MV design guide - Schneider Electric
MV design guide - Schneider Electric
MV design guide - Schneider Electric
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Switchgear<br />
definition<br />
Medium voltage circuit breaker<br />
IEC 60 056 and ANSI C37-06<br />
define on one hand the operating conditions,<br />
the rated characteristics, the <strong>design</strong> and<br />
the manufacture; and on the other hand<br />
the testing, the selection of controls<br />
and installation.<br />
Introduction<br />
c The circuit breaker is a device that ensures the control and protection<br />
on a network. It is capable of making, withstanding and interrupting<br />
operating currents as well as short-circuit currents.<br />
c The main circuit must be able to withstand without damage:<br />
v the thermal current = short-circuit current during 1 or 3 s<br />
v the electrodynamic current:<br />
2.5 • Isc for 50 Hz (IEC)<br />
2.6 • Isc for 60 Hz (IEC)<br />
2.7 • Isc (ANSI), for a particular time constant (IEC)<br />
v the constant load current.<br />
c Since a circuit breaker is mostly in the "closed" position, the load<br />
current must pass through it without the temperature running away<br />
throughout the equipment's life.<br />
Characteristics<br />
Compulsory rated characteristics<br />
c Rated voltage<br />
c Rated insulation level<br />
c Rated normal current<br />
c Rated short-time withstand current<br />
c Rated peak withstand current<br />
c Rated short-circuit duration<br />
c Rated supply voltage for opening and closing devices<br />
and auxiliary circuits<br />
c Rated frequency<br />
c Rated short-circuit breaking current<br />
c Rated transient recovery voltage<br />
c Rated short-circuit making current<br />
c Rated operating sequence<br />
c Rated time quantities.<br />
Special rated characteristics<br />
c These characteristics are not compulsory but can be requested for<br />
specific applications:<br />
v rated out-of-phase breaking current,<br />
v rated cable-charging breaking current,<br />
v rated line-charging breaking current,<br />
v rated capacitor bank breaking current,<br />
v rated back-to-back capacitor bank breaking current,<br />
v rated capacitor bank inrush making current,<br />
v rated small inductive breaking current.<br />
Rated voltage (cf. § 4.1 IEC 60 694)<br />
The rated voltage is the maximum rms. value of the voltage that the<br />
equipment can withstand in normal service. It is always greater than the<br />
operating voltage.<br />
c Standardised values for Ur (kV) : 3.6 - 7.2 -12 - 17.5 - 24 - 36 kV.<br />
<strong>Schneider</strong> <strong>Electric</strong><br />
Merlin Gerin <strong>MV</strong> <strong>design</strong> <strong>guide</strong><br />
45