Application of ThermoLables to MV Switchgears

What are Thermolabels?

See  here

What was the problem or aim of MV switchgear owner?

The key problem to be solved is the detection of defective elements of electrical installations for heating. Thermolabels are an alternative to thermal (infrared) imaging diagnostics of contacts and contact joints at the highest permissible heating temperature.

Where were the sticker installed?

Thermolables rFPT (with gas) were installed on bolted contact joints, on ABB switchgears, UniGear ZS1 type cell. 

For SF6 monoblock switchgear, protection is possible in the cable compartment of the cable terminal block, electrical bus.

Stickers can be installed on all contacts (fixed parts), contact connections (bolted, welded, adapter type). rFPT thermolables shall be installed as near to the joint as possible.

Is it mandatory to install the rFPT on the bare copper?

On bare copper is better, but not mandatory. On isolation, sensitivity decreases slightly.

How many turn shall we do with the ThermoLabels?

rFPT should be stick so that its end is glued to itself, i.e. gluing in a ring. This is a guarantee that it will not fall off within 10 years. Of course, the points usually fall on the body of the sticker. There is no particular problem. Their sensitivity will change a little - i.e. they will be colored to black with some delay and the error will be slightly higher, however, this is not a problem for indicator technology, and even more so it will not affect the reliability of the system.

What size of sticker for how many mm2 of copper bar

Select the size so as to wrap in a ring. If there isn't the required size in the standard grid, then there must be a special order. Important! The permissible dimensions of rFPT are strictly tied to the volume! rFPT 0.1 can not be used in a volume of more than 100 liters, rFPT 0.3 more than 300, rFPT 1 more than 1000. But you can easily use rFPT 1 (usually for 1000 liters) for 50 liters, that's not a problem.

To what was the sensor connected? A tripping element or an indicator?

The user connected the dry contact of the sensor to an alarm of the switchgear on its front side.

What was used as supply for the sensor?

Additional 110-230VAC to 24VDC power supply unit

Posted by Matthieu
on September 20, 2019 at 09:40

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