LEAP - Life Expectancy Analysis Program For Electrical Rotating Machines Marcio Gennari ABB Brazil Automation Products Machines Service Osasco
LEAP - Introduction ABB India (excellence center in insulation studies) with over 40 years of experience in the field services and Manufacturing of Electrical Rotating Machines, have developed several innovative and patented tests and technologies for assessing sing the current physical condition of the machine. LEAP is a special bouquet of electrical tests that is able to identify failure mechanisms in stator insulation system of Motors and Generators (AC / DC) therefore achieving the Maximum Operational Reliability. LEAP is not just a package of inspections; it is a systematic approach a to managing machine maintenance. Finger Print from stator insulation system: - Contamination / charge storage - Coils / wedges loose in slots - Voids within main insulation - Partial Discharges - Aging / insulation material degradation - Calculate the remaining life of the insulation system - Planning the maintenance actions (short / long term)
LEAP Machine Life Curve Thermal, Electrical, Ambient and Mechanical stresses act on materials and components of an electric machine, leading to a process of degradation - represented by the blue curve as a reduction of strength with time. When operating stresses both transient and steady state - in the red curve, exceeds the strength, failure is imminent. LEAP is all about drawing the red and blue curves. What makes LEAP special, is its ability to relate the development t of defects to the dimension of time with a life expectancy analysis, that enables its direct integration into a maintenance plan.
LEAP Machines tested August 2002 - August 2006 358 Electrical Rotating Machines only in Brazil!!! Turbine Generator Synchronous Generators/ Motors Induction Motors Slip Ring Motors Hydro Generators - OUTPUT RATE 300 kw to 250 MW DC Machines
LEAP Tests General Information Can be applied in Machines from any Manufacturer (due large ABB India Database) Time for data collection approximately 10 hours with the equipment ent stopped (off line tests) Not necessary open covers / machine for data collection Only access to the terminal box (disconnect exit cables / power cables) Non destructive tests, due Maximum Voltage Test = Phase to Ground Voltage)
THE IEEE AND EPRI SURVEY FINDINGS ON MOTORS AND GENERATORS FAILURES
Failure Estatistics IEEE and EPRI Survey 70% 60% 50% 40% 30% 37% 61% 33% 20% 10% 8% 8% 6% 5% 5% 2% 4% 3% 7% 11% 10% 0% Bearing Stator Winding Shaft/Coupling Rotor External Devices Brushes/Slipring Unspecified Failure during operation Failure initiators identified during inspection / traditional tests
Failure Estatistics Insurance Company Bearing / Shaft / Coupling Rotor winding Stator core (sheet plates) Stator winding Others (diodes, excitation system etc) Source: Allianz Insurance, Germany (1996-1999), 1999), VDE Colloquium, June 28, 2001
Survey Conclusions Bearings fail frequently Windings also share a significant failure rate Very few winding failures are detected in maintenance (8.3%) as against the total failure of 33% in normal operation This indicates deficiency in traditional tests to detect stator winding problems and achieve Operational Liability in Machine
Insulation system: A complex structure MICA: material used to retard the failure Various process applied during coil manufacturing: Resin (pre-impregnated tapes) VPI, global VPI (vacuum pressure impregnation) Old Machines: mica splittings, asphalt shellac All materials and structure are subjected to stresses and aging!! One More reason to explain the needs for accurate Diagnostic techniques!!!
