Electrical Load Scheduling
for Industrial Facilities:
Demand Factor, Diversity & Cable Sizing

An electrical load schedule is the foundation document of every industrial electrical design. It is the engineering basis for transformer sizing, LV switchgear selection, cable sizing, distribution board capacity, and generator sizing. It should be a calculated engineering document — but on too many Indian industrial projects, it is a list of equipment ratings copied from vendor datasheets, with no demand factors, no diversity, no power factor correction, and no load flow analysis.

The result is systematic over-specification: transformers sized for a load that will never be reached simultaneously, cables sized for nameplate currents that motors never draw under normal operation, and switchgear with MCB ratings that nuisance-trip under the inrush currents that were never calculated. Or worse — under-specification where harmonic distortion from VFDs and UPS systems was ignored, causing cable overheating at loads well below rated capacity.

Demand Factor and Diversity: The Two Essential Concepts

Every load in an industrial facility has a demand factor — the ratio of the maximum demand of the load to its installed (connected) capacity. A 37 kW motor driving a pump against a partially open valve may draw only 26 kW. The demand factor is 26/37 = 0.70. Summing nameplate ratings without demand factors produces the connected load — never the actual maximum demand.

Power Factor: The Invisible Load

Active power (kW) is what does work. Apparent power (kVA) is what the electrical distribution system must carry. The ratio of the two is the power factor (PF): kW = kVA × cos(φ). Most Indian industrial facilities have natural power factors of 0.75–0.85 due to induction motor loads. This means the electrical infrastructure must be sized 15–25% larger than the active load alone would suggest.

• 01

  Calculate Active Power (kW) Per Load

  Motor nameplate kW × demand factor × number of units running. For loads with duty cycle, apply the running hours factor. This is the ‘real power’ column of the load schedule.

• 02

  Apply Power Factor to Get kVA

  Divide active power by the anticipated power factor at that load level. Motors at partial load have worse power factor than at full load — use actual operating PF, not nameplate PF.

• 03

  Calculate Reactive Power (kVAR)

  kVAR = kVA × sin(φ). This is needed for capacitor bank sizing and power flow analysis.

• 04

  Apply Diversity to Load Groups

  Sum active powers within each load group (e.g., all motors on a production line). Apply diversity factor to the group total — not to individual loads.

• 05

  Sum Groups for Transformer/Generator Sizing

  Sum all load groups with appropriate inter-group diversity. Add HV auxiliary, lighting, and HVAC loads. Apply a total site diversity factor. The result is the maximum demand — the basis for transformer sizing.

• 06

  Add Future Expansion Reserve

  Transformers and switchgear should be sized for 80% utilisation at current maximum demand, leaving 20% for expansion. Specifying equipment at 100% utilisation leaves no headroom and accelerates ageing.

Harmonic Distortion: The VFD and UPS Problem

Variable frequency drives, UPS systems, and switch-mode power supplies are non-linear loads. They draw current in pulses rather than sinusoidally, injecting harmonic currents (3rd, 5th, 7th harmonics and above) into the distribution system. These harmonic currents do not appear in a simple nameplate-based load schedule — but they cause real cable heating, neutral conductor overloading, and transformer derating.

Short Circuit Calculation and Protection Coordination

Every switchgear and protection device must be rated for the maximum prospective short circuit current at its installation point. Under-rated devices fail catastrophically during fault events — the MCB or MCCB that is rated at 10 kA cannot interrupt a 25 kA fault safely. This is a safety-critical calculation, not an optional refinement.

Cable Sizing: Current Capacity and Voltage Drop

Cable sizing balances three constraints: current-carrying capacity (thermal limit), voltage drop (quality of supply at the load), and short circuit withstand (energy the cable can absorb during a fault). All three must be checked — cables that meet current capacity may fail voltage drop for long runs, or may be undersized for short circuit withstand on large feeders.

The KVRM Electrical Load Scheduling Approach

• 01

  Equipment List Review

  We review the complete equipment list with vendor datasheets — not just nameplate ratings. Starting kVA, running power factor, duty cycle, and harmonic content are captured for every significant load.

• 02

  Load Schedule Development

  Full load schedule with connected load, demand factor, running kW, power factor, kVA, and kVAR for every circuit. Load groups summed with diversity factors. Maximum demand calculated for each distribution board and the main incomer.

• 03

  Power Factor Correction Design

  Reactive power requirement calculated. Capacitor bank rating and connection point specified to achieve target power factor without causing resonance with harmonic loads.

• 04

  Harmonic Assessment

  Where VFD or UPS loads exceed 20% of transformer rating, harmonic distortion is assessed. Cable derating, neutral sizing, and filter requirements are specified.

• 05

  Short Circuit and Protection Study

  IEC 60909 short circuit calculations for all busbars. Protection device ratings verified. Discrimination study confirming selectivity of protection cascade.

Conclusion: A Load Schedule Is a Safety Document

An electrical load schedule that correctly applies demand factors, diversity, power factor, and harmonic effects is not a conservative document — it is an accurate one. The accuracy matters because every downstream electrical safety decision — cable sizing, protection ratings, transformer capacity — follows from it.

The cost of getting the load schedule right is the engineering time to do it properly. The cost of getting it wrong is repeated nuisance tripping, overheating cables, under-performing power factor correction, and — in the worst case — protection devices that fail to interrupt fault currents they were never sized to handle.