IQ Partial Discharge Testing
The POWER PLUS Engineering, Inc. IQ Partial Discharge Testing Services consists of three integral steps. IQ Sampling involves POWER PLUS collecting field samples of electronic signals emitted from electrical components using special sensors. IQ Diagnostics consists of analyzing the signals and IQ Reporting to provide the customer with results and recommendations related to the condition of the components that were sampled.
What is Partial Discharge Testing?
Since the mid-1950's, partial discharge testing has been successfully used to determine electrical insulation condition. Most of these tests were performed in a controlled laboratory setting within semi-shielded enclosures. Cables, transformers and other components are tested today at manufacturer's facilities for quality assurance purposes in much the same manner. Since partial discharge activity was recognized as such a good indication of insulation quality, field partial discharge testing was adopted extensively in Europe since the 1980's for in-service equipment evaluation. The field technology migrated to the U.S. in the mid-1990's where the value of partial discharge testing was quickly recognized. Today, the IQ Program utilizes the world's most advanced technology to provide unprecedented signal conditioning and diagnostic results to determine equipment condition. By performing annual partial discharge testing surveys, in the same manner that infrared surveys are performed, electrical reliability will be significantly enhanced.
A high percentage of medium and high voltage equipment failures occur due to partial discharges (PD). Partial discharges are partial failures of the insulation. These partial failures create minute sparking or arcing activities across the surface or within the bulk of the insulation. This micro-sparking produces signals in the radio frequency spectrum that are sampled, measured and analyzed using high frequency instruments and custom software. Once partial discharge activity occurs, insulation failure is imminent. Partial discharges generally occur at voids, cracks or other flaws where the localized electrical stresses exceed the capacity of the insulation.
Our Insulation Quality Program
The Insulation Quality (IQ) program will significantly enhance your ability to detect partial discharges and increase electrical reliability by identifying and targeting the problem areas requiring maintenance and repair. In the past, predicting where the next failure will occur was like trying to find a needle in a haystack. With the IQ program, finding those needles is now possible.
The IQ program has been designed to be used without disrupting electrical service. This is also referred to as "on-line", "in-service" or "no-outage" testing. On-line testing is very attractive to facilities because productivity does not need to be interrupted, which is not the case with conventional testing. PD testing also differs from conventional testing in that no potentially damaging over-potentials are applied to the test object. With PD testing, non-intrusive sensors measure the signals, which are present on the test object when partial insulation failure is occurring.
The IQ program also has some limitations. Insulation failure can occur quickly, so certain types of failure could be "missed" between annual surveys. Lightning or switching surges may initiate electrical trees at dormant flaw sites, which can fail rapidly. Environmental and operating conditions can influence partial discharge activity and could vary results. The IQ program assesses insulation condition and cannot predict the mechanical condition of the equipment. It is thus necessary to still perform time-based preventive maintenance testing and inspection of certain equipment, which require regular service.
The IQ program is best utilized by performing annual surveys so that insulation degradation trends can be spotted. While partial discharge survey is being performed, visual access to many electrical components is possible. This provides POWER PLUS with opportunities to discover many other problems with the installation. In addition to taking advantage of visual inspections, this is also a good time to perform an infrared evaluation. By combining PD, visual and infrared inspections, POWER PLUS can provide value-added service to the customer.
IQ Applications & Uses
- PD Testing of MV/HV Cables after manufacture for Quality Assurance
- PD Testing of MV/HV Cables in service for degradation
- PD Testing of field prepared splices & terminations
- PD Testing of molded devices such as elbows & all field installed cable kits
- Measurement of Switchgear PD activity
- Installation & commissioning tests on Switchgear & other MV/HV distribution & transmission equipment
- PD Testing of Transformers & other MV/HV distribution & transmission equipment
- HV Bushing & Insulator PD testing
- Testing the PD activity of Surge Arrestors up to the MCOV (maximum circuit operating voltage)
- Measuring PD & quality assurance on MV Generators and Motors
- Commission testing of New and Repaired MV/HV Cables
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