# 스코트 변압기 보호계전기 오동작 사례분석 및 개선방안 고찰

• Lee, Jong-Hwa (Department of Railroad Electrical System Engineering, Woosong University) ;
• Lho, Young-Hwan (Department of Railroad Electrical System Engineering, Woosong University)
• 이종화 (우송대학교 철도전기시스템학과) ;
• 노영환 (우송대학교 철도전기시스템학과)
• Accepted : 2017.07.07
• Published : 2017.07.31
• 41 5

#### Abstract

In Korean AC power railway substations, SCOTT winding transformers are under operation to have a single phase power supply together with a phase angle of $90^{\circ}$ on the secondary side of the main transformer. In the case of an internal fault of the transformer, the transformer protection relay should be cut off on the primary side, the transformer should be inoperative to the external fault of the transformer or to the normal train operation. Reducing the malfunction of the relay through an exact fault determination is very important for securing a stable power system and improving its reliability. The main transformers are protected using Buchholtz's relay and a differential relay as the internal fault detection devices, but there are some cases of the main transformer operation under the deactivation of this protection function due to a malfunction of the differential relay. In this paper, the characteristics of the SCOTT transformer and differential relay as well as the malfunctioning of the protection relays are presented. The modeling of the SCOTT transformer protection relay was accomplished by the power system analysis program and the Comtrade file from 'A substation', which was used as the input data for the fault wave, and the harmonics were analyzed to determine if the relay operates or not. In addition, an improvement plan for malfunctioning cases through wave form analysis is suggested.

#### Keywords

Buchholtz's relay;differential relay;malfunctioning;protection relay;railway substations;SCOTT

#### Acknowledgement

Supported by : 국토교통부

#### References

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