Effective use of continuity testing to assess grounding system integrity

While continuity based testing is a relatively well accepted method for assessing the integrity of a grounding grid, no specific continuity based test has distinguished itself with practitioners at large. Why this continues to be the case is not completely understood but it is likely a combination of ignorance of more effective procedures and the availability of better instrumentation. This paper reviews the various continuity based methods used for integrity testing and the characteristics required of a test procedure to make it effective at assessing integrity. This is considered primarily due to a lack of review of the various methods and instrumentation available to perform integrity testing. Accurate measurement of resistance in the electrically noisy environment of a power substation is a difficult task. In the case of grounding grid measurements, not only are the noise levels quite high but the resistances to be measured are relatively small, and the absolute significance of a specific measurement can be obscure. In practice the context of any given measurement is crucial to determining the significance of the measurement. While continuity testing can be performed at any power installation this paper concentrates specifically on the integrity assessment of a major substation. Most power utility substations are of a reasonable size, typically a few thousand square meters of real estate, which usually defines the extent of the grounding system and hence the extent of the integrity testing. This paper identifies the obstacles to performing an accurate measurement of resistance in the noisy environment of a power substation, establishing measurement targets and specific instances of poor integrity.