Substation Ground Grid Tester GGT200

A typical application is accurate low resistance measurement of non-inductive test objects such as:

• Earthing systems integrity/continuity test (as per IEEE 80 – 2013)
• High- and medium-voltage circuit breakers test (live and dead tank)
• Circuit breaker contact resistance measurement under BSG conditions
• High and medium voltage disconnecting switches
• High-current busbar joints
• Terminals of the conductors on HV power lines
• Continuity test of protective bonding conductors
• Oil and gas pipelines bonding
• Cable splices, welding joints, fuses, etc.

Test modes

The GGT is supplied with five different modes, GGT, SINGLE, CONTIN, DTR, and BSG. Under SINGLE mode, only the test current can be selected (up to 200 A), and under CONTIN mode, the test duration can be selected as well (up to 10 min). The DTR test mode enables testing of the dead tank circuit breakers, while BSG test mode enables contact resistance measurement of the circuit breakers when grounded from both sides. The GGT mode is implemented for grounding systems integrity/continuity tests (as per IEEE80).

Ground grid continuity and integrity test using GGT

The ground grid integrity and continuity test is described in the IEEE 80 standard, and it is one of the most efficient test methods and techniques for measuring the electrical characteristics of grounding systems. It is also known as a high-current test method, whose purpose is to check the continuity of buried ground conductors and connectors, ground rods, and bonding connections by injecting a high-test current. The integrity of earthing systems is critical to its effectiveness as the key reliability and safety mechanism of the installed equipment and electrical installations.

GGT series design

This micro-ohmmeter is a precise measuring tool that generates a true DC ripple-free current with automatically regulated test ramps. During a test the GGT ramps with increasing current before measuring and decreasing current after the measurement. This significantly decreases magnetic transients and ensures great accuracy. The pass/fail criteria is another feature that can be activated and gives the alarm if the measured resistance value is higher than the set Rmax value.

Test set

When performing a test with GGT, a single pair of current cables should be used, together with the appropriate voltage sense cables. The black marked cable (e.g., 10 m / 33 ft.) is connected to the reference grounding point in the substation (usually the transformer’s grounding). The red-marked current cable (e.g., 50 m / 165 ft.) is connected to the substation ground point under test. Since an operator needs to check several grounding points, it is very practical to use the GGT-M module for setting/changing the test parameters and remote control of the test.