IEEE PC37.110/D3, Jan 2019 is an inactive draft standard for the application of current transformers used for protective relaying purposes. It focuses on how current transformers support relay performance in power and energy systems, where accurate sensing and dependable operation are essential. IEEE PC37.110/D3, Jan 2019 is relevant to engineers who need guidance on selection, application, and evaluation of CTs in protective schemes, especially where measurement accuracy and system protection must work together.

Overview of IEEE PC37.110/D3, Jan 2019

This draft guide addresses the technical use of current transformers in protective relaying applications, with emphasis on how CT characteristics affect relay behavior under normal and fault conditions. It provides context for understanding CT performance in electrical power systems, including practical considerations tied to burden, accuracy, and protection requirements. As a draft document, IEEE PC37.110/D3, Jan 2019 is typically useful for reviewing proposed guidance related to relay input quality and overall protection scheme dependability.

Typical use cases

This standard is typically consulted when specifying or reviewing current transformers for feeder protection, transformer protection, generator protection, and substation relaying applications. It is useful during engineering design, protection coordination, procurement review, and test planning for CTs used with protective relays. IEEE PC37.110/D3, Jan 2019 may also support work on selection of CT ratios and performance expectations in utility and industrial power systems where correct relay operation depends on the CT response.

Why it matters

Protective relaying depends on current transformers that behave predictably during both normal load and fault events. This document matters because it can help reduce application errors that lead to nuisance operation, missed trips, or poor relay performance. IEEE PC37.110/D3, Jan 2019 supports more consistent design decisions, clearer acceptance criteria, and better alignment between CT capabilities and protection requirements. In practice, that can improve system reliability, testing confidence, and overall risk control.

• Protective relaying application guidance
• Current transformer performance in fault conditions
• CT selection and burden considerations
• Power system protection and relay coordination
• Draft guidance status: inactive