• Check Nameplate and Test Certificate: Capacity (kVA), High Voltage (kV), Low Voltage (V), Vector Group, Tapping (Off-load) at HV side.  
• Verify that installed accessories are according to contract such as Thermometer, Oil Level, Buchholz Relay, Breater (Silica Gel) etc
• For conservator type, ensure silica gel has blue color and blocked seal has been removed
• If equipped with pressure gauge, ensure transformer pressure within 0.1- 0.4 bar or 1.4 - 6 PSI.
• Verify that oil level in Sight Glass or R.I.S is full (maximum pointer).
• Inspect physical appearance against scratch, damage, fracture, leak, or any damage that might occurs during transportation.

II.    TRANSFORMER INSTALLATION

• Provide good air ventilation. Recommended room ambient temperature at 100% load is 30 ^oC.  Load should be de-rated if ambient is higher than 30 ^oC. Please see user manual.
• Provide solid base structure heavier than transformer’s weight to reduce unwanted noise.
• Do not place transformer in the room corner, low ceiling height or direct contact with floor as this will boost audible noise due to acoustic reflective room
• Install grounding according to local regulation (PUIL, NEC, etc).
• Use appropriate cable schoon. Ensure tight contact to avoid excessive losses and heat. Use cable support / duct for secondary bushing to maintain bushing integrity against cable forces.

III.    TRANSFORMER OPERATION

1. Measure hvdc insulation resistance (Megger) HV-LV, HV-G, LV-G. See user manual for recommended minimum Mohm value.

2. Check with megger for phase to phase connections, they should read 0 MOhm.

3. Applied to single phase transformers:

• In single bushing type, one HV is grounded so megger H1 with body results 0 MOhm.  
• In 4-bushing type, between X1-X2 and X3-X4 is open, X1 connects X2, X3 with X4.
• In CSP type, cgheck breaker mechanism by operating it on-off. When on phase X1-X2 and X3-X4 is short, and open when off position.

4.   Check tap changer for all taps.
With megger, masure tap changer from tap 1 to the last tap by loosen the locking head, pull tap changer head upward, hold and rotate to desired tap. At every tap, phase A-B, B-C, C-A should read 0 Mohm. Bring back tap changer to nameplate tap and lock it.

5. Changing tap position after energize.

• Break incoming voltage by open Fuse Cut Out / Circuit Breaker in incoming cubicle panel. Ensure no high voltage goes to transformer. To prevent load shock when re-energize, break the load in outgoing panel.
• Open tap changer lock, pull the head and hold upward while rotating it to desired tap.
• Example of calculations: transformer rated 20kV/400 V, in tap 3 LV goes down to 390 V (no load) so 20.000/400 x 390 = 19.500. Therefore, tap should be changed to tap 4, (see name plate). LV will supply 400 V.
• Ensure tap in the correct position, megger between phases should read 0 Mohm. Locks tap changer.
• Apply incoming voltage and make load in sequence to avoid excessive starting currents