Complete Solution of SZ-31.5MVA-33/11kV On-Load Tap-Changing Oil-Immersed Main Transformers Customized for Iraq’s Power Grid Upgrade

I. Project Overview and Technical Specifications of the 16 Three-Phase Oil-Immersed Power Transformers for Iraq

This complete integrated solution of 16 sets of SZ-31.5MVA 33kV/11kV on-load tap-changing oil-immersed main transformers is tailor-made by Hengfengshuai Electric for the power supply renovation project of urban power grids in Iraq. Having years of experience in exporting power transmission and transformation equipment to the Middle East, Hengfengshuai Electric strictly designs its products in compliance with IEC 60076, GB 1094 and Iraq’s COSQC power standards. The transformers are engineered to operate reliably under harsh outdoor conditions in Iraq, including extreme ambient temperatures up to 55°C, year-round heavy sandstorms, salt fog in southern coastal areas, drastic day-night temperature swings and severe grid voltage fluctuations. Compatible with Iraq’s 50Hz national grid standard, the units facilitate two-tier power transmission across the 33kV transmission network and 11kV medium-voltage distribution network, supporting stable grid connection and power supply for oil & gas exploitation, refinery plants, industrial and commercial loads, as well as distributed photovoltaic power systems.

All transformers adopt high-purity electrolytic copper windings and are uniformly equipped with on-load tap-changers to accommodate wide voltage fluctuations on local power grids. Designed with low no-load loss and low total load loss for energy conservation, the units feature a composite dual cooling system of ONAN/ONAF. With high temperature resistance, sandstorm resistance and salt fog corrosion protection, they enable continuous operation under Iraq’s year-round high temperatures while balancing stable wide-range voltage regulation and long-term low energy consumption.

General Technical Parameter Table of Transformers

II. Advantages of Adopting Hengfengshuai Electric’s Custom SZ-31.5MVA-33/11kV Oil-Immersed Transformer Solution for Iraq

Tailored for Iraq’s two-tier 33kV-11kV power grid and extreme harsh working conditions of oil & gas industries, the complete set of 16 SZ-31.5MVA step-up transformers from Hengfengshuai Electric features six core highlights: bulk integrated delivery, high temperature and sandstorm weather resistance, low loss under both light and full loads, on-load voltage regulation for fluctuating grids, all-copper windings with strong short-circuit resistance and optimized harmonic management for simplified operation and maintenance. The solution fully addresses the demands of oil refinery parks, newly built urban substations and photovoltaic supporting step-up stations across Iraq.

1. Integrated Bulk Configuration of 16 Uniform Units to Meet Full-Scale Grid Expansion & Renovation Needs

Traditional projects with transformer procurement in separate batches suffer from long delivery cycles, incompatible spare parts and inconsistent on-site commissioning standards. Hengfengshuai Electric provides unified design, centralized production and integrated logistics delivery for all 16 SZ-31.5MVA units:

1. All 16 Yd11 connection group main transformers jointly undertake voltage regulation and interconnection tasks between the regional 33kV transmission network and 11kV distribution network, covering power supply for numerous oilfields and multiple substations in new urban districts;

2. Uniform model units enable flexible allocation of one unit for operation and one for standby, as well as partitioned power supply across multiple sites, supporting flexible load scheduling and matching the expansion of Iraq’s oil & gas bases and nationwide urban power grid reconstruction projects;

3. Unified overall installation dimensions, standardized spare parts and consistent commissioning criteria greatly reduce supporting procurement costs for substation civil engineering, cables and switchgears, lowering customers’ overall investment and pressure on spare parts inventory in later operation phases.

2. Optimized No-Load & Full-Load Loss Indicators for Non-Stop High-Temperature Operation All Year Round

The no-load and full-load loss values of the 16 SZ-31.5MVA transformers are strictly controlled below specified limits, far exceeding the energy-saving performance of conventional transformers used in the Middle East:

1. High-purity electrolytic copper windings paired with ultra-low-loss high-permeability silicon steel sheets maintain outstanding energy efficiency under both light/no-load and peak full-load conditions;

2. Iraq’s year-round high temperatures require 24/7 continuous equipment operation. Each transformer can save tens of thousands of kilowatt-hours of power loss annually, bringing remarkable overall energy-saving benefits for the 16-unit batch and aligning with Iraq’s policies on energy consumption reduction and new photovoltaic energy development;

3. The Class A high-temperature resistant insulation system maintains controllable temperature rise under an extreme ambient temperature of 55°C, preventing accelerated insulation aging and failures caused by high-temperature overload and extending the service life of outdoor equipment.

