Capacitor Fuse Fail Detector

Exhibitor: Katie-Jayne Illing

Supervisor: Tapan Saha

Research Group: Complex and Intelligent Systems

Industry Sector: Energy and Utilities

Capacitor banks are applied in transmission and distribution systems to minimize reactive power transfer, and also to stabilize and maintain voltage levels [1]. Each phase of a capacitor bank comprises a number of capacitor cans connected in series and parallel. Each can is built up of series and parallel connected internal elements. The dielectric materials of capacitor elements are very often subject to electric fields of the order of 55 – 60V/μm [2]. Given these very high stresses, the risk of dielectric breakdown in service is a reality and an adequate protection system must therefore be employed.

Existing balance protection schemes are based on current level detection. Balance protection settings are not sensitive enough to detect the failure of a single capacitor element. Instead, balance protection schemes detect the cumulative affect of a number of capacitor element failures. However, failures of elements in opposite quadrants have a cancellation affect on the balance current level. It is therefore possible that existing protection schemes may not trip the bank until the number of element failures reaches a critical level that could lead to the explosion of a faulty capacitor can or cause damage to healthy cans in parallel to the failed can.

This thesis details the design, development and implementation of a system to detect, record and alarm the failure of a single capacitor element in capacitor banks. The hardware and software has been specifically designed for the ‘Ross’ filter capacitor banks in Townsville, North Queensland, but this system could also be used for other shunt capacitor banks.

[1] Moore, B., Advanced Power System Protection. Queensland: School of Electrical and Electronic Systems Engineering, QUT, 2001. [2] ASEA KABEL AG, Power Capacitors with Internal Fuses. Sweden: REPRO PRINT AB, 1985.

Thesis Document (PDF)