ABB Emax 2 Protection Relay LSIG Settings Calculation Guide

26 May, 2026
Posted by: Muhammet KUL

What is an ABB Emax 2 LSIG protection relay setting? An ABB Emax 2 LSIG protection relay setting is a four-function overcurrent trip configuration — Long-time (L), Short-time (S), Instantaneous (I), and Ground-fault (G) — applied to Emax 2 air circuit breakers rated 400–6300 A under IEC 60947-2, where each stage defines a discrete pickup current and time-delay threshold for selective fault isolation. Miscalculated I1 pickup levels, overlapping S and I stages, or an improperly coordinated G threshold will collapse selectivity, cause upstream breakers to trip on downstream faults, or generate persistent ground-fault nuisance trips. This guide covers L-stage pickup calculation, S-stage delay coordination for selectivity, instantaneous I-stage sizing and disable conditions, ground-fault G-stage threshold setting, and a consolidated LSIG pickup-and-delay worked example.

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

What LSIG Actually Means on an Emax 2 Trip Unit

Before any calculation, get the vocabulary straight. The Ekip trip units fitted to the ABB Emax 2 — Ekip Dip, Ekip Touch, Ekip Hi-Touch, and the G-series variants — implement protection functions according to IEC 60947-2 Annex F. Each letter in LSIG refers to a defined curve segment with its own pickup, time delay, and (sometimes) curve shape.

LSIG protection is defined as a four-stage overcurrent and earth-fault scheme where L handles thermal overload, S handles short-circuit with intentional time delay for selectivity, I handles instantaneous high-magnitude faults, and G handles ground/earth faults (per IEC 60947-2 Annex F and IEEE Std 1015-2006).

L — Long-time Protection

L emulates the I²t heating of a conductor. On an Emax 2, the threshold is labelled I1 and is adjustable from 0.4 to 1.0 × In, where In is the rating plug current. The trip time at 6 × I1 (the standard reference point per IEC 60947-2) is the t1 setting, typically 3 s, 6 s, 12 s, 18 s, or 24 s for Ekip Dip units. In our experience, plant engineers default to t1 = 12 s and never touch it again. That is fine for a transformer secondary feeder, but wrong for a motor MCC bus where 3 s is usually preferred to protect downstream cable insulation.

S — Short-time Protection

S, threshold I2, ranges from 0.6 to 10 × In. It can run with definite-time (t=k) or inverse-time (I²t=k) characteristic. The inverse-time mode is what gives Emax 2 its selectivity edge against downstream MCCBs and fuses — a point we will return to.

I — Instantaneous Protection

I, threshold I3, is settable from 1.5 to 15 × In. There is no intentional time delay; the trip time is the breaker's own opening time, typically 30 ms total clearing for an E1.2 or E2.2. Some engineers turn I OFF on incoming feeders to enable full zone selectivity downstream. That is a defensible choice only if the breaker's Icw (rated short-time withstand) covers the prospective fault current for the full S-stage delay.

G — Ground-fault Protection

G, threshold I4, ranges from 0.2 to 1.0 × In with t4 from 0.1 to 1 s. On Ekip Dip LI units, G is not available — you need at least an LSIG or Ekip Touch unit. This is precisely why the ABB 1SDA070782R1 E1.2B 1000 Ekip Dip LSI covers L, S, and I but cannot do ground-fault by itself; you'd add an external residual sensor or specify a G-equipped Ekip Touch.

Key takeaway: Confirm the trip unit suffix before quoting. LI, LSI, LSIG, and LSIG with measurement (M) variants look identical on the outside but cost and behave very differently. Procurement mistakes here cause the most expensive change orders we see.

Detailed technical specifications, Ekip trip unit configurations, and protection curves for the ABB Emax 2 air circuit breaker family are documented in the manufacturer's official ABB SACE Emax 2 product portfolio.

How Do You Calculate the L (Long-time) Pickup I1?

