The consequences of electrical insulation failures in ... · The consequences of electrical...

The consequences of electrical insulation failures in ageing umbilicals: copper loss and hydrogen generation.

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Earthing Arrangements

IEC has standardised on three families of earthing – TN, TT, IT

1st Letter is connection between earth and supply

2nd Letter is connection between earth and device being supplied

TN TT IT


Monitoring of IT Systems

IEC 60364 is the international harmonised standard that details requirements for low voltage electrical installations.

•Part 4-41 (Protection for safety – Protection against electric shock) specifies that an IT (floating earth) system shall always be equipped with a suitable protective or monitoring device.

•For high system availability, an IMD should be used, to indicate the first fault, with suitable automatic disconnection of the supply


Cable Insulation Integrity Measurement

Leakage current 𝑓() of 3 sub-currents


Experimental Set-Up

Viper


The IMD two-week effect

Single point damage to insulation equivalent to an insulation resistance of 30kΩ

Day 1 Day 14

Copper Corrosion


The IMD Electrochemical Cell


IMD Experimentation

At the positive surface:


AC Power Experimentation

At the negative surface:


The two conductors after AC power applied

Tarnishing of copper: 2 Cu(s) + O2(g) → 2 CuO(s)


Copper Corrosion after AC power applied


V-LIM Changes to Reduce Copper Loss

IMD current is a minimum at High IR and a maximum at low IR

The output voltage from the IMD can be reduced as the IR reduces without loss of accuracy.

Date post:	24-Sep-2020
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