IEEE PC37.110/D911Oct 07 is a technical guide for applying current transformers used in protective relaying purposes within power, energy, and industry applications. It focuses on the practical selection and use of current transformers where accurate current sensing is essential for relay operation and system protection. For engineers, utilities, and industrial users, IEEE PC37.110/D911Oct 07 helps define a clearer basis for designing, specifying, and evaluating protection-related transformer applications.

Overview of IEEE PC37.110/D911Oct 07

This standard addresses the application of current transformers in protective relay systems, where measurement quality and response behavior can directly affect fault detection and protective action. It is relevant to equipment used in electrical power systems and related industrial installations, especially where relaying accuracy, burden, and operating conditions must be considered together. IEEE PC37.110/D911Oct 07 provides a focused technical reference for understanding how these transformers should be applied in protection schemes and related engineering decisions.

Typical use cases

This guide is typically used when specifying current transformers for feeder protection, transformer protection, bus protection, and other relay-based control schemes. It is also useful during substation design, protection coordination, retrofit planning, and equipment review in power and industrial systems. Engineers may rely on IEEE PC37.110/D911Oct 07 when checking relay input requirements, CT performance under fault conditions, or the suitability of a transformer for protective relaying duties in a particular installation.

Why it matters

Current transformers play a critical role in relay accuracy, and application errors can lead to nuisance trips, delayed clearing, or missed fault detection. IEEE PC37.110/D911Oct 07 supports more consistent design and procurement decisions by giving users a common technical basis for evaluating CT behavior in protective applications. That can reduce risk, improve coordination between relays and transformers, and help maintain dependable system protection in power and industrial environments.

• Protective relaying application guidance
• Current transformer selection considerations
• Relay accuracy and burden awareness
• Power and industrial protection systems
• Design and compliance reference