CTSizer — CT/VT Dimensioning

CTSizer is a free online tool for dimensioning current transformers (CTs) and voltage transformers (VTs) for protection and metering to IEC 61869. It checks the knee-point voltage, the accuracy limit factor (ALF), burden and transient dimensioning factors, and shows every formula and calculation step.

Supported applications

• Overcurrent protection
• Distance protection, including auto-reclosure (C-O-C-O) analysis
• Line differential protection
• Transformer differential protection
• Busbar protection
• Metering cores
• Voltage transformers: burden, voltage drop and thermal checks

Results can be exported as a documentation report (RTF) for Word or LibreOffice. Available in English and Danish.

CTSizer is a free, non-commercial open-source project (GNU AGPL-3.0): github.com/maar0005/CTSizer. No account, no cookies, no tracking.