Fortified Sentinel: The CIT Solution for Uncompromising Reliability & Safety in Substations

Wone Store

07/22/2025

Core Problem Addressed

Traditional ITs represent critical single points of failure. Core malfunctions due to overload, thermal stress, or internal faults lead to inaccurate metering/protection signals or complete loss of data. Transient surges specifically challenge CITs due to combined voltage/current proximity. These vulnerabilities compromise grid stability and personnel safety.

The Fortified CIT Solution

This solution transcends basic combination by embedding layers of reliability and safety engineering:

Active Redundancy:

Multiple Independent Cores: Incorporates **≥2 functionally isolated current measurement cores and ≥2 independent voltage measurement cores** within the single unit housing.
Fail-Operational Principle: The secondary signal processing continuously monitors all cores using cross-comparison and predefined thresholds. Upon detecting an anomaly in any single core (current or voltage), the system instantly and seamlessly switches to a healthy redundant core without disrupting the output signal or triggering a breaker trip. Primary functions remain fully operational.

Proactive Condition Monitoring:

Per-Core Self-Diagnostics: Each measurement core (current & voltage) features embedded sensors and algorithms continuously monitoring its own health parameters:

Temperatures (Internal/Ambient): Monitored continuously via embedded probes.
Signal Characteristics: Core saturation indicators, harmonic distortion checks, phase shifts.
Insulation Resistance: Periodic checks for degradation trends.

Advanced Algorithms: Diagnostic data is processed using AI/ML algorithms to predict core degradation and differentiate transient disturbances from permanent failures.

Active Temperature Compensation (ATC):

Real-Time Accuracy Preservation: Integrated high-precision temperature sensors feed data into compensation algorithms embedded in the secondary electronics.
Continuous Calibration: ATC dynamically adjusts the gain and phase angle of the outputs from all cores (primary and redundant), neutralizing thermal drift errors across the operational temperature range (-40°C to +70°C). Ensures consistent accuracy regardless of ambient or load conditions.

Enhanced Mechanical & Electrical Resilience:

Fail-Safe Physical Design: Utilizes robust materials and a mechanical layout where critical path integrity (e.g., support structure, primary conductor connection) is maintained even under significant stress or localized internal component failure (e.g., a failing core module doesn't compromise overall mechanical stability).
Integrated Surge Protection: High-energy Metal Oxide Varistor (MOV)-based Surge Arresters are integrated within the CIT housing, strategically positioned at the voltage terminals and control cable entry points. Catastrophic voltage spikes (e.g., lightning, switching surges) are suppressed before they can damage internal cores or electronics.
Optimized Creepage & Clearance: The internal design and external insulation profile incorporate specifically extended creepage distances and increased phase-to-phase/phase-to-ground clearances. This accounts for the combined electromagnetic stresses unique to the CIT, preventing surface tracking flashovers, especially under contamination (dust, moisture, salt) or high humidity.

Tangible Reliability & Safety Benefits

Dramatically Reduced Forced Outages: Redundant cores ensure continuous signal availability. Core failure transitions from a critical event to a monitored maintenance trigger.
Predictive Maintenance Capability: Self-diagnostics provide actionable health data, enabling planned maintenance before failure occurs, improving resource allocation and asset lifespan.
Absolute Signal Integrity Under Thermal Stress: ATC eliminates thermally-induced measurement errors, guaranteeing protection accuracy and metering validity in fluctuating environments.
Robustness Against Transients: Integrated MOVs dramatically mitigate the risk of surge-induced damage to the CIT itself and downstream relays/protection equipment.
Enhanced Personnel Safety: Eliminates hazards from open-circuited CTs or uncontained core failures within the unit. Redundancy minimizes the need for emergency interventions. Extended creepage prevents surface flashovers.
Unmatched Resilience: Fail-safe mechanics combined with functional redundancy and surge protection create a sensing unit vastly more resistant to internal faults, external electrical stresses, and environmental extremes than any standard IT solution.

Enhanced Benefit Overview

Feature	Reliability Impact	Safety Impact	Grid Stability Benefit
Redundant Cores	✓ Uninterrupted operation during core failure ✓ Eliminates single points of failure	✓ Prevents hazardous open-circuit conditions ✓ Maintains protective functions	✓ Continuous data flow ✓ Prevents false trips or failure-to-trip
Self-Diagnostics	✓ Early failure detection ✓ Enables predictive maintenance	✓ Alerts before critical failure ✓ Reduces exposure to hazards	✓ Optimized maintenance planning ✓ Prevents unexpected outages
Active Temperature Compensation	✓ Eliminates thermal drift errors ✓ Consistent accuracy across all conditions	✓ Ensures correct protection signals ✓ Prevents misoperation	✓ Accurate load flow data ✓ Stable voltage regulation
Integrated Surge Arresters	✓ Protects internal components ✓ Prevents catastrophic failure	✓ Contains surge energy internally ✓ Prevents cascading damage	✓ Protects downstream equipment ✓ Minimizes transient disturbances
Optimized Creepage/Insulation	✓ Prevents surface flashovers ✓ Handles contaminated conditions	✓ Eliminates external arcing ✓ Reduces fire risk	✓ Stable operation in harsh environments ✓ Higher uptime in adverse weather

Typical Failure Probability Comparison :

Configuration	Probability of Complete Measurement Failure
Standard CT or VT	1 in 20 years
Standard CIT	1 in 15 years (combined failure points)
This Fortified CIT Solution	1 in 150+ years (redundant cores + protection)