Download Blake Lloyd - IEEE Industry Applications Society

Blake Lloyd, PEng. Fellow IEEE, Director – Product
Development, Iris Power. Mr. Lloyd is an Electrical Engineer with
extensive experience in instrumentation and product development.
In past lives, he worked in software development and then in the
Electrical Research Department at Ontario Hydro, where he was
responsible for conducting research into advanced measurement,
testing, and diagnostic monitoring techniques for rotating machines
and insulation systems. Since co-founding Iris Power in 1990, Mr.
Lloyd has been one of the principle architects of Iris’s line of
diagnostic instrumentation and analysis software for rotating
machine condition assessment. Products include on-line partial discharge monitoring, air gap
flux monitoring, current signature analysis, end-winding vibration, shaft voltage and current
monitoring, as well as several off-line test instruments. Mr. Lloyd has two US patents, and has
published 20 refereed papers in IEEE and CIGRE, as well as over 40 conference papers. He
has been a Member of IEEE since 1985 serving in the following capacities:
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1992-1994 - Committee Member – IEEE/PES Hydro-generator Subcommittee
2002-2003 – Canadian Expert – IEC Technical Committee 2: Rotating Machines, WG
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2006-2007 - Chairman - IEEE/IAS Pulp and Paper Technical Committee
2008-2009 – Chair IEEE/IAS Executive Board Electronic Communications Committee
2010 Meritorious Engineering Award Winner of IEEE/IAS Pulp and Paper Technical
Committee
2013-2014 – President IEEE Industry Application Society
Contact information
Director of Development
Iris Power, 3110 American Drive,
Mississauga, ON, Canada
L4V-1T2
Office: +1 905-364-4582
Web: www.Irispower.com
Email: [email protected]
Lecture topics
1. Effects of Modern Variable Speed Drives on Motor Winding Insulation
For over 70 years, researchers have understood that fast rise-time voltage surges from a circuit breaker
closing can lead to an electrical breakdown of the turn insulation in motor stator windings. Rapid
advances in power electronic components in the past decade have lead to a new source of voltage
surges. Inverter-fed drivers (IFDs) of the pulse width modulated (PWM) type that use insulated-gate
bipolar junction transistors (IGBTs) can create tens of thousands of fast rise-time voltage surges per
second. Anecdotal evidence suggests that the large number of voltage surges from IFDs can lead to
gradual deteriorations and eventual failure of the turn insulation—both in low voltage (less than 1,000V)
and medium voltage (2.3 to 4.16kV) motors . This presentation describes the characteristics of voltage
source PWM drives Impact on random wound (LV) motor stators as well as the impact on form wound
(MV) stators. It will also describe the relevant standards to qualify insulation systems for converter fed
motors .
2. Turbine Generator Rotor Monitoring thru air gap flux monitoring
On-line magnetic flux monitoring via permanently installed air gap flux probes is well established
technology to determine the presence of shorted turns in a turbine generator rotor winding. The flux
measurements are normally performed using flux probes installed in the machine air gap (on a stator
wedge) and connected to portable or permanently installed instruments. In this “flux probe” test, to
achieve a reliable diagnostic, the signal from the flux probe has to be measured under different load
conditions ranging from no load to full load. This requirement presents a serious obstacle when applying
this method on base load generating units. Recently, a new design of magnetic flux probe installed on a
stator tooth was implemented. In addition, new algorithms used to analyze measurements using
different types of flux probes were developed to minimize the need for tests at different load
conditions. A Finite Element Model (FEM) has been created to verify these new algorithms in different
loading conditions. Based on this model, and real world measurements, it has been demonstrated that
accurate detection of shorted turns can be obtained without the need to vary the load on the machine if
suitable sensors and algorithms are applied. This presentation describes the new method and its
advantages, comparing results obtained from on-line measurements on working generators and the
Finite Element Model created to simulate different rotor conditions.
3. The use of Fiber Optic Sensors for Stator Endwinding Vibration Monitoring
In the past few years, as manufacturers have reduced stator endwinding support to lower costs, stator
endwinding vibration has emerged as an important failure mechanism of large motors and generators.
