Preamplifers & Preacquisition Units

For measuring noise mitigation

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 RPA1DRPA1ERPA1F, 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.

TypeFrequency RangeInput ImpedanceSensitivity InputRoll-OffBipolarRemarks
RPA140 kHz - 800 kHz10 kΩ//50 pF<200 µV40 dB/decYesStandard preamplifier
RPA1D40 kHz - 800 kHz10 kΩ//50 pF<200 µV40 dB/decYesBuilt-in sensor supply, switchable (15/28 V)
RPA1E40 kHz - 800 kHz10 kΩ//50 pF<200 µV40 dB/decYes0/20 dB attenuation
RPA1G40 kHz - 800 kHz10 kΩ//50 pF<200 µV40 dB/decYesBuilt-in sensor supply, switchable (Off/15/28 V)
RPA1H40 kHz - 20 MHz1 kΩ//50 pF<400 µV40 dB/decYesOil/paper cable, DSO
RPA1L40 kHz - 20 MHz1 kΩ//50 pF<200 µV40 dB/decYesCable, DSO
RPA22 MHz - 20 MHz50 Ω//50 pF<800 µV40 dB/decOnline measurements on rotating machines
RPA2B2 MHz - 20 MHz50 Ω//50 pF<200 µV40 dB/decCable sensors
RPA3200 MHz - 1 GHz50 Ω//50 pF<300 µV40 dB/decGIS sensors
RPA3D50 MHz - 400 MHz50 Ω//50 pF<300 µV40 dB/decNearfield detection
RPA3E20 MHz - 200 MHz50 Ω//50 pF<300 µV40 dB/decNearfield detection
RPA440 kHz - 800 kHz10 kΩ//50 pF<200 µV40 dB/decYesFiber optic insulation

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 µV40 dB/decFor gating, selectable frequency range, logarithmic output
FCU100 MHz - 1.8 GHz50 Ω//50 pF<200 µV40 dB/decLogaritmica output
UHF1200 MHz - 1 GHz50 Ω//50 pF----GIS sensors
UHF2300 MHz - 2 GHz50 Ω//50 pF----GIS sensors
HSTB20 Hz - 400 Hz10 MΩ//200 pF----YesICMsystem, SYNC IN

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