Users Contributions

Grounding Safety Evaluation of Fault Sequence of Events

Carl Moller, P.Eng

High Time Industries

Introduction

A significant part grounding safety for power substations involves the analysis of the ground fault level and the clearing times. The IEEE 80 includes a computation of time-dependent fibrillation threshold for the human heart based on a fixed energy. As a result, computation of threshold touch and step voltages become dependent on clearing time. The IEEE 80 also includes an asymmetrical offset decrement factor which is a function of both the clearing time and the system X/R ratio. Under real system ground fault conditions in a substation, multiple contributions into the ground fault are cleared at different times due to different protection settings and equipment. All these factors are changing with respect to time throughout the entire fault event sequence. This paper investigates the sequence of events and changing parameters and attempts to develop a philosophy for assessing grounding safety throughout the ground fault event.

Building Grounding Under 240 kV Lines

Carl Moller, P.Eng

High Time Industries

Introduction

The installation of a 100m by 30m office building below six 240kV transmission lines required specialized grounding considerations. The study required consideration of conductive, inductive, and capacitive effects under steady state and ground fault conditions. The erecting of the building including the structural supports, purlins, girts, metal cladding, roof, gutters, downspouts, interior wall studs and service electrical required grounding, bonding and induction analysis during all stages of the construction. Installation and design of the grounding system required specific consideration of circulating currents and inductive effects.

A safe grounding system was developed and installed at the site to ensure public and personnel safety.

Application of Finite Volume Modeling and Soil Measurement Correction

Carl Moller, P.Eng

High Time Industries

Introduction

A practical application of CDEGS finite soil volumes in conjunction with the soil measurement correction is explored in this paper. The proposed methodology for correcting soil resistivity measurements where interference with bare metallic structures presented by SES in the 2010 CDEGS User Group conference proceedings was used in conjunction with CDEGS finite volume soil volumes to evaluate the safety of a substation and generating station grounding system.