- +61 7 3374 2877
- Email Us
Menu
It was November 1996 when I wrote my first editorial in PTD introducing the first “multi-method” earth tester from Norma Instruments of Austria.
It was about to revolutionise earth testing by allowing “in-service” earth resistance measurement.
Benefits of the Multi-Method Earth Tester
Prior to that time is was necessary to de-energise a distribution substation, separate the connections to the earth electrodes and measure the earth resistance by the time honoured 3 or 4-pole fall of potential method, then reconnect and re-energise the substation.
The new technology eliminated the need for planned outages for all types of distribution substations including SWER and saved utilities many hours of work and reduced inconvenience to customers.
The concept was extended to measuring the footing resistance of transmission towers. The new method was to fit a very large split core CT around each leg and by measuring the component of test current flowing through each leg in turn, the resulting resistance of each leg could be summated as four parallel resistances.
Complicated but a lot faster, easier and safer than the old practice of climbing the tower, isolating the overhead earth while the ground crew measured the earth resistance by the traditional method.
The technology was just what utilities needed and they purchased hundreds.
This and other products from LEM-Norma were the basis for the establishment of Pacific Test Equipment 3-years later in November 1999.
While the original instrument of 1996 is well and truly obsolete and the LEM-Norma company no longer exists, the multi-function earth tester technology has been refined by AEMC and Sonel and continue as industry favourites as the 6471 and MRU-120HD.
The laborious split-core method of tower resistance measurement was updated with the Ground-Flex using four Rogowski Coils to wrap around each leg to measure and summate the tower resistance in a few seconds!
While it was earth testing innovation that kick started Pacific Test Equipment, other new technologies were soon to be added.