The L pickup on an ABB Emax 2 must protect the downstream cable and any equipment thermally, while not tripping on legitimate load. The governing inequality, taken from IEC 60364-4-43 §433.1 and IEC 60947-2:

Formula: L Pickup Selection — Source: IEC 60364-4-43 §433.1.1

I_B ≤ I₁ × I_n ≤ I_Z

Symbol	Description	Unit
I_B	Design current of the circuit (continuous load)	A
I₁	L pickup multiplier (0.4–1.0)	p.u.
I_n	Rated current of the trip unit / rating plug	A
I_Z	Continuous current-carrying capacity of the cable	A

Worked example: a 1250 A bus tie protected by an ABB 1SDA070821R1 E1.2B 1250 feeding a 2 × 240 mm² Cu cable run with Iz = 1240 A per phase (derated for grouping and 35 °C ambient per IEC 60364-5-52 Table B.52.4). Design current IB = 1100 A. Then I1 × 1250 must lie between 1100 and 1240 A. Set I1 = 0.95, giving 1187 A pickup. Headroom is tight but workable. If the cable were further derated to 1150 A, you would need to either go to 2 × 300 mm² or step up to the ABB 1SDA070861R1 E1.2B 1600 with I1 = 0.75. We see this trade-off — copper vs. breaker frame — argued in nearly every pre-construction review.

Picking the L Time Delay (t1)

t1 is referenced at 6 × I1. Common values:

For motor feeders with starting currents around 6× FLA for 8–10 s: choose t1 = 12 s or 18 s. Anything shorter and across-the-line starts will trip the breaker. For a 400 kW motor on a soft starter with 3.5× FLA for 15 s, you can reduce to t1 = 6 s.

For transformer secondary mains: t1 = 18 s is conservative and rides through magnetising inrush, which decays in roughly 0.5–1 s but with a thermal envelope that L can mistake for overload if the curve is too aggressive.

For sub-distribution feeders without rotating loads: t1 = 3 s gives the cleanest cable protection.

How to Set the S (Short-time) Stage for Selectivity

On the ABB Emax 2, S is where selectivity is won or lost. The job of S is twofold: trip fast enough to protect the bus, slow enough to let the downstream device clear its own fault first. In practice, this means coordinating with the next device's instantaneous reach.

The rule we apply on retrofit projects: S pickup (I2 × In) must sit at least 1.3 × above the highest downstream instantaneous setting, and the S delay must exceed the downstream total clearing time by at least one CTI (coordination time interval). Per IEEE Std 242-2001 (Buff Book) §15.3, CTI for solid-state-to-solid-state coordination is 0.10 s minimum; we use 0.15 s for field margin.

Formula: S Stage Coordination — Source: IEEE Std 242-2001 §15.3

t_2,upstream ≥ t_{clear,downstream} + CTI

Symbol	Description	Unit
t_2,upstream	S delay setting on upstream Emax 2	s
t_{clear,downstream}	Total clearing time of downstream device at the coordination point	s
CTI	Coordination time interval	s

Definite-time vs. I²t-on for S

Engineers often overlook that the I²t-on characteristic on Emax 2's S stage gives you an inverse-time slope that mirrors fuse and MCCB behaviour. When coordinating with downstream Tmax XT or T-series MCCBs, I²t-on lets you sit closer to the downstream curve without crossing it. Definite-time S is simpler but eats selectivity margin at high fault levels. For a comprehensive coordination workflow, the step-by-step Emax 2 sizing calculator article walks through the curve-stacking process.

Key takeaway: Set S pickup at 1.3× to 2× above the largest downstream instantaneous setting, and use I²t-on when coordinating with thermal-magnetic devices to preserve selectivity at high fault current.

Calculating I (Instantaneous) — and When to Disable It

I3 on the ABB Emax 2 has one purpose: clear a near-source bolted fault before the breaker's withstand rating is exceeded. The setting must satisfy:

Formula: Instantaneous Threshold — Source: IEC 60947-2 §4.3.6.4

I₃ × I_n ≤ I_cw AND I₃ × I_n > I_inrush,peak

Symbol	Description	Unit
I₃	Instantaneous multiplier (1.5–15)	p.u.
I_cw	Rated short-time withstand current of the breaker (1 s)	kA rms
I_inrush,peak	Peak inrush from transformers / motors / capacitor banks	kA peak

An ABB 1SDA070981R1 E2.2B 1600 has Icw = 42 kA for 1 s. If your transformer secondary inrush peaks at 12 × FLA = 19.2 kA peak (decaying in 100 ms), an I3 setting of 12 × In = 19.2 kA is right on the edge. Push it to I3 = 15 × In = 24 kA to ride through, or accept that I might trip on energisation. Some plants accept that — they energise off-line through a soft-start maintenance bypass.

