### **1. What is Transformer TTR?**
A **Transformer Turns Ratio (TTR) Tester** is a specialized instrument used to measure the **turns ratio** between the primary and secondary windings of a transformer. The turns ratio is the ratio of the number of turns in the primary winding to the number in the secondary winding and determines the voltage transformation ratio. Accurate turns ratio measurements are crucial for verifying transformer performance and detecting winding faults.
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### **2. Purpose**
* **Verify correct winding ratio:** Ensures transformer provides the expected voltage transformation.
* **Detect winding faults:** Such as shorted turns, open circuits, or incorrect connections.
* **Quality control:** During manufacturing or post-repair validation.
* **Maintenance diagnostics:** Identify deterioration or damage affecting transformer operation.
* **Confirm compliance:** With design specifications and relevant standards.
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### **3. Types of Transformer TTR Testers**
* **Manual TTR Testers:** Basic models requiring manual connection and reading.
* **Digital/Automatic TTR Testers:** Provide automated measurements, digital displays, and data storage.
* **Portable Handheld TTR Testers:** Compact, battery-operated devices for field testing.
* **Bench/ Laboratory TTR Testers:** Higher accuracy units used in factory environments.
* **Multifunction Testers:** Include TTR measurement along with other transformer tests like winding resistance, insulation, and excitation.
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### **4. Applications**
* **Manufacturing:** Factory acceptance testing of new transformers.
* **Field Testing:** Routine maintenance and commissioning tests at substations and power plants.
* **Post-Repair Testing:** Verification after transformer rewind or repair work.
* **Troubleshooting:** Diagnose suspected winding problems or incorrect tap changer connections.
* **Calibration:** Verify and calibrate protection and metering transformers.
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### **5. How to Use a Transformer TTR Tester**
1. **Preparation**
* Ensure the transformer is de-energized and properly isolated.
* Refer to transformer wiring diagrams for correct terminal identification.
2. **Connection**
* Connect the test leads to the primary and secondary winding terminals according to the device manual.
* Ensure good contact and avoid loose connections.
3. **Set Parameters**
* Input rated voltages or specify the tap position if applicable (for transformers with on-load tap changers).
4. **Perform Measurement**
* Start the test; the tester applies a low voltage to one winding and measures the output voltage on the other winding.
* The turns ratio is calculated automatically and displayed.
5. **Interpret Results**
* Compare measured ratio to the rated ratio.
* Differences beyond standard tolerances may indicate winding faults.
6. **Record and Report**
* Save the data and generate test reports if supported by the instrument.
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### **6. FAQs**
**Q1: What tolerance is acceptable for turns ratio measurements?**
**A:** Typically, a deviation of ±0.5% to ±1% is acceptable, but specific tolerance depends on transformer design and standards.
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**Q2: Can TTR testers detect all types of winding faults?**
**A:** They detect ratio-related faults such as shorted turns or incorrect connections but may not detect insulation degradation.
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**Q3: Is it safe to test transformers on-load?**
**A:** No, TTR testing should be done only on de-energized transformers.
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**Q4: What standards govern turns ratio testing?**
**A:** IEC 60076-1, IEEE C57.12.90, and IEC 60044-1.
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**Q5: Can TTR testers measure tap changer positions?**
**A:** Some advanced models detect tap position and can test multiple tap settings.
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**Q6: How often should transformer turns ratio be tested?**
**A:** During commissioning, after repairs, and periodically (typically every 1-3 years) as part of maintenance.
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**Q7: Can a TTR tester be used on instrument transformers?**
**A:** Yes, specialized TTR testers are available for current and voltage instrument transformers.