introduction - circuit breaker testing
Switchgear Test Systems / Circuit Breaker Testing
Switchgear devices are situated at the key points of electrical energy transmission and distribution systems.
Their reliability has a decisive influence on the availability, safety and economic efficiency of electricity supply systems.
Only regular, on-site tests can ensure that switchgear devices function perfectly throughout their operational life.
ACTAS test systems provide precise information as to the condition of the chamber and drive unit without requiring them to be opened. The sheer number of parameters to be determined, the wide variety of different types of switchgear equipment in use and the harsh environmental conditions encountered during on-site tests place extreme demands on test equipment.
Comprehensive measurements for switchgear analysis
ACTAS test systems allow comprehensive analysis of all types of switchgear based on a number of factors, including an assessment of the following parameters:
- Status of main and resistive contact
- Status of the auxiliary contacts
- Coil current and voltage
- Operating current of spring-tensioning motors or pump motors
- Pressure, travel and temperature values
- Mechanical main contact travel
The test fulfils all the requirements stipulated in IEC 62271-100 for assessing the mechanical behaviour of high-voltage circuit breakers.
Carrying out tests automatically
Once the device under test has been connected up to the test system, the test plan prepared in advance can be started immediately and run automatically. All the measured values and parameters required are determined during the course of a single test cycle.
The assessment of the measurement results is carried out using saved limit values and is displayed clearly directly in the test monitor.
Reliable operation even in extra-high-voltage environments
The use of tried and tested hardware components and the excellent electromagnetic compatibility of the test systems guarantee their safe functioning, even during on-site tests in extra-high-voltage environments.
A basic accuracy of 0.1% with an absolutely linear frequency response ensures that tests are carried out with extremely high precision. The sampling rates for the acquisition of analog measurement signals can be freely selected between 100 and 15000 Hz; the resolution is 16 bit.
External PC control for high flexibility and easy operation
ACTAS test instruments are controlled with ergonomic, easy-to-use software for Windows® operating systems. External opera-tion, independent of the test instrument itself, brings significant benefits, including the possibility of using existing PCs. Not only does this make economic sense, the familiar PC environment also helps users get to grips with the software more easily.
A further advantage is that tests can be prepared and analysed without having to connect a test instrument or even leave the comfort of the office. Once on site, tests can be controlled from outside the danger zone, while the test instrument itself is posi-tioned in the direct vicinity of the
Test plans for efficient test preparation and evaluation
Test plans containing all the necessary switchgear and test parameters can be prepared in full with the aid of the ACTAS operating software. No further settings need to be made on site, the desired test can be carried out without delay. The algorithms and limit values which are needed for automatic evaluation are also saved in the test plan.
Test plans created with the ACTAS software can be used as a templates with any ACTAS test instrument. They can be applied to manual tests consisting of a single test step or to more complex tests which are run automatically.
With the DYNAMIC Timing function, ACTAS manages to combine extended measurement and analysis functions with improved safety and convenience.
DYNAMIC Timing allows tests to be carried out simultaneously on up to six chambers with earthing on both sides, without using ferrite cores or other fault-prone aids. A detailed visualization of contact travel is provided. Even switchgear devices with different contact materials, such as graphite, tungsten or silver, can be tested reliably and precisely with DYNAMIC Timing.
Contact travel visualization
Unlike evaluation based on a simple binary signal, as is used in high-frequency measuring methods, DYNAMIC Timing enables a sound diagnosis of interrupter units throughout the whole switching operation. The result of the measurement is displayed in the form of a curve which visualizes in detail all the events of a switching operation. This allows an accurate assessment of the start of travel and the final position of the contacts and even reveals time differences between the move-ments of the main and resistive contacts.
Testing with earthing on both sides
Switchgear equipment should be earthed on both sides when people are in the vicinity in order to prevent danger caused by capacitively coupled voltages from neighbouring components.
However, when switchgear equipment is tested using conventional measuring methods, earthing must be removed on at least one side.
With DYNAMIC Timing, measurements can be carried out with earthing on both sides. Not only does this make tests much safer, it also makes them simpler and quicker because all the steps which need to be taken in order to remove the earth lead are no longer required.
Earthing on both sides in GIS installations
When testing gas-insulated switchgear installations in particular, measuring the breaker contacts with earthing on both sides is problematic.
ACTAS uses the possibility of determining current differences during the switching operation to solve the problem. The constant current sources of the DYNAMIC Timing function are connected to the interrupter unit for this purpose. The current in the earth leads is measured with high-accuracy current sensors and used for calculating the operating times.
Assessing the interrupter unit by analysing contact resistance
Regular measurements of the static and dynamic contact resistance allow accurate assessment of the state of the whole contact system, enabling maintenance requirements to be identified at an early stage and down times to be kept to a minimum.
Contact resistance measurements can be carried out on three poles with KoCoS PROMET ohm meters and can be incorporated within the test procedure. The test current can be set to a maximum of 600 A. Even very low resistance values in the single-digit micro-ohm range can be measured extremely accurately. The measured values are used in the evaluation of tests and are included in the test report.
A high contact resistance within a switchgear device leads to high power loss coupled with thermal stress which can poten-tially cause serious damage to the switchgear device. Problems, such as high transfer resistance resulting from poor connections, can be identified by measuring static contact resistance.
Dynamic contact resistance measurements can be used to determine the resistance characteristic during a freely definable switching operation. Measurements of this type give an indication of the length and state of the arcing contacts of high-voltage breakers, for example.