The "I OFF" Decision

On main incomers above 2000 A, many designers turn I off entirely (Emax 2 allows this on G-suffix trip units) so that S handles all faults with a delay long enough to let downstream breakers clear first. This works only when:

The breaker's Icw at the prospective fault current is rated for the full S delay you've programmed. For an E2.2 with Icw = 65 kA at 1 s, an S delay of 0.4 s at 50 kA is well within thermal limits. For an E1.2B with Icw = 42 kA at 1 s, the same scenario is also fine, but at 60 kA prospective fault you're overcommitted.

The argument among senior engineers usually splits along industry lines: petrochemical favours full selectivity (I off) because process continuity outweighs the marginal stress; data centers also favour it for the same reason; commercial buildings and utilities tend to keep I enabled to limit let-through energy and protect cheaper downstream gear. There is no universal answer.

Setting the G (Ground-fault) Stage Without Nuisance Trips

Ground-fault protection on the ABB Emax 2 is mandated by NEC 230.95 for solidly grounded wye services rated 1000 A or more at 150–600 V phase-to-ground; in IEC-land, IEC 60364-4-41 governs and gives you more flexibility but the engineering logic is the same.

I4 (G pickup) must be:

Above the natural unbalance of the system. We typically measure 50–150 A of standing zero-sequence current on a 2000 A bus due to single-phase loads and harmonics — set I4 above that or you'll chase ghost faults forever. A common starting point is I4 = 0.3 × In, giving 600 A on a 2000 A breaker like the ABB 1SDA071021R1 E2.2B 2000.

Below the maximum allowable arcing-fault current per NEC 230.95, which caps the trip at 1200 A regardless of breaker size for service entrance applications.

The G time delay t4 should coordinate with downstream ground-fault devices. If there are none, t4 = 0.2 s is a sensible default. If the downstream Tmax XT also has G, coordinate with CTI = 0.1 s.

Key takeaway: A G stage that trips during normal operation is almost always set too low, not the result of a real fault. Measure standing zero-sequence current on a clamp meter before committing to I4.

LSIG Calculator: Pickup and Delay Worked in One Place

LSIG Settings for Common Industrial Scenarios

Transformer Secondary Main

2500 kVA, 11/0.4 kV, Dyn11, Z = 6%. Secondary FLA ≈ 3608 A. Use an ABB Emax 2 E2.2B 4000 with 3600 A rating plug. I1 = 1.0 (3600 A pickup), t1 = 18 s to ride magnetising inrush. I2 = 6 × In = 21.6 kA, t2 = 0.4 s with I²t=on. I3 OFF (Icw 65 kA covers the 0.4 s delay at the 21 kA prospective fault). I4 = 0.4 × In = 1440 A, t4 = 0.4 s.

Motor Control Center Feeder, 800 A

An ABB 1SDA070741R1 E1.2B 800 on an MCC bus with mixed DOL and VFD-fed motors. Continuous load 720 A. I1 = 0.95 (760 A), t1 = 12 s. I2 = 8 × In = 6.4 kA, t2 = 0.2 s, definite-time. I3 = 12 × In = 9.6 kA. G is not available on Dip LI — specify the LSIG variant if NEC 230.95 applies.

Data Center MDB Tie Breaker

For dual-corded data center MDBs running 2N redundancy, the tie breaker must clear bus faults without opening either incomer. We cover this in detail in the Emax 2 in data center MDB design article. The short version: I1 = 1.0, t1 = 24 s, I2 set 1.5× above the largest downstream branch instantaneous, t2 stepped 0.15 s above branch t2, I OFF, G enabled with t4 = 0.4 s.

Capacitor Bank Feeder

Capacitor inrush peaks at 100× rated current for tens of microseconds and 30× for a few cycles. The L stage doesn't see it (I²t too small), but I will trip if set below 30× FLA. For a 400 kvar bank at 400 V (FLA 577 A) on an E1.2B 630, set I3 OFF and rely on S with I2 = 8 × In, t2 = 0.1 s. Always confirm with the capacitor manufacturer's inrush curve.

