Utility equipment needs the same maintenance attention as any other electrical gear. Working with electric utilities, we perform thorough surveys of utility equipment to prevent equipment failures and maintain safety. Electric power companies use electrical IR testing in all three areas of their businesses:
Utilities need cost-effective and reliable power plants to serve the demands of their customers. Whether that’s baseload power plants, cyclic generation, or peaking power –Power Plants must be reliable and infrared thermography is an integral part of any P/PM program for all utilities. We have found that success with generation equipment depends mostly on the knowledge of the people performing the inspection.
Personnel must have the knowledge of how the equipment operates, how it is constructed, and what its function is in the operation of the power plant.
We survey transmission lines in several ways. First, we fly over the transmission lines with light aircraft or helicopters. Problem areas are found, and exact coordinates are marked with an integrated signal processor which displays on the screen and is digitally recorded along with the infrared image, displaying the date, time (to the millisecond), altitude, Latitude/Longitude (differential) and speed over ground.
Subsequently, the areas that have shown anomalies are given a more thorough and closer inspection from the ground or by using UAVs operated from the ground. This method is obviously the most efficient and effective way to find problems and document them.
All across the country, distribution line infrared surveys take place every day. Because these lines are smaller and lower to the ground, and often run through populated areas, electrical distribution lines are much more difficult to see against all the thermal clutter on the ground such as trees, streetlights, people, animals, etc., than transmission lines using aerial infrared techniques -so we must survey distribution lines by driving down the lines.
Our thermographers can help your utility by scanning the lines and substations quickly from one of our fully-equipped scanning vehicles. Using your system maps, our experts quickly & efficiently gather information on your system with state-of-the-art navigation and imaging systems and record all imagery and GPS position data onto digital storage. When a problem is discovered, we mark the area on the map and immediately produce reports detailing the fault information so that repair crews can be mobilized to remedy the problem.
Large oil filled power transformers are the most expensive component in a transmission / distribution system. Our expertise with transformers is #1 in the industry. Combining several technologies during a transformer inspection is imperative. Testing using Infrared Thermography (IR), Partial Discharge (PD), Vibration analysis and DGA review along with expert visual and functional testing completes the condition assessment (CA). An experienced CA Tech can provide the necessary test results to determine whether to continue normal operation, reduce load, remove from service or schedule a replacement. Remaining life is difficult to calculate, but necessary in the scheme of transformer life.
LTC’s are attributed to more transformer failures than any other sub-system associated with the transformer. A normal signature for an LTC is included in the severity criteria for transformers and their sub-systems. Acquiring data from an operating LTC is imperative to determining the health of this system. Oil analysis and wave shape analysis of the arc during a step change aid in the CA of the LTC.
The cooling system on a transformer consists of oil and a heat exchanger. The heat exchange process must be fully understood to complete this assessment. Knowing the differential temperatures with pumps running compared to pumps not running can make the difference between a long term overheating problem which causes premature aging of the paper insulation systems AND??.
Lighting arresters (LAs) are also known as surge arresters. A switching or lightning surge can create enough movement in a winding to cause damage to the coil and core assembly. Using IR for LAs is only one test which must be done. The leakage current on a good arrester is so low that the arrester should not have any temperature rise above ambient. Any temperature rise that is detectable with an IR camera indicates that the leakage current is on the rise and it will continue to increase until thermal runaway and failure. Using the high frequency current transducer clamped to the LA ground lead will give clues that the IR will not see.
Electromechanical regulators are used to regulate the voltage on AC power distribution lines. These regulators generally operate by selecting the appropriate tap on a transformer with multiple taps. The taps of a voltage regulator are inside the main tank and share the same oil as the transformer. If the output voltage is too low, the tap changer switches connections to produce a higher voltage. If the output voltage is too high, the tap changer switches connections to produce a lower voltage. The controls provide a dead-band wherein the controller will not act, preventing the controller from constantly hunting (constantly adjusting the voltage) to reach the desired target voltage. The primary connections to the voltage regulator are easily viewed with IR and should use the normal severity criteria for direct line-of-sight connections. The main tank is very difficult to diagnose and therefore we must incorporate ultrasound and oil analysis to complete these inspections. Each regulator in the substation will be under a different load since each circuit demand is different, thus creating more or less heating of these units. A hot contact inside will be masked by the large amount of oil, which is being moved and cooled during normal operation of most regulators.
Disconnects allow the operator to isolate various pieces of equipment in the substation. When opened, they are essentially like removing a section of bus. There are contacts on both end of the disconnect. Most contacts on high voltage disconnects are made of a highly conductive material such as silver. These contacts will remain closed for years between normal maintenance and during that time will be subject to every kind of weather known to man. High resistance in the connection will exhibit heating, thus easily detected by infrared inspection. However several scenarios can cause heating of a good contact, of which the thermographer must be aware. Many times simply operating the switch will remove the problem by realigning itself and or cleaning surface corrosion. If operated while the infrared thermographer is present, he/she can verify the problem has been temporarily fixed. This does not eliminate the need of having to schedule maintenance for that switch.
Utility systems use a variety of circuit breakers for switching and circuit protection. These breakers can be many different voltages and vary in insulation medium from air, vacuum, gas, and oil. All of these switches have different IR characteristics. In order for thermographers to accurately analyze the IR data it is important that they have extensive knowledge of the type switch and the internal configuration of the contacts.
Connections are everywhere on the distribution system. They can be squeeze-on, compression, clamp-on, bolted and automatic sleeves. Any conductor connection mid-span or under tension that has a temperature rise is a critical problem. These connections need immediate attention. IR can and has identified problems with connections that resulted in design changes and standard practice changes. We have identified an issue with ½ inch stainless steel bolted connections and an improper torque value that resulted in changes to a large utility’s standard practice.
An infrared inspection on the inner-cell connectors during normal float charge should show no signs of heating because there is less than 1 amp flowing to keep the battery in full charge. The best time for IR inspection is during a discharge test of the battery. Any heating will be subject to the direct line of sight criteria for action.
Over the years the group developed the market, and members performed work for electric utilities, constantly improving the data collection and reporting processes. In the summer of 2006, Stockton Infrared Thermographic Services, Inc. (SITS) formed UtilityScanIR™ to operate the company. In 2019, Stockton Infrared Thermographic Services, Inc. (SITS) ElectriSCAN™ division absorbed UtilityScanIR™ and operates it as ElectriSCAN –A Division of Stockton Infrared Thermographic Services.
ElectriSCAN – a Service of Stockton Infrared Thermographic Services, Inc. Copyright 2020
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