Frequency Variable Series Resonant Test Systems For High Voltage Applications
Frequency Variable Series Resonant Test Systems For High Voltage Applications
Application
Frequency variable series resonant test systems are mainly used for on-site dielectric and diagnosis tests of capacitve line equipment as
- GIS/GIL/Switchgear Arrangements
- Power Cables
- Power Transformers
agea-kull series resonant test systems are of modular design with low weight components, especially designed for the requirements of on-site testing. Easy to handle and robust reactors with the possibility of series and parallel connection of more units allows an optimised adaptation of the system to the load capacitance and enables testing of different kind of test objects with the same system.
No special equipment for transportation or erection is required, a small lorry and a low weight crane is enough.
Cable Testing
In difference to other on-site test techniques as 0,1 Hz or DC, resonant test sets generate a voltage stress for the insulation similar to the service condition. This gives the test result more evidence and is nowadays the preferred on-site test method.
GIS/GIL/Switchgear-Testing
The systems cover a wide load range and test frequencies above 100 Hz prevent saturation of the instrument transformer cores. Therefore testing with installed instrument transformers and cable connections is possible.
Transformer Testing
The modular series resonant test systems can be used for applied voltage testing in the factory or on-site. A suitable selection of the system inductance allows testing of typical winding capacitances (8 nF to 12 nF) with frequencies between 45 Hz and 65 Hz.
Partial Discharge Measurements
Different kinds of partial discharge measurements like conventional method, non-conventional method with integrated sensors or UHF-method can be applied with frequency variable test systems
Design of Components
Reactor Coils
The bar core reactors are oil impregnated and built-in a hermetical closed resign cylinder. Up to four units can be stacked to increase the output voltage of the system.
Besides the application as reactors for variable frequency series resonant test systems, they can be used to increase the load range of conventional test systems (partly compensation of the load capacitance at power frequency).
Exciter Transformer
Tank type transformers with surge arrestor protection and automatic grounding are used to excite the resonant circuit. Voltage and power are adapted to the requirements of the system.
Frequency Converter
The converter works with an intermediate direct voltage circuit. The line voltage is rectified and stabilised. A following IGBT-bridge generates a square wave voltage of adjustable frequency between 15 Hz and 250 Hz.
The converter generates only four switching impulses per cycle which do not disturb the PD-pattern or can be suppressed by gating.
Two types of frequency converters are available:
FUE 75 with 75 kVA power
FUE 150 with 150 kVA power
Control Unit / Voltage Measurement
The control unit is integrated in the frequency converter housing and enables automatic and manual operation of the system. An operator panel displays pre-selected and measured parameters.
The high voltage is measured by a built-in peak voltmeter in collaboration with a high voltage divider which is at the same time used as a base load and coupling capacitor.
Transport Frames
Transport frames for easy and safe transportation of one or two reactor coils are available. The upper part of the frame is removable and the lower part can be used as a testing console
