Successful Case Study of 24 Units of 14.4kV Oil-Immersed Voltage Regulators for the El Salvador Project

01 Project Overview

1.1 Project Background

In September 2025, 24 units of 14.4kV single-phase oil-immersed voltage regulators were officially exported. These units were deployed in El Salvador’s medium-voltage distribution network modernization project.

They were independently researched, developed, and manufactured by Vziman. The units are specifically engineered for precise voltage regulation, dynamic load adaptation, and power quality enhancement across El Salvador’s grid.

The equipment has been successfully installed at multiple locations. These include 13.8kV substations, industrial parks, and urban-rural distribution nodes. Since commissioning, the equipment has operated stably and efficiently.

As a core stabilization device in medium-voltage networks, the voltage regulator features a controller with millisecond-level detection speed. This allows it to dynamically compensate for line voltage drops during severe fluctuations or abrupt load changes.

This effectively eliminates voltage violations and flicker. Consequently, it significantly reduces equipment failure rates and outage frequency. Thus, the regulator serves as a critical asset for grid resilience upgrades and industrial energy security. All units strictly comply with El Salvador’s 60Hz grid standard.

The design is tailored for Central America’s tropical maritime climate. This climate features year-round temperatures above 38°C, coastal salinity, high humidity, and monsoon dust. To address this, the regulators feature a fully sealed oil-immersed cooling structure. They also have a marine-grade anti-corrosion coated enclosure and salt-corrosion resistant sealing technology.

Critically, they maintain output voltage stability within ±0.8% under a wide ±16% input fluctuation. The project is further supported by Spanish-speaking technical teams, an intelligent remote monitoring system, and a preventive maintenance system.

Due to these features, the project has earned high acclaim from the El Salvador National Electric Company (CEL) and key industrial clients. Ultimately, this delivers robust power support for manufacturing, residential use, and infrastructure sustainability.

1.2 Technical Parameters

The detailed technical specifications are summarized as follows:

02 Product Manufacturing

2.1 Voltage Regulation Coil Winding and Curing

Coil winding is the core process for achieving precise voltage regulation in the 14.4kV single-phase oil-immersed voltage regulator.

High-precision fully automatic CNC winding equipment is employed to strictly control tension, density, and turn count. This ensures a uniform, compact coil structure with turn error maintained within ±0.5%, establishing the foundation for ±1% output voltage stability.

After winding, the Vacuum Pressure Impregnation (VPI) process is applied. The coil is immersed in Class 155°C high-temperature resistant, salt-spray resistant insulating varnish—specially formulated for Central America’s tropical maritime environment. Through vacuum degassing followed by stepwise high-pressure curing, the varnish deeply penetrates microscopic gaps, forming a dense, highly adhesive composite insulation layer.

The cured coil undergoes rigorous testing: insulation resistance, dielectric loss factor, and partial discharge. These validations confirm reliable long-term operation under El Salvador’s harsh conditions—temperatures ≥38°C, high humidity, salt spray, and monsoon dust.

The coil effectively resists environmental erosion and electrical stress, eliminating risks of insulation aging or breakdown. This fully ensures equipment reliability and safety throughout its entire lifecycle in demanding field conditions. 

2.2 Assembly of Voltage Regulation Mechanism and Transmission System

The modular assembly process is applied to precisely integrate the high-precision voltage regulation mechanism, transmission gear set, and adjustment shaft of the 14.4kV single-phase oil-immersed voltage regulator.Fitting clearance is strictly maintained within ±0.02mm to ensure smooth transmission operation and accurate voltage regulation positioning.

Marine-grade anti-salt-spray synthetic lubricating grease is applied to critical transmission components. This formulation is specifically optimized for El Salvador’s tropical maritime climate (15°C to 45°C, high humidity, salt spray, monsoon dust). It effectively resists high-temperature degradation, salt-induced hardening, and dust ingress.

Post-assembly enhanced mechanical testing includes:

• Continuous verification of 10,000 voltage regulation and locking cycles inside a salt spray simulation chamber (40°C, 95% RH, 5% NaCl). Confirmed smooth operation with zero jamming incidents.
• Accelerated aging tests validate a mechanical life exceeding 2,000,000 cycles.
• These results fully satisfy the distribution network’s demand for reliable, long-term frequent voltage regulation.

03 Testing and Inspection

3.1 Component Fit Precision Test

Precision measurement of fitting clearance and concentricity for the voltage regulation mechanism, transmission gear set, and adjustment shaft. Ensures compliance with ±0.02mm assembly tolerance to guarantee smooth transmission operation and precise voltage positioning under El Salvador’s long-term high-temperature, high-humidity conditions.

