Wind Energy

190 D. Schulz et al.
DFIG outages due to crowbar ignitions. The crowbar closing itself provides no
clue about the origin of the failure. Although the failure-time-circle first suggested
an external distortion source, dc-link problems were the real cause of
the device outages. This reaction was only triggered by some external voltage
events far from limits.
During tripping, high voltage peaks on the WEC output were detected
by the protection devices. Current increase up to short-circuit values, followed
by the shutdown of the WEC were measured on some turbines, see
Fig. 34.3a,b. These results show, that the external effects may only trigger an
internal device problem.
34.4 Conclusions
The measurements show, that the allocation of failures to internal and external
sources causes some effort. This is not always acceptable for wind park operators
in practice. Such outages reduce the economic efficiency of wind parks
considerably. A detrimental influence on the gear is obvious, but not specified,
yet, by simulations or measurements.
References
1. EN 50160 (2000) Voltage Characteristics of electricity supplied by public
distribution systems
2. IEC 61000-2-12 (2003) Electromagnetic compatibility (EMC) – Part 2–12:
Environment – Compatibility levels for low-frequency conducted disturbances
and signalling in public medium-voltage power supply systems
3. Plotkin Y., Saniter C., Schulz D., Hanitsch R. (2005) Transients in doubly-fed
induction machines due to supply voltage sags, PCIM Power Quality Conference,
November: 342–345
4. Venikow V. (1977) Transient processes in electrical power systems, Moscow, Mir
5. Miri A.M. (2000) Transient processes in electrical power systems (In German:
Ausgleichsvorgänge in Elektroenergiesystemen), Springer, Berlin Heidelberg
New York