Transformer direct winding hot spot
temperature monitoring

Neoptix offers a complete range of instruments, probes and accessories for temperature monitoring directly inside cast and oil filled power transformers. Fiber optic temperature monitoring systems allow you to take full advantage of the benefits inherent to fiber optic sensing technology. They offer accurate and reliable temperature measurements, combined with extraordinary insensitivity to EMI/RFI, high voltage insulation and disturbance free sensing due to the non-electrical nature of the sensor element used.

Our transformer temperature probes have been designed and are ideally suited to measure hot spots inside the windings of power transformers. Experience has shown that temperatures calculated using simulated measurement models may deviate significantly from direct measurements using fiber optic temperature measurement techniques. Only by directly measuring the hot spots using fiber optic technology can the temperature rise truly be known.

The main advantages of using fiber optic temperature sensors in transformers are:

• Accurate, direct temperature reading of winding hot spots
• Predicts or adjusts the dynamic loading of high voltage transformers
• Prevents premature failures
• Provides cost effective monitoring of transformers temperature
• Extends transformer life and helps estimate the insulation degradation rate
• Complements predictive hot-spot algorithm simulations

Want to know more about instrumenting transformers with optical temperature probes? Take a look at our product chart.

Neoptix products are specifically designed for transformer applications with long term reliability in mind. Our temperature probes are tough and ruggedized to help you achieve a safe and successful installation into your transformers.

Not only does the T/Guard family of products gives users’ access to reliable measurements, but it also offers a simple user interface that makes the technology easy to use. The technology behind Neoptix sensors relies on the measurement of a fundamental characteristic (band gap) of a GaAs semiconductor chip; this characteristic is intrinsic to the material, and thus ensures that the probes will give years of trouble free operation. Furthermore, the light source used in the T/Guard subsystem is rated to provide continuous service for more than 300 years.

Moreover, probes do not require complex gage factor or calibration to enter into the signal conditioner: install them into the windings, connect them to signal conditioner and voilà! ; no more steps before reading a valuable and accurate temperature.

Neoptix offers several signal conditioners specifically designed for transformer monitoring:

All of these signal conditioners are taking advantages of our T2™ probes (contact Neoptix for fluorescence probes) which are robust, oil-permeable fiber optic temperature sensors for use inside oil-filled power transformers. They are specifically designed to withstand initial manufacturing conditions, including kerosene desorption and heat runs, as well as long-term oil immersion and vibration. The probes can be embedded in a standard spacer or attached directly onto any other location inside power transformer windings. T2 probes have been installed with success by a large number of transformer manufacturers.

The electrically inert fiber optic probes used with the T/Guard family of signal conditioners are manufactured from materials specifically tested for long-term compatibility in oil-filled high-voltage power transformers. The fiber consists of a robust all-silica optical fiber, with a polyimide buffer. The fiber is inserted inside a PTFE Teflon tubing, which is longitudinally slitted to allow complete oil filling and avoid partial discharges.

All materials used in the probe construction are compatible with hot transformer oil and hot kerosene vapor used in the vapor phase drying process. In addition, the 60Hz dielectric strength of the fiber materials is tested to verify their dielectric performance, using the ASTM D-149 test procedure.

Probes are available in several standard lengths, and can be specially ordered to fit various transformer designs and sizes. The probe-sensing tip can be taped directly to the winding conductor or mounted in radial spacers between conductors.

The probe is routed from the sensing point to one side of the tank, where a tank feedthrough would be used. This oil-tight feedthrough is designed into a ¼ inch NPT fitting, which can be installed using an appropriately threaded hole from the outside of the tank. A mounting plate, containing up to twenty-four predrilled and threaded holes to receive up to twenty-four tank feedthroughs, is available from Neoptix, for bolting or welding to the tank. External extension cables can then be connected to the outside side of the feedthroughs, and routed to the signal conditioner enclosure.

Neoptix also offers a full range of accessories to achieve a complete and economical installation. Among many, accessories include:

Other accessories include:

• Fiber optic ruggedized extension cable
• NEMA protective enclosure for your T/Guard and T/Guard+ systems
• Heating and cooling for the NEMA enclosures
• DIN rail mounting brackets
• Power supply
• Transformer side conduits