Externally Gapped Line Arrester with Segmented Sparkover Gaps

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Solution Overview

Problem

Designing an externally gapped line arrester (EGLA) that effectively handles lightning-induced flashovers without overloading the series varistor unit (SVU) and ensures the transmission line remains operational, especially at higher voltages, is challenging due to conflicting requirements for sparkover during lightning and switching impulses.

Innovation Solution

Incorporating a secondary series gap that only activates when the SVU is out of function, allowing the primary gap to handle lightning and switching impulses while preventing sparkover during power frequency temporary overvoltages, and using a disconnecting device with an explosive charge to visually indicate SVU status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single gap is used in the traditional EGLA design, then the structure is simple, but it is difficult to meet conflicting sparkover requirements for different impulse types

Engineering Contradiction:

ImproveEGLA structure simplicityVSAvoidsparkover performance for different impulses

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The gap is divided into two separate series gaps: a primary sparkover gap unit (G1) configured to sparkover for lightning impulses, and a secondary gap (G2) configured to prevent sparkover for switching impulses. This segmentation allows each gap to be optimized for its specific function, resolving the contradiction between preventing SVU overload during switching and ensuring reliable sparkover during lightning events.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design enhances the EGLA's ability to manage switching impulses without flashover, even at ultra-high voltages, ensuring the transmission line's reliability and safety by preventing unnecessary sparkover and providing a visual fault indicator for operational status.

Implementation Method 1

the primary sparkover gap unit configured to sparkover for lightning impulses

Methodology Applied

Scientific EffectElectrical breakdown (sparkover): Electric Spark

Implementation Method 2

The disconnecting device may comprise an explosive charge with a passive trigger

Methodology Applied

Scientific EffectExplosion: Explosion

Data Source

PatentEP3629430B1Externally gapped line arrester

Publication Date: 2022.11.02 HITACHI ENERGY SWITZERLAND AG

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AI summary

Embodiments presented herein relates to an externally gapped line arrester, EGLA, for transmission lines. The EGLA comprising a series varistor unit, SVU, (1) having a first end and a second end, the SVU configured to be connected between a transmission line and ground, a primary sparkover gap unit (8) serially connected to the first end of the SVU, a secondary gap arranged between the second end of the SVU and ground, and the secondary gap serially connected to the second end of the SVU, a shorting-link device (3) connected in parallel with the secondary gap, and a disconnecting device (4) arranged in the shorting-link device, the disconnecting device configured to open the shorting-link device when the SVU is overloaded. A method for impulse protection performed by an EGLA is also presented.