Refer to the Hardware section in this manual for a detailed description of REX060.
7.9.9.2
Generator system earthing methods
There are several principles for system earthing of synchronous generators. The
choice of earthing method depends on different factors:
•
Limitation of earth fault current at stator earth fault
•
Damping of transient overvoltages in the generator system
•
Required insulation level to withstand overvoltage in “healthy” phases at single
phase earth fault
•
Δ or Y coupled stator windings
•
Connection of a single generator via a step up transformer or connection of more
than one generator via a common step up transformer
Normally the generator system has some kind of high resistance earthing, giving earth
fault current within the range 5 – 20 A, thus preventing serious damages in case of
stator earth faults. Direct earthing will give too high earth fault current level. Isolated
generator system will give risk of transient overvoltages.
Below some alternatives for generator system earthing are shown;
A
B
C
IEC110000066-1-en.vsd
IEC11000066 V1 EN
Figure 135:
Generator earthing alternatives
A
High-resistance earthing with a neutral point resistor
B
Effective high-resistance earthing via a distribution transformer
C
High-resistance earthing via a delta, grounded-wye transformer
Section 7
1MRK502052-UEN B
Impedance protection
302
Technical manual
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