Effective bushing monitoring: A technical guide to avoiding failure and making critical decisions

Abstract Bushing monitoring is an important component of an effective condition monitoring program. Bushings play an important background role in the smooth operation of the...

byTony McGrail


Abstract

Bushing monitoring is an important component of an effective condition monitoring program. Bushings play an important background role in the smooth operation of the power grid, but they are not perfect, and allow for some current to reach the ground: this is called the bushing leakage current. The right monitoring tools and strategy can help record the magnitude and phase of the bushing leakage current and capture information about the state of bushing insulation. This article will address why and how bushing failure occurs and the steps companies can take to protect their systems against bushing deterioration.

Keywords: bushings, failure, condition monitoring, asset health, maintenance

1. Introduction

Bushings, devices that allow conductors to pass through a barrier, may seem like simple and minor components of the power grid, but they are vital parts of the electric supply system – without them, power transformers and circuit breakers would not operate effectively or efficiently, Figure 1. Bushing failure can cause residual effects that could lead to catastrophic impacts on the entire grid structure [1].

Bushings have an insulating medium that must be sustained to prevent the passage of excess current to the ground, but just like any other part of the power grid, bushings are not perfect insulators. Bushing leakage current is the current that flows through the bushing insulation to ground. The right monitoring tools can help measure and record the bushing leakage current, including magnitude, harmonic content and relative phase of the leakage currents in a set of three bushings, which provides information about the state of the bushing insulation. Ongoing monitoring is incredibly important for ensuring bushings effectively do their job.

To read the article, subscribe and choose the option which suits you best. We offer both free and paid options, and the registration takes only a minute.
Subscribe to Transformers Magazine