RATIO DIFFERENTIAL RELAY FOR TRANSFORMER PROTECTION

RATIO DIFFERENTIAL RELAY FOR TRANSFORMER PROTECTION

PURPOSE:To obtain a ratio differential relay for transformer protection in which a discrimination can be made accurately between internal fault current and excitation surge current when a transformer is thrown into a system by determining ' the content of second harmonic in the basic wave of ex...

Ausführliche Beschreibung

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Bibliographische Detailangaben
1. Verfasser: ISHIZAKI YOSHIAKI
Format: Patent
Sprache:eng
Schlagworte:
CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
ELECTRICITY
EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
GENERATION
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Beschreibung
Zusammenfassung:PURPOSE:To obtain a ratio differential relay for transformer protection in which a discrimination can be made accurately between internal fault current and excitation surge current when a transformer is thrown into a system by determining ' the content of second harmonic in the basic wave of excitation surge current accurately. CONSTITUTION:Only basic wave and second harmonic are passed through first to third filters 7-13 and subtractors 14, 15. A comparator 16 then calculates the content of second harmonic with respect to the basic wave thus making a decision whether it is an excitation surge current or not.