High Voltage Engineering
EE 751
Question 93
Question
2075 Bhadra2072 AshwinChapter 4: Insulation Coordination4.3 Insulation Protection Level for Temporary, Switching and Lightning Over Voltages
A 132 kV transmission line is terminated by transformer at a substation. The transformer is protected by an arrester of rating 120 kV located at the incoming line. The BIL of the transformer is chosen to be 500 kV. The protective ratio required for transformer protection is 1.2. Check whether the transformer is properly coordinated with the arrester if a lightning stroke results in the arrester discharge current of 40 kA. Relationship between discharge current and residual voltage:
| Discharge Current | Residual Voltage |
|---|---|
| 10 kA | 300 kV |
| 20 kA | 360 kV |
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