Advanced Load Flow Calculator

Meta Description: Plan transmission studies with this load flow calculator. Estimate current, drop, losses, and efficiency. Review clear results, charts, exports, and examples fast today.

Filename: load_flow.php

Load Flow Results

Enter system data and press calculate. Your results will appear here above the form.

Calculator Inputs

Receiving Voltage (kV)

Active Power (MW)

Reactive Power Magnitude (MVAr)

Reactive Power Mode

Line Length (km)

Resistance per km (Ω)

Reactance per km (Ω)

Base Power (MVA)

Base Voltage (kV)

Voltage Profile Labels

Use comma-separated labels for the Plotly voltage profile.

Example Data Table

Case	Receiving Voltage (kV)	Active Power (MW)	Reactive Power (MVAr)	Length (km)	R/km (Ω)	X/km (Ω)	Mode
Base Feeder	11	5.0	2.0	15	0.18	0.32	Lagging
Industrial Bus	33	12.5	4.8	22	0.11	0.28	Lagging
Compensated Line	66	18.0	3.2	35	0.09	0.20	Leading

Formula Used

Three-phase apparent power:
S = P + jQ

Line current:
I = conjugate(S) / (√3 × V_R,LL)

Total line impedance per phase:
Z = (R/km × Length) + j(X/km × Length)

Sending-end phase voltage:
V_S,ph = V_R,ph + I × Z

Sending-end line voltage:
V_S,LL = √3 × |V_S,ph|

Active line loss:
P_loss = 3I²R

Reactive line loss:
Q_loss = 3I²X

Voltage regulation and efficiency:
Regulation = ((V_S - V_R) / V_R) × 100
Efficiency = (P_received / P_sending) × 100

This tool uses an approximate short-line load flow model suitable for feeder studies, teaching, and preliminary engineering checks.

How to Use This Calculator

Enter the receiving-end line voltage in kilovolts.
Provide total three-phase active power in megawatts.
Enter reactive power magnitude and choose lagging or leading mode.
Add line length plus resistance and reactance per kilometer.
Set base MVA and base kV for per-unit values.
Optionally edit the voltage profile labels for the chart.
Press Calculate Load Flow to display results above the form.
Use the export buttons to save CSV or PDF output.

Frequently Asked Questions

1. What does this load flow calculator estimate?

It estimates line current, voltage drop, sending-end voltage, real loss, reactive loss, efficiency, regulation, and per-unit impedance for a three-phase feeder.

2. Is this suitable for full network Newton-Raphson studies?

No. It is a practical short-line engineering estimator for one feeder section. Large meshed networks still need dedicated power-system software.

3. What is the difference between lagging and leading mode?

Lagging means the load absorbs positive reactive power. Leading means compensation or capacitive behavior reduces or reverses reactive demand.

4. Why are resistance and reactance entered per kilometer?

Transmission and distribution data are usually given per unit length. The calculator multiplies them by route length to get total phase impedance.

5. Why does voltage regulation increase with load?

Higher current produces a larger impedance drop. That increases the sending-end requirement and worsens regulation, especially on long or reactive feeders.

6. What are per-unit values used for?

Per-unit values normalize impedance on a chosen base. They simplify comparison between feeders, transformers, and system components.

7. Can I use this for underground cables?

Yes, if you enter appropriate cable resistance and reactance values. Results depend directly on the impedance data quality.

8. What exports are included?

The page provides CSV export for spreadsheet analysis and PDF export for reporting, review, or sharing with colleagues.