Testing of Electrical Switchgear

To ensure reliability and safety of switchgear and circuit breakers, testing against applicable standards must be done in both R&D facilities for development purposes as well as at independent test houses for certification.

Because of its importance in the economy of a country, a set of strict regulations of how these apparatus should behave, and how they need to be tested, has been defined.

The “Short-Circuit Testing Liaison (STL)” has created an internationally accepted report called “Harmonization of Data Processing Methods for High Power Laboratories”.

This standard describes a set of rules on where and how to measure values in the digitized information.

The Challenge
In an electric power system, switchgear is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect, and isolate electrical equipment. Switchgears are used both to de-energize equipment to allow work to be done and to clear faults downstream.

During measurements in switchgear testing, the contacts will be opened (O), closed (C) and depending on the test type opened(O) again, this is called OC or OCO measurement.

The contacts movement is typically controlled by using electrical signals. These signals initiate the movement of contacts in the mechanical switch for the circuit to be opened or to be closed.

For medium and low voltage switchgear measurements there is often no signal available for registering the exact position of the contacts, therefore the time between the open or close action and the measured moment of contact touch or separation will be determined in a no-load test first.

These variables then later can be used for the full load (short-circuit) tests. To enable harmonized testing in both R&D as certification processes, required analysis routines are fixed in STL routines.

The HBM Solution
The Perception Switchgear application allows easy setup of the testing routine by providing the user with an interface to identify his type of switchgear and type of test.

For the type of switchgear one has the choice for single or three phases, using travel and/or open-close signals and the applicable mains frequency required for some STL calculations.

The corresponding circuit is shown to conveniently select and connect the appropriate DAQ hardware channels and nalizing the setup by choice of required test type and equipment related variables.

Based on selected configuration, all required formulas and equations will be written to the Perception formula database which allows the user to review any calculations used improving test transparency, troubleshooting and auditability. Data display and result tables are automatically populated with most used variables for easy reporting and can be adapted to further application or customer requirement:

Supporting Hardware
The HBM Switchgear testing solution is driven by software, though there is a set of specific hardware needs to safely acquire high voltages and currents in this application, as well as correctly and safely controlling the test procedure itself.

Acquisition
The Genesis Highspeed DAQ hardware ensures capturing all relevant data without missing a single event, especially relevant when performing tests which are potentially destructive to the tested device.

Paired with the 6600 series fiber optic Isolated digitizers the system ensures maximum safety for the operator, equipment and reliable, noise free transmission of measured signals.

Test Control
The BE3200 test sequencer is a high-speed controller providing precise timing for the operation of devices used for testing in low/high voltage and high power laboratories.

For this purpose up to 64 optically-isolated outputs are available, with extensive interlocking and safety features. The timing pattern of the BE3200 can be synchronized to the mains generator, the external mains or derived from an internal timer. The outputs switch on and off in a programmed sequence and are fully synchronized. The synchronization signal tracks the input signal frequency. All outputs and inputs of the BE3200 are fiber optically isolated.

All of this is configurable within the dedicated Perception software section for sequencer control and linked to the discussed switchgear testing application.

For more information visit www.hbkworld.com
Email: sundaresan.sridharan@hbkworld.com