TECHNICAL PAPER PRESENTATION

Transcription

1 1 W E L C O M E T O A C O M E T TECHNICAL PAPER PRESENTATION

2 2 Analytics for Dissolved Gas Analysis BY RANDY COX

3 A B O U T T H E A U T H O R Randy Cox is the Domain Expertise Manager for GE Grid Solutions, M&D. His current duties include interfacing with the industry, committee work and education of customers on the technical advantages of GE Randy Cox DOMAIN EXPERTISE MANAGER GE GRID SOLUTIONS M&D technology, products, software and solutions. Randy is also a current member of IEEE.

4 4 O V E R V I E W & ABSTRACT SUMMARY Dissolved Gas Analysis has proven to be one of the most useful tools in analyzing the condition of oil filled power transformers. By observing the discreet values of the various combustible gases, developing faults can often be detected in their early stages. In recent years it has been discovered that trending the CO2/CO ratio, over time, can also be very useful in predicting a transformer s end of life. By trending this ratio, it may also be determined whether the severity of an incident is life ending, or simply an isolated event.

5 5 THE RELEVANT GASES It is important to distinguish and categorize the gases. This is vital in our efforts to diagnose issues within a power transformer. Hot metal gases are well known and understood by the industry. However, the carbon oxide gases (carbon dioxide and carbon monoxide) have continued to be problematic for the average technician.

6 U S E F U L I N D U S T R Y T O O L S C O M E T TRADITIONAL RATIOS FOR KEY GASES UTILIZING INDUSTRY TOOLS Industry tools can be very useful for determining the temperature of a given fault, or post-trip fault. While determining the temperature of the fault is important, another important piece to this puzzle is determining the location of the fault. Faults which occur in the winding insulation are not conducive to onsite repairs, while overheated connections (such as a de-energized tap changer) may make an on-site repair possible.

7 7 T H E T R A D I T I O N N A L V I E W TRADITIONAL DATA EVALUATION DISCREET VALUES As gases begin to generate, we determine what the temperature of the fault is based on individual levels and rate of change HOT METAL GAS RATIOS Early pioneers of DGA created charts with HMG ratios for us to calculate so that we could distinguish partial discharge from overheating SNAPSHOT CO2/CO RATIO Industry standards, such as IEEE and CIGRE provide guidance with a specific range where the ratio is considered to be normal

8 8 CO2/CO RATIO EXPERIMENT SETTING UP THE TEST 9 The testing was performed utilizing a YOUR TITLE HERE D877 oil tester, which holds a very small amount of oil, about the size of a coffee cup. New oil was used for each test. First, oil was flashed, a DGA collected with CO2 and CO measured and the CO2/CO RATIO oil flash oil w/paper appropriate ratio reflected. YOUR TITLE Next, the HERE oil 3 test cup was flushed with new oil, then 2 another sample of new oil added, but 1 this time with a single piece of transformer Kraft paper added between the electrodes with the test repeated. The test was repeated a total of 1 test1 test2 test3 test4 test5 test6 tes 7 test8 test9 test1

9 9 CATEGORIZING FAULTS Nitrogen Sealed #1 36 MVA Nitrogen Sealed #2 3 MVA 4% 35% YOUR 3% TITLE HERE 25% 2% 15% 1% 5% 4% 35% 3% 25% 2% 15% 1% 5% % H2 CH4 C2H6 C2H4 C2H2 % H2 CH4 C2H6 C2H4 C2H2 12 CO2/CO 7 CO2/CO 1 YOUR TITLE HERE Pre Event Post Event 4 3 Pre Event Post Event

10 1 CATEGORIZING FAULTS CONTINUED Winding Failure #1 Primary Lead Repairable #2 Transformer Replaced Transformer Repaired

11 11 CATEGORIZING EVENTS 2136 ppm 21 ppm CO Failed the following year, CO CO CO C2H C2H6 185 ppm 2 ppm 12 CO2/CO Ratio 2136 ppm 21 ppm ppm 2 ppm Failed the following year,

12 , 15 MVA, 1 kv TRANSFORMER M Date H2 O2 CO2 CO CH4 C2H6 C2H4 C2H2 CO2/CO 211 < < < < < <1 <1 < < <1 <1 < < <1 < CO2/CO 8 CO2/CO 83% Drop

13 , 15 MVA, 1 kv, Complete Picture Date H2 O2 CO2 CO CH4 C2H6 C2H4 C2H2 CO2/CO 211 < < < < < <1 <1 < < <1 <1 < < <1 < post fault CO2/CO 96% Drop CO2/CO CO2/CO Linear (CO2/CO)

14 14 SUMMARY Trending the CO2/CO ratio is a useful tool for detecting breakdown of the solid insulation. The CO2/CO ratio appears to provide insight into deteriorating insulation in the absence of hot metal gases. The CO2/CO ratio is also useful in determining if an incipient fault is occurring in the winding insulation, or perhaps a more repairable location, such as a DETC, bushing connection, etc. This method is also useful in determining the need for offline testing, as well as the effect loading may have on the solid insulation. Trending of the carbon oxide ratios is most reliable when performed over time, using multiple samples. Special attention should always be given to all gases measured, including oxygen and nitrogen.

15 15 PAPER Q&A C O M E T C O L L A B O R A T E S H A R E K N O W L E D G E P R O G R E S S

16 16 GET IN TOUCH RANDY COX. GE Grid Solutions Monitoring & Diagnostics LINKEDIN