Self-adaptive transformer differential protection

• Published in: IET generation, transmission & distribution Vol. 7; no. 1; pp. 61 - 68
• Main Authors: Zhang, Wenkui, Tan, Qian, Miao, Shihong, Zhou, Liangsong, Liu, Pei
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering and Technology 01.01.2013; Institution of Engineering and Technology; The Institution of Engineering & Technology
• Subjects: Applied sciences; Connection and protection apparatus; Constraints; Criteria; differential relays; Electrical engineering. Electrical power engineering; Exact sciences and technology; external faults; Faults; fixed predetermined characteristic curve; internal faults; knee point; percentage restraint differential criteria; pickup current; Power electronics, power supplies; power transformer protection; Protective; protective relay; relay protection; restraint coefficient; restraint current; Security; security improvement; self‐adaptive transformer differential protection; self‐regulation; sensitivity improvement; slope characteristic; Transformers; Transformers and inductors; sensitivity improvement; internal faults; slope characteristic; differential relays; knee point; fixed predetermined characteristic curve; restraint coefficient; percentage restraint differential criteria; relay protection; external faults; pickup current; self-adaptive transformer differential protection; self-regulation; power transformer protection; protective relay; restraint current; security improvement; Relay; Regulation(control); High sensitivity; Differential protection; Transformer protection; Protective device; Relay protection; Power electronics; Safety; Power transformer; Damage prevention; Operating conditions
• ISSN: 1751-8687; 1751-8695; 1751-8695
• DOI: 10.1049/iet-gtd.2011.0739

Setting the pickup current and slope of differential relays of power transformer protection is a well-known compromise. It has been the focus of study to improve both the security and sensitivity of transformer differential protection recently. However, it is difficult to achieve a high degree of security and sensitivity at the same time by conventional percentage restraint differential criteria based on a fixed predetermined characteristic curve. Therefore a novel adaptive protection criterion is proposed in this study, which can self-regulate the parameters of percentage differential characteristic (e.g. pickup current, restraint coefficient and restraint current at the knee point of the slope characteristic) on the basis of operating conditions of power transformers. The test results show that the proposed scheme provides a high operating sensitivity on internal faults, while retaining higher security on all external faults. Furthermore, because of self-regulation of the setting values of relays, it is more convenient for engineers in the field who only need to give the upper and lower limits but not the exact value of the settings of protective relay.