RMM — partial discharge monitor for stator insulation of MV and HV generators and motors
RMM (Rotating Machine Monitor) is a continuous monitoring system for partial discharges in the stator winding insulation of medium- and high-voltage motors and generators, including those powered from frequency converters. It measures, calculates and records all generally accepted graphical forms of PD presentation and the quantities defined by IEC standards. The data is correlated with operating conditions.
- PD channels
- at least 15 per module, simultaneous data acquisition
- Additional inputs
- 6 × winding RTD, 3 load currents, 3 voltages, 6 × 4–20 mA
- Dynamic range
- 70 dB, from 3 mV to 10 V without gain adjustment
- Phase resolution
- 7.5°
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
According to IEEE and EPRI research, up to 40% of electrical failures of high-voltage motors are related to the stator insulation. The main cause of damage to windings and cables is partial discharge. The RMM connects to PD sensors of any manufacturer, including those already installed on the machine, so new sensors do not have to be purchased. At least 15 independent configurable channels are polled simultaneously.
In addition to the PD channels, there are inputs for six winding RTDs, three load currents, three voltages and six user-defined 4–20 mA signals. Analysis of the motor current signature detects broken rotor bars in induction machines. Data is stored for up to two years on a FIFO basis. Dynamic range is 70 dB (from 3 mV to 10 V) without gain adjustment, band 1–20 MHz, phase resolution 7.5°, memory 8 MB. Power supply 90–264 V AC 47–63 Hz or 100–300 V DC, operating temperature from −40 to 70 °C.
For PD detection, coupling capacitors, GPCS sensors in the earthing circuit, RFCT high-frequency current transformers and the RTD-PD module are used. This module uses the standard winding RTDs in the slots as high-frequency PD sensors deep inside the winding, and together with coupling capacitors it extends the monitoring zone. For turbogenerators, small hydrogenerators and motors, a typical arrangement has two sets of coupling capacitors, one on the line terminals and one in a phase-segregated busduct at least 2 m away, with signals separated by arrival time. Large hydrogenerators need two to four sets across the parallel branches. For correlation with PD, monitoring of winding and ambient temperature, humidity and load current is recommended.
The monitor works standalone, without a connected computer. Communication runs over Ethernet, USB and RS-485 with Modbus, and DNP-3 on request. A Windows program is used for setup, data download and analysis of phase patterns, histograms and trends. For hazardous areas, a stainless steel 316 cabinet with a flange seal is offered, certified to Class I Division 1 Groups B, C, D, Class II Division 1 Groups E, F, G and Class I Zone 1 IIB T4 for temperatures from −20 to 40 °C.
Technical specifications
| PD channels | at least 15 per module, simultaneous data acquisition |
|---|---|
| Additional inputs | 6 × winding RTD, 3 load currents, 3 voltages, 6 × 4–20 mA |
| Dynamic range | 70 dB, from 3 mV to 10 V without gain adjustment |
| Phase resolution | 7.5° |
| Measurement band | 1–20 MHz |
| Power supply | 90–264 V AC (47–63 Hz), 100–300 V DC |
| Operating temperature | from −40 to 70 °C; in the explosion-proof cabinet from −20 to 40 °C |
| Data storage | up to 2 years (FIFO), memory 8 MB |
| Explosion-proof version | Class I Div 1 Groups B, C, D; Class II Div 1 Groups E, F, G; Class I Zone 1 IIB T4 |
| Communication | Ethernet, USB, RS-485 (Modbus); DNP-3 on request |
Request a price and lead time
RMM — partial discharge monitor for stator insulation of MV and HV generators and motors. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Questions and answers
Can the RMM be connected to PD sensors that are already installed?
Yes, the monitor works with PD sensors of any manufacturer, including those already fitted to the machine. Coupling capacitors, GPCS sensors, RFCT transformers and the RTD-PD module are also available.
Is the RMM suitable for motors powered from frequency converters?
Yes, the monitor checks the stator insulation of medium- and high-voltage motors and generators, including those running from frequency converters. Measurement band 1–20 MHz, dynamic range 70 dB.
Is there an explosion-proof version of the RMM?
Yes, in a stainless steel 316 cabinet certified to Class I Division 1 Groups B, C, D, Class II Division 1 Groups E, F, G and Class I Zone 1 IIB T4. The temperature range for this version is from −20 to 40 °C.
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