ABB SACE Emax 2 for Renewable Energy: Solar and Wind Power Plant Protection
What is ABB SACE Emax 2 in renewable energy applications? ABB SACE Emax 2 is a low-voltage air circuit breaker rated 400–6300 A under IEC 60947-2, engineered with true RMS measurement and adaptive protection functions that address the bidirectional fault currents, harmonic distortion, and inverter-driven fault profiles characteristic of solar PV and wind power plants. Misapplying a conventional LV breaker in these installations — ignoring non-sinusoidal loading, inverter current-limiting behavior, or upstream–downstream selectivity with internal inverter protection — leads to coordination failures, nuisance tripping, or undetected faults that compromise plant availability. This guide covers AC main breaker sizing for solar PV arrays, converter and generator-side protection in wind turbines, selectivity coordination with inverter internal protection, harmonic loading impact on trip calibration, and a performance comparison against alternative LV breakers in renewable applications.
Why Renewable Plants Need Different LV Breaker Logic
A conventional industrial LV switchboard sees fault current flowing one way: from the utility transformer downstream to the load. A solar inverter skid or a wind turbine converter does the opposite for most of its operating life. Power flows from the generator toward the grid. Then, during a grid fault or anti-islanding event, the direction reverses in milliseconds — a behavior the ABB Emax 2 platform was specifically designed to handle through its symmetric trip logic.
In our experience, this is where engineers often underestimate the protection challenge. A breaker selected purely on rated current and Icu can perform poorly when the actual duty cycle includes 200+ daily switching operations (typical for a PV plant cycling at sunrise/sunset and during cloud transients), low power factor harmonic loading from inverters, and bidirectional fault contributions.
The Emax 2 platform handles this because the Ekip Dip and Ekip Touch trip units use true RMS current sensing across all three phases plus neutral, and protection thresholds (L, S, I, G) operate symmetrically regardless of current direction. That sounds obvious. It isn't — older electromechanical breakers and some thermal-magnetic MCCBs have asymmetric trip behavior under reverse flow.
For complete technical specifications and application guidance on the ABB Emax 2 air circuit breaker family, refer to ABB's official SACE Emax 2 product documentation, which details Ekip trip unit configurations, frame ratings, and compliance with IEC 60947-2.
Solar PV Plant Application: Sizing the AC Main Breaker
A typical utility-scale PV plant is built around inverter blocks of 1 MW to 5 MW. Each block has a step-up transformer (often 0.6 kV / 33 kV or 0.8 kV / 33 kV) and an AC main LV breaker on the inverter side. This breaker is where the ABB Emax 2 family fits naturally.
Continuous current calculation
For a 1.5 MW central inverter at 600V AC output, the rated continuous current is:
Formula: Three-phase rated current — Source: IEEE 141 (Red Book), §3.4
In = P / (√3 × U × cos φ)
| Symbol | Description | Unit |
|---|---|---|
| In | Rated continuous current | A |
| P | Active power (inverter AC output) | W |
| U | Line-to-line voltage | V |
| cos φ | Displacement power factor | — |
For 1.5 MW at 600V with cos φ = 0.99 (modern grid-tied inverters), In ≈ 1458 A. Add the IEC 60364-4-43 derating margin of 1.25 for continuous duty in switchboards above 35°C ambient, and the design current rises to 1822 A. That pushes you out of the E1.2 frame and into the E2.2.
In practice, what we typically see in the field is engineers selecting the ABB 1SDA071021R1 E2.2B 2000A Ekip Dip LI here. The 2000A frame gives ~10% headroom above the derated continuous current, the 42 kA Icu is sufficient for most PV collector systems where the upstream MV transformer limits prospective fault current to 25–35 kA, and the F HR (front, horizontal rear) terminal arrangement matches the busbar geometry of standard inverter skid switchboards.
Smaller blocks: 630–1250A range
For string inverter combiner panels and smaller central inverters (250–600 kW), the E1.2 frame fits well. The ABB 1SDA070701R1 E1.2B 630A, ABB 1SDA070741R1 800A, and ABB 1SDA070781R1 1000A are the workhorses. For detailed sizing methodology, the step-by-step Emax 2 sizing calculator article walks through the full margin calculation including ambient correction.
