kVA Tools^BETA — Standby Planner

The Standby Planner enables the user to size a standby generator based on running load demand, motor starting voltage dip, and step load acceptance, per IEEE Std 446-1995 and NFPA 110.

Project Title

Input — Running Load

#	Description	Load Type	Power Rating		Power Factor	Efficiency (%)	Demand Factor	Quantity	NL Derate (%)	kVAr	kVA

Populating the Load Type field activates Efficiency and Non-linear (NL) Derate fields.

Input — System & Generator Configuration

System Voltage	Nominal (V)
Phase	Configuration
Generator PF	Nameplate Power Factor
Engine	Engine type
Engine	Turbo derate threshold
Site Derating	Altitude above sea level
Site Derating	Ambient Temperature
Design Margin	Applied to running load (%)

Input — Largest Motor Starting

Motor Rating	Largest motor to start (HP) no motor loads in table	—
Starting Method	Motor starting method
Starting Factor	LR kVA multiplier
NEMA Code Letter	Locked-rotor kVA/HP
Generator X'd	Transient reactance (p.u.)
Max Voltage Dip	Allowable bus dip (%)

Voltage dip is estimated using the snapshot method per IEEE 446-1995 §4.2.11: generator modelled as a constant voltage source behind X'd. For full motor acceleration studies, use dedicated power-system software.

Input — Step Load Acceptance

Block Load	Largest single-step load
Max Step Fraction	Max single-step kW (% of rated)

Default 30% per NFPA 110 for standard generator sets. High-performance prime-power units with fast electronic governors may accept up to 100% in a single step — confirm with manufacturer data.

Output — Sizing Analysis

Parameter	Value	Units
Running Load
Total running kW	—	kW
Total running kVAr	—	kVAr
Total running kVA	—	kVA
Running kVA (with margin)	—	kVA
Req. Running nameplate kVA	—	kVA
Step Load Acceptance
Step load min. kVA (at nameplate)	—	kVA
Motor Starting
LR kVA — Terminals	—	kVA
LR kVA after starting method reduction	—	kVA
Estimated voltage dip	—	%
Min. generator kVA for dip limit	—	kVA
—
Governing Result
Min. required nameplate kW	—	kW
Min. required nameplate kVAr	—	kVAr
Min. required nameplate kVA	—	kVA
Governing constraint	—
Recommended Size
Next standard nameplate kW	—	kW
Equivalent nameplate kVA	—	kVA
Headroom above required	—

Recommended size is selected from an industry-typical ladder of nameplate kW ratings offered by major OEMs. These rungs are not IEEE or NEMA standardised; confirm the exact rating with the chosen manufacturer's catalogue.

Output — Parameter Status

Parameter	Value	Units
Site Derating
Altitude derating factor f_alt	—	p.u.
Temperature derating factor f_temp	—	p.u.
Combined derating factor f_combined	—	p.u.
Check		Status
Load inventory		—
Altitude derating		—
Temperature derating		—
Motor starting voltage dip		—
Step load acceptance		—
Generator X'd range (0.10–0.50)		—