Condition Assessment of Electrical Equipment Presented by: Sandip Patel, P.E. Electrical Engineer Orange County Sanitation District

Overview Types of Maintenance/Condition Assessment Activities Types/Causes of Electrical Failures Industry Standards & Guidance Condition Assessment Methods and Technologies for Electrical Equipment

TYPES OF MAINTENANCE ACTIVITIES Reactive Maintenance (Corrective) - CM “Run it till it breaks” / “Run to maintenance” Preventive Maintenance (Time-Based) - PM Actions performed on a time or machine-run based schedule that detect, preclude, or mitigate degradation of a component or system with the aim of sustaining or extending its useful life through controlling degradation to an acceptable level (regardless of its condition at the time). Predictive Maintenance (Condition-Based) - PdM Measurement or detection of the onset of system degradation, thereby allowing causal stressors to be eliminated or controlled prior to any significant deterioration in the component’s physical state. Results indicate present and future functional capability. Looks at actual condition of the machine rather than some preset schedule. Reliability Centered Maintenance A process used to determine the maintenance requirements of any physical asset in its operating context. Typical implementation would consist of: < 10% Reactive 25% to 35% Preventive 45% to 55% Predictive *Based on U.S. Department of Energy definitions

Types/Causes of Electrical Failures Top Causes of Electrical Distribution System Failures Loose connections/parts30.3% Moisture17.4% Line Disturbance10.4% Defective/Inadequate Insulation9.9% Lightning8.1% Foreign Objects/Short-circuits7.3% Collision3.9% Overloading/Inadequate Capacity2.4% Accumulation of dust, dirt, and oil2.2% All other causes8.1% *Based on Hartford Steam Boiler Claims Data

Industry Standards & Guidance 70B NFPA 70B Recommended Practice for Electrical Equipment Maintenance 2013 Edition Manufacturer Manuals

Condition Monitoring – Medical Analogy Waveform Analysis

Common Condition Monitoring Technologies *Based on U.S. Department of Energy

Condition Monitoring Technologies – Electrical Equipment Type PdM Tools Infrared Thermography Insulation Oil Testing Motor Oil Testing Motor Circuit Analysis Ultrasound Power Cable Analysis High Voltage Switchgears X X Low Voltage Switchgears X X Low Voltage MCC's X X Stand-alone VFD's X X Low Voltage Switchboards X X Panelboards X X Oil filled transformers XX X 12kV cables X All Motors over 5 HP X X Motors over 200HP and Generators X X X Motors with oil X X X

Infrared Thermography (IRT) Infrared thermography uses an infrared camera to capture images of objects (electrical equipment & connections) and translates the info. into a visual image: Detects radiated electromagnetic energy (in the IR portion of the frequency spectrum) of objects and converts it to temperature. IR radiation spectrum is outside visible light spectrum so it is invisible to the human eye. This technology can be used at all levels of the power distribution system from the high voltages to 120 volt receptacles and cords.

Types of Defects Detected The images can reveal overheating electronics, loose or corroded connections increasing circuit resistance, insulation failure, wiring mistakes, and overloaded wires & power equipment.

X The disadvantage to infrared thermography is that the equipment being scanned must be visible to the camera and therefore exposes the camera operator to voltage and arc flash risks. Adequate PPE must be worn. Some equipment have infrared viewing windows installed to allow for safer and quicker inspections.

Electrical Ultrasound Electrical ultrasound scanning uses a listening device that shifts the high frequency sounds of electrical leakage current or sparks (also known as partial discharge - PD or corona) into the audible range. Typically applicable for higher voltages. By interpreting these sounds the operator can detect minor insulation failures and even the seriousness of the leakage. Catching these leakages early prevents catastrophic failures. A big advantage to this technology is that it can be used with equipment doors closed and not expose the operator to the electrical hazards.

Types of Defects Detected Corona or PD creates ozone, UV light, nitric acid, electromagnetic emissions, and sound: The high frequency sound can be heard by ultrasonic scanning devices. PD deteriorates rubber-based insulation and can attack copper and other metals. Typically caused by geometry of installation, spatial factors, and environmental conditions. Source of sound is investigated by de-energizing equipment and looking for signs of current leakage, arcing, or white powder residue.

Insulation Oil Analysis Insulation oil testing reveals any deterioration of the insulating value of the oil or of the insulation of the wire in the device. Based on the abnormality in the machine, various particles breakdown and form as dissolved gasses in the oil. The study or evaluation of these gases is known as ‘dissolved gas analysis’ or DGA. Used for oil filled transformers. Viscosity and other properties are also analyzed.

Motor Circuit Analysis Motor circuit analysis (MCA) allows the analyst to test and view various motor circuit parameters to determine the condition of the electric motor (windings, rotor, insulation, etc.). When defects or impending failure degrade the motor circuit, it is seen in the measurements of current, voltage, resistance, reactance, etc. Testing would include: Offline: Phase-to-phase resistance & inductance, ground capacitance, polarization index (PI), dielectric absorption ratio, ground resistance, field inductance/resistance/capacitance Online: Electrical Signature Analysis (ESA) – capture motor’s current & voltage signals and analyzing them to detect various faults. Harmonics generated by various faults will show up differently.

Vibration Analysis Vibration can provide information on: Motor/load imbalance Bearing faults Looseness in fasteners Broken motor rotor bars (electrical faults) Misalignment of drive train (rotor → bearings → shaft → couplings → load) Collect vibration data on vertical, horizontal, and axial directions to detect vibration in all 3 planes/dimensions.

Conclusions The criticality of an asset is used to determine the strategy for maintaining or condition monitoring the equipment. The more critical assets should be managed/maintained to a greater degree than less critical assets. Other factors such as the environment, redundancy, etc. should also be factored. Different PdM technologies, combination of technologies, and approaches should be utilized for different equipment based on type and criticality. Visual Inspections and trending of data by the Engineer is also key to success. Root Cause Analysis (RCA) should be utilized. RCA is a systematic process for the identification and evaluation for the reason(s) or cause(s) for the undesirable condition. Corrective actions are developed to prevent the specific failure mode(s) from occurring in the future (for that specific equipment and others as applicable). Other considerations: Program Workflows, Procedures, and Routes Training Communications Strategy, Metrics, and Benchmarks

Questions?