Have you signed up? Transformer Seminar Aug 16-17

It is well established that Partial Discharge (PD) activity is one of the leading indications of insulation health and should be measured as part of an asset management program. A thorough, condition-based maintenance program should include equipment for continuous on-line monitoring, detection, and analysis of PD in HV apparatus. Following an initial detection of PD, results can be further verified by high precision off-line techniques, and appropriate corrective action can be taken.

Hand-held instruments can provide routine, external PD survey and testing capabilities while the apparatus is still in service. Other systems provide a solution for on-line, continuous monitoring of PD activity in transformers. This session will highlight the next generation systems for periodic, online PD monitoring. These rugged, portable units can be used for day-to-day field use, for in-house and on-site applications on all types of HV apparatus. The versatile systems use state-of-the-art technology for multichannel, synchronous PD measurements, with a user-customized software interface for faster, easier PD testing. The best type of system measures both the PD

and the actual applied voltage under test so that users can ascertain the effect of the voltage applied, as well as the PD produced. Phase resolved analysis provides keen insight into the characteristic and source of the PD. Using internationally recognized algorithms approved by IEEE and IEC, the system's analysis tools enable the best possible diagnosis for fault conditions to be realized.

3:00pm - 3:15pm Break

3:15pm - 4:15pm SFRA (Sweep Frequency Response Analysis)

This presentation presents technical details regarding Sweep Frequency Response Analysis (SFRA) and the role it plays in transformer test and maintenance. Details of the SFRA test method are discussed, along with practical results and case studies. For reasons of range, resolution and repeatability, the SFRA technique is shown to be superior to other frequency response techniques, providing results that may be used in key decisions by transformer engineers and asset managers. Northwest examples will be discussed.

4:15pm - 5:00pm Advantages of and Advances in Complete, Portable Field DGA -and-
How can you verify the accuracy of the laboratory you are using for your oil maintenance samples?

Dissolved gas analysis (DGA) has been an industry standard for the detection and determination of faults in transformers for over 30 years. In this session, the speaker will present the advantages of complete, portable field DGA using a precise analytical instrument, a micro Gas Chromatograph (GC), to analyze the measure separately the seven fault gases found in transformer oil when a problem is developing, as well as measure oxygen and nitrogen. Recent advances in portable DGA will be discussed.

Just as a doctor analyzes blood to determine a patient's health, DGA provides the engineer with the means to determine the health of transformers. However, once the analysis is performed, can you trust that the results are valid? Provided the methods are followed properly, the results obtained from DGA should give the engineer the information needed to make an informed decision on the operating status of a functioning transformer. However, lab accuracy and repeatability are critical, and the reliability of many labs can be inconsistent at best. This problem will be discussed.

Day 2

8:00am - 8:30am Sign-in (coffee & donuts provided)

8:30am - 9:30am Transformer Failure prevented by Hydrogen On-Line Monitoring

This presentation discusses an actual event at a utility in the Northwest when a step-up transformer was urgently taken out of service. Data used to make this decision consisted primarily of dissolved gas measurements generated by an on- line dissolved hydrogen and water monitor, and of on-site DGA measurements made using a portable multi-gas analyzer.

The first section of the presentation describes the situation that led to the use of on-line and on-site monitoring technologies for this critical transformer. The second section covers the analysis of the collected data and summarizes the hypotheses that were made prior to taking the transformer off line. The third section outlines the observations and conclusions that were made regarding the most likely source of incipient fault, pursuant to the transformer repair. Finally, the last section includes recommendations on the decision making process which should be undertaken to evaluate the scope of application of on-line dissolved gas monitoring systems and includes a post-event update on the "transformer designation" behavior at the time of publication of the present paper.

9:30am - 10:30am Comprehensive Transformer Monitoring

System reliability can be improved when advanced monitoring diagnostics catch problems earlier. This session discusses a comprehensive system for monitoring, control and communications for power transformers, which offers:

Data Consolidation- Consolidates control, monitoring, data acquisition and analysis into a single device.
Open Architecture- Connectivity and data consolidation from a wide variety of sensors. All functions are provided in the control cabinet, on the transformer. No PC or special software required.
Actionable Information- General alarms provide alerts of equipment trouble. Detailed alarms allow better management of labor resources. Dynamic rating calculations improve contingency planning.
Communications- Offers multiple communication options (including serial, Ethernet SCADA and LAN types). Integrated web server pages provide graphical interface. Provides multiple data security solutions.

10:30 - 10:45am Break

10:45am - 11:45am Cost Justification of Transformer Monitoring

The trends are universal. Utilities are producing and distributing more power, running assets harder but the budgets and manpower used to service and support the infrastructure is shrinking. Transformer monitoring is proving to be a key element in helping managers survive in a work environment that continually expects more to be achieved with less. This session will discuss how, by utilizing data collected from both generation and transmission/distribution utilities, we have been able to help utilities evaluate what amount of transformer monitoring is cost justified, how to best implement a monitoring system, and how to utilize the information that will ensure that the benefits are gained.

Noon - 1:00pm LUNCH (provided)

1:00pm - 2:00pm Bearing Monitoring on Transformer Pumps

Six precision, ultrasonic sensors are mounted in both thrust and radical bearings at strategic points, becoming part of the bearing surface. A signal from the instrument excites a piezoelectric crystal in each sensor, which emits a high-frequency sound wave, which echoes off the face of the sensor, re-exciting the crystal, which sends a signal back to the instrument. The instrument translates the echo time into distance (sensor length) and bearing condition. A multiple array of sensors provides the safety of redundancy and accuracy of +/- .0002". Measurements are compared to the baseline readings to determine if bearing wearing has occurred.

2:00pm - 2:15pm Break

2:15pm - 3:15pm Fiber Optic Measurements Inside Transformers
The use of fiber optics based thermometers to measure transformer winding hot spots is a safe, practical, and economic means to utilize transformer temperatures for cooling control, alarms, and protection that can not be reliably obtained otherwise. Fluoroptic Thermometry (FOT) is the best technology available today for transformer temperature measurement. The FOT method best fits large power transformers, as well as transformers that are UHV, EHV, HVDC, and all reactors. FOT technology and transformer hot spot fiber optic temperature sensors will be discussed in this session. Successful applications at the Salt River Project (SRP) are described.

Benefits of Fiber Optic & Actual Winding Temperature Measurement:

Actual WHS measurements - placed where OEM design specifies

Verification of design characteristics - heat run
Base line for customer to track transformer performance

Accurate information on transformer performance

Asset management strategies (dynamic loading/maintenance)
Life of transformer (Life=Insulation=Temperature)
Early diagnosis of potential problems - cooling or design

Accurate control of cooling/alarms/protection of transformer

Base cooling on actual hot spot to control temperature

Safely maximize performance of transformer
No calibration - lifetime components

3:15pm - 4:15pm On-Line Bushing Monitoring

Over the last ten years, the utility industry has undertaken the task of identifying a reliable approach to evaluating the condition of bushings while in service. This exercise has been driven by the challenge of maximizing resources, without compromising system reliability. With the more common techniques (DGA, infrared) of assessing the condition of an apparatus while in service, proving impractical, and/or inconclusive for bushings, efforts have focused on replicating the traditional off-line capacitance and power/dissipation factor measurements.

This session will discuss the obstacles that need to be dealt with when on-line measurements are used to assess the state of a bushing. It will chronicle the evaluation of this technology, and present field experiences that highlight both the successes and shortcomings of the various technologies.

It will examine how a utility in the Northwest saved their transformer and prevented a major outage in a major city using real-time monitoring of bushings in another state.