PalladiumMembraneHydrogen SensorIn Oil-immersedTransformer

Introduction1. What’s Oil-immersedTransformer[1]

For large transformers used inpower distribution or electricalsubstations, the core and coilsof the transformer areimmersed in oil which coolsand insulates. Oil-immersed Transformer

2. What’s Transformer Oil[2]

Transformer oil or insulating oil isa highly refined mineral oil that isstable at high temperatures andhas excellent electrical insulatingproperties.

3. The impact of water vapor [3]

Since Transformer is always placedin the wilderness that’s full ofmoisture, and the moisture hashuge influence on breakthroughvoltage of Transformer, controllingthe moisture content oftransformer oil is one of the mostsignificance improvement forextending transformer services life

[1]http://en.wikipedia.org/wiki/Transformer_types#Oil_cooled_transformer[2]http://en.wikipedia.org/wiki/Transformer_oil[3]LIN Guo-jiu, etc., Research on Production Technology of Low MoistureContent, Lubricating oil, Vol.28,No.2,2013(4).

PMHSensor

Introduction

Au-Eutecticcombination

Etching Chamber

Pt micro heater

Si Base

SiNX

SiO2

Au Bonding Pad Pd sensing component Temperature Probe

Palladium Membrane Hydrogen Sensor[1] (CH)N 2 + 2d + H2→Reaction Principle

Transformer Oil decomposes into H2 and CO2 withinhigh pressure and temperature situation. Then, H2will integrate with Pd into PdH.

Because PMH sensor is to monitor the percentageof Hydrogen by testing the voltage of Pd-PdHcomponent, when Pd is reacting into PdH, theelectrical preferment of Pd sensing componentwould change immediately so that we could knowhow much Hydrogen in the system by simplecalculation.

[1] ZHANG Hong-yan, et al., Hydrogen Micro-sensor for Real-time Diagnosticof Transformer Oil, Instrument Technique and Sensor, supplement, 2009,P187-188.PMH

Sensor

Impact from MoisturePMHSensor

The percentage of Moisture

Control PointControl Point

PMH Sensor

Transformer

MoisturePMHSensor

1. Since moisture can take away heat from surface, causingbubbles relate to surface stress disproportion thatmight badly crack and undulate component surface

2. Cracked and undulating surface has invisible pores andmicro-fractures, what H2 molecule could easily passthrough, impacting the performance of Pd sensingcomponent

Cracked and Undulating Surface[1]

The Aging Sensitivity Curve of PMH Sensor[2]

3. Moisture also accelerate the aging problem of PMH Sensor. Watermolecules or droplets would be condensed on the surface to occupyand reduce the H2-Pd contact area so that it would weaken thesensitivity of PMH sensor and further impact the long-termperformance of PMH sensor.

[1] HU, et al, Experimental Research on Micro Electrochemical Machiningwith Hydrophobic Side-insulated Electrode, Nanotechnology and PrecisionEngineering, CNKICNKI:12-1351/O3.20130517.1115.002, 2013(05).

[2]FENG Wei, et al, Effect of water vapour poison on the surface conditionand deuterium permeability of palladium membrane, Rare metal materialsand engineering, Vol.42, No.4, April 2013.

Redesign PMH Sensor

Au-EutecticCombination

Etching Chamber

Pt micro heater

Si Base

SiNX

SiO2

Au Bonding PadPd sensing component

Temperature Probe

Palladium Membrane Hydrogen Sensorwith Super Hydrophobic Cover

Design concept1. Use TMMOS[1] membrane as the Super

Hydrophobic Cover2. Use MPECVD[2] technology to deposit the

TMMOS membrane on the Pd sensingcomponent directly with specializedmask protecting other structure

Design concept1. Use TMMOS[1] membrane as the Super

Hydrophobic Cover2. Use MPECVD[2] technology to deposit the

TMMOS membrane on the Pd sensingcomponent directly with specializedmask protecting other structure

PMHSensor

Super Hydrophobic Cover

MPECVD apparatus

[1] Trimethylsilane, is a compound with the formula C3H10Si, or with thestructural formula (CH3)3SiH.[2] Microwave Plasma Enhanced Chemical Vapor Deposition.

Manufacturing ProcessPMHSensor

①

②

③

④

Placed PMH sensorin the MPECVDapparatus

Use the specializedmask to coverirrelevant structure

Use MPECVDtechnology todeposit TMMOSmembrane on thePd component

Remove the mask

Simulation & RepresentationPMHSensor

Fig1.Simulation results of largevolume bubble’s movement at thejunction between hydrophobicfilms[1]

In Fig1, we can easily learn that bubbles caused by water vapourwould move persistently away from hydrophobic films at shortnotice, so that they wouldn’t occupy any H2-Pd contact area andfurther reduce the H2 reaction rate.

In Fig2, after depositing TMMOS hydrophobic cover, theresponsiveness of PMH sensor is improved dramatically.

Simulation equation:Fig3. SEM image of the comparison between Pd surfaceand TMMOS membrane surface(a b. original Pd surface,c d. TMMOS hydrophobic surface) [1]

TMMOS hydrophobic surface has ≥150°contact angleforbidding droplets and bubbles, a large amount ofmicrospore allowing H2 molecule pass through andcontact with Pd membrane, so that adding TMMOShydrophobic membrane on the Pd surface has no effectedthe performance of H2-Pd sensing but enhanced the H2contact rare to improve the sensitivity of PMH sensor.

Contact angle equation: (Young’s)

Fig2.Simulation results of comparisonabout H2 responsiveness between PHMsensor and PMH sensor with TMMOScover.

[1]Hu Manhong, et al, Experimental research onmicro electrochemical machining withhydrophobic side-insulated electrode,Nanotechnology and Precision Engineering, DOI：CNKI:12-1351/O3.20130517.1115.002,2013(05).

NAME: WEI Zhaohong

THANKSSID: 53417403

Email: weijia1990@foxmail.com