The GGT500 ground grid integrity tester is designed for inspection of the substation ground grid. It can also be used as a portable micro-ohmmeter with Both Sides Grounded and Remote Control functionalities. It is intended to inspection the conditions of a grounding system beneath substations, testing of medium- and high-voltage circuit breakers, disconnecting switches, high-current bus bar joints, cable splices, and different high-current links.
In the United States when inspecting the quality of the grounding systems beneath a substation, the proper procedure is to inject 300 A DC during a time period of 60 s. This is what the GGT500 will do, and in that time period, the current path and voltage drop are checked. Also acting as a micro-ohmmeter, the GGT500 can test low resistance values by producing high test currents of up to 500 A.
The instrument is placed in an unbreakable, plastic case with IP67 protective rating (with closed lid). Although very portable and lightweight, micro-ohmmeters have very high output power capabilities. High output voltage enables a wider measurement range at higher test currents, as well as the use of thinner/longer test cables. GGT500 generates a true DC ripple-free (less than 1 % ripple) current with automatically regulated test ramps. This significantly decreases magnetic transients and ensures great accuracy.
When used for testing in Both Sides Grounded conditions, a special current clamp powered from the instrument is used for measuring a current through groundings. If even a higher safety level is required, the remote control feature enables the operator to perform measurements from a distant location, away from the instrument and test object.