2. Switching off load currents
You'd think that the main difficulty would be switching off very high currents. In fact, certain load currents make disconnection difficult due to arc/network interactions. In this section, we'll look in turn at the various normal and fault situations encountered on networks.
2.1 Switching off resistive currents
In normal MV operation, a circuit is cut:
on a load current of a few amperes to a few hundred amperes, low compared with the short-circuit current (10 to 50 kA);
with a power factor greater than or equal to 0.8; the phase shift between circuit voltage and current is small, and the voltage minimum occurs around the current minimum (highly resistive circuit).
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Switching off load currents
Fault current shutdown
Bibliography
Standards
- Coordination de l'isolement (1993-11). - CEI 60071-1 -
- Coordination de l'isolement (1996-12). - CEI 60071-2 -
- Interrupteurs à haute tension (1998-01). - CEI 60265-1 -
- Interrupteurs à haute tension (1988-03) ; amendement 1 (1994-07) ; amendement 2 (1998-08). - CEI 60265-2 -
- Contacteurs pour courant alternatif haute tension et démarreurs de moteurs à contacteurs - CEI 60470 - (2000-05)
- Amendement...
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