Endwinding vibration, which is primarily driven by magnetic forces in normal operation and much larger
forces in fault conditions, leads to high voltage insulation abrasion and copper conductor cracking from
high cycle fatigue. Many catastrophic generator and motor failures have resulted. The most effective
method to monitor if dangerous endwinding vibration is starting to occur is to continuously monitor the
vibration levels and frequencies using fiber-optic accelerometers. Such sensors have been available for
over 20 years, but it is apparent that incorrect results are sometimes obtained, leading to false
indications on the condition of the stator endwinding support structure. False indications could be the
result of multiple causes, and one of them is improper location of the sensors, i.e. the sensors are
installed in locations of minimum vibration, making one believe there is no vibration problem. Modal
testing is sometimes used to determine the optimum location of the sensors. However, since this test
can only be performed at ambient temperature, not at winding operating temperature, it is possible
that with a temperature increase, the optimum location positions could be changed. This paper will
discuss the requirements for end-winding vibration of turbine generators, the sensing technology and
installation and monitoring systems typically employed for this application.
4. Shaft Voltage and Current Monitoring on large Turbine Generators
Early warning of developing problems in rotating machinery using shaft voltage and current monitoring
with intention to protect shaft bearings from stray current and detect other related problems has been
used in the industry since mid-1970’s. There has been an increase in occurrences and intensity of shaft
current damage as machines became larger, operated at higher speeds, and increased use of high alloy
steels. The shaft electrical profile of a specific rotating unit is determined by measurement of shaft
voltages and grounding currents. Changes in this profile could provide early warning of developing unit
problems on rotating machines, such as turbines, high and low voltage generators and motors and
compressors.
During the normal operation of electrical machines, AC voltages can be induced in the shaft, or created
by the rotating elements of the turbine, connected to the same shaft. If voltages are high enough, shaft
currents can reach levels capable of causing bearing failures. The main sources of shaft voltages are:
 Potential applied to the shaft as result of rotor winding ground fault or spikes caused by
excitation system (spikes up to 200 V)
 Asymmetry of magnetic fields caused by design or manufacturing details or by large stator core
faults (can induce up to 150 V AC)
 Flux generated by axially magnetized turbine and generator parts (up to 5 V DC)
 Shaft movement off magnetic center
 Electrostatic effects caused by charged steam or lubricants
Voltages of up to 150 Vp-p can be created on the shaft and as a result of potential difference between
shaft and other, grounded parts of the machine, damage to bearing surfaces and oil seals can occur. In
addition to pitting (mechanical damage resulting from arcing between shaft and bearing) shaft currents
may also alter chemical properties of lubrication oil. Without effective shaft grounding, bearings and oil
films are the only insulation between shaft and grounded parts and shaft currents are not confined and
cannot be controlled.
This presentation will discuss shaft voltage and current measurement on turbine generators and how
the technology can combined with other diagnostic parameters to detect machine condition and the
need for maintenance.
5. Condition Based Maintenance of large HV rotating machines
Predictive Maintenance (PdM), also called Condition‐Based Maintenance, is rapidly being accepted as
the best way to minimize overall maintenance costs in capital‐intensive equipment, such as, large
motors and generators. PdM is an approach to planning maintenance, where equipment is removed
from service when, and only when, an online monitor gives an indication that some failure mechanism is
imminent. Thus equipment shutdowns are NOT based on operating hours or the elapsed time since the
last maintenance shut‐down. Having confidence in planning maintenance, based on the actual condition
of the machine, involves the following prerequisites:
 The monitors must be able to detect most of the failure mechanisms that are likely to
 occur. If not, unanticipated failures transpire, which undermine confidence in the PdM
approach.
 There must be few false alarms. That is, if a monitor indicates a problem, an actual problem
must
 be present.
 The monitor itself should not lead to a failure, and the monitoring cost must not be an
unreasonable percentage of the motor or generator cost.
This presentation will discuss the failure mechanisms of machines, and the type of on-line monitoring
that can be applied to detect these failure mechanisms to move to a state of condition based
maintenance.
6. Experience with an on-line Hydro Generator Expert System Monitoring
System
Current technological advances in condition monitoring are employing an increasing number of complex
sensors and advanced monitors to diagnose the operating status and condition of hydro generators and
turbines. Advanced systems routinely employed may include bearing vibration, air gap, shaft voltage
and current monitoring, partial discharge, and flux monitoring. Proper interpretation of this often
complex information can lower operating and maintenance expenses, in addition to reducing
unscheduled outages and catastrophic failures. However, the volume of available data from these
monitors, and the extensive interpretation necessary to evaluate the complex waveforms and
spectrums, can overwhelm plant personnel and resources. Sophisticated software and algorithms are
often necessary to correlate and interpret this data to establish the overall generator and drive train
condition. HydroX™ (for Hydro Expert) is a commercial knowledge-based expert system program for online monitoring of hydro-generators. Working with the New York Power Authority, the system was
developed over five years by Iris Power and GE -Bently Nevada. After a further two years of prototype
evaluation at NYPA’s St. Lawrence Power Project on two 60MVA generators, the validated system is now
commercially available and will be described.