3. Uniform OLTC On-Load Voltage Regulation to Resolve Severe Voltage Fluctuations on Iraq’s Power Grid

Aging infrastructure leads to wide voltage fluctuation ranges on Iraq’s power grid, aggravated by industrial load surges and volatile photovoltaic output. All units are equipped with an on-load voltage regulation system to target unstable power supply issues:

1. Each unit is standard-fitted with an OLTC on-load tap changer of ±8×1.25%, enabling real-time automatic voltage regulation under load to counteract long-distance line voltage drop on the 33kV transmission side and day-night output fluctuations of distributed photovoltaic systems;

2. The standardized 8% short-circuit impedance fully complies with Iraq MoE power grid design specifications, enabling controllable short-circuit currents. Customers avoid recalculating protection settings for each unit individually, greatly improving commissioning efficiency for differential, backup and earthing protection in substations and lowering technical barriers for local Iraqi power technicians;

3. Unified voltage regulation logic across the entire station enables synchronous voltage adjustment for multiple transformers running in parallel, preventing unbalanced load distribution within the substation.

4. Dual Weather Resistance Design for High Temperatures, Sandstorms and Coastal Salt Fog to Adapt to All Regional Conditions in Iraq

The equipment structure is comprehensively upgraded to withstand Iraq’s extreme operating conditions: summer temperatures up to 55°C, perennial sandstorms, salt fog in Basra coastal areas and drastic day-night temperature variations:

1. High-pour-point high-temperature special insulating oil and high-temperature resistant EPDM sealing components are adopted. The oil fluidity and tank sealing performance do not degrade under sustained 55°C high temperatures, eliminating oil leakage and insulation failure risks;

2. The outer tank walls are coated with a composite multi-layer system of high-temperature resistant epoxy zinc-rich primer and UV-resistant salt-fog topcoat, preventing sand accumulation, resisting sea salt fog and enduring intense high-temperature sunlight exposure. Units can be installed outdoors long-term in both inland desert oilfields and coastal refinery plants;

3. The dual-mode ONAN/ONAF cooling system operates in energy-saving natural cooling mode under light loads in spring and autumn, and activates forced air cooling in summer at 55°C to stabilize oil temperature all year round and avoid shutdowns due to heatwave overload.

5. Standard Yd11 Connection Group for Efficient Industrial Harmonic Mitigation and Improved Grid Power Quality

The low-voltage delta winding effectively offsets third harmonics in the system, addressing harmonic pollution caused by non-linear loads including oilfield frequency converters, large motors and photovoltaic inverters across Iraq:

1. Reduces harmonic voltage distortion on the 11kV distribution side, protecting downstream oil & gas extraction equipment, photovoltaic grid-connected devices and industrial/commercial loads in plants;

2. The star-connected high-voltage side features a flexibly grounded neutral point, matching the mainstream neutral grounding grid architecture of Iraq’s 33kV network, enhancing operational stability under grid short-circuit faults and minimizing harmonic interference during parallel operation of multiple substations.

6. All-Copper Windings with Strong Short-Circuit Resistance for Lightweight Unattended Operation & Maintenance in Oilfields

Equipped with high-purity electrolytic copper windings, the transformers feature optimized conductor cross-sections and rigid reinforced winding ends, and have passed all full short-circuit withstand type tests in accordance with Iraq’s COSQC standards:

1. Windings are less prone to deformation and insulation damage during sudden grid short-circuits. The batch of 16 units significantly cuts maintenance and replacement costs for scattered remote oilfield plants;

2. Ultra-low no-load loss eliminates hidden heat risks under long-term light-load high-temperature operation, fitting the unattended substation operation mode for remote Iraqi oilfields and reducing labor and spare parts investment for later maintenance.

III. Design & Development Phase of Iraq High-Temperature SZ-31.5MVA Oil-Immersed Transformers

Combining Iraq’s 33/11kV power grid parameters, 55°C high-temperature environment, sandstorm & salt fog conditions and COSQC standards, the technical team of Hengfengshuai Electric completes electromagnetic simulation with targeted optimizations: widened heat dissipation oil channels, low-loss silicon steel sheets, precisely matched standard 8% impedance and extended insulation creepage distance to suppress partial discharge. Three-dimensional structural drawings are specially optimized for iron core vibration reduction, high-temperature resistant composite insulation, double anti-corrosion oil tanks and a full set of high/low temperature resistant dust-proof accessories. Hengfengshuai organizes joint reviews by teams specializing in electromagnetism, manufacturing processes, quality inspection and Middle East projects to verify grid compatibility, weather-resistant structure, ocean shipping dimensions, local certification and bulk on-site installation conditions. Mass production commences only after review approval.

IV. Production & Manufacturing Phase of Iraq SZ-31.5MVA Oil-Immersed Transformers

Hengfengshuai Electric implements full-process quality control for the batch production of the 16 units under the ISO9001 quality management system:

1. 100% incoming inspection of all raw materials. Copper, silicon steel sheets, Class A insulation, high-temperature resistant oil and sealing components undergo special weather resistance testing and are stored in separate dust-proof zones;

2. Automatic cutting and stacking of iron cores for vibration and noise reduction. Each unit undergoes loss testing before proceeding to subsequent production procedures only after passing inspection;

3. Copper windings with Yd11 connection are wound in a Class 10,000 clean workshop with reserved high-temperature heat dissipation oil channels. Each winding undergoes independent electrical testing;

4. Precision wrapping of insulation components followed by deep vacuum drying to eliminate dust and moisture;

5. Air tightness testing of welded oil tanks, multi-layer high-temperature resistant anti-corrosion coating and double dust-proof sealing treatment;

6. Cleanroom assembly of iron cores, coils and OLTC on-load tap-changer assemblies, with terminals matched to Iraq’s 33kV/11kV grid standards;

7. Three-stage vacuum drying to eradicate moisture and dust trapped inside insulation materials;

8. Vacuum filling of the complete unit with high-temperature resistant insulating oil, plus reinforced multi-layer flange sealing.

