ABB Emax 2 for Oil and Gas Offshore Platform Electrical Systems

What is the ABB Emax 2 for oil and gas offshore platforms? The ABB Emax 2 is an air circuit breaker rated 400–6300 A under IEC 60947-2, with breaking capacities up to 150 kA and an IP54 ingress protection option, engineered to meet the environmental and fault-coordination demands of offshore LV power distribution. Specifying a breaker without verified salt-mist, vibration, and humidity qualification — or without correct short-circuit coordination on an isolated IT system — risks protection failure, unplanned platform shutdown, or non-compliance with IEC 60092 marine and offshore electrical standards. This guide covers offshore environmental qualification requirements, short-circuit coordination on isolated generators, Zone-Selective Interlocking on LV main switchboards, generator protection via the Ekip G-Hi-Touch unit, and a direct comparison against alternative ACBs for offshore use.

Published: 2026-04-27 | Last updated: 2026-04-27 | By Stoklink Engineering Team

Offshore electrical systems are not friendly. The air carries chloride aerosols measured in milligrams per cubic meter, the platform deflects under wave loading, and a tripped main breaker can mean a process shutdown costing six figures per hour. The ACB you specify for a Floating Production Storage and Offloading (FPSO) main switchboard is doing far more than interrupting fault current — it is the spine of a power system that often cannot be de-energized for repair. That changes how engineers evaluate every parameter on the datasheet.

Why Emax 2 fits offshore power systems

Offshore platforms run isolated power systems, and the ABB Emax 2 is frequently specified into them. Generation is typically 2–4 gas turbine generators in the 6–25 MW range stepping down to a 690 V or 400 V LV bus through dry-type transformers. Unlike onshore plants, you cannot fall back on a utility tie. That means every breaker on the LV main board must coordinate with generator decrement curves, manage motor inrush from large process drives, and survive an environment classified IEC 60721-3-3 class 3C3 or worse for corrosive gases.

The Emax 2 platform — covered in detail in What Is the ABB SACE Emax 2? Features, Models and Key Benefits — addresses these constraints in three ways. First, the Ekip Touch and Ekip Hi-Touch trip units provide programmable Long-time, Short-time, Instantaneous and Ground (LSIG) protection with adjustable I²t curves, which matters when you are coordinating with a generator that can deliver only 3× nominal current for 10 seconds. Second, the mechanical frame is qualified for shock and vibration per Lloyd's Register, DNV and ABS marine type approvals. Third, the Ekip Com modules support Modbus RTU, Modbus TCP, Profibus and IEC 61850 — the last of which is increasingly mandated for new offshore Power Management Systems (PMS).

Frame sizes typically used offshore

For a typical FPSO LV main switchboard at 690 V, the breaker selection follows generator output and feeder ratings. A 12 MW gas turbine generator at 690 V draws roughly 10,040 A — outside Emax 2 range, so two parallel E6.2 6300 A or larger custom solutions are used. But on the feeder side, where the bus is segmented into process loads, the E1.2, E2.2 and E4.2 frames dominate. Common picks include the ABB 1SDA070861R1 E1.2B 1600 A for transformer secondaries feeding 400 V utility boards, the ABB 1SDA071021R1 E2.2B 2000 A for main process feeders, and the ABB 1SDA070781R1 E1.2B 1000 A for outgoing motor control center (MCC) supplies.

For complete technical specifications, type-test certificates and configuration options of the ABB Emax 2 family, refer to the manufacturer's official product documentation available at ABB SACE Emax 2 product portfolio.

Environmental qualification: what offshore actually means

In our experience, the single biggest specification mistake on offshore projects — including those using the ABB Emax 2 — is treating "tropicalized" and "marine certified" as the same thing. They are not. Tropicalization is a coating treatment for high humidity. Marine certification covers salt fog, inclination, vibration, and electromagnetic compatibility on a vessel.

The Emax 2 is supplied with conformal coating on Ekip electronic boards as standard, which addresses condensation but not the chloride attack on copper bus connections inside the breaker compartment. For platforms in the North Sea, Persian Gulf or Gulf of Mexico, engineers should also specify silver-plated main contacts (factory option) and additional cabinet pressurization. The switchboard manufacturer typically maintains +50 Pa positive pressure inside the breaker compartment using filtered HVAC supply — without this, even a marine-certified ACB will accumulate salt deposits on the arc chute over 18–24 months.

Vibration and seismic considerations

Fixed-pattern offshore platforms are relatively stiff, but FPSOs and semi-submersibles see continuous low-frequency motion. The Emax 2 is qualified to IEC 60068-2-6 at 0.7 g acceleration, which covers normal operation. For modules located near reciprocating compressors, however, we have measured panel-level vibration above 1.2 g RMS in the 20–60 Hz band. In those cases the breaker should be mounted on a vibration-isolated subframe, and the cable terminations torqued and re-torqued at 30-day, 90-day and 180-day intervals during commissioning. A loose terminal at 1500 A produces enough heat to fail an Ekip current sensor within weeks.