Wind Turbine Application: Converter and Generator Side Protection
Wind turbines have a fundamentally different LV architecture than PV, and the protection device selected — typically an ABB Emax 2 frame at the tower base — has to accommodate that difference. A modern 3 MW doubly-fed induction generator (DFIG) turbine has a stator circuit at 690V directly connected to the LV side of the pad-mount transformer, plus a rotor-side converter that handles roughly 30% of the rated power. Full converter (PMSG) turbines route 100% of the power through the LV converter at 690V.
Both topologies need a main LV breaker at the tower base. This is where Emax 2 earns its reputation: the breaker has to survive 25-year service life with 30+ daily switching operations during wind ramping, mechanical endurance demands above 12,500 operations (per IEC 60947-2 §8.3.3.1), and a corrosive nacelle/tower-base environment with salt, condensation, and vibration.
Mechanical and electrical endurance
Per the Emax 2 technical specifications, the E2.2 frame offers 25,000 mechanical operations and 10,000 electrical operations at 1600A, which translates to roughly 23 years of service at 3 daily operations — comfortably beyond a typical wind turbine's design life. For grid-side connections in offshore platforms where ambient conditions are harsher, some operators specify the Ekip Touch trip unit for predictive maintenance data via the Modbus RTU or IEC 61850 interface.
Selectivity Coordination with Inverter Internal Protection
Engineers often overlook one thing: the inverter has its own internal AC contactor and DC disconnect, with their own protection logic. The ABB Emax 2 must coordinate with these without nuisance tripping during inverter startup inrush or during grid fault ride-through (LVRT/HVRT) events mandated by grid codes like IEEE 1547-2018 and IEC 61400-21.
A common mistake is setting the instantaneous (I) protection too low. An inverter performing LVRT may inject up to 1.2× rated current for 150 ms during a remote grid fault. If the Emax 2 instantaneous trip is set at 8× In with no time delay, you may not have a problem — but if it's set at 4× In, you will. Set the L (long-time) pickup at 1.05–1.1× In, S (short-time) at 6–8× with 200 ms delay, and I (instantaneous) at 10× In minimum. For a deeper treatment of this issue, see Emax 2 nuisance tripping root causes and fixes.
Trip curve coordination calculator
Harmonic Loading and True RMS Measurement
Inverter output is not a clean sine wave. Even modern IGBT inverters with LCL filters produce 2–3% total harmonic distortion (THD) at full load, rising to 8–10% at low load (10–20% inverter loading during low-irradiance morning hours). Older breakers using peak-detecting electronic trips overestimate the RMS current and trip prematurely — a failure mode the ABB Emax 2 avoids through its true RMS sampling architecture.
The Ekip trip units in the Emax 2 sample at 4.8 kHz and compute true RMS up to the 50th harmonic. This matters in two scenarios. First: PV plants in cold climates with reflective snow conditions can briefly exceed nameplate output by 5–8% due to over-irradiance. A peak-sensing trip would trip nuisance. The Emax 2 won't. Second: wind turbines during converter mode transitions briefly inject high-order harmonics that look like overcurrents to a poor sensor.
Comparison: Emax 2 vs Alternatives in Renewable Applications
| Criteria | ABB Emax 2 E2.2 | Schneider MasterPact MTZ2 | Siemens 3WL |
|---|---|---|---|
| Rated current (max in 1600A class) | 1600A | 1600A | 1600A |
| Icu @ 690V | 42 kA (B), 66 kA (N), 100 kA (S) | 42–100 kA | 50–66 kA |
| Mechanical operations | 25,000 | 25,000 | 20,000 |
| True RMS to 50th harmonic | Yes (Ekip) | Yes (Micrologic X) | Yes (ETU) |
| IEC 61850 native | Yes (Ekip Com) | Yes | Optional |
| Bidirectional metering | Yes, full 4-quadrant | Yes | Yes |
| Operating temperature | −25 to +70°C | −25 to +70°C | −25 to +55°C |
For a more thorough head-to-head, see Emax 2 vs Schneider MasterPact MTZ technical comparison. In renewable plants, the Siemens option falls short on operating temperature ceiling, which matters for desert PV installations. Between the ABB Emax 2 and MasterPact MTZ, the deciding factor is usually the SCADA integration ecosystem the EPC has standardized on.