Comparing LSIG Capability Across Emax 2 Trip Units

Criteria	Ekip Dip LI	Ekip Dip LSI	Ekip Touch LSIG
L pickup range	0.4–1.0 × In	0.4–1.0 × In	0.4–1.0 × In
S stage	Not available	0.6–10 × In, definite/I²t	0.6–10 × In, definite/I²t
I stage	1.5–15 × In	1.5–15 × In	1.5–15 × In, can be OFF
G stage	Not available	Not available	0.2–1.0 × In, definite/I²t
Display	DIP switches	DIP switches	Color touchscreen
Measurements	None	None	V, I, P, Q, S, THD, energy
Communications	Optional Modbus	Optional Modbus	Modbus, Profibus, Profinet, EtherNet/IP, IEC 61850
Zone selectivity	No	Yes (S only)	Yes (S and G)
Typical application	Simple feeders, no GF requirement	Sub-distribution with selectivity needs	Mains, ties, GF-mandated services, BMS-integrated
Relative cost	1.0×	1.15×	1.6–2.0×

For the ABB Emax 2, the cost gap between Dip LI and Touch LSIG is real but often overstated in procurement debates. On a 1600 A frame, the trip-unit upcharge is dwarfed by the breaker frame cost, and the diagnostic value of energy and THD measurements during commissioning typically pays back in the first year. We recommend Touch LSIG by default for any breaker rated 1000 A or above, unless a stripped-down LI variant like the ABB 1SDA070701R1 E1.2B 630 Ekip Dip LI is being deployed in a generator output cubicle where the genset controller already handles measurement.

Zone Selectivity Interlocking (ZSI) — The Trick to Fast Bus Protection

Conventional time-graded selectivity forces the upstream ABB Emax 2 to wait. The further up the system, the longer the delay, and the higher the let-through energy at the source. ZSI breaks that compromise.

Zone Selectivity Interlocking (ZSI) is defined as a hardwired or bus-based signaling scheme where each protective device that detects a fault sends a "blocking" signal upstream; an upstream device that receives no block from any downstream device knows the fault is on its own bus and trips with minimum delay (per IEC 60947-2 Annex S guidance and IEEE Std 242 §15.10).

How ZSI Changes the LSIG Calculation

With ZSI active on the S stage, you can program t2 = 0.1 s on the upstream breaker but rely on the blocking signal from a downstream Emax 2 or Tmax XT to extend it dynamically only when needed. The result: a fault on the main bus clears in roughly 100 ms; a fault on a feeder bus still clears in the same time on its own breaker; selectivity is preserved without the thermal punishment of a 0.4–0.5 s upstream delay.

What we typically see in the field: ZSI is wired during installation, then nobody tests the blocking circuit during commissioning, and a year later the wiring is found cut or terminated wrong. Always primary-inject through the downstream device and verify the upstream timer extends correctly. ABB's Ekip Connect software logs the blocking events, which makes the test straightforward if you have the time.

Key takeaway: ZSI lets you have low let-through energy and full selectivity simultaneously, but only if you commission the blocking circuit. Treat ZSI loop test as a mandatory FAT and SAT step.

How Harmonics and VFD Loads Distort Your LSIG Settings

Modern industrial loads are dirty. A VFD bank, an LED lighting array, or a server farm pushes total harmonic distortion (THDi) into the 25–40% range. The ABB Emax 2's Ekip trip units measure true RMS, which is good, but the implications for LSIG are subtle.

The L stage protects against I²t heating, and harmonic currents heat conductors more than their fundamental-equivalent value suggests because skin effect rises with frequency. IEEE Std 519-2014 and IEC 61000-3-4 give the framework, but the practical rule we use: when measured THDi exceeds 15%, derate the L pickup by 10–15% to compensate. So a calculated I1 = 0.95 becomes 0.85 in a VFD-heavy switchgear.

