IEEE C37.110-2023

IEEE C37.110-2023 is a technical guide for the application of current transformers used for protective relaying purposes in power, energy, and industry applications. It addresses how current transformers should be selected and applied so relay systems receive accurate current information under operating and fault conditions. That matters because protective relaying depends on dependable transformer performance for correct decisions, coordination, and system protection.

IEEE C37.110-2023 overview

This standard focuses on the practical use of current transformers in protective relay schemes, where measurement accuracy and transient behavior can strongly affect relay response. IEEE C37.110-2023 helps engineers understand application limits, expected performance, and the relationship between transformer characteristics and relay requirements. It is especially relevant when specifying equipment, reviewing protection settings, or evaluating whether a current transformer is suitable for a particular power-system duty.

Typical use cases

Typical use includes protection design for substations, switchgear, and feeder circuits where current transformers feed relays for fault detection and system isolation. The guide is also useful during equipment procurement, protection studies, and commissioning checks for utility and industrial power systems. Engineers may use it when assessing CT ratios, accuracy needs, burden, and relay compatibility in applications where dependable current sensing supports safe and selective operation.

Why this standard matters

In protective relaying, poor current transformer application can lead to misoperation, delayed clearing, or unnecessary outages. IEEE C37.110-2023 provides a common technical basis for design review and specification, helping teams reduce risk and improve consistency across projects. It supports clearer procurement decisions, more reliable testing expectations, and better alignment between transformer capability and relay performance in demanding power-system conditions.

• Protective relaying application guidance
• Current transformer selection and suitability
• Relay performance under fault conditions
• Burden, ratio, and accuracy considerations
• Power-system protection design support