Transformer Testing and Commissioning
Load Bank Testing for Transformer Fed Systems
For a transformer-fed test, define the purpose, load profile and measurement points before selecting the temporary equipment.
A load bank applies a controlled electrical load so a source or distribution system can be evaluated under planned conditions. For a transformer-fed test, define the purpose, load profile and measurement points before selecting the temporary equipment.
Match the load to the test objective
A resistive load bank draws active power at approximately unity power factor. Combined resistive and reactive equipment can reproduce a specified power factor. Select voltage, phase, frequency, steps and duration to match the agreed test plan and connected system.
Specify power consistently
For an illustrative 500 kVA test at 0.80 power factor, active power is 400 kW and reactive power is 300 kVAR under the sinusoidal power-triangle model. A 400 kW resistive-only test has a different current and apparent-power demand. State all three quantities in the test schedule.
| Item or condition | What to compare | Input or result |
|---|---|---|
| Resistive load | Approximately unity PF | kW loading |
| Illustrative mixed load | 500 kVA at PF 0.80 | 400 kW and 300 kVAR |
| Test package | Profile, connections and readings | Approved criteria and report |
Example · sinusoidal power-triangle model
S = 500 kVA · PF = 0.80
P = S × PF = 400 kW
Q = √(S² − P²) = 300 kVAR
A 400 kW resistive-only load is approximately unity PF, so its apparent-power demand differs from this 500 kVA mixed-load example.
Prepare the site and record
Coordinate temporary connections, protection, cable ratings, ventilation, access and emergency shutdown with qualified personnel. Record voltage, current, power, temperature and timing at the defined test points. Compare observed results with the agreed criteria and document any follow-up.
Test objective
Define load steps, voltage, phase, frequency and duration in the agreed plan.
Temporary installation
Coordinate connections, protection, cable ratings, ventilation, access and shutdown.
Measurement record
Capture voltage, current, power, temperature, timing and agreed criteria.
Frequently Asked Questions
Does a load bank test replace factory transformer tests?
Include each factory and site test in the procurement and commissioning plan according to its purpose.
What data is needed to hire a load bank?
Supply voltage, phase, frequency, kW, kVAR or power factor, load steps, duration and site connection arrangement.
Prepare a transformer load test plan
Share voltage, phase, frequency, kW and kVAR targets, load steps, duration, connection arrangement and measurement criteria.