By hvhipot 
The Transformer Turns Ratio tester under HV Hipot Electric Co., Ltd. can help many power workers conduct various power tests more conveniently.
1. Safety Preparation
Isolate and De-energize: Disconnect all HV/LV power series resonances. Verify de-energization and apply safety grounds.
Discharge & Ground: Short-circuit and ground all windings for discharge.
PPE: Wear insulated gloves and safety glasses.
2. Instrument Connection
Use a dedicated TTR tester.
Connect HV leads (H1/H2/H3) to transformer HV terminals.
Connect LV leads (X1/X2/X3) to LV terminals.
Ground both tester and transformer tank reliably.
3. Parameter Setup
Enter rated HV/LV values (e.g., 11kV/400V).
Select winding configuration (e.g., Dyn11).
Set tap changer to rated position.
4. Execute Test
Start tester. Measure phase-by-phase (A-a, B-b, C-c).
Record measured ratio and % error.
Acceptance Criteria:
% error ≤ ±0.5% (GB/IEEE standards);
Phase deviation ≤ 0.2%.
5. Tap Changer Check
Cycle through all tap positions (e.g., +5%, 0, -5%).
Verify ratio matches step value at each tap (e.g., ±0.625%/step).
6.Result diagnosis
Excessive error: incorrect number of turns, poor tap contact.
The ratio of one stage is significantly lower: the high-voltage turn to turn short circuit in this stage.
No reading/infinite ratio: open circuit winding.
Abnormal tapping behavior: burnt or misaligned contacts.
7. Key Notes
Off-circuit tap changers: Must be switched manually after de-energization.
OLTC (On-Load Tap Changer): Use tester’s remote control. Strictly prohibit manual switching under voltage!
Re-ground windings after testing.