Andreas Nenning has a degree in automation engineering and mechatronics from the University of Applied Science in Dornbirn, Austria. He’s been the product manager for OMICRON’s new circuit breaker test set CIBANO 500, since September 2013. In this exchange with T&D India, Nenning explains in depth how CIBANO 500 and OMICRON’s current sensor measurement (CSM) method help overcome practical difficulties in performing on-site tests on gas-insulated switchgear.
In general, what are the practical difficulties while testing GIS or its components, when compared with conventional (air-insulated) switchgear?
Gas-insulated switchgear (GIS) is often used in applications where space is limited and the current carrying parts are embedded in SF6 gas. On-site testing of GIS is therefore often a challenge as the conductor is only accessible via grounding switches.
When measuring operating times on GIS with grounding on both sides, common test methods don’t deliver reliable results due to the low-ohm ground connections that run parallel to the circuit breaker. For this reason, timing measurements are often conducted with insulated grounding switches where a shunt can be removed to interrupt the low-ohmic parallel measuring path. Yet this carries the risk of capacitive coupling from adjacent components or switchbay sections on the non-grounded conductor part. Therefore, on-site testing using these methods is often impossible or prohibited in many cases.
The circuit breaker test system CIBANO 500 offers a new, alternative method for measuring operating times in GIS – called Current Sensor Measurement (CSM) method. This new method allows the operating times to be determined accurately while the GIS is grounded on both sides.
The ground connections (shunt) on the grounding switch don’t need to be removed and additional components don’t need to be installed. A current sensor just needs to be wrapped around the shunt on the grounding switch. Since these sensors have a flexible design and can easily be installed on a multitude of different grounding switches, they are ideal for on-site applications in GIS installations.
Please explain the role of CSM while testing the operation of a circuit breaker, especially when it is part of a gas-insulated switchgear.
Generally, the circuit breaker test system CIBANO 500 can test all performance-, motion-, as well as coil and motor-related parameters of GIS circuit breakers with the same test setup. The connection to the circuit breaker only needs to be done once. With the optional CB MC2 modules, this can save a lot of testing time, as conventional measuring devices require this wiring to be done at least twice.
When a timing measurement on a GIS breaker must be performed with both sides grounded, CIBANO 500 offers the possibility to use the new current sensor measurement method (CSM).
How does the CSM work in conjunction with CIBANO 500 when it comes to testing of GIS?
The CSM method measures the operating time via an inductive current change measurement using the parallel ground connection or the circuit breaker, while the GIS remains grounded on both sides. In order to do this, the circuit breaker is connected to CIBANO 500 via the CB MC2 accessory. The CB MC2 has a constant current source (e.g., IDC = 200 A) and a measurement channel for the current sensor. The sensor is laid around the ground connection of the grounding switch. The current change that is measured through the ground connection or the circuit breaker is then used to determine the switch response times. The circuit breaker remains grounded on both sides throughout the entire measurement.
Has the CSM-CIBANO 500 technique been launched in India?
The CIBANO 500 circuit breaker test system and the new CSM method are available in India. This product was featured at the recent Indian User Meeting on 1-3 November 2017, in Delhi.
Apart from the CSM and CIBANO 500, what are the innovative testing solutions by Omicron OMICRON for testing of GIS?
After timing measurements or high residual currents with transient DC components, there may be some residual magnetism left over in the GIS’s current transformer. CIBANO 500 also features the “CT Demagnetization” function, which quickly and easily demagnetizes the current transformer after contact resistance or timing measurements.
OMICRON also offers a mobile, scalable high-voltage source and a reliable partial discharge measurement system. This combination allows fast and easy on-site PD measurements on gas-insulated switchgear in the ultra-high frequency range.
Additionally, OMICRON offers a solution to perform voltage withstand tests on GIS in accordance with the IEC 62271-203 standard. It provides test voltages of up to 235 kV on GIS with nominal voltages of 145 kV.
