Proper dry-type transformer installation and commissioning are critical for safety, performance, and long service life. This guide walks you through each stage – from pre-installation inspection to trial run – helping you avoid common mistakes and ensure reliable operation.
1. Pre-Installation Inspection: What to Check Before You Start
Before installing your dry-type transformer, perform a thorough inspection. This step prevents future failures and confirms that the transformer arrives in good condition.
Follow this checklist:
Verify the packaging is intact with no signs of damage.
Check the nameplate data against your design requirements.
Ensure all factory documents are complete.
Look for external damage, displaced parts, or broken components.
Inspect electrical supports and connecting wires for damage.
Confirm that spare parts are present and undamaged.
✅ A careful pre-installation inspection saves time and avoids unexpected issues during commissioning.
2. Transformer Installation: Positioning and Leveling
Proper foundation and leveling directly affect noise levels and operational stability.
Step-by-step installation process:
Check the foundation – Verify that the pre-embedded steel plate is level. Ensure no cavitation exists under the plate. Good foundation shock resistance and sound absorption reduce transformer noise.
Move the transformer into position – Use rollers to move the unit to the designated spot, then remove the rollers.
Adjust leveling – Precisely position the transformer according to design requirements. The leveling error must meet specifications.
Secure the transformer – Weld four short channel steel pieces at the four corners of the transformer base onto the pre-embedded steel plate. This prevents movement during operation.
Therefore, proper foundation work and secure mounting minimize vibration and keep your dry-type transformer quiet and stable.
3. Transformer Wiring: Clearance, Busbars, and Soft Connections
Correct wiring ensures safety and prevents mechanical stress on terminals.
Key wiring rules:
Maintain minimum distance between live parts and from live parts to ground. Pay special attention to cable clearance from the high-voltage coil.
For high-current low-voltage busbars (e.g., 2000A or above), use separate supports. Do not connect busbars directly to transformer terminals – this causes excessive mechanical tension and torque.
When current exceeds 1000A, install a soft connection between the busbar and transformer terminal. The soft connection compensates for thermal expansion and contraction while isolating vibration.
Thus, following these wiring practices prevents terminal damage and extends transformer life.
4. Transformer Grounding: Safety First
Proper grounding protects both equipment and personnel.
Grounding requirements:
The grounding point is located on the low-voltage side base, marked with a dedicated grounding bolt and symbol.
Connect this point reliably to the protective grounding system.
If the transformer has an enclosure, ground the enclosure as well.
When the low-voltage side uses a three-phase four-wire system, connect the neutral wire securely to the grounding system.
⚡ Remember: A reliable ground path is your first line of defense against electric shock and fault currents.
5. Pre-Operation Inspection: Final Checks Before Power-On
Before energizing your dry-type transformer, perform these final inspections:
Ensure all fasteners are tight.
Verify electrical connections are correct and reliable.
Confirm insulation distances (live-to-live and live-to-ground) meet regulations.
Remove any foreign objects near the transformer.
Clean the coil surface.
6. Pre-Operation Testing: Key Electrical Tests
Run these diagnostic tests before commissioning:
A. Transformation Ratio and Connection Group
Measure the transformation ratio and verify the connection group.
Measure DC resistance of high-voltage and low-voltage windings.
Compare results with factory test data.
B. Insulation Resistance
Measure insulation resistance between coils and from coil to ground.
If resistance is significantly lower than factory measurements, the transformer may be damp.
Critical threshold: When insulation resistance falls below 1000Ω per volt of operating voltage, the transformer requires drying.
C. Withstand Voltage Test
Follow regulatory test voltage requirements.
During low-voltage withstand testing, remove the temperature sensor (TP100) . Replace it immediately after the test.
D. Fan Test (if equipped)
Energize and run the cooling fan to ensure normal operation.
Consequently, performing these tests before energization prevents costly failures and ensures safe startup.
7. Trial Run: What to Monitor During First Power-On
After all inspections and tests are complete, energize the transformer for a trial run. During this phase, pay close attention to:
Abnormal sounds, noise, or vibration
Unusual smells – such as burning or overheated insulation
Discoloration – signs of local overheating
Ventilation – ensure adequate airflow
Two Critical Warnings for Dry-Type Transformers
Warning 1 – Moisture Sensitivity Although dry-type transformers have good moisture resistance, their open structure makes them susceptible to high humidity. They achieve high reliability only when relative humidity stays below 70%. Avoid long-term outages, as extended idle periods can cause severe moisture absorption. If insulation resistance drops below 1000Ω/V (operating voltage), stop the trial run immediately and dry the transformer.
Warning 2 – Never Operate with Low-Voltage Side Open For step-up dry-type transformers in power stations (unlike oil-immersed types), do not open the low-voltage side during operation. Doing so can cause overvoltage from the grid side or lightning strikes, leading to insulation breakdown. To prevent this hazard, install a set of overvoltage protection surge arresters (e.g., Y5CS zinc oxide arresters) on the voltage bus side of the dry-type transformer.
Conclusion
Installing and commissioning a dry-type transformer requires careful attention to each step – from pre-installation inspection to trial run monitoring. By following this guide, you ensure safe operation, prevent common failures, and maximize the service life of your equipment.
