Preamplifiers and preacquisition units serve to condition, filter, and amplify the partial discharge signal to be measured. Because the frequency range in which PD signals are measured is strongly dependent on the preamplifier used, proper selection of a preamplifier is an important part of noise mitigation and can have a strong effect on the appearance of the partial discharge pattern itself.
We provide a complete line of modular preamplifiers for various testing applications. The most significant difference among the preamplifiers is the frequency range in which they detect partial discharge signals. Other features that distinguish one preamplifier from another are options for transparency and on/off switching, unipolar vs bipolar charge detection, and the possibility of galvanic isolation in the test setup.
The external signal conditioning modules and preamplifiers are remote supplied and remote-controlled through a simple coaxial signal cable (RG58). This technique allows the placement of these units close to the sensor or signal source. Furthermore, as these modules act as an impedance converter and line driver, the weak signal source, such as voltage divider or coupling impedance, is not loaded by the cable capacitance or impedance.
This technique also provides enhanced over-voltage protection. All preamplifiers of the RPA series can drive a 50 W cable up to 50 m long.
The RPA1 is the standard preamplifier for measurements in the low-frequency range according to standards such as the IEC 60270. The RPA1D, RPA1E, RPA1F, and RPA1G are variations on the RPA1.
The RPA1D and RPA1G are suited to connect directly to ultra-sonic acoustic sensors. To simplify connection, they provide the selectable power supply for the sensor (15 VDC or 28 VDC).
The RPA1L and RPA1H are intended primarily for measurements on medium- and high-voltage power cables using the ICMcompact.
The RPA2 primarily measures the PD signal spectra found with rotating machines, while the RPA2B is used with capacitive sensors to monitor cables and cable accessories at a higher sensitivity.
The RPA3 module is well-suited for measuring PD signal spectra, detected by sensors and antennas installed with gas-insulated switchgear (GIS).
The RPA4 is a preamplifier set with fiber optic transmission, offering outstanding isolation properties.
The frequency converter unit FCU2 is an ultra-wideband preacquisition unit, covering 100 to 1800 MHz. It has a logarithmic output and is mainly used for GIS applications.
The UHF1 and UHF2 offer amplification of 27 dB in the range from 200 MHz to 1 GHz resp. 300 MHz to 2 GHz, and are suitable for boosting weak signals from GIS sensors.
| Type | Frequency Range | Input Impedance | Sensitivity Input | Roll-Off | Bipolar | Remarks |
| RPA1 | 40 kHz - 800 kHz | 10 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | Standard preamplifier |
| RPA1D | 40 kHz - 800 kHz | 10 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | Built-in sensor supply, switchable (15/28 V) |
| RPA1E | 40 kHz - 800 kHz | 10 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | 0/20 dB attenuation |
| RPA1G | 40 kHz - 800 kHz | 10 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | Built-in sensor supply, switchable (Off/15/28 V) |
| RPA1H | 40 kHz - 20 MHz | 1 kΩ//50 pF | <400 µV | 40 dB/dec | Yes | Oil/paper cable, DSO |
| RPA1L | 40 kHz - 20 MHz | 1 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | Cable, DSO |
| RPA2 | 2 MHz - 20 MHz | 50 Ω//50 pF | <800 µV | 40 dB/dec | Online measurements on rotating machines | |
| RPA2B | 2 MHz - 20 MHz | 50 Ω//50 pF | <200 µV | 40 dB/dec | Cable sensors | |
| RPA3 | 200 MHz - 1 GHz | 50 Ω//50 pF | <300 µV | 40 dB/dec | GIS sensors | |
| RPA3D | 50 MHz - 400 MHz | 50 Ω//50 pF | <300 µV | 40 dB/dec | Nearfield detection | |
| RPA3E | 20 MHz - 200 MHz | 50 Ω//50 pF | <300 µV | 40 dB/dec | Nearfield detection | |
| RPA4 | 40 kHz - 800 kHz | 10 kΩ//50 pF | <200 µV | 40 dB/dec | Yes | Fiber optic insulation |
| RPA6 | 40 kHz - 800 kHz 2 MHz - 20 MHz 200 MHz - 500 MHz | 10 kΩ//50 pF 50 Ω//50 pF 50 Ω//50 pF | <200 µV | 40 dB/dec | For gating, selectable frequency range, logarithmic output | |
| FCU | 100 MHz - 1.8 GHz | 50 Ω//50 pF | <200 µV | 40 dB/dec | Logaritmica output | |
| UHF1 | 200 MHz - 1 GHz | 50 Ω//50 pF | -- | -- | GIS sensors | |
| UHF2 | 300 MHz - 2 GHz | 50 Ω//50 pF | -- | -- | GIS sensors | |
| HSTB | 20 Hz - 400 Hz | 10 MΩ//200 pF | -- | -- | Yes | ICMsystem, SYNC IN |
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