P37.117: Using Voltage and Current Measurements for Monitoring Asset Conditions
Objective
This project quantifies the insights that instrument transformer data can provide about the health of various substation assets. Although voltage and current signals are typically collected for relay or metering purposes, the project is motivated by the question: “what more can utilities do with the data they already have?”
Near-term research interests include improving our understanding of how voltage transformers (VTs) and coupling capacitive voltage transformers (CCVTs) fail; identifying how standard control house instrumentation (i.e. relays, power quality monitors, phasor-measurement units) portrays that failure; and identifying post-processing methods or technologies to better identify incipient VT/CCVT failures prior to loss of potential.
Long-term research interests include identifying how VT/CCVT/CT signals change when the instrument transformer is healthy but adjacent assets are failing. The overall goal of this project is to inform member utilities on practical approaches to identifying substation equipment degradation using existing data streams.
Research Value
- Understanding the causes and manifestation of instrument transformer failures enables the creation of guidelines to maximize VT/CCVT service life
- Identifying how well control house instrumentation (i.e., relays, power quality monitors, and phasor merging units) captures degrading or failing VT/CCVT signals allows utilities to monitor some level of asset health without additional capital expenditures
- Participating in a forum dedicated to sharing progress, lessons learned, and challenges of peer utility pilot deployments enables member utilities to accelerate their own failure detection efforts
- Evaluating VT/CCVT failure signals in a methodical, lab-controlled environment enables the creation of guidelines grounded in measured data rather than theory alone, allowing members to more reliably detect VT/CCVT degradation
Approach
Perform forensic analysis of VTs/CCVTs: Forensic analysis of healthy and failed VTs and CCVTs provided by project members informs what underlying mechanisms lead to failure. By better understanding the causes of instrument transformer failure and how that failure physically manifests inside this equipment, we may be better able to design means of identifying failure and offer guidelines to maximize VT/CCVT life.
Capture VT/CCVT signals during VT/CCVT degradation using standard control house instrumentation: Recording voltage waveform signatures during instrument transformer failure in an EPRI lab– using control house instrumentation like relays, power quality monitors, and phasor merging units– allows us to observe how failing VT/CCVT data presents in these instruments. This task evaluates how failing VT/CCVT behavior appears within these devices and assesses the effects of built in filtering, sampling rates, and triggering capabilities on signal fidelity for VT/CCVT health monitoring. The objective of this task is to determine how effectively existing station instrumentation can capture failing VT/CCVT behavior.
Perform post-processing of VT/CCVT failure data: The purpose of post processing is to identify future thresholds or guidelines for proactively identifying VT/CCVT health degradation before complete failure. This task leverages commercially available technologies and theoretical methods to analyze known VT/CCVT failure data and report on how well these algorithms performed at identifying failure.
Anticipated Deliverables
| Deliverable | Date |
|---|---|
| Evaluation of Voltage Recordings During VT/CCVT Failure | 12/31/2027 |
| VT/CCVT Failure Detection Methods | 12/31/2027 |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002032941 | Evaluation of Voltage Recordings During VT Failure | This is a report documenting the results of recording healthy VT online signals and offline insulation measurements. This report is the baseline testing to which 2026+ defect testing results will be compared. | September 2025 |
| 3002032943 | Voltage Transformer Teardown | This report describes the results of dissecting a healthy voltage transformer. The dissection of a healthy VT is intended to serve as a baseline for comparison against future dissections of failed VTs, with the purpose of informing readers on VT failure mechanisms. | September 2025 |
| 3002027138 | Using Voltages and Currents: Applicable Assets | This report is a review of literature to determine which substation assets are likely candidates for health monitoring using voltage and current signals. The selection of CCVTs/VTs for P37.117’s 2025-2027 evaluation is based in part on the outcomes of this report. | December 2023 |
| TR-100205 | Workshop Proceedings: Failed High-Voltage Instrument Transformers | These workshop proceedings describe utility field failures, identify failure modes, and identify possible mitigation measures associated with high voltage current and potential transformers. The field data from these proceedings may inform failure modes identified in upcoming P37.117 testing. | January 1992 |
| TR-113649 | Proceedings: High Voltage Current Transformers and Bushings: Failure Prediction and Prevention Symposium | These conference proceedings include several reports and papers documenting high voltage Current Transformer (CT) accelerated aging tests sponsored by EPRI, including approach, monitoring techniques, and analysis of failed units. The lessons learned from accelerated aging tests in this space inform approaches to accelerated aging test for other instrument transformers in 2026+ for P37.117. | December 1999 |