Sizing and short-circuit coordination on isolated systems

This is where offshore engineering diverges from onshore practice, and where ABB Emax 2 selection has to be revisited. On a utility-fed plant, the available short-circuit current at the LV main bus is often 50–80 kA, set by the upstream transformer and grid impedance. On an offshore platform, the prospective short-circuit current depends entirely on the running combination of generators and is highly variable.

For a single 12 MW generator with sub-transient reactance X"d of 0.14 pu, the three-phase fault contribution at the machine terminals is roughly 1/X"d × full-load current ≈ 71,700 A. With four such generators paralleled, the contribution can exceed 250 kA before considering motor back-feed. That is why offshore main bus breakers are typically rated 100 kA Icu or higher, while feeder breakers downstream of current-limiting reactors or transformers can use standard 42 kA Emax 2 B-class versions.

For full sizing methodology including bus stress factors and time-current curve overlays, see How to Size ABB Emax 2: Step-by-Step Calculator for LV Distribution Panels. The critical point for offshore use: do your fault calculation for the worst-case running combination, not the design maximum, because the PMS may force atypical generator combinations during maintenance windows.

Selectivity with generator decrement

A common mistake is setting the Long-time pickup on a feeder Emax 2 too close to the generator's continuous overload curve. Gas turbine generators with brushless excitation typically follow a decrement curve where short-circuit current decays from sub-transient (~7× FLA) to steady-state (~3× FLA) in 0.5–2 seconds, depending on AVR action. If your downstream Long-time delay is set above 2 seconds at 3× pickup, the generator may collapse before the breaker trips, taking the platform black.

In practice, we set Ekip Touch Long-time pickup I1 at 1.05× nominal, time t1 at 6 s at 6× I1, and Short-time I2 at 4× with t2 = 0.2 s using I²t = ON for selectivity with downstream MCCBs. Instantaneous I3 is often disabled on the main incomer to allow zone-selective interlocking (ZSI) to handle bus faults — more on that next.

Zone-Selective Interlocking on the LV main board

Zone-Selective Interlocking is one of the underused features of Ekip trip units on the ABB Emax 2. The principle is simple: when a feeder breaker sees a fault, it sends a blocking signal to the upstream incomer, which delays its trip. If no downstream breaker reports the fault, the incomer trips immediately. The result is fast clearing of bus faults without sacrificing selectivity for downstream faults.

Engineers often overlook ZSI on offshore boards because it requires a hardwired loop between Ekip units, which adds termination work. But on a FPSO main board with 8–12 outgoing feeders and a fault current of 80 kA, removing 200 ms from bus fault clearing can mean the difference between localized damage and a full switchboard rebuild. The Ekip Dip versions on breakers like the ABB 1SDA070741R1 E1.2B 800 A support ZSI as standard via the Z-IN and Z-OUT terminals.

Comparing Emax 2 against alternatives for offshore use

The honest answer is that Schneider MasterPact MTZ, Siemens 3WL10 and ABB Emax 2 all have valid marine certifications and can do the job. The choice often comes down to standardization with the platform's existing PMS and the EPC contractor's experience. For a deeper feature-by-feature comparison, see ABB Emax 2 vs Schneider MasterPact MTZ: Technical Specs, Features and Price Compared.

Generator protection and Ekip G-Hi-Touch

Where the ABB Emax 2 has a clear edge offshore is the Ekip G-Hi-Touch trip unit, which adds generator-specific protection functions: voltage-dependent overcurrent (ANSI 51V), reverse power (32R), under/over voltage (27/59), under/over frequency (81U/81O) and earth fault directional. On smaller platforms running 1–2 MW emergency generators, this can replace a separate multifunction relay like a SEL-700G or Woodward MRG, simplifying the panel.

That said, on main generation above 5 MW, classification societies typically require a separate generator protection relay regardless of what the ACB can do. The Emax 2 then becomes the switching device, and the relay sends trip signals via the Ekip Signalling 4K module or directly to the shunt trip coil. We have seen engineers specify dual trip paths — one via the multifunction relay, one via the Ekip trip unit — for redundancy on critical generators. It is good practice when budget allows.

Common field failures and procurement lessons

What we typically see in the field after 5–7 years of offshore service falls into three categories. First, contact erosion on breakers that operate frequently as part of load-shedding schemes — the PMS opens and closes them dozens of times per month, exceeding the design assumption of a few operations per year. The fix is specifying breakers one frame size larger than the calculated rating to give margin on contact wear, and scheduling maintenance per IEC 60947-2 Annex M.

Second, nuisance tripping on harmonic-rich buses feeding Variable Frequency Drives (VFDs) for ESP or compressor motors. The Ekip true-RMS measurement handles harmonics correctly, but the issue is often capacitor inrush from harmonic filters mis-classified as a fault by aggressive Instantaneous settings. For root-cause analysis, see ABB Emax 2 Nuisance Tripping: Root Causes, Diagnostic Steps and Fixes.

