zishengelectric
Project Partners
Phone/WhatsApp: 8619131285373
Email: info@zishengtransformer.com
Factory Headquarters: No. 118, Jingyi Street, Economic Development Zone.
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Project Partners
Phone/WhatsApp: 8619131285373
Email: info@zishengtransformer.com
Factory Headquarters: No. 118, Jingyi Street, Economic Development Zone.
The 133kV power transformer, also available as a 135kV design, is a three-phase oil-immersed transformer for high-voltage substations and medium-to-large transmission and distribution systems.
It converts high-voltage electrical power to the required medium- or low-voltage level for subsequent distribution or industrial use. Zisheng can configure the transformer for the grid arrangement, site conditions, load characteristics and specified technical standards.
The oil-immersed construction combines a magnetic core, HV/LV windings, an oil-paper insulation system, a tank and a selected cooling arrangement. Applications include utility networks, industrial substations, renewable energy, mining and infrastructure projects.
Specify the highest voltage for equipment, AC and impulse withstand levels, neutral insulation and bushing creepage for each winding.
Evaluate no-load loss, load loss and temperature-rise limits at the stated rating, frequency and reference conditions. Guaranteed values belong in the approved technical offer.
Coordinate winding mechanical strength, system fault level, impedance and protection clearing time. The verification method is defined by the applicable standard and contract.
Material selection, drying and oil processing support the insulation design. The accessory schedule defines temperature indication, pressure relief, oil level and any gas-actuated protection.
ONAN, ONAF and OFAF are design options rather than simultaneous standard equipment. Select the cooling-stage ratings and tap-changer arrangement for the operating duty.
The core uses grain-oriented electrical steel as specified in the approved design. Copper or aluminum winding conductors follow the order specification; neither material should be assumed from the product photograph. Solid cellulose insulation and insulating liquid provide the coordinated internal dielectric system.
The main tank houses the active part. Radiators or coolers transfer heat to the surrounding air. Bushings provide insulated connections to the external circuit; their voltage class, current rating, terminal geometry and pollution performance must match the substation interface. A conservator and associated pipework are used where the selected oil-preservation system requires them.
The approved bill of materials identifies valves, lifting and jacking provisions, earthing terminals, marshalling cabinet, cooling controls and protection devices. Buchholz relay applicability depends on the oil-preservation arrangement. Bushing CTs, online dissolved-gas monitoring and communication interfaces are supplied only when specified.
ONAN means oil natural, air natural; ONAF adds forced-air cooling; OFAF uses forced oil and forced air. Compare the stated MVA rating at each cooling stage, available auxiliary supply, control logic and maintenance access. Do not use a forced-cooling rating as the natural-cooling rating.
An off-circuit tap changer is operated only with the transformer isolated and de-energized. An on-load tap changer (OLTC) is selected when voltage adjustment during operation is required. Confirm the tapping winding, range, steps, drive supply and local/remote control in the order documents.
| RFQ item | Information to provide |
|---|---|
| Electrical duty | Required MVA at each cooling stage; voltage and frequency of every winding; simultaneous demand, power factor, future load and contingency duty. |
| System compatibility | Single-line diagram; vector group and neutral earthing; network fault level; target impedance; existing transformer nameplate and test data where parallel operation is required. |
| Insulation and terminals | Highest voltage for equipment, impulse/AC withstand requirements, bushing creepage and terminal arrangement for each winding and neutral. |
| Regulation and auxiliaries | Tap range and steps, OLTC or off-circuit arrangement, auxiliary AC/DC supplies, protection contacts and control interfaces. |
| Site and logistics | Ambient temperature, altitude, pollution, corrosion, seismic and sound requirements; footprint, foundation loads, access route and lifting constraints. |
| Acceptance and documents | Governing standard and edition, inspection and test plan, witness/hold points, report format, drawings, packing list, manuals and shipment-release requirements. |
A regional utility substation retrofit brings a 133kV incoming supply onto an existing 33kV distribution bus. The load combines daytime industrial demand, evening residential demand and transferred feeders during an adjacent-bay outage. Selection starts with simultaneous demand and the required contingency operating condition, rather than the sum of feeder breaker ratings.
