This is practical work for testing and pre-commissioning the LV MCCB using the guidelines to guarantee that the work is carried out in accordance with the plan requirements.
After separating all incoming and outgoing cables.
IR for PVC insulated cables is to be a minimum of 100 Megaohm-km, and for signal cables: 10,000 M.
All measured phase-to-phase and phase-to-ground distances must meet the criteria.
Procedure
Using an IR tester, apply 1000 Vdc between phases R, Y, and B to load terminals A, B, and C for 1 minute with the CB position set to off.
Using an IR tester, apply 1kVdc between phases R, Y, and B to the ground terminal for 1 minute with the CB in the ON position.
Most likely, the same approach is used throughout all phases.
With the CB turned on, apply a DC voltage between phases R and Y for one minute.
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For 1 minute, apply the DC voltage between phases Y and B with the CB switch turned on.
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For 1 minute, apply the DC voltage between phases R and B with the CB switch turned on.
The IR range refers to how well a capacitor’s dielectric material resists leakage current. Leakage current measurements after applying DC voltage are typically very modest, in the nano-ampere range.
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