Communication and SCADA Integration
A wind farm or utility-scale PV plant has 50–500 LV breakers across its inverter blocks and pad-mount transformers. Manual maintenance of all of them is uneconomic. The ABB Emax 2 with Ekip Com module supports Modbus TCP, Profibus DP, Profinet, EtherNet/IP, DNP3, and IEC 61850 — the latter being increasingly required by grid operators for plants above 50 MW.
What we typically see in the field: the Ekip Com Hub aggregates up to 30 breakers on a single fiber link to the plant SCADA, providing per-breaker current, voltage, energy, harmonic distortion, contact wear percentage, and trip event logs. For O&M teams, this means a 6-month preventive visit can be scheduled by data, not by calendar. The cost saving on a 100 MW PV plant is typically 30–40% of the LV maintenance budget.
Environmental Considerations: Desert PV and Offshore Wind
Renewable plants live in hostile environments. Desert PV plants in the MENA region and Australia operate at +55°C ambient with daily 30°C swings; offshore wind sees salt fog, condensation, and constant vibration. The ABB Emax 2 is rated for −25 to +70°C operation, but practical derating curves show a 10–15% reduction in continuous current capacity above +50°C. Plan for it during sizing.
For offshore and coastal applications, specify the optional anti-condensation heater and IP54 enclosure with conformal-coated electronics. Some engineers argue that standard IP30 panels with HVAC are equivalent. In my experience, they aren't — HVAC fails, and when it does, condensation builds up overnight on the breaker terminals. The conformal coating is a $200 option that prevents a $50,000 outage.
For the broader product family, browse Air Circuit Breakers at Stoklink and complementary protection relays often paired with Emax 2 in renewable applications.
Anti-Islanding and Reverse Power Protection
Grid codes require generation sources to disconnect within 2 seconds of a grid loss to prevent islanding — the dangerous condition where a generator continues energizing a section of the grid that operators believe is de-energized. The ABB Emax 2 with Ekip G Hi-Touch supports under/over-voltage (27/59), under/over-frequency (81U/81O), and reverse power (32R) protection functions natively.
Reverse power protection is especially relevant in PV plants. At night, the inverter can draw a small magnetizing current from the grid (typically 2–5% of rated). Set the 32R pickup at 8–10% of rated power to avoid nuisance tripping at dusk while still detecting genuine reverse-flow faults.
Maintenance Strategy for Renewable Plants
A typical industrial ABB Emax 2 installation sees 50–500 operations per year. A PV plant breaker sees 700+ (one cycle per day plus cloud-induced operations). A wind turbine breaker sees 1000+. Maintenance intervals must be adjusted accordingly.
Per IEC 60947-2 §10, electrical endurance is specified at rated current. The Ekip Touch trip unit tracks operations and contact wear in real time, providing a percentage indicator visible on the SCADA. Schedule contact inspection at 50% wear, replacement at 80%. Between operations, verify torque on power connections annually — thermal cycling in PV plants loosens lugs faster than steady-state industrial loads. The Emax 2 data center MDB design article covers maintenance protocols that apply equally to renewable plants where uptime is critical.
Related Reading
- What Is the ABB SACE Emax 2? Features, Models and Key Benefits
- 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
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Frequently Asked Questions
Can the ABB Emax 2 be used at both 600V and 690V in the same wind farm?
Yes. The Emax 2 is rated up to 690V AC across all frame sizes, and the Ekip trip unit auto-adapts to the line voltage measured at the integrated voltage taps. The Icu rating drops slightly at 690V vs 600V — for the E2.2B at 1600A, Icu is 42 kA at both voltages, but the E1.2B drops from 42 kA at 600V to 42 kA at 690V (no drop on Bversion specifically). Always cross-check against the official Emax 2 specification tables for the exact frame and version you specify.
What size Emax 2 fits a 2 MW solar inverter at 800V AC output?
For a 2 MW inverter at 800V AC with cos φ ≈ 0.99, rated current is approximately 1458 A. Apply the 1.25 derating factor for switchboard ambient and continuous duty, giving 1822 A. The ABB 1SDA071021R1 E2.2B 2000A is the standard choice. Verify Icu against the actual prospective fault current at the inverter LV terminals — typically 25–35 kA in a PV collector system, well within the 42 kA Icu of the E2.2B.
