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Effective and Safe Testing of GIS Switchgear

By Christian Studen
switching times on medium and high voltage Gas Insulated Switchgear

To fully assess the functionality of medium and high voltage circuit breakers, various mechanical and electrical parameters must be tested. Gas-insulated switchgear (GIS) in particular poses unique and special challenges, including the connection of the test equipment. In today‘s world, where testing is increasingly performed in a non-invasive manner, test systems must offer a certain flexibility and a wide range of testing solutions in order to get proper results in a timely manner.

Passive determination of switching times for gas-insulated medium-voltage switchgear
Normally, the breaker operating time and the contact resistances are measured on medium-voltage breakers. In addition, corresponding travel curves are also recorded in order to obtain conclusions about the state of the entire mechanism. For Contact time, the connection of the measurement leads is made directly to the main contacts or to easily accessible points such as busbars.
In gas-insulated medium-voltage installations, there are hardly any possibilities for attaching the measurement leads to the main contacts of the circuit-breakers. The connection could possibly be made via reserve panels, or, other components. If the installation is currently under construction and initial commissioning tests are to be carried out, there are usually ways of performing the tests in the conventional way. That is, testing is performed before the gas is in place, and, the enclosure is closed, so the main contacts are still accessible. However when the system is in operation, and, tests are to be carried out, the costs and benefits of are disproportionate. To perform a conventional test, one must completely isolate the breaker, and, must remove the gas. This can take multiple days. The conventional measuring method in gas-insulated medium-voltage switchgear is simply uneconomical. KoCoS offers a measuring method using the ACTAS switchgear test systems and external sensors which enables this type of system to be tested at a reasonable cost. As the system does not need to be isolated, the measurement procedure is even less time consuming than testing a non-gas-insulated medium-voltage switchgear using the conventional measurement procedures. The VDS (Voltage Detection System) installed in the systems is used to measure the switching times. These are capacitive measuring points for voltage indicators or integrated capacitive voltage indicators according to VDE 0682-415 or IEC 61243-5. If no voltage transformers are installed, these measuring points are the only and safe way to establish a connection to the main contacts of the circuit breakers.

Read full article in the Special SUBSTATIONS Issue

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