The G stage is more affected. Triplen harmonics (3rd, 9th, 15th) add arithmetically in the neutral, producing a measurable zero-sequence current that the G CT will see as ground fault. On a four-pole Emax 2 with neutral protection, this can drive G nuisance trips. The fix: raise I4 to 0.4–0.5 × In on harmonic-rich buses, or use an external sum-CT with appropriate filtering. The companion article on Emax 2 nuisance tripping causes and fixes dives deeper.

Capacitor Bank Switching

Back-to-back capacitor switching produces transient currents in the tens of kA peak, lasting under a millisecond. The Ekip's instantaneous algorithm uses a half-cycle window, so most of these transients are filtered out — but not all. If you see I3 nuisance trips on capacitor switching, raise I3 to 12–15 × In or, if the breaker is dedicated to the capacitor, turn I OFF and let S handle short circuits.

Procurement Pitfalls When Specifying LSIG-Capable Emax 2

For procurement managers, the LSIG specification is where requisitions go wrong. A few patterns we keep seeing:

Pattern 1: Ordering "LI" When the Spec Calls for GF Protection

NEC 230.95 and equivalent jurisdictional rules require ground-fault protection on services rated ≥1000 A at 480Y/277 V or 600Y/347 V. An LI trip unit cannot meet that. We have seen 1600 A LI breakers arrive on site, get rejected by the AHJ, and require a trip-unit swap that takes 6–8 weeks. The lesson: read the single-line carefully and confirm the protection scheme letters match the specified trip unit suffix.

Pattern 2: Forgetting the Rating Plug

An ABB 1SDA070781R1 E1.2B 1000 ships with an In = 1000 A rating plug, but you may need a smaller In (e.g., 800 A) to push I1 into the achievable range for a smaller load. Rating plugs are field-installable but not free, and they're not inventory items at most distributors. Check the load schedule before issuing the PO.

Pattern 3: Specifying LSIG Without Specifying Communications

If the project's BMS or SCADA needs to read trip events, you need either Modbus RTU, Modbus TCP, Profibus, Profinet, EtherNet/IP, or IEC 61850 — and the Ekip Com module that supports your chosen protocol is an add-on. The base Ekip Touch ships with the trip unit but not the comms card. Spec the Ekip Com module explicitly. For comparison shopping against competitor platforms, the Emax 2 vs Schneider MasterPact MTZ technical comparison covers comms differences.

Pattern 4: Ignoring Icw at the Required Time

Catalog Icw is usually quoted at 1 s. If your S delay is 0.5 s, the breaker can withstand more (typically Icw_0.5 ≈ 1.4 × Icw_1.0 for the same I²t). If your S delay is 3 s, you have less. The withstand is governed by I²t = constant, so plan accordingly. For a full breakdown of withstand and breaking capacity, see the Emax 2 full technical specifications article.

Commissioning the LSIG Settings — From Paper to Live Bus

A coordination study output is not a working installation. The settings must be loaded, tested, and documented. Our checklist:

Step 1 — Set per study. Load settings either via the front DIP switches (Dip variants) or via Ekip Connect over the test connector or front USB (Touch variants). Save a settings PDF report. Print it. Put it in the panel.

Step 2 — Secondary inject. Use an Ekip T&P test set (or any IEC 60255-compliant relay tester) to verify pickup and timing on each stage. Tolerances per IEC 60947-2 are ±10% on pickup and ±20% on timing — Emax 2 typically performs to ±5% / ±10%. If it doesn't, the trip unit is suspect.

Step 3 — Primary inject. On critical breakers, primary inject through the main contacts at 2× I1 to confirm CT polarity, sensor wiring, and trip mechanism. This catches reversed sensors that secondary injection cannot.

Step 4 — ZSI loop test. If ZSI is wired, test the blocking signal end-to-end as discussed earlier.

Step 5 — Document. A printed settings report inside the panel door, a soft copy in the project archive, and a record in the CMMS. The next engineer to touch this breaker — five years from now, at 2 a.m., during a fault — will thank you.

Key takeaway: Settings on a screen are not protection. Secondary injection plus ZSI verification plus printed documentation is the minimum acceptable commissioning standard for any LSIG-equipped breaker.

