Transformer-Based vs Transformerless UPS in Petrochemical Facilities: Field Observations from China

In 2019, an engineering team at Jilin Petrochemical Company's refinery was dealing with a recurring problem: the DCS system was experiencing communication errors, and no one could pin down the cause. The plant had been operating for years, but something had changed in the electrical environment. The control system was stable one week and unreliable the next.

After several months of troubleshooting, the root cause was traced to ground loops—multiple ground reference points across the plant's electrical infrastructure were causing errors between PLCs and the central DCS. The fix was not obvious at first, and the team tried several approaches before settling on a solution.

This article summarizes what we observed across multiple petrochemical deployments in China between 2018 and 2025. It includes successful cases, one case where the solution didn't work as expected, and some lessons learned along the way. The observations are based on published Prostar case studies and field service records.

Why UPS Reliability Matters in Petrochemical Facilities

Petrochemical production processes are characterized by continuous operation, high temperatures, high pressures, flammable materials, and explosive atmospheres. Any sudden power failure in critical control equipment can have serious consequences—not just production losses, but safety risks as well.

Control devices in petrochemical applications need reliable UPS power to ensure uninterrupted operation. SCADA systems, PLC cabinets, DCS networks, and fire detection instruments all depend on stable power. In the facilities we worked with, the most common power-related issues fell into several categories:

• Lightning-induced surges on exposed transmission lines
• High inrush currents from motors and compressors during startup
• Ground potential drift across distributed electrical systems
• Environmental factors—fine dust, conductive dust, and corrosive gases

Each of these presents challenges individually. The greater difficulty arises when multiple conditions occur simultaneously—which is not uncommon in petrochemical production environments.

Jilin Petrochemical: A Ground Loop Problem

Jilin Petrochemical is a large state-owned petrochemical group with a refining capacity of 7,000,000 tons per year, ethylene capacity of 980,000 tons, and synthetic ammonia capacity of 300,000 tons. In 2019, the refinery began experiencing intermittent DCS communication errors. The issue had been present for several months, with no clear pattern.

After tracing the problem to ground loops, the plant deployed three Prostar GT100K UPS units in a parallel redundant configuration with built-in isolation transformers. The transformers provided independent neutral references for each load segment, eliminating the ground loop issue.

According to maintenance records reviewed in 2020, communication-related alarms became infrequent after commissioning. Exact figures varied by production unit, but the plant operators reported that the DCS system became more stable overall.

Jiangsu Linggu Chemical: Harmonic Pollution and Harsh Environment

Jiangsu Linggu Chemical Co., Ltd. is a fertilizer manufacturing enterprise with an annual production scale of 1 million tons of synthetic ammonia and 1.7 million tons of urea. In 2021, the plant introduced a Baoxing 60KVA industrial UPS to provide power protection for instruments, PLC cabinets, and fire-fighting equipment.

The production environment includes conductive dust, corrosive gases, and temperature extremes. The UPS unit's built-in output isolation transformer and five-stage filters reduced harmonic pollution, with harmonic content measured below 10% after installation.

The unit withstood the environmental conditions—which include fine dust, conductive dust, and corrosive gases—and has remained in service.

One Site That Changed Our Thinking

In 2021, we recommended a transformer-based UPS for a chemical facility in Shandong. The assumption was straightforward: the incoming utility power appeared unstable based on the plant's description, and transformer isolation seemed like the right solution.

After installation, the UPS operated correctly, but the end-user reported that the original problem—unexplained PLC communication errors—had not improved. The UPS was not the cause, but it also wasn't the solution.

We spent two weeks on-site taking measurements. The actual problem was traced to a grounding loop inside a recently expanded production line. The expansion had introduced a second ground reference point, and the communication errors were coming from the load side, not the utility side.

The transformer was never the root solution. That project changed how we approach site assessments today.

Not Every Transformer Solved the Problem

In one petrochemical installation we reviewed, the UPS replacement delivered almost no measurable improvement. The root cause was eventually traced to a load-side grounding issue—a completely separate problem from the utility-side concerns that the transformer-based UPS was designed to address.

The UPS was blamed initially, but the actual issue was outside the UPS boundary. This highlighted an important limitation: transformer isolation addresses problems that originate upstream of the UPS. It cannot fix issues that are downstream—on the load side.

This is not a failure of the product, but a failure of the initial site assessment. In this case, we should have performed a more thorough investigation before recommending the solution.

When a Transformer-Based UPS May Not Be Necessary

Transformerless UPS designs are lighter, smaller, and typically more efficient—96-97% in standard operation and over 98% in ECO mode. For data centers, commercial buildings, and IT rooms with stable grid conditions, they are often the appropriate choice.

We don't recommend transformer-based UPS for every application. In facilities with clean utility power, consistent grounding, and no history of lightning-related issues, a transformerless unit may perform as well as or better than a transformer-based alternative at a lower initial cost.

However, in the petrochemical sites we reviewed, those conditions are rarely present. The efficiency difference becomes less relevant when a transformerless unit experiences downtime due to surge or grounding issues. A UPS that is offline is less efficient than one that is running—regardless of its rated efficiency.

Compliance and Standards

Prostar industrial UPS systems are designed to align with IEC 62040-3 performance requirements. The built-in output isolation transformers and five-stage filters reduce harmonic pollution to the power grid, with harmonic content below 10%.

IEEE 446 (Orange Book) and IEEE 1100 (Emerald Book) provide guidance on emergency power systems and facility grounding—issues that are central to the observations described in this article.

Industry standards are comprehensive, but field conditions often deviate from what the standards assume. In several installations we reviewed, the UPS was specified to meet IEC 62040-3 requirements, but the grounding system was designed to a different reference. The UPS passed factory testing but encountered issues in the field. In most of those cases, the issue was related to installation conditions rather than the product itself.

Frequently Asked Questions

Summary

Across multiple petrochemical deployments in China between 2018 and 2025, transformer-based UPS systems with built-in isolation transformers have demonstrated reliable performance in challenging environments—including facilities with ground loop issues, harmonic pollution, conductive dust, corrosive gases, and variable grid conditions.

However, not every installation followed the expected pattern. In one case, the transformer-based UPS did not resolve the issue because the root cause was on the load side, not the utility side. That experience reinforced the importance of thorough site assessment before recommending a solution.

The line we draw in the dirt is pretty straightforward: if you are looking at frequent lightning, sketchy remote grounding, or big motor loads pushing your lines around, the transformer provides a layer of defense. But if you are building a facility with clean utility power and consistent grounding, you may not need it. We've installed both, and both have their place.

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