V. FAT Factory Acceptance Test & Verification for Iraq SZ-31.5MVA Oil-Immersed Transformers

Hengfengshuai Electric conducts a full suite of factory tests in compliance with IEC, GB, Iraq COSQC and MoE standards, issuing bilingual Arabic-English test reports, with unit-by-unit inspection for all 16 transformers:

1. Routine tests for each unit: DC resistance measurement, transformation ratio & connection group verification, insulation testing, power frequency withstand voltage test, oil quality inspection, loss & impedance verification, dual ONAN/ONAF cooling linkage test and simulated temperature rise test at 55°C;

2. Sampled additional type tests: lightning impulse test, high-temperature salt fog partial discharge test, short-circuit thermal & dynamic stability test, 720-hour salt fog aging test, 55°C temperature cycle durability test and simulated sandstorm dustproof test. Mass shipment is only authorized after all tests pass.

VI. Cross-Border Packaging & Transportation Phase of Iraq SZ-31.5MVA Oil-Immersed Transformers

Hengfengshuai adopts split dust-proof and moisture-proof sealed packaging. Accessories are separately protected in wooden crates, while transformer bodies are filled with nitrogen for rust and dust prevention, secured on heavy steel brackets and wrapped with multi-layer weather-resistant tarpaulins. Bilingual documents, certification files and spare parts lists are delivered with each shipment. The logistics route integrates domestic highway transportation, ocean shipping and local transshipment within Iraq. Customs clearance and land transportation permits for the 16 large-scale equipment units are processed in advance. Temperature and vibration data loggers are installed on each unit throughout transit, with additional dust and salt fog protection reinforcements for ocean shipping. Units are delivered to individual oilfield and substation project sites in separate consignments.

VII. On-Site Delivery, Installation & Commissioning

1. Batch joint unpacking acceptance: Overseas engineers from Hengfengshuai Electric conduct joint inspections with the customer and local supervisors to verify appearance, nitrogen sealing and transportation temperature & vibration data for each unit, followed by signing formal acceptance documents;

2. Standardized high-temperature sandstorm-proof installation: Precise positioning of units, all accessories fitted with high-temperature resistant dust-proof sealing glue, and secondary vacuum oil filtration & exhaust for the complete equipment;

3. SAT Site Acceptance Test: Full set of electrical retests performed on-site against factory FAT reports, producing test records recognized by Iraq’s local power authorities;

4. Single-unit no-load impulse testing, 24-hour stable trial operation, staged load connection to Iraq’s 33/11kV power grid, and parallel operation commissioning for all transformers.

VIII. Full-Process Quality Control & Localized Operation & Maintenance Support

Six Special Quality Control Nodes for Hengfengshuai Electric’s Middle East Export Projects

Closed-loop quality control covers the full lifecycle: design, raw material procurement, batch production processes, unit-by-unit factory testing, cross-border batch transportation and on-site installation, with full traceability of all quality records. Non-conforming products are prohibited from factory shipment and field operation.

Localized Operation & Maintenance Support

Hengfengshuai Electric provides complete Arabic-English bilingual drawings, test reports, certification documents and operation & maintenance manuals customized for high-temperature and sandstorm environments upon delivery. Specialized training sessions are held for Iraqi maintenance personnel covering salt fog inspection, high-temperature heat dissipation management, sandstorm protection and maintenance of OLTC on-load tap-changers. Standardized unified operation and maintenance procedures are established for the 16 identical units, significantly lowering technical barriers for the customer’s maintenance team.

IX. Solution Summary

This complete set of 16 SZ-31.5MVA-33/11kV oil-immersed transformer solutions represents a benchmark bulk export project of Hengfengshuai Electric for the Middle East market. Tailored to Iraq’s extreme 55°C high temperatures, sandstorms, salt fog and volatile two-tier power grid, the integrated solution addresses core pain points including power conversion for full-scale substations, stable long-term operation under high temperatures, harmonic mitigation and energy conservation through high-temperature anti-corrosion structures, all-copper low-loss windings and unified on-load voltage regulation systems. Proficient with Iraq’s COSQC, MoE grid access requirements as well as IEC and GB standards, Hengfengshuai Electric can customize oil-immersed transformers of all specifications for the Middle East to support nationwide development of Iraq’s power grid upgrade, oil & gas and photovoltaic sectors. General contractors, project owners and foreign trade partners are welcome to enquire for cooperation.
Contact Email: hfs@hengfengshuai.com