BEFORE GOING FOR THE DIAGNOSTIC TESTS LETS HAVE A LOOK AT THE FAILURES
Failures manifestation Delamination / deterioration of insulation
Failures manifestation Partial Discharges in slot regions / stress grading system Damage due to excessive looseness and rubbing of coil with core (loose wedges)
Failures manifestation Contamination
Arrhenius curve
Failures manifestation Coils / wedges loose in slots
Where the problem is located? LEAP indicates which machine component needs maintenance activities ies Cleaning the endwindings regions or slot Re-wedging stator (customer can plan for acquire wedges) Re-taping tasks in slot exits / Repair stress grading system Indicate when insulation reached critical levels (and then a rewinding or acquisition of a spare coils is needed) LEAP also is indicated for new machines (to detect possible problems in manufaturing tasks)
LEAP Package of tests LEAP Level II 1) DC Absorption Test 2) Tan Delta and Capacitance analysis 3) Partial Discharges analysis 4) Non Linear Behavior analysis LEAP Level I - Operational Hours. - Number of stops / starts - Stator winding temperatures (Arrhenius Curve) LEAP Level III and IV - Contamination / charge storage - Coils / wedges loose in slots - Voids within main insulation - Partial Discharges - Aging / insulation degradation - Remaining life of the insulation - Planning the maintenance actions - Stress analysis with FEA (Finite Element Analysis)
Case studie - 1 August 2004 Customer Power Plant Turbine Generator HITACHI 75 MW ABB in April 2003 performed the Analysis, and the report presented some risks in the machine due high contamination in endwindings and slot section, because the contaminants were blocking the ventilation ducts and also the type of contaminants were conductive. We also identify contamination in slot portions, so was necessary remove the rotor from stator. The wedges system was ok, so were not necessary to acquire spare wedges. Even with the condition of the Generator, Report said that the machine could still operate for more one year, but to get more Operational Liability in the machine, after one year a MAJOR INSPECTION should be planned. I will present a short video (2 minutes)
Case studie - 2 June 2005 LEAP On Board Oil Rig Platform 03 BBC Synchronous Generators 12.5 MVA 13.8 kv LEAP Report: High amount of contamination in windings (also spread in slot sections), oil contaminants ingress in insulation system, overhauling within 1 year (cyclic cleaning in workshop), insulation not aged, wedges / coils tight in slots, high surface PD due carbonized oil. Customer s s action: Decided to send the 03 machines to ABB Workshop Osasco (1 machine each 4 months) to perform Major overhauling, including i rotor inspections, rewinding rotor poles, replacing rotor coil supports s and implementations of new labyrinth seals system (to avoid further ingress of oil in endwindings).
Case studie - 2 April 2006 - ABB Field Team removing 01 Machine and ship to ABB Osasco Workshop
Case studie - 2 April 2006 Machine in ABB Osasco Workshop
Case studie - 3 March 2006 Oil Refinery Customer - BBC Generator 12.5 MVA March 10, 2006 - Flash over in V / W phase terminal, customer called ABB to evaluate insulation stator condition (after stresses) and check if machine could be put in operation. March 12, 2006 LEAP Data Collection (Report sent in March 15,2006) V phase shows inherent weakness and it is likely stressed. Either r the level of contamination is high or the insulation strength has weakened slightly for this phase. The non-linear patterns for V and W phases are very similar and different from other phases. The patterns show a general even harmonic dominance but the 15th harmonic component Expected degradation due to overheating in between V and W phases. s. Also some residual effects are suspected at the terminations (slot exits)
Case studie - 3 LEAP Report Recommendations: The results indicate that the unit is contaminated to a significant extent along the endwindings with oil/carbonized oil and dust type contaminants. Also the flash has possible resulted in additional thermal stresses ses particularly in V and W phases. It is recommended to open up the machine for overhauling (at earliest) is not advisable operation of the unit. The main areas of maintenance are as under: Carry out the thorough cleaning of the machine especially along the endwinding areas followed by dry-out The slot exits portions need to be inspected for presence of contaminants at the terminations and overheating marks and insulation degradation or burning. The corresponding re-taping of the leads to the bushings may be correspondingly repaired red. Even with information regarding the machine conditions customer decided to put the machine in operation...
Case studie - 3 Only 4 days of operation (failure in V/W phase): Customer ship the machine to ABB Osasco Workshop
Case studie - 3 Machine in Workshop Osasco: Stator rewinding Rotor rewinding (catastrophic failure) Rotor balancing Installation and commissioning (Sept. 2006)
Case studie - 4 June 2006 Mining Plant Ball Mill GE Synch. Motor 4085 cv 4.160 V - 1978 LEAP Report: Even machine operating in an aggressive environment, the general condition of the stator insulation system is good. ABB also calculated the remaining life (thermal only) from machine and we found a remaining life of 47.565 equivalent hours (corresponds to 5.47 years) 80% of Reliability in Life information. No maintenance actions is necessary for this insulation system for the next 10.000 operating hours (or 1 year).
LEAP: A value proposition Optimizes Maintenance Planning of Electrical Machines by moving from Time Based Maintenance to Condition Based Maintenance. Provides an opportunity for Life Extension of machines, which would w lead to increased earnings capability and greater Return on Investment. Facilitates decision making: : A single occasion of measurements is sufficient to enable short and long term maintenance plans, repair-run run-replace replace decisions. Focuses on essential maintenance,, and machines that are vulnerable, to reduce downtime at lower risk levels Provides important lifetime inputs for more realistic estimates of Life Cycle Costs