Does the Emax 2 support IEC 61850 communication for grid-code compliance?
Yes, via the Ekip Com module configured for IEC 61850-8-1 MMS and GOOSE messaging. This is increasingly mandatory for plants above 50 MW connecting to transmission-level grids. The implementation requires the Ekip Touch trip unit (not the simpler Ekip Dip) and the Ekip Com IEC 61850 module. For SCADA architecture details in critical applications, the data center MDB design guide covers similar communication topologies.
How do I prevent nuisance tripping during inverter LVRT events?
Set the long-time (L) protection at 1.05–1.1× rated current with thermal memory enabled, the short-time (S) at 6–8× with a 200 ms intentional delay, and the instantaneous (I) at 10× minimum. This window allows the inverter to ride through grid faults per IEEE 1547-2018 without unnecessary breaker operations. The Emax 2 nuisance tripping diagnostic guide covers more detailed setting strategies.
Are residual current devices (RCDs) needed downstream of the Emax 2 in a PV plant?
It depends on the inverter topology and grounding scheme. Transformer-isolated inverters typically don't require external RCDs because they have integrated insulation monitoring. Transformerless inverters in TT or IT systems usually require Type B RCDs to detect DC residual currents. Browse compliant Residual Current Devices for downstream protection requirements.
What is the typical lead time and what spare strategy makes sense for a 100 MW PV plant?
Lead times for standard Emax 2 frames in stock configurations are typically 4–8 weeks ex-works; engineered variants with non-standard accessories run 12–16 weeks. For a 100 MW plant with roughly 50–70 inverter blocks, we recommend stocking 2 spare breakers per frame size used (typically 2× E1.2 1600A and 2× E2.2 2000A), plus one spare Ekip Touch trip unit. Trip units are interchangeable across compatible frames, which simplifies inventory significantly.
Can the same Emax 2 be reused if the plant repowers with higher-output inverters?
Sometimes, but check three things. First, the new inverter's continuous current must remain below 80% of the breaker's rated current after applying ambient derating. Second, the prospective fault current at the upgraded plant configuration must remain below the breaker's Icu. Third, the trip unit settings must be reviewed against the new inverter's LVRT and harmonic profile. In our experience with PV repowering projects, roughly 60% of Emax 2 breakers can be reused after settings adjustment; the rest require frame upsizing.
Conclusion
Specifying air circuit breakers for renewable energy plants is not the same exercise as specifying them for industrial loads. Bidirectional power flow, harmonic content, frequent switching, grid-code compliance, and harsh environmental conditions all shift the engineering priorities. The ABB SACE Emax 2 platform addresses these requirements through true RMS sensing to the 50th harmonic, mechanical endurance well beyond typical industrial duty cycles, native IEC 61850 communication, and integrated 27/59/81/32R protection functions that eliminate the need for external relays.
For a solar PV plant, focus on the AC main breaker sizing methodology, true RMS measurement, and SCADA integration via Ekip Com. For wind turbines, mechanical endurance and predictive diagnostics matter most. In both cases, the trip unit settings — particularly the L/S/I curves and reverse power thresholds — are where field experience pays off. A correctly sized breaker with poor settings will trip nuisance during grid events; a slightly oversized breaker with thoughtful settings will run for 25 years with minimal intervention.
Standard products like the ABB 1SDA070861R1 E1.2B 1600A, ABB 1SDA070981R1 E2.2B 1600A, and ABB 1SDA070821R1 E1.2B 1250A cover the bulk of inverter block applications from 250 kW string clusters up to 2 MW central inverters. For the full selection methodology, coordination studies, and maintenance planning, consult the complete ABB SACE Emax 2 selection, application and maintenance guide, and for the underlying technology fundamentals, the Air Circuit Breaker engineering guide remains the authoritative reference.
The renewable energy market will continue pushing LV breaker requirements: higher voltages (1500V DC PV is moving toward 2000V; wind LV may rise to 800V or 950V), more aggressive grid codes, and tighter SCADA integration. The Emax 2 platform has the architectural headroom to evolve with these demands, which is ultimately why it remains the default choice for engineers specifying LV protection in solar and wind plants worldwide.