For the full stocked range of Emax 2 frames and trip-unit variants discussed above, see Air Circuit Breakers at Stoklink. For downstream coordination devices such as branch-circuit MCBs, the Miniature Circuit Breaker collection covers IEC and UL ranges. Where ground-fault detection is mandated by local code on smaller circuits, refer to the Residual Current Device collection, and for control and signaling the Relay collection rounds out the panel BOM.

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Frequently Asked Questions

What is the difference between LSI and LSIG on an ABB Emax 2?

LSI provides Long-time, Short-time, and Instantaneous overcurrent protection. LSIG adds Ground-fault (G) protection, which is required by NEC 230.95 on solidly grounded wye services rated 1000 A or more at 480Y/277 V or 600Y/347 V. If your jurisdiction or single-line requires earth-fault protection at the breaker, you must specify a trip unit with the G suffix — adding it later means swapping the trip unit. The Emax 2 features overview lists the trip-unit options by family.

Can I turn off the I (instantaneous) stage on an Emax 2?

Yes, on Ekip Touch and Hi-Touch trip units, I3 can be set to OFF. This is common on main incomers and ties where the priority is full selectivity with downstream devices. You can only do this safely if the breaker's Icw rating covers the prospective fault current for the duration of the S stage delay — typically Icw_1s of 42–85 kA for Emax 2 frames depending on size.

How do I coordinate an Emax 2 with a downstream Tmax XT MCCB?

Set the Emax 2 S stage with I²t-on characteristic, with I2 pickup at 1.3–2.0× the Tmax XT instantaneous setting and t2 at least 0.10–0.15 s above the XT total clearing time at the coordination point. ABB publishes selectivity tables in the Emax 2 technical catalog that give pre-verified combinations; use them as the starting point and refine with a coordination study. For the full sizing workflow, see the Emax 2 sizing calculator article.

Why does my Emax 2 G stage trip on energisation?

Three usual suspects. First, residual unbalance from single-phase loads or magnetising inrush exceeds I4 — raise I4 to 0.3–0.5 × In and add 50–100 ms delay. Second, a four-pole breaker with the neutral CT incorrectly polarised will see phase current as residual current — verify polarity. Third, on harmonic-rich buses, triplen harmonics in the neutral conductor produce real zero-sequence current that the G stage detects correctly but interprets as fault.

What standards govern Emax 2 LSIG settings calculation?

Primary: IEC 60947-2 (low-voltage circuit breakers) for the protection function definitions and tolerances. Secondary: IEC 60364-4-43 and IEC 60364-4-41 for installation-side cable and shock protection requirements. For coordination methodology, IEEE Std 242-2001 (Buff Book) is the reference. For ground-fault, NEC 230.95 in the U.S. and IEC 60364-4-41 internationally. For harmonics, IEEE Std 519-2014 and IEC 61000-3-4.

Do I need a coordination study or are the catalog selectivity tables enough?

Catalog tables are a fine starting point for simple radial systems with two or three levels of breakers and no special loads. For anything with multiple sources, ties, generators, large motors, capacitor banks, or VFDs, run a proper coordination study in software (ETAP, SKM, EasyPower, or DOC by ABB). The tables assume worst-case fault levels and standard settings; real installations rarely match.

Conclusion

LSIG settings on an ABB Emax 2 are not a one-time configuration exercise. They are the live, tunable bridge between a coordination study on paper and a working low-voltage system that protects copper, equipment, and people. Get the L right and the cable doesn't burn. Get the S right and the bus stays up when a feeder faults. Get the I right and the breaker survives the worst short circuit your transformer can deliver. Get the G right and you meet code, full stop.

The best engineers we work with treat LSIG as a living document — reviewed when the load schedule changes, retested when the fault level shifts, and re-coordinated when downstream equipment is added or replaced. The Ekip platform makes that workflow tractable: settings reports, event logs, ZSI, and communications all reduce the friction of doing it right.

For the complete selection methodology — frame sizing, trip-unit choice, accessory selection, installation, and maintenance — see our ABB SACE Emax 2 Air Circuit Breaker Selection, Application and Maintenance Guide, the pillar reference for the platform. And when you're ready to source the hardware, the Stoklink Emax 2 stock — from the 630 A E1.2B through the 2000 A E2.2B — ships with full traceability and current firmware, ready to commission.