The replacement unit must fit the available bay, foundation and oil-containment area. Bushing positions, bus clearances, neutral connections and transport access require a coordinated drawing review. If temporary parallel operation with an existing transformer is needed, compare voltage ratio, vector group, tap positions and impedance characteristics before approving the arrangement.
| Engineering issue | Configuration and acceptance requirement |
|---|---|
| Electrical interface | 133kV/33kV, three-phase; project-approved MVA and cooling-stage ratings; matching vector group, earthing and protection interfaces. |
| Voltage regulation | Select OLTC and automatic control only where required; coordinate settings and parallel-control logic with the existing bus. |
| Site restrictions | Verify foundation loads, terminal geometry, oil containment, crane or jacking access and the outage sequence against approved drawings. |
| Release and site acceptance | Require serial-number-linked FAT reports, inspection release and transport records; verify reassembly, fluid condition and protection operation before energization. |
A water-supply pumping substation uses a 135kV incoming connection and an 11kV motor bus. Duty and standby pumps, staged starts and service continuity govern the load schedule. The transformer rating must reflect simultaneous electrical demand, operating power factor and the agreed reserve; motor shaft power also requires the motor efficiency to determine electrical input.
The main engineering issue is maintaining an acceptable bus voltage during pump starting and recovery after a supply interruption. Confirm the starting method, largest permitted motor start, restart sequence and interlocks. Where variable-frequency drives are used, assess harmonic current and heating with the drive supplier instead of applying a blanket transformer derating.
| Engineering issue | Selection and acceptance requirement |
|---|---|
| Supply and load | 135kV/11kV, three-phase; approved duty/standby schedule, power factor, starting duty and MVA rating at each cooling stage. |
| Starting and harmonics | Review impedance with the network and motor-starting study; coordinate drive harmonic data, starting-voltage limits and protection. |
| Site conditions | Place equipment above the agreed flood level; coordinate oil containment, earthing, cable interfaces and maintenance access. |
| Acceptance documents | Check the approved datasheet, loss/impedance and dielectric reports, tap/control records and installation instructions; prove the agreed pump restart and interlock sequence during site commissioning. |
Cooling and tap control should support the required operating duty during hot weather and planned maintenance. The electrical designer must coordinate transformer protection with the motor feeders, neutral-earthing arrangement and site emergency operating procedure.
The 133kV / 135kV Three-Phase Power Transformer is engineered for high-voltage substations, utility networks, industrial power systems, and large-scale renewable energy projects. Technical parameters can be customized according to the project specification and applicable international standards.
| Item | Technical Specification |
|---|---|
| Product Type | Three-Phase Oil-Immersed Power Transformer |
| Rated Voltage Class | 133kV / 135kV |
| High Voltage | 133kV / 135kV |
| Medium Voltage | 33kV / 13.8kV / 11kV / Customized |
| Low Voltage | Customized |
| Rated Capacity | 5MVA–250MVA+ / Customized |
| Frequency | 50Hz / 60Hz |
| Phase | Three Phase |
| Cooling Type | ONAN / ONAF / OFAF |
| Tap Changer | OCTC / OLTC |
| Tap Range | Typically ±2 × 2.5% / ±8 × 1.25% / Customized |
| Vector Group | Dyn11 / YNd11 / YNd1 / Customized |
| Impedance Voltage | Customized according to project requirements |
| Winding Material | Copper / Aluminum |
| Core Material | High-Grade Grain-Oriented Silicon Steel |
| Insulation Medium | Mineral Transformer Oil / Customized |
| Neutral Configuration | Solidly Grounded / Resistance Grounded / Customized |
| Installation | Outdoor / Indoor |
| Temperature Rise | According to applicable standard |
| Noise Level | According to applicable standard |
| Altitude | Standard / High-Altitude Design Available |
| Ambient Temperature | Standard / Customized for Extreme Climates |
| Insulation Level | According to IEC / ANSI / IEEE requirements |
| Short-Circuit Withstand | Designed according to IEC 60076-5 / Project Specification |
| Protection | Buchholz Relay / Pressure Relief Device / Temperature Protection |
| Standards | IEC / ANSI / IEEE / GOST / Customer Specification |
| Service | OEM / ODM / Custom Engineering |
The transformer can be configured for different substation voltage levels, including:
The transformer can be optimized according to the required:
For 133kV/135kV-class applications, the insulation system can be designed according to the specified:
ONAN — Oil Natural Air Natural
Suitable for transformers with relatively moderate capacity and natural heat dissipation requirements.
