ON-LINE DIAGNOSTIC ON HV BUSHINGS

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2 ON-LINE DIAGNOSTIC ON HV BUSHINGS Presented by: Engr.Eduardo M. Pabuna Jr. Manager, Technical Solutions 42 ND IIEE ANNUAL NATIONAL CONVENTION NOVEMBER 18, 2017 SMX CONVENTION CENTER, PASAY CITY

3 AGENDA: Role of HV Bushings Bushing Insulation Construction Bushing Typical Design and Technologies Common Bushing Failure Mechanism On-line Measurement Technology Installations & Case Studies

4 ROLE of HV BUSHINGS A bushing is simply a device that allows a conductor to pass through a barrier: it has an insulating medium, which must be sustained to prevent the passage of excess current to ground.

5 BUSHINGS INSULATION CONSTRUCTION

6 TYPICAL BUSHING DESIGN Capacitor/Condenser Type: RBP-Resin Bonded Paper (Start 1913) OIP-Oil Impregnated Paper (Since 1950s) RIP-Resin Impregnated Paper (Since 1960s) RIS-Resin Impregnated Synthetics (Since 2010) Non-Condenser Type: Solid Alternate Layers of Solid RIS and Liquid Insulation Gas-Filled

7 Transformer Bushing Technologies Oil Impregnated Paper Resin Impregnated Paper Resin Impregnated Synthetic

8 PERFORMANCE AND RISK COMPARISON OIP Excellent PD Cost effective Overloading capability But.. Explosion risk Maintenance required Needs careful handling & storage to avoid damage Can absorb moisture over time RIP Excellent PD Much Safer No Explosion Risk Less Maintenance But.. Sensitive to Moisture Still needs special dry Storage Less overloading Capability RIS Same Excellent Safety & Less Maintenance Excellent PD Best Possible Moisture Performance Shorter Manufacturing Time But.. Less overloading capability Only Available up to 170KV

9 COMMON BUSHING FAILURE MECHANISM AGEING CONTAMINATION CRACKING EXCESSIVE MOISTURE LEAKING LIGHTNING PARTIAL DISCHARGE SYSTEM EVENT

10 ON-LINE MEASUREMENT TECHNOLOGY The approach of determining the capacitance and percent power factor of an insulating medium relies on measuring the real and reactive components of the leakage current through the test specimen. ABSOLUTE MEASUREMENT RELATIVE MEASUREMENT

11 ABSOLUTE MEASUREMENT For traditional off-line capacitance/power factor measurements, that reference is the applied voltage. Reporting the leakage current vector angle with reference to the applied voltage constitutes an ABSOLUTE MEASUREMENT (True Power Factor)

12 RELATIVE MEASUREMENT On-line measurements rely on the leakage current of another bushing as the reference, signifying the leakage current vector is being measured relative to another bushing. The relative measurement method, with the middle current vector used as the reference. The limitation of this approach is that the on-line measurement provides a relative value which can only identify change. A C. 1 C 2 I A. B. C1 I B. C C. 1 I C C 2 I C 2

13 IDEALIZED LEAKAGE CURRENT Ideally, each leakage current in a set of three would be a sine wave. All three of identical magnitude and be separated by 120deg phase difference. This would mean that their sum would be zero but this is rarely the case, as is shown below

14 THE NEW DOBLE APPROACH Analyzing individual currents, and the raw data which gives the currents provide much more information. dprime IDD applies an expert system to learn what is normal at each set of bushings In addition, limit values are set which provide a means to identify insulation degradation.

15 SIMPLE CONNECTION Bushing Monitoring Device DOBLE IDD

16 ACTUAL INSTALLATIONS

17 ACTUAL INSTALLATIONS

18 CASE STUDY 1 Normal Measurements Ph A - B - C Daily PF Ph A - B - C Daily Capacitance

19 CASE STUDY 2- Power Factor Deterioration 2.5 POWER FACTOR GRAPH Daily %PF1 Daily %PF3

20 CONCLUSION Bushing monitoring requires appropriate data in depth and with built in expert system analysis. More than just a simple capacitance measurement or sum current approach. The online technology has proven to be a valuable tool for insuring the reliability of the apparatus, especially in an environment where outages are rarely available.

21 REFERENCES UPDATE ON ON-LINE BUSHING DIAGNOSTICS Robert C. Brusetti, P.E. Doble Engineering Company 73 RD Annual Doble Client Conference Bushing Monitoring more than just sum current, Rev 1.0 Doble Engineering Company Why Transformer Bushing Fails Dr. HongZhi Ding and Dr. Richard Heywood 2015 EuroDoble Colloquium and Workshop

22 Thank You! Questions? Address: 8F 68 Kalayaan VCP Building, 68 Kalayaan Avenue, Teachers Village West, Quezon City 1101 Tel No.: sales@westco-phil.com Website: