Why is MVA sometimes listed at more than one cooling stage?

Natural and forced cooling can have different agreed ratings. State the continuous duty required with and without fans or pumps, the ambient conditions and the auxiliary supply; do not compare headline MVA values without the cooling basis.

Can a new transformer operate in parallel with an existing unit?

Only after checking ratio, vector group, phase sequence, impedance and tap settings against the network study. Similar nameplate power alone does not establish acceptable load sharing or circulating current.

Should I specify an on-load tap changer?

Choose it when the operating scheme requires voltage adjustment without de-energizing the transformer. Specify range, steps, control philosophy and monitoring. An off-circuit tap switch cannot perform the same operating duty.

Which tests should appear in the purchase specification?

Agree the applicable IEEE/IEC basis and a named inspection/test plan. Separate routine tests from any required impulse, temperature-rise, sound or other type/special tests, and identify witness and report requirements before ordering.

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1-888-688-8077 contact@entogo.ca

Power Transformers

High-Voltage Power Transformer

Representative configuration. The offered model, dimensions and interfaces are confirmed with the technical proposal.

Overview

Entogo supplies high-voltage power transformers for substations and industrial networks. The design brief covers MVA, voltage ratio, insulation coordination, impedance, tap regulation, cooling and transport limits.

Entogo supplies this project equipment through manufacturing partners. Entogo Inc. in Toronto coordinates technical selection, supply scope and order support.

Specification	Value
Construction	Three-phase, liquid-immersed power transformer
Rated power	MVA stated separately for each agreed cooling stage
Voltage ratio	HV/LV rated voltages, vector group and neutral terminal requirements
Insulation	Highest equipment voltage, impulse withstand and neutral insulation
Tap regulation	Off-circuit or on-load; range, steps and control interfaces to agree
Cooling	Natural/forced cooling stages and auxiliary supply defined in the offer
System study	Impedance, guaranteed losses and short-circuit duty specified together
Acceptance	Routine/type/special test schedule, drawings and transport envelope

Reference configurations and selection criteria are shown together. The technical offer defines the matched ratings, tests and guaranteed performance for the ordered unit.

Build the guarantee schedule around the network study

A nominal voltage and MVA value do not define a power transformer. The specification must identify insulation levels, neutral treatment, impedance and cooling stages, along with the agreed test basis.

For a replacement, check parallel operation, phase displacement, tap positions and physical interfaces. For a new substation, include transport mass, dimensions, access and the division of assembly work before freezing the design.

Applications

Utility substations
Industrial power systems
Renewable energy interconnection

Selection & project requirements

Why is MVA sometimes listed at more than one cooling stage?: Natural and forced cooling can have different agreed ratings. State the continuous duty required with and without fans or pumps, the ambient conditions and the auxiliary supply; do not compare headline MVA values without the cooling basis.
Can a new transformer operate in parallel with an existing unit?: Only after checking ratio, vector group, phase sequence, impedance and tap settings against the network study. Similar nameplate power alone does not establish acceptable load sharing or circulating current.
Should I specify an on-load tap changer?: Choose it when the operating scheme requires voltage adjustment without de-energizing the transformer. Specify range, steps, control philosophy and monitoring. An off-circuit tap switch cannot perform the same operating duty.
Which tests should appear in the purchase specification?: Agree the applicable IEEE/IEC basis and a named inspection/test plan. Separate routine tests from any required impulse, temperature-rise, sound or other type/special tests, and identify witness and report requirements before ordering.

For Canadian and US projects, include the utility specification, service frequency and required approvals. State whether the order is for the transformer alone or an integrated equipment package.

Discuss your equipment requirements

Send your single-line diagram, load or process data, target market and required schedule. We will identify the configuration and documents needed for a technical quotation.

Design references

Power transformer at an electrical substation, where nameplate percent impedance sets fault current and voltage regulation

Power & Distribution

What transformer impedance should you specify? How %Z shapes fault current and voltage drop

Transformer percent impedance (%Z) sets how much fault current the secondary can deliver and how far voltage sags under load. Lower %Z means higher available fault current and better regulation; higher %Z limits fault duty but drops more voltage. Here is how to choose it and what to specify.

View

Power transformer at an electrical substation with an on-load tap changer for voltage regulation

Power & Distribution

De-energized taps or a load tap changer? Specifying transformer voltage regulation

Transformer regulation is %R cos θ + %X sin θ plus a small quadratic term. A 1500 kVA, 5.75 %Z unit at 0.85 PF drops 3.85 %, so a 13.3 to 14.0 kV primary needs the 13 455 V tap to hold 456 to 504 V. The full ANSI C84.1 Range A primary swing needs an OLTC or a step regulator.

View

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