Page 166 - Practical Power System and Protective Relays Commissioning
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166 Practical Power System and Protective Relays Commissioning
FIGURE 16.4 Sequence network representation.
16.3.1 Power Transformer, Generator, Cables, Transmission
Lines Sequence Networks
A power transformer can be represented as Z% between a high- and low-
voltage terminal regardless of voltage level, as shown in Fig. 16.5.
Refer also to Figs. 16.6 and 16.7, respectively, for two-winding and
three-winding transformer sequence network representations.
Refer to Fig. 16.8 for an autotransformer with tertiary winding sequence
networks.
Refer to Fig. 16.9 for earthing transformer sequence networks:
16.3.1.1 Conclusion
Transformer sequence impedances are described here.
Positive-sequence impedance:
Z 1 5 Z% (transformer percentage impedance)
Negative-sequence impedance:
Z 2 5 Z% (transformer percentage impedance)
Zero-sequence impedance:
Refer to Fig. 16.10.
Cable sequence impedances are described here.
Positive-sequence impedance:
Z 1 can be calculated or determined by testing.
