Example Data Table
| Case |
Ambient °C |
Wind m/s |
Wind Angle |
Solar W/m² |
Load A |
| Summer Peak |
40 |
0.6 |
90 |
950 |
720 |
| Still Air Emergency |
45 |
0.2 |
60 |
1000 |
780 |
| Night Rating |
25 |
1.5 |
90 |
0 |
700 |
Formula Used
The calculator uses a simplified steady heat balance for overhead conductor screening.
I²R(Tc) + Qs = Qc + Qr
R(Tc) = R20 × [1 + α × (Tc - 20)]
Qs = absorptivity × solar radiation × conductor diameter
Qr = π × diameter × emissivity × σ × [(Tc + 273.15)⁴ - (Ta + 273.15)⁴]
Qc = h × π × diameter × (Tc - Ta)
Ampacity = √((Qc + Qr - Qs) / R(Tmax))
Here, Tc is conductor temperature. Ta is ambient temperature. Qs is solar heat. Qc is convection cooling. Qr is radiation cooling.
How to Use This Calculator
Enter conductor diameter, resistance, thermal coefficient, maximum conductor temperature, surface factors, elevation, line voltage, and route length.
Add each batch case on a new row. Use comma separated values. Keep the order shown in the input help text.
Press the calculate button. Review the result table above the form. Check ampacity, margin, conductor temperature, loss, and status.
Use the CSV button for spreadsheet work. Use the PDF button for review reports and design notes.
Electrical Batch Thermal Planning
A batch thermal calculator helps line designers test many weather cases at once. It is useful when a project needs several operating scenarios. Each case can use a different ambient temperature, wind speed, wind angle, solar level, and loading current. The result shows how close the conductor is to its thermal limit.
Why Thermal Rating Matters
Overhead conductors heat because current creates I squared R losses. Sunlight adds more heat. Wind and radiation remove heat. A safe design must keep conductor temperature below the selected maximum value. That limit protects strength, sag, clearances, fittings, and long term reliability. It also supports planning work in line design studies.
Batch Case Review
One single weather case can miss a weak point. Batch review is better. Summer peak, still air, high solar, emergency loading, and night operation can be tested together. The table then ranks each case by ampacity and margin. A negative margin means the entered load is above the estimated rating. A positive margin gives spare capacity.
How This Tool Helps
This calculator uses practical heat balance terms. It estimates conductor resistance at temperature. It calculates solar heat gain, convection cooling, and radiation cooling. It then finds the maximum current allowed at the chosen conductor temperature. It also solves the expected conductor temperature for each entered load. That result is helpful before a detailed sag and tension check.
Good Input Practice
Use conductor data from the correct catalog. Enter resistance in ohms per kilometer at 20 degrees Celsius. Use the actual outside diameter. Keep emissivity and absorptivity realistic for conductor age and surface condition. Use measured or approved weather cases when possible. For conservative planning, choose low wind, high ambient temperature, and high solar radiation.
Engineering Notes
The calculator is a planning aid. It does not replace a full standard based thermal rating study. Local rules, utility criteria, and software settings can differ. Use it to screen many cases quickly. Then verify critical cases with approved engineering methods. Save the CSV or PDF file for review notes, design records, and comparison meetings. Document assumptions beside every export. Clear notes help reviewers trace inputs, spot severe cases, and repeat the same thermal check during later revisions without confusion.
FAQs
What does this calculator estimate?
It estimates conductor ampacity, heat balance, operating temperature, thermal margin, losses, and sag review notes for multiple weather cases.
Can I use it with PLS CADD studies?
Yes. It can help screen cases before detailed line design work. Final values should still be verified with approved project settings.
What is a batch case?
A batch case is one weather and loading scenario. Each row includes ambient temperature, wind speed, wind angle, solar radiation, and load current.
Why does wind angle matter?
Wind crossing the conductor cools better than wind along the conductor. The calculator applies an angle factor to approximate this effect.
What does negative margin mean?
A negative margin means the entered load is greater than the estimated ampacity for that case. The case should be reviewed carefully.
Does it calculate final sag?
No. It provides a sag note based on conductor temperature. Use dedicated sag tension software for final clearance checks.
Which emissivity value should I use?
Use values approved by your utility or conductor data source. Older or weathered conductors often use higher surface factors.
Is this a standards replacement?
No. It is a planning and screening tool. Always follow local standards, project criteria, and approved engineering procedures.