The process is based on a cleaning and drying of damaged elements, then checking of insulation resistance.
Do not make a dielectic test which can damage the insulating materials.
In order to not take into account capacitive current, the test has to be done with a DC voltage of at least 500V.
The value expected by the measurement is 1000 ohm/ V of nominal operating voltage.
As the KT has a nominal operating voltage of 1000V, the value should be at least 1.000.000 ohm(1 Mohm) and the more we get the better it is.
Typical values for new elements are more close to 10 Mohm.
Do not make a dielectic test which can damage the insulating materials.
- Dismantle all wet junction blocks and clean them thoroughly, take all dirty parts out and dry them with an air compressor .
- Checking of all tap-off outlets - clean them thoroughly, take all dirty parts out and dry them with an air compressor.
- Draining of residual water in junction blocks and straight lengths :
- drying with a free air circulation and element in vertical position for at least 2 days
- or drying in an oven with a maximum temperature = 60°C
- or drying by supplying each damaged element with a low voltage power supply: for example 24 to 48V , 200A
- or drying in an oven with a maximum temperature = 60°C
- or drying by supplying each damaged element with a low voltage power supply: for example 24 to 48V , 200A
- For each damaged element, check all insulation resistances : between phases; phases-casing, phase-neutral
In order to not take into account capacitive current, the test has to be done with a DC voltage of at least 500V.
The value expected by the measurement is 1000 ohm/ V of nominal operating voltage.
As the KT has a nominal operating voltage of 1000V, the value should be at least 1.000.000 ohm(1 Mohm) and the more we get the better it is.
Typical values for new elements are more close to 10 Mohm.
- If every measurement is correct reassemble the total installation and redo the resistance insulating test.
- If the value is lower do not supply the equipment, as it is possible to get a short circuit inside the junction blocks.
Released for: Schneider Electric UK
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