Gas-Insulated Switchgear Testing
Compact gas-insulated switchgear (GIS) represent a space-saving alternative to classic air-insulated installations. The low insulation distances are guaranteed by the high dielectric strength of insulating gas, the most common of which is sulfur hexafluoride (SF6). A perfect condition of the GIS is essential for its reliable operation. A GIS malfunction would be a calamity and therefore tests are inevitable to make such an event as unlikely as possible.
Solutions
Visual Inspections (GIS)
Show moreVisual Inspections (GIS)
Visual inspections are among the most used test methods worldwide. These inspection tasks usually take a considerable amount of time due to the manual process. Test device software with integrated visual inspection tests can support the process by providing highly configurable check lists and the possibility to easily attach pictures to the final test reports.
Voltage Withstand Test (GIS)
Show moreVoltage Withstand Test (GIS)
Voltage withstand test voltages are primarily sinusoidal AC voltages above rated voltage. Originally, this dielectric test was a go/no-go test, where the test object either passed the test or it broke down electrically. Later, more sophisticated diagnostic tools were introduced. Today, the parallel measurement of partial discharges has become an indispensable tool.
Partial Discharge Measurement (GIS)
Show morePartial Discharge Measurement (GIS)
Partial discharge measurement is one of the most important tools for GIS insulation condition assessment. During the test, a high voltage is applied to the insulation and the inception and extinction of partial discharges is being noted. Partial discharge (PD) in gas insulated switchgear is a leading indicator that a fault is going to occur and immediate action needs to be taken. A GIS failure would be a calamity.
Circuit Breaker Operation Time (Off-Service) (GIS)
Show moreCircuit Breaker Operation Time (Off-Service) (GIS)
For measuring GIS operating times we recommend the Current Sensor Measurement (CSM) method. With this method, the ground connections on the grounding switch do not need to be removed and the GIS remains grounded on both sides. The operating time is measured via an inductive current change measurement using the parallel ground connection of the breaker. The current change that is measured through the ground connection is then used to determine the switch response times.
Circuit Breaker Operation Time (In-Service) (GIS)
Show moreCircuit Breaker Operation Time (In-Service) (GIS)
In-service testing methods First trip and Voltage Based Timing (VTM) show degradation accumulated during long idle times better than their off-service counterparts because to prepare a breaker for off-service testing, it has to be operated at least once. For the First trip test method connections are made at the trip coils and the CT’s secondary side. For the VTM measurement method, the connections are made at the trip coils and the VT’s secondary side.
Static Contact Resistance (GIS)
Show moreStatic Contact Resistance (GIS)
The static contact resistance belongs to the most important tests on circuit breakers. The test verifies whether the resistance of the current carrying contacts, in particular the joints, allows the flow of rated current within specified losses. The resistance depends on contact surface properties which are the connection points on microscopic level, the contact pressure and the oxidation of the surface.
Dynamic Contact Resistance Measurement (DRM) (GIS)
Show moreDynamic Contact Resistance Measurement (DRM) (GIS)
During dynamic contact resistance measurements, the contact resistance traces are recorded while the breaker operates. These traces deliver information about wear-related problems with the main and arcing contacts within the interrupter chamber. When the contact movement is recorded simultaneously, the length of current carrying part of the arcing contacts can be measured. Arcing contacts commonly burn off and become shorter for each interruption of current.
Coil Current Measurement and Analysis (GIS)
Show moreCoil Current Measurement and Analysis (GIS)
During coil current measurement, the current signature curve of the command coils is being recorded during breaker operation. Deviations detect potential mechanical and/or electrical problems in the trip or close control components in order to prevent their emergence as actual faults well in advance, and extract information about lubrication and latch operation. This measurement can be performed online or offline. The quality of the control voltage supply is also detectable from these tests.
Motor Current Measurement and Analysis (GIS)
Show moreMotor Current Measurement and Analysis (GIS)
This measurement can be applied with circuit breakers equipped with a spring energy storage system and spring release mechanism. During spring drive motor current measurement, the current signature curve of the spring charging motor is recorded. The recording allows for analysis of the inrush and steady-state currents as well as the spring charging time.
Motion Recording and Analysis (GIS)
Show moreMotion Recording and Analysis (GIS)
The motion or contact travel measurement verifies the operating mechanism and the mechanical linkage and can indicate potential mechanical wear. It is used to reveal the performance by evaluating the velocity of the main contacts when traveling through the arcing zone and evaluating the damping when reaching the end of the movement. A variety of condition indicators are computed, such as total travel, contact wipe, velocity, rebound.
Power Factor / Grading Capacitance Measurement (GIS)
Show morePower Factor / Grading Capacitance Measurement (GIS)
Measuring the power factor, or the dissipation factor, also known as the tangent delta (tan δ), provides effective means for verifying the integrity of the insulation condition of circuit breaker components. In particular, the insulation condition of high voltage breaker bushings should be verified with this measurement. If the measurement is performed outside of mains frequency, interferences from nearby live station components can be filtered out and minimized.
CT Performance Measurement
Show moreCT Performance Measurement
Current transformers integrated in GIS can be difficult to test as they are sealed within its steel housing. Nevertheless, a number of measurements should be made in order to determine the magnetization characteristic, the saturation behavior (ALF/FS), the transformation ratio, the accuracy, the polarity, the load, the winding resistance, the withstand voltage and the remanence.
