms and status signals can be interfaced with the Electrical Power Monitoring System (EPMS), Building Management System (BMS), or SCADA system.

MV & LV Connections

Medium-voltage connections are coordinated with the selected transformer terminals, cable type, conductor size, termination system, system voltage, and manufacturer requirements.

MV cable terminations require correct cable preparation, insulation treatment, screen handling, stress control, and termination installation using compatible approved materials and procedures.

Low-voltage transformer connections can be made using power cables, busduct, or other approved connection arrangements depending on the transformer rating, current level, LV switchgear configuration, and project design.

Where busduct is used between the transformer and low-voltage switchgear, the transformer terminals, flexible connections, busduct orientation, phase arrangement, supports, and interface dimensions are coordinated between the equipment manufacturers and installation teams.

Earthing & Bonding

Transformer earthing is coordinated with the overall facility earthing design. This can include equipment body earthing, neutral earthing, cable screen connections, enclosure bonding, and other connections required by the approved system design.

The transformer neutral arrangement depends on the selected distribution system and grounding philosophy. Neutral-to-earth connections should be installed only at the locations defined by the approved electrical design.

Transformer Room Coordination

Transformer installation requires coordination of equipment dimensions, access routes, unloading and positioning, maintenance clearances, ventilation, cable routes, busduct interfaces, fire-safety provisions, and other architectural and MEP requirements.

Transformer heat losses should be considered when coordinating room ventilation or cooling. The required ventilation arrangement depends on transformer losses, room conditions, equipment configuration, ambient temperature, and manufacturer requirements.

Access arrangements should allow the transformer to be transported, installed, inspected, and maintained in accordance with the project design and equipment requirements.

For large transformers, transportation and positioning can require coordination of equipment weight, lifting points, route clearances, floor loading, crane or lifting arrangements, and final installation location.

Technical Submittals & Drawings

Before procurement, transformer technical submittals can include data sheets, guaranteed technical particulars, dimensions, weights, losses, impedance, vector group, tap arrangement, accessories, protection devices, terminal details, and other project-required information.

Coordination documentation can include Single Line Diagrams (SLD), General Arrangement (GA) drawings, transformer room layouts, cable and busduct interfaces, protection diagrams, and equipment schedules.

Factory Acceptance Testing

Where required by the project, Factory Acceptance Testing (FAT) can be performed before delivery to verify specified transformer characteristics, construction, accessories, and test results according to the approved inspection and testing requirements.

Transformer factory tests can include routine tests applicable to the selected transformer, while additional type or special tests may be required by the project specification. The exact test program should be defined by the approved Inspection & Test Plan (ITP).

Site Installation & Testing

Following delivery, the transformer is inspected for transportation condition, physical damage, completeness, accessories, nameplate information, terminal condition, and other relevant installation requirements.

Installation verification includes transformer positioning, clearances, mechanical installation, MV and LV connections, earthing, auxiliary wiring, protection interfaces, monitoring connections, and required accessories.

Site testing is selected according to transformer type, rating, manufacturer requirements, project specification, and approved commissioning procedure.

Tests can include insulation resistance, winding resistance, transformation ratio, vector-group or polarity verification, earthing checks, protection testing, temperature-monitoring verification, and other applicable pre-commissioning tests.

Protection relay testing and functional verification are coordinated with the associated MV and LV switchgear before transformer energization.

Where required, Site Acceptance Testing (SAT) can be performed to verify the installed transformer and its interfaces with MV switchgear, LV switchgear, cables, busduct, protection systems, and monitoring systems.

Energization is carried out after completion of the required inspections, electrical tests, protection verification, earthing checks, approved commissioning procedures, and relevant project authorization.

Standards & Project Requirements

Transformers are selected, manufactured, installed, and tested according to the approved project specifications, applicable utility requirements, manufacturer requirements, and relevant standards for the selected transformer.

Depending on the transformer type and project requirements, relevant standards can include the IEC 60076 series for power transformers, together with other applicable standards and project-specific requirements.

Perfect Solution Contracting provides complete power transformer solutions covering engineering coordination, technical submittals, procurement, transportation and installation coordination, MV and LV connections, protection interfaces, earthing, monitoring, FAT/SAT support where required, testing, commissioning, energization support, and final handover.