Line capacitors are used ubiquitously for voltage regulation, power factor correction, and reactive power management on distribution circuits. Utility companies spend considerable money installing and maintaining these banks. Capacitor banks are widely known for experiencing internal short circuits, fuse operations, and other failure modes.
As part of ongoing projects at Texas A&M University, researchers have documented multiple, real-world failures and other improper behavior of line capacitors. They also have documented the unique electrical current and voltage waveforms signatures these failures produce, as measurable from conventional, substation-based current and potential transformers. The resulting database contains many examples of failures detectable by conventional utility inspection and testing practices, but also many examples of failures not detectable by those conventional methods. Some failure modes can have consequences more deleterious to system health than simple loss of voltage support, voltage balance, or reactive power support. Based on the field experience and library of electrical signatures, researchers have developed a system known as Distribution Fault Anticipation (DFA) technology, which detects and warns utilities about a variety of line apparatus failures and pre-failures, including those involving capacitors, thereby enabling system condition awareness and condition-based maintenance for circuit apparatus, including capacitor banks.
This paper presents selected case studies from operational circuits, and describes the benefit of using DFA technology to detect capacitor problems in their pre-failure state, enabling timely repair.