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Fibre Optic Temperature Monitoring

Complete End‑to‑End System
Optional Environmental Control

Real-Time Insight Into Transformer Hot Spot Performance

The Qualitrol T/Guard 408 and 408XT Fiber Optic Winding Temperature Monitor delivers direct, real-time measurement of transformer winding hot spot temperatures. Using proven GaAs fiber optic sensing technology, it provides precise, drift-free temperature data that helps operators maximize transformer performance, protect insulation life, and confidently manage dynamic loading conditions.

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Fiber Optic Winding Temperature Monitoring You Can Trust

Rugged multi-channel fiber optic real-time hot spot monitoring system for dry-type and oil-filled transformers.

  • Provide essential data during transformer heat run

  • Maximize cooling efficiency with accurate hot spot temperature measurement

  • Optimize loading dynamically without compromising transformer life

  • Complements predictive hot-spot algorithm simulations

  • Compatible with Qualitrol Q-Link™ for Apple® iPhone®, OptiLink and OptiLink-II

  • Available with 4, 6, 8, 10, 12 or 16 channels

What We Solve For

Traditional transformer temperature measurements rely on indirect methods that can lag behind real conditions, especially during rapid load changes or emergency overloads. The T/Guard 408 solves this by providing:

  • True winding hot spot temperatures rather than estimated values

  • Near-instantaneous detection of overloads and thermal stress

  • Long-term measurement stability without sensor drift or recalibration

  • Confidence to increase loading without compromising transformer life

This results in improved asset utilization, enhanced reliability, and reduced risk of unexpected failures.

TECHNICAL

Features & Functionality

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Direct Fiber Optic Hot Spot Measurement

The system measures actual winding temperatures using GaAs-based fiber optic probes embedded directly in critical locations. This provides a realistic and immediate view of transformer thermal behavior, far more accurate than indirect measurements or thermal algorithms alone.

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High-Speed Multi-Channel Monitoring

With support for 4 to 16 fiber optic channels, the T/Guard 408 scans all probes with a 250 ms switching rate per channel, ensuring rapid detection of peak temperatures during load changes or emergency conditions.

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Long-Term Stability with Zero Drift

Solid-state semiconductor sensing technology ensures absolute temperature accuracy over the full transformer lifespan. Unlike fluorescent decay systems, the sensors do not fade or drift, eliminating recalibration requirements.

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Flexible Communication and Smart Grid Integration

The 408XT model is Ethernet-enabled and supports modern substation protocols, including IEC 61850. Data can be accessed locally or remotely via web browser, serial communication, or SCADA systems.

Functionality & Options

  • Available in 4, 6, 8, 10, 12, 14, or 16 channel configurations

  • Built-in 2 GB data logging memory (optional 4 GB upgrade)

  • User-adjustable data logging rates from 1 second to 1 hour

  • Eight programmable Form-C relays plus dedicated system fault relay
    4–20 mA analog outputs for each channel (up to 16 outputs)
    Serial (RS-485) and Ethernet communication options

  • Web-based configuration and monitoring on 408XT models

  • Optional NEMA 4 enclosure for outdoor installations

  • Compatible with Qualitrol Q-Link™ software for visualization and reporting

Key Technical Specifications

  • Measurement resolution: 0.1°C (0.1°F)

  • Accuracy: ±1.0°C from –20°C to 150°C

  • Temperature range: –50°C to +200°C system measurement

  • Sampling speed: 250 ms per channel

  • Light source MTBF: >300 years equivalent continuous operation

  • Power consumption: 18 W (all relays enabled)

  • Supply voltage: 95–240 VAC or 135–240 VDC

  • Operating temperature: –40°C to +72°C

  • Probe technology: All-dielectric GaAs fiber optic sensors

EXPERIENCE

Projects featuring Qualitrol Condition Monitoring

Explore project highlights to see where Qualitrol Condition Monitoring is making an impact.

For tailored advice on whether this solution suits your network, please connect with our team here.

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ADVANTAGES

Why Choose Qualitrol
Fibre Optic Temperature Monitoring

Engineered for performance, reliability, and long-term value, the Qualitrol T/Guard 408 Series combines proven fiber optic sensing technology with robust industrial design. It empowers utilities and asset owners with accurate, real-time winding temperature data to improve operational confidence, extend transformer life, and safely unlock greater loading capability in even the harshest environments.
 
Proven Accuracy for Critical Assets
Qualitrol’s GaAs fiber optic technology delivers direct, absolute temperature measurements with no drift over time. This ensures reliable data for critical transformer protection and asset management decisions throughout the equipment’s life.
Designed for Harsh Substation Environments
Built with rugged components, industrial-grade electronics, and dielectric sensing elements, the T/Guard 408 is engineered to withstand vibration, oil immersion, wide temperature extremes, and long service intervals with minimal maintenance. 
Maximize Loading Without Sacrificing Transformer Life
By revealing the real winding hot spot temperature in real time, operators can safely optimize transformer loading, respond quickly to abnormal conditions, and extend insulation life—unlocking greater operational efficiency without added risk. 
IMPLEMENTATION

Services & Support

Insulect offers comprehensive services and support for the products we specialise in, enhancing value for local utilities, major energy users, equipment manufacturers, and service operators. 

LOCAL TECHNICAL TEAM

Our local technical team provides exceptional support and expertise, ensuring quick response times and personalised service to tackle any challenges that may arise during project execution.

  
ENGINEERING EXPERTISE

Through Qualitrol, our team utilises advanced technology and industry knowledge to assist customers.


  
PROCUREMENT & LOGISTICS

We facilitate smooth procurement and logistics processes by sourcing from trusted, proven partners and coordinating timely deliveries, ensuring projects remain on schedule and within budget.


  
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