General Electric Company

Electric Power Research Limited

Josef Urbanek

Einar Vaughn Larsen

Kara Clark

Larry E Bock

John Charles Hill, Jr

Murray A Eitzmann

David S Birrell

Sandeep Nyati

This series-capacitor compensation equipment comprises a series-capacitor bank in series with a power line and an overvoltage protection circuit for the capacitor bank comprising the series combination of a surge arrester and electric bus structure connected in series with the power line and in parallel with the capacitor bank. The surge arrester includes metal-oxide varistor elements which impart a relatively high resistance to the arrester when the voltage across the arrester is in a normal range and a relatively low resistance when the voltage across the arrester rises to a predetermined value that produces arrester operation. The capacitor bank will discharge through the overvoltage protective circuit should a varistor element fail during arrester operation. The bus structure comprises stainless-steel bus conductor having a resistance that is sufficiently high to effectively limit the energy duty on the arrester during discharge of the capacitor bank through the overvoltage protection circuit in the event of failure of a varistor element during arrester operation.

Series-capacitor compensation equipment

This overvoltage surge arrester has a tubular porcelain housing having a bore, metal terminals at opposite ends of the porcelain housing, stacks of metal-oxide varistor disks located within the housing in angularly-spaced relationship about the bore, and venting means within the terminals for venting gases from the housing should an electric arc develop within the housing as a result of failure of a varistor disk. First liners of electrical insulating material having relatively high thermal conductivity are sandwiched between the stacks and the bore for providing effective heat transfer between the stacks and the porcelain housing. Additional liners are disposed on the bore in locations angularly between the first liners. These additional liners are of a thermal and electrical insulating material, a major portion of which is a ceramic selected from the group of alumina, thoria, zirconia, zircon, and spinel. This thermal and electrical insulating material has a relatively low thermal conductivity and low ablation compared to the material of the first liners and is collapsible in response to arc-produced pressures developing within said porcelain housing, thereby protecting the housing from pressure and temperature shock waves developed by the arc.

Overvoltage surge arrester with means for protecting its porcelain

A thyristor controlled series capacitor (TCSC) system, including a method and apparatus, uses phase controlled firing based on monitored capacitor voltage and line current. For vernier operation, the TCSC system predicts an upcoming firing angle for switching a thyristor controlled commutating circuit to bypass line current around a series capacitor. Each bypass current pulse changes the capacitor voltage proportionally to the integrated value of the current pulse. To damp the natural oscillatory response of the inductive commutating circuit and the capacitor, a bypass mode firing angle is introduced to create a nonlinear response. The harmonic distortion on the commutating circuit current waveform is determined from the capacitor voltage, which is then used to determine the magnitude of the firing angle. Preferably the firing angle magnitude decreases in response to decreasing capacitor voltage, eventually returning to steady-state conditions.

Transient damping thyristor controlled series capacitor system

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Media, PA, United States of America

Josef Urbanek