Wound type current transformer

When sourcing wound type current transformers (CTs), you must prioritize Accuracy Class (e.g., 0.2s, 0.5, or 5P20 for protection), Rated Primary Current, and Rated Burden (VA). Ensure the Insulation Level matches your system voltage (e.g., 0.66kV, 11kV, or 33kV). For wound types specifically, verify the Short-time Thermal Current (Ith) and Dynamic Current (Idyn) ratings, as these determine the unit's ability to withstand high-stress fault conditions without mechanical failure.

Suppliers must demonstrate compliance with IEC 61869-2 (the international standard for current transformers) or IEEE C57.13 for the North American market. For European markets, CE marking and RoHS compliance are essential. If the CT is used for billing purposes, ensure it has Legal Metrology certification or specific utility-grade approvals to guarantee measurement integrity.

Wound Type Current Transformers feature a primary winding consisting of more than one turn, which allows for higher accuracy at low primary currents. They are the ideal choice for applications requiring high transformation ratios and precision in low-current circuits where a single-bar primary would not provide sufficient magnetic flux. However, they have lower short-circuit strength compared to bar types, so ensure the supplier provides epoxy resin vacuum casting for enhanced mechanical durability.

Request a Routine Test Report for every unit, covering Insulation Resistance, Power-frequency Voltage Withstand, and Polarity Checks. For critical infrastructure, demand a Type Test Report from an independent lab (like KEMA or CPRI). Additionally, check the Excitation Curve (Saturation Curve) to ensure the CT will not saturate under expected fault conditions, which is vital for protective relaying.

The biggest risks include Technical Mismatch (frequency differences like 50Hz vs 60Hz) and Transit Damage. Because CTs often use fragile ceramic or heavy epoxy components, improper packaging can lead to internal hairline cracks. Always specify IP65-rated protective packaging and use shock-absorbent wooden crates with vacuum-sealed moisture barriers to prevent oxidation of copper terminals during sea freight.

Utilize the Secured Trading Service on Made-in-China.com to protect your payment until delivery is confirmed. When negotiating, insist on a 30% deposit and 70% balance payment after a successful Pre-shipment Inspection (PSI) by a third party like SGS or Intertek. Clearly define the Warranty Period (minimum 18-24 months) and ensure the contract includes a clause for technical support and replacement parts.

Current transformers are heavy and classified under HS Code 850421. Ensure the supplier provides a detailed Packing List and Certificate of Origin to benefit from potential preferential tariff rates under trade agreements. For shipping to regions with strict electrical codes, ensure the Nameplate is etched in English with all technical parameters clearly visible to avoid customs delays or rejection at the port of entry.