ONAF — Oil Natural Air Forced
Cooling fans increase heat dissipation and allow higher transformer loading capacity.
OFAF — Oil Forced Air Forced
Forced oil circulation and forced-air cooling can be used for higher-capacity transformers.
OCTC — Off-Circuit Tap Changer
Suitable where voltage adjustment is required only when the transformer is de-energized.
OLTC — On-Load Tap Changer
Suitable for substations requiring continuous voltage regulation while the transformer remains energized.
The tap position, range, control system and motor-drive mechanism can be customized according to grid requirements.
For EPC and utility projects, the technical design can be customized based on:
Grid Voltage → Capacity → Load Profile → Short-Circuit Level → Cooling → Tap Regulation → Insulation Level → Environmental Conditions → Applicable Standard
This allows the 133kV / 135kV transformer to be configured specifically for each substation rather than using a one-size-fits-all design.
Technical Note: Final specifications should be confirmed against the project single-line diagram, utility technical specification, required capacity, system short-circuit level, voltage regulation requirements and applicable standard before production.
Zisheng can customize the transformer according to the customer's electrical and mechanical requirements.
For projects located in challenging environments, the transformer can be engineered for:
| RFQ item | Information to provide |
|---|---|
| Electrical duty | Required MVA at each cooling stage; voltage and frequency of every winding; simultaneous demand, power factor, future load and contingency duty. |
| System compatibility | Single-line diagram; vector group and neutral earthing; network fault level; target impedance; existing transformer nameplate and test data where parallel operation is required. |
| Insulation and terminals | Highest voltage for equipment, impulse/AC withstand requirements, bushing creepage and terminal arrangement for each winding and neutral. |
| Regulation and auxiliaries | Tap range and steps, OLTC or off-circuit arrangement, auxiliary AC/DC supplies, protection contacts and control interfaces. |
| Site and logistics | Ambient temperature, altitude, pollution, corrosion, seismic and sound requirements; footprint, foundation loads, access route and lifting constraints. |
| Acceptance and documents | Governing standard and edition, inspection and test plan, witness/hold points, report format, drawings, packing list, manuals and shipment-release requirements. |
Prepare the transport arrangement from the actual shipping mass, dimensions, center of gravity and route survey. The main unit may require a heavy-haul trailer, rail or project-cargo arrangement. Confirm bridge and road limits, port handling, unloading capacity and access to the foundation before dispatch.
Where the approved shipping arrangement requires removal, pack bushings, radiators, conservator, fans and instruments separately with protected connection faces, identification and a component packing list. Fragile components may need braced wooden crates; pallets or skids are sized for detached parts rather than used as a generic package for the complete high-voltage transformer.
The manufacturer’s approved transport instructions define the insulating-liquid or dry-gas preservation condition, sealing, monitoring and restoration procedure. Do not assume an oil-filled or gas-filled shipping state. Use designated lifting, jacking and restraint points; never lift by bushings, radiator connections or pipework.
On arrival, record serial numbers, crate quantities, damage, oil leakage, seals and any specified pressure/moisture or shock-indicator readings. Quarantine damaged components and notify the responsible parties. Reassemble and process the insulating liquid as instructed, complete the approved electrical and protection checks, and close outstanding acceptance items before energization.
Agree the inspection and test plan before production. Manufacturing checks address material identity, core and winding assembly, insulation clearances, drying and oil-processing records, tank workmanship and the accessory schedule. These process inspections are distinct from final electrical acceptance tests.
Define material certificates, dimensional records, component certificates and traceability requirements in the purchase specification. Identify the transformer serial number, drawing revision and approved deviations in the final quality dossier. Witness access and document-review hold points should be agreed before the relevant work stage.
