Voltage Transformer Ratio Selection Guide
Engineering Intent
Voltage transformer ratio should match system voltage, metering input, relay input and grounding method.
This article is written for engineers, EPC buyers and procurement teams who need to turn VT ratio selection into a clear technical request instead of a vague product inquiry.
Key Selection Data
| Item | Data to Confirm |
|---|---|
| Check 1 | Primary system voltage |
| Check 2 | Secondary voltage 100V or 110V |
| Check 3 | Single-phase or three-phase measurement |
| Check 4 | Meter or relay burden |
Standards and Evidence to Request
- IEC 61869 voltage transformer references
- Relay or meter datasheet
- Panel wiring diagram
For project approval, request a technical datasheet, outline drawing, wiring or terminal diagram where applicable, routine test report and nameplate information before shipment.
Common Specification Mistakes
- No secondary voltage stated
- Ignoring grounding arrangement
- No burden value
RFQ Checklist
- Provide system voltage
- Confirm secondary voltage
- State accuracy class
- Share wiring diagram if available
Related Product Paths
Ziyao Power can review the single-line diagram, load schedule, panel drawing or tender sheet and convert the requirement into a practical quotation package.
Download This Guide as PDF
Save this technical guide for offline reference. Includes all tables, specifications, and contact information.
Related Articles
Current Transformer Ratio Selection Guide
CT ratio should match feeder current, meter or relay input, accuracy requirement and future load margin.
CT Accuracy Class 0.5 vs 5P Explained
Metering CTs and protection CTs use different accuracy classes, so 0.5 and 5P should not be treated as interchangeable.
Current Transformer Burden Calculation
CT burden must include meter or relay load plus secondary cable resistance to maintain accuracy.