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A Spanish research group has developed an inductive sensor that can detect and measure partial discharge that are characteristic in electrical machines (its analysis allows to estimate the aging degree of the internal insulation).
The sensor can take real measures without galvanic contact with the tested machine, in situ and in real operation without stopping the machine, which facilitates an advanced and scheduled maintenance. The research group is looking for license agreement.
The inductive sensor sensor can take real measures
without galvanic contact with the tested machine, in situ and real operation without stopping the
machine, which facilitates the advanced and scheduled maintenance. Furthermore, its low-cost design
allows replacing expensive items used in traditional techniques.
Partial discharges are an
unavoidable well known problem. They are current pulses of small amplitude and short duration, due
to degradation or breakage of the insulating materials of lower dielectric strength, where the
electromagnetic field is intensified.
The classical analysis of partial discharges PRPDA
(‘Phase-Resolved Partial Discharge Analysis’) relates the number of partial discharges, apparent
charge and position relative to the power cycle. This method connects, in parallel to the tested
machine, a coupling capacitor in serial with one impedance where pulses are detected. It requires a
galvanic connection, it is very sensitive to noise and its bandwidth is small. For PRPDA, the
analysis is enough, but not to evaluate the temporal evolution of the pulses. The solution in the
laboratory is complicated and it requires adjustments. The impedance can be replaced by a very high
frequency intensity transformer, which improves bandwidth and avoid galvanic contact, in exchange
for excessive volume, weight and cost of the sensor.
The developed sensor solves these problems,
and it is a very effective and economical alternative.
The design is based on inductive coupling
of one or more coils arranged in the plane of the tested wire, either an internal wire or the power
cord of the tested machine. The response is linear and it faithfully reproduces the temporal shape
of the pulses.
The inductive coupling is inherent to the design, it has enough sensitivity and
provides galvanic isolation to any measuring apparatus connected to the sensor.
Another advantage
is its low cost and volume, so the sensor can be embedded on the machine even since its
construction. Providing an external connection to the sensor, a measuring device may be connected
when the electrical machine is running, without stopping it for making connections or transporting
to a laboratory, which would alter the normal operation.
Continuous monitoring without service
interruption is very attractive to analyze the operation in situ. This allows the anticipated and
scheduled for less harmful times maintenance. In addition, this avoids the cost associated with
unscheduled service interruptions when using other methods.
The electrical response of the sensor
depends on three geometrical aspects: length, width and distance from the electrical machine wire.
Its design allows the adaptation to different needs for bandwidth, frequency band and desired
sensitivity.
Finally, it is noteworthy that the structure of the sensor performs effective
filtering of the primary and secondary harmonics induced from the main power. So it is not needed a
specific filter in the subsequent measuring apparatus.
Innovative Aspects:
- The sensor faithfully
reproduces the waveform of the partial discharges with time resolution.
- It eliminates the galvanic
contact with the measuring apparatus.
- It replaces elements of much higher cost and complex
adjustments.
- It has reduced size and weight, and it is inexpensive.
- It can be embedded on the
machine since its manufacturing.
- It allows tests in real time operation without service
interruptions (avoiding the associated costs).
- It allows scheduling maintenance in those less
harmful times.
The advantages for any company are in the improvement of maintenance processes and
associated costs:
- It is not necessary to interrupt service.
- Monitoring can be continuous and in
real operation, without transfer to the laboratory.
- The maintenance can be scheduled in those less
harmful times of the service.
- The unscheduled service interruptions are less probable.
- The cost
of the sensor is much smaller compared to other solutions.
- Its bandwidth is appropriate for new
identification and diagnosis techniques being developed recently.
Stage of Development
Available for
demonstration - field tested
Exploitation of RTD
Results
National Programmes
IPR
Patent(s) applied for but not yet granted
- Spanish application: P200801174. Date: 23-04-2008.
- PCT application:
PCT/ES2009/070093. Date: 7/04/2009
Company Details
Collaboration Type
- Adaptation to specific needs
- License Agreement
- Type of partner sought: Industry
- Specific area of activity of the partner:Utilities, Electrical Equipment Manufacturers (Generators, Motors, Transformers, Cables, Insulation). Electrical Installations Maintenance.
- Task to be performed by the partner sought: license agreement
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