Power System Studies

Generator Sizing and Selection Study

Right-size the backup. Survive the next grid event without oversizing capex.

Standby, prime, peaking, black-start. Diesel, gas, dual-fuel. We size the generator to match your real load profile · not the connected kW nameplate · and engineer the transition for transient stability under N-1 grid loss. ETAP and DigSILENT modelled, ISO 8528 and IEEE 446 compliant, signed by a Chartered Engineer.

Why this matters

Why most brownfield DG sizing is wrong in both directions

Two failure modes dominate. The first is undersizing · the DG was sized for connected kW, not for actual starting kVA of the largest motor in the priority bus. The first attempt to start the chilled-water pump dips the bus voltage, the underfrequency relay trips, and the standby system fails when it was needed. The second failure mode is oversizing · the DG was sized for total connected load including non-essential loads. It runs at 25% during the actual outage, glazes the cylinder liners over 18 months, and costs three times what was needed. A generator sizing study models the priority bus dynamically · starting current, voltage dip, frequency response, transient stability · and gives you the smallest DG that meets the actual restoration scenario.

Method

How we deliver Generator Sizing and Selection

CEng MIE India-signed deliverables · LiDAR-powered where applicable · digital twin handover ready · routes to the Power System Studies practice lead within 24 hours.

Load priority audit

Connected loads categorised · life safety, process-critical, comfort, non-essential. Priority bus definition aligned to your business continuity policy. Starting sequence engineered (motor stagger, group starts, soft-starter intervention).

Dynamic load modelling

Largest motors modelled with locked-rotor kVA, accelerating torque profile, voltage dip response. Step-load profile authored. Transformer inrush, capacitor pre-charge, UPS rectifier loads included.

DG transient simulation

ETAP or DigSILENT generator model with prime mover and excitation dynamics. Voltage dip, frequency dip, recovery time computed per ISO 8528 Class G2 / G3 / G4 acceptance criteria.

Sizing + selection matrix

Standby kW, prime kW, paralleling options compared. Diesel vs gas vs dual-fuel evaluated against fuel logistics, emissions compliance, and total cost of ownership. AVR + governor specification authored.

Sign-off + procurement spec

Report signed by a Chartered Engineer. Bid-evaluation-ready procurement specification with vendor-neutral acceptance test protocol attached.

Standards + compliance

Built to the standards your auditors quote

Reports reference the international and national standards your regulators, F500 audit teams, and corporate process safety leads cite. Every deliverable signed by a Chartered Engineer (CEng MIE India).

ISO 8528 (all parts) · Reciprocating internal combustion engine driven alternating current generating sets
IEEE 446 (Orange Book) · Emergency and Standby Power Systems for Industrial and Commercial Applications
NFPA 110 · Emergency and Standby Power Systems
NFPA 70 (NEC) Article 700/701/702 · Emergency / Legally Required Standby / Optional Standby Systems
BS 5514 / IS 10001 (India) · Reciprocating internal combustion engines · Performance

Anonymous case anchors

What this looks like in production

Three landmark engagements from our verified roster · quantified outcomes, no client names disclosed without written permission.

Refinery, India · 2 × 2000 kVA standby

Priority bus audit identified 1500 kVA actual restoration load vs 4000 kVA installed. Right-sized to 2 × 1500 kVA paralleled · avoided nine-figure DG capex and 18% fuel saving.

Hospital, USA · NFPA 110 Level 1 Type 10

Sized 1250 kW prime + 800 kW Level 1 emergency. Transient simulation confirmed 8-second restoration to all life-safety circuits. Passed AHJ acceptance test on first attempt.

Data centre, KSA · Tier III standby

Dynamic transient model with chiller startup + UPS rectifier load. Sized 3 × 2500 kW N+1 paralleled with sync gear. Designed for 30-second restoration of all critical IT load.

Frequently asked

Generator Sizing and Selection · the practical questions

How do you size a generator for an industrial plant?

Sizing starts from the load priority list, not the connected kW total. Loads are categorised as life safety, process-critical, comfort and non-essential, the priority bus is defined against your business continuity policy, and the largest motors are then modelled with locked-rotor kVA and accelerating torque. The set is sized for the starting duty, which is almost always more demanding than the running duty.

Why does my generator stall or trip when a large motor starts?

Because the set was sized on running kW. A direct-on-line motor draws several times full-load current at start, and the resulting voltage dip can collapse the alternator field or stall the engine before the motor reaches speed. The remedy is dynamic modelling of the starting sequence, then staggered starts, group starts or soft-starter intervention engineered against that model.

What is step load acceptance and why does it govern the rating?

Step load acceptance is how much load the set can absorb in a single block while keeping voltage and frequency inside limits. On diesel sets the limit is usually turbocharger response rather than alternator capability. Rating against the ISO 8528 step-load classification frequently drives a larger set than the steady-state kW figure would suggest.

What data do you need to start a generator sizing study?

A connected load schedule with duty categories, the largest motor ratings and their starting method, the existing single line diagram, site ambient and altitude, and your business continuity policy for what must remain live. Where the drawing set is stale, LiDAR capture rebuilds the as-built before any modelling begins.

Do you specify the generator, or only the rating?

Both. The deliverable is a report signed by a Chartered Engineer covering the kVA rating, step-load profile and starting sequence, together with a procurement specification you can tender against. We do not supply equipment, so the specification stays vendor-neutral.

Scope your Generator Sizing and Selection engagement.

Tell us your plant, region, and scope · a named Chartered Engineer responds within 24 hours.

4 fields. No phone interview to start.
Per-discipline routing to the Power System Studies practice lead.
Anonymous case anchors sent with first reply.
Same-day callback for deadline-driven enquiries.

Power System Study Scoping

ETAP/DigSILENT/PSCAD-led · routes to Practice Lead PSS · 24-hour response.