The testing of the quality of the grounding (G) of power transmission towers poses a serious problem as they are all electrically inter- connected by means of Ground Wires which act as lightning rods, protecting the lines from atmospheric discharges.
Because of this connection, any attempt to measure a tower grounding (G) resistance using a conventional earth meter leads to incorrect results as what is really being measured is all the shunt towers grounding (G) resistance (or more precisely, its impedance at low frequency). Trying to disconnect the ground wire from an energized line is a risky operation due to the need to climb the tower to its highest point as well as the close proximity of the high voltage conductors.
The ER25K grounding resistance meter for high frequency makes this kind of test feasible, which is of vital importance to ensure the transmission of electrical power without interruptions. It is the appropriate tool for fast, safe, and reliable grounding resistance measurement in each tower of a working line transmission, without disconnecting the ground wire.
The ER25K is based on the use of a high frequency measurement current (25 kHz), for which ground wire inductive impedance – taking into account a typical length span is reasonably high, making it possible to reduce the effect of the adjacent towers under measurement. The ER25K measures only the ground resistance of the surveyed tower, including its base. The extensive G system, such as meshes, buried wires, metal pipes, are measured only considering the closest section to the connection point. The measured value represents the performance, against a pulse signal similar to an atmospheric discharge. Values obtained better represent the system capacity to ground lightning currents than the ones obtained with low frequency conventional equipment, even when disconnecting the ground wire.
The test is performed by making current of a known-value flow through the earth diffusion resistance and an auxiliary electrode, called the current electrode, and by measuring the voltage produced between grounding and another auxil-iary electrode thrust into the ground in the area of the potential created by flowing current (Potential Plateau).
The current injected by the earth meter is automatically adjusted to the predetermined value and the equipment and it directly indicates the resistance value on its ohms-grades scale.
Bluetooth interface and software gives you the capability to save photos of the towers and their GPS coordinates, plus record voice comments for each measurement.
Testing Applications
Used for measuring earth resistance of electrical pylons. The influence of adjacent pylons is minimized by a Guard cable connection.