Third — and this is an organizational rather than technical issue — spare parts. Offshore logistics being what they are, a failed Ekip Touch unit can mean weeks of waiting if the model was not stocked. We recommend keeping at least one complete spare breaker per frame size on platform, plus spare trip units, racking handles and auxiliary contact blocks. The ABB 1SDA070701R1 E1.2B 630 A and ABB 1SDA070821R1 E1.2B 1250 A are the most common spare frames we see specified for North Sea and Mediterranean platforms.

Communications and integration with offshore PMS

Modern offshore platforms run a Power Management System that handles load shedding, generator dispatch, fast bus transfer and blackout recovery. The PMS needs real-time data from every main breaker — status, currents per phase, power, energy, harmonic distortion, trip cause. The Ekip Com IEC 61850 module on Emax 2 publishes GOOSE messages with sub-10 ms latency, which is fast enough for fast load-shedding schemes that must shed non-essential loads within one cycle of a generator trip.

For data center comparisons where similar redundancy considerations apply onshore, see ABB Emax 2 in Data Centers: MDB Design, Redundancy and Uptime Considerations. The architectures are different but the breaker-level requirements — fast communication, high availability, predictive maintenance data — overlap considerably.

Procurement checklist for offshore Emax 2 orders

Based on full project specifications we have reviewed for FPSO and fixed-platform projects, the order should explicitly list: frame size and rated current, breaking capacity Icu and Ics at the actual system voltage (not the maximum), trip unit model with required protection functions (LI, LSI, LSIG, G), communication module, marine type approval certificate (specify which society — DNV-GL, Lloyd's, ABS), conformal coating confirmation, silver-plated main contacts if required, accessories (motor operator, shunt trip, undervoltage release, auxiliary contacts), and spare parts package.

For full ratings and dimensional data needed during board layout, refer to ABB Emax 2 Full Technical Specifications: Current Ratings, Breaking Capacity and Dimensions. The frame depth matters offshore because switchboards are often installed in restricted electrical rooms with limited rear access.

Stoklink stocks the full Emax 2 range alongside complementary protection devices — see our air circuit breakers collection for ACB options, and the miniature circuit breaker, residual current device and relay ranges for downstream protection on the same platform.

Maintenance strategy in offshore service

IEC 60947-2 Annex M defines mechanical and electrical endurance categories. The Emax 2 E1.2 to E6.2 frames are rated for 12,500 to 25,000 mechanical operations and 6,000 to 10,000 electrical operations at rated current, depending on frame size. For a feeder breaker that operates once per month, that is decades of life. For a tie breaker switched twice per shift during PMS load balancing, you may exhaust the electrical endurance in 8–10 years.

Offshore maintenance windows are scarce. A four-yearly major overhaul aligned with shutdown turnaround is realistic; anything more frequent requires hot work permits and isolation procedures that erode availability. The Ekip Touch trip unit logs operation counters and contact wear estimation based on interrupted current, which feeds directly into a condition-based maintenance plan. Pull the data via Ekip Connect or the IEC 61850 reporting and you have a defensible basis to defer or accelerate intervention rather than blindly following calendar dates.

Insulation resistance and primary injection

During shutdown maintenance, the standard tests are: insulation resistance phase-to-phase and phase-to-ground at 1000 V DC (acceptance > 100 MΩ for clean dry contacts), contact resistance via micro-ohmmeter (typical 35–50 µΩ across main contacts on E2.2 frame), primary injection at 1.5× and 6× pickup to verify trip times, and mechanical operation count. The E2.2B 1600 A frames with HR (horizontal rear) terminals tend to accumulate dust on the rear bushings — clean them with isopropyl alcohol, never with water-based solvents.

Related Reading

• ABB Emax 2 Full Technical Specifications: Current Ratings, Breaking Capacity and Dimensions
• How to Size ABB Emax 2: Step-by-Step Calculator for LV Distribution Panels
• ABB Emax 2 Nuisance Tripping: Root Causes, Diagnostic Steps and Fixes
• ABB Emax 2 in Data Centers: MDB Design, Redundancy and Uptime Considerations

Conclusion

Offshore power systems impose constraints that punish lazy specification. Salt fog, vibration, isolated generation, restricted maintenance windows and process criticality together mean a breaker must be more than electrically correct — it has to be the right variant of the right frame, with the right certificates, communication module and spares plan behind it. The ABB SACE Emax 2 platform handles these demands well when specified completely. The Ekip trip unit family covers everything from basic LI feeder protection on the E1.2B 630 A to integrated generator protection with G-Hi-Touch on main incomers, and the IEC 61850 communication option matches the direction modern offshore PMS designs are heading.

For the full selection methodology, coordination workflow and lifecycle planning that supports decisions on any LV ACB project — onshore or offshore — refer to the ABB SACE Emax 2 Air Circuit Breaker: Selection, Application and Maintenance Guide. And when specifying for a real platform project, build the procurement document around the certificates and options listed here, not the catalog page alone. The cost of a retrofitted certificate during commissioning is always higher than getting it right at PO.