Q 1) What is the purpose of ungrounded system. Is it not to trip the circuit breaker when

the first fault occurs? (for more controlled deactivation?)

Q 2) In a grounded system, having one conductor connected to earth provides the reference

for steady voltages supplied to loads. How is stable voltage accomplished in an ungrounded

system?

Q 3) Actually, there is no such thing as an ungrounded system, right? (Because an ungrounded

system is capacitively grounded.. whatever that means)


Thanks for your answers

Sung

Sung,
Welcome to ECN,
Most Electrical systems throughout the world have a reference to Earth.
This is mainly for Safety reasons.
It is so that there is a limit on the Line to Ground voltage.

I wouldn't trust an ungrounded system where the primary has a higher voltage than the secondary to be very stable. Impedance grounding is generally adequate for a one fault tolerant system. And you'd need that grounding point to set an alarm to know where there is a fault.

I wouldn't even trust an article 411 system (411.5(A) requiring it to be ungrounded) unless it is isolated with a grounded electrostatic shield between primary and secondary, or has 2 transformers with an intermediate grounded loop at the final secondary voltage.