3.2 Lubricant Environmental Adaptability Test

Marine-grade anti-salt-spray synthetic grease is validated under El Salvador’s typical conditions (15°C–45°C, humidity ≥85%, 5% NaCl salt spray). Confirms no high-temperature oil separation, salt-induced hardening, or low-temperature solidification—eliminating transmission jamming risks.

3.3 Mechanical Action Reliability Test

10,000 continuous cycles of voltage regulation switching and locking actions performed in a 40°C, 95% RH, 5% NaCl salt spray chamber. The entire voltage regulation controller response time is ≤150 ms with smooth operation—ensuring zero jamming in harsh coastal environments.

04 Packaging and Transportation

4.1 Packaging

• Custom steel structural frames provide overall reinforced packaging. High-density moisture-proof EPE foam and intelligent inflatable cushioning air columns are precisely fitted to the 4kV single-phase oil-immersed voltage regulator’s contour. This configuration effectively withstands continuous vibration, impact, and stacking pressure during trans-Pacific ocean freight and El Salvador land transport, maintaining core component displacement error below 0.5 mm.
• The regulator body (including oil tank, porcelain bushings, and tap changer) receives triple-layer protection: sealed in vacuum moisture-proof bags, equipped with built-in humidity indicator cards and silica gel desiccants, and wrapped in an outer salt-spray resistant PE protective film. This fully isolates the unit from ocean freight hazards—humidity >90%, salt spray corrosion, and handling impacts—ensuring arrival at the Port of Acajutla, El Salvador in pristine condition.

4.2 Transportation

• Shipping Method: Ocean freight is adopted, optimized for long-distance transport of large-scale power equipment. The method ensures stable transit conditions and a controlled environmental profile throughout the journey.
• Carrier: An experienced professional logistics provider is engaged to guarantee safe, on-time delivery and to facilitate end-to-end customs clearance procedures.

05 On-Site Implementation and Summary

5.1 On-Site Implementation

This project forms part of El Salvador’s medium-voltage distribution network upgrade. Installation and commissioning of the 14.4kV single-phase oil-immersed voltage regulator strictly comply with IEEE/IEC C57.15-2017 and are optimized for tropical maritime conditions (ambient temperatures above 40°C, high humidity, salt spray):

• Precise Pre-Inspection: Verify foundation base integrity; inspect equipment appearance, protective coating, and technical parameters; prepare climate-adapted auxiliary materials.
• Modular Assembly: Precisely assemble the voltage regulation mechanism with clearance controlled within ≤±0.02mm; apply anti-salt-spray lubricant; validate response time ≤150ms and service life exceeding 2 million cycles via operational testing.
• Enhanced Sealing: Hoist core assembly into dual-layer anti-corrosion housing; implement double sealing on flanges; pass IP54 certification and 96-hour salt spray test.
• Oil Filling & Wiring: Perform vacuum oil filling (moisture content ≤15 ppm, breakdown voltage ≥45 kV); complete standardized main circuit and grounding wiring; achieve ground resistance ≤2.5 Ω.
• Electrical Commissioning: Under ±16% input voltage fluctuation, maintain output stability within ±0.8% with harmonic distortion <1.8%.
• Environmental Validation: Conduct 72-hour continuous operation test under high-temperature, high-humidity, and salt spray conditions; confirm zero performance degradation.
• Load Commissioning: Complete 72-hour full-load trial operation with all parameters meeting standards; deliver Spanish-language commissioning reports and digital archives; obtain joint acceptance certification from CEL (Comisión Ejecutiva Hidroeléctrica del Río Lempa) and end-users.

5.2 On-Site Summary

In El Salvador’s medium-voltage distribution network upgrade project, installation and commissioning of the 14.4kV single-phase oil-immersed voltage regulator strictly followed IEEE C57.15 and specifications of El Salvador’s National Electric Company (CEL).

The modular assembly process efficiently adapted to the tropical maritime environment (temperatures above 40°C, high humidity, salt spray, monsoon dust). Precise transmission mechanism assembly, dual sealing protection, and full-parameter commissioning effectively mitigated risks of salt-induced jamming and insulation degradation.

The 72-hour full-load trial operation confirmed: output voltage stability accuracy ±0.8%, ground resistance ≤2.5 Ω, harmonic distortion rate <1.8%—all indicators fully compliant. The project significantly enhanced voltage quality at 13.8kV distribution nodes, providing reliable power support for industrial zones and residential areas. Joint acceptance by CEL and key users affirmed the product’s robust reliability in harsh conditions and the value of localized service support.

06 Full Lifecycle Operation and Maintenance Management Service

This service covers the entire lifecycle of oil-immersed voltage regulators—from procurement and adaptation, installation and commissioning, daily operation, maintenance and servicing, fault handling, to decommissioning and disposal. With end-to-end managed oversight and dedicated personnel accountability, it ensures safe and stable equipment operation, fully traceable management, and worry-free power supply.

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