Doble Engineering has introduced an innovative approach to test generators, motors, exciters, isophase bus, switchgear, transformers, and power cables – Electromagnetic Interference (EMI) Diagnostics. This newest addition to Doble’s consulting services is a non-invasive on-line surveillance technique that can detect and identify defects in a motor or generator and associated electrical systems while each power system remains in service. "EMI testing is a new diagnostic offering for Doble and is virtually unknown to the electric power industry. However this is a tried and tested technology, developed over 25 years ago, and proven with over 5,000 successful tests in the field on more than 500 different designs with over 65 types of defects and conditions have been identified and catalogued," said Richard Ladroga, manager of business development for Doble Engineered Strategies.
EMI analysis techniques can provide critical information useful for developing targeted maintenance strategies for power systems and can also identify equipment that does not need attention or repair. This is a passive, totally non-invasive measurement technique, with no applied signal. Data are collected without affecting operations, and the process is inherently safe. EMI Diagnostics can provide valuable maintenance recommendations on the first test. The testing equipment is sensitive, and measurement accuracy is traceable to NIST standards. EMI presents an opportunity for companies to dramatically improve their condition assessment and maintenance programs. EMI Diagnostics can save money and time by identifying specific areas that require maintenance, repair, or replacement allowing strategic, proactive, planned decisions to be made well in advance of an upcoming scheduled outage. Generators - EMI Diagnostics can detect stator bar slot discharges from conductive coating erosion, stator slot side-packing erosion, stator bar stress grading system deterioration, loose stator wedging (loose stator bars), loose end winding ties, blocking and circuit rings, loose/broken stator sub conductors, dirt on stator end windings, and much more. Motors - EMI can detect stator coil partial discharge, deterioration in slots and on ends, winding contamination, oil, dirt, carbon black, coal dust; defective bolted/crimped stator lead connections, broken induction motor rotor bars, wiped bearings, shaft oil seal rub plus more. Bus & Cables - EMI can find contaminated/loose/cracked bus support insulators, loose bolted joint hardware, deteriorated enclosure insulation, foreign objects in the isolated phase bus enclosures, defective potential transformer (PT) fuses and connections among many other items.