About the Reactive Power Requirement
Reactive power requirement analysis determines how much reactive power (kVAR) a solar inverter or plant must supply or absorb to maintain grid voltage within limits — fulfilling CERC/SERC grid codes and avoiding power factor penalties for C&I consumers.
Formula
Power factor (PF) = Active power (kW) ÷ Apparent power (kVA)
- Active power (kW)
- Real power doing useful work
- Apparent power (kVA)
- Vector sum of active and reactive power
Reactive power needed (kVAR) = Active power × tan(arccos(PF_target) − arccos(PF_existing))
- PF_target
- Target power factor (typically 0.95 or unity under grid code)
- PF_existing
- Existing load power factor before solar compensation
How to calculate it
- 1Measure load's existing power factor from the DISCOM bill or energy meter.
- 2Identify grid code requirement: CERC requires grid-connected plants to operate at 0.95 PF lead/lag; most C&I DISCOMs require ≥ 0.90.
- 3Modern string and central inverters can absorb or inject reactive power without extra hardware — verify the inverter's Q capability from its datasheet (typically ±0.8–0.9 PF rated).
- 4For C&I plants with reactive power penalties: size inverter reactive power capability to bring the combined plant + load PF above 0.90.
Worked example
A factory with 500 kW load at 0.80 PF (reactive demand = 375 kVAR). A 300 kWp solar plant with inverters capable of injecting 225 kVAR. Net reactive demand after solar: 375 − 225 = 150 kVAR. Combined PF = 500 ÷ √(500² + 150²) = 0.958 — above the 0.95 CERC requirement.
What you can calculate
- MVAR sizing
- PF correction
- CEA Grid Code
- STATCOM/Cap
Frequently asked questions
Can solar inverters improve my factory's power factor?
Yes — modern grid-tied solar inverters can operate as reactive power sources or sinks in addition to generating active power. By configuring the inverter's power factor set-point or reactive power curve (Q(V) characteristic), the solar plant can compensate for the lagging reactive demand of motors and other inductive loads — reducing or eliminating demand for external capacitor banks.
What are power factor penalties in India?
Many state DISCOMs levy a surcharge of 1–3% of the energy bill per 0.01 unit of PF below the minimum requirement (typically 0.90). Conversely, some DISCOMs offer a rebate for maintaining PF above 0.95 or unity. A large industrial consumer can save ₹5–20 L/year in PF penalties and demand-charge savings by improving PF from 0.80 to 0.95 using solar inverters and capacitor banks.
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