Routine tests follow the governing standard and the approved design. The final test schedule must identify the applied standard and edition, rating and tap conditions, instruments, acceptance limits and report references. A general website checklist does not replace the contract test schedule.
| Test or check | Purpose and scope |
|---|---|
| Winding resistance; ratio; phase displacement and tap checks | Check winding connections and the specified relationship between terminal voltages and tap positions. |
| No-load loss and current | Assess core excitation and loss at the specified applied voltage and frequency. |
| Load loss and short-circuit impedance | Establish loss and impedance under the specified rating, tap and reference-temperature conditions. |
| Dielectric tests and partial-discharge measurements | Confirm the insulation test programme using the highest voltage for equipment, winding/neutral insulation and the governing standard. Applied/induced tests, lightning impulse and PD requirements must be classified explicitly; they are not universally optional at this voltage class. |
| Tank, accessories and control circuits | Check the agreed leak/tightness procedure, accessory functions, interlocks, cooling controls, alarms and wiring against approved drawings. |
| Type, special and other agreed verification | Temperature rise, sound, short-circuit withstand verification and additional diagnostics follow the applicable classification and contract. Specify the evidence required, test configuration and witness points. |
Factory acceptance testing (FAT) should link each report to the serial number and approved technical schedule. Agree the datasheet, general arrangement, connection/control diagrams, bushing and tap-changer documents, accessory list, inspection release, packing list and operating instructions. Resolve recorded deviations before shipment release; site acceptance remains a separate activity.
Specify the applicable parts and editions of IEC 60076-1 and IEC 60076-3, or the agreed IEEE C57 requirements, in the technical schedule. These are technical standards, not product certifications.
Step down a 133kV or 135kV connection to the specified distribution voltage. Review contingency demand, bus arrangement, voltage regulation, parallel operation and utility protection interfaces.
Supply a major industrial substation serving motors, process equipment and auxiliary loads. Evaluate simultaneous demand, motor starting, harmonics, fault duty and the available maintenance outage.
Connect an approved collector-system voltage to the high-voltage grid where the required voltage ratio and design support the duty. Provide the active/reactive power envelope, bidirectional operation requirements and grid-code interface.
Supply a mine or heavy-process distribution bus where the site voltage and MVA requirement match the design. Include altitude, dust, corrosion, fluctuating loads and constrained access in the selection review.
Serve regional pumping and other major infrastructure loads with a coordinated high-voltage supply. Define starting sequences, service-continuity requirements, flood constraints and commissioning interfaces.
It is a three-phase oil-immersed power transformer designed around a specified 133kV or 135kV system connection. Confirm whether the quoted voltage is the nominal system voltage or winding rated voltage, and specify the highest voltage for equipment and insulation levels separately.
Provide the MVA and cooling-stage ratings, voltage ratio, frequency, load profile, vector group, neutral earthing, fault level, impedance, tap requirements and site conditions. Include existing nameplate and test data when replacing or paralleling another unit.
133kV/33kV is one of the listed voltage configurations. Confirm the winding ratings, vector group, insulation coordination, impedance and terminal arrangement through the approved technical offer.
135kV/33kV is a listed configuration; 135kV/11kV and other listed ratios are also subject to project engineering. A voltage ratio alone does not establish capacity, fault duty or suitability for parallel operation.
An OLTC can be selected where voltage regulation during operation is required. It is included only when specified. Confirm the tapping winding, range, steps, drive supply, regulator and control interfaces. Off-circuit tap changing requires isolation and de-energization.
The listed ONAN, ONAF and OFAF arrangements are selected for the approved design. Confirm the continuous MVA rating at each stage and the auxiliary supply and controls; forced cooling is not automatically included.
Identify the applicable IEC 60076 parts, IEEE C57 documents or other agreed standards and their editions in the purchase specification. Technical standards define requirements and test methods; naming a standard is not evidence of product certification.
Agree the routine, type, special and other required tests in the inspection plan, including the applicable dielectric and PD requirements. Request serial-number-linked reports, approved drawings, accessory records, inspection release and transport/packing documents. After arrival, inspect condition and complete the approved reassembly, fluid and pre-energization checks.
Compare the 110kV / 115kV power transformer for a different network interface, or browse oil-immersed transformers.
Prepare the transformer inspection and test plan and use the site acceptance test checklist to coordinate document review, witness points and energization readiness.
133kV 135kV Three-Phase Power Transformer – High Voltage Substation Equipment