Protective relay travelling wave fault location

January 18th, 2016, Published in Articles: Energize

 

For decades, various versions of the Takagi algorithm have been used by microprocessor-based relays for fault location. This system provides accurate fault location, limited by nonhomogeneous infeed, load flow, fault resistance, and series-compensated or parallel lines. With the emphasis placed on reliability in today’s power systems, the need for improved accuracy in fault location has increased.

Cases involving transmission lines spanning rivers or large valleys mean that a small error in fault location can force maintenance crews to spend added hours, or days, to find broken insulators or other faulted line components. Travelling wave fault location overcomes the issue of measuring distance using high-frequency fault transients measured from a single line end or both line ends. The complications that have to be overcome include connections to protect current transformers and voltage transformers, filters on incoming circuits to avoid surges and spikes, and processing both power system frequencies (1 Hz to 3 kHz) and travelling wave transient frequencies (10 kHz to 600 kHz) all in the same device.

Fig. 1: CVT frequency response.

Fig. 1: CVT frequency response.

This article discusses the implementation and application aspects of travelling wave fault location in protective relays. Performance limitations are discussed, as well as system requirements and practical installation considerations.

A complete travelling wave fault location system includes more than just the detection of the travelling wave itself. The practical aspect of adding this capability without multiplying entire measuring systems means it needs to be combined with existing devices… (more)

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