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Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 1

The Team:

Jim McBride: IEEE Member Larry Coffeen: IEEE Senior MemberPresident, JMX Services, Inc. Senior Research Engineer, NEETRAC BS EE Georgia Tech BS EE Georgia TechTesting, DAQ, and Measurement Substation Testing and Research26 Years 43 Years

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 2

Transients from 345/138 kV & 230/115 kV Substation Apparatus Recorded by

NEETRAC/JMX On-line FRA Equipment• Sensors located at H & X transformer bushing taps & across transformer neutral bushing

Bushing Tap

Neutral Bushing

Sensor

Sensor Connection

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 3

OLFRA & OLRPF Cabinets

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 4

OLRPF

OLFRA

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 5

OLFRA Cabinet

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 6

Typical bushing tap + high pass filter + cabling frequency responsescompared to laboratory reference divider (red trace in left column)

345kV System, Lapp POC, 2000A, Bottom Conn.,1999 yr 230kV System,Trench COTA 750,1400A,Draw Lead,1999yr

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 7

Pre-strike of the 345 kV OCB contacts onenergizing 345 kV transformer from high side

The top trace is the magnitude vs. time overlay of the H1 bushing tap, the X1 bushing tap, & the Neutral bushing waveforms for the 345kV OCB prestrike transients on energizing the transformer. The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the H1 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 8

Zoom-in on highest burst from left upper waveform set. 2 uSec. / big division. Blue = H1 bushing tap. (Bushing input max. approx. 10kV pk.) Red = X1 bushing tap. Green = Neutral bushing & represents pulse travel through H1 transformer winding / insulation combination from H1 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 9

Picking Up Load with 138kV, SF6, Low Side Bank Breaker

The top trace is the magnitude vs. time overlay of the H3 bushing tap, the X3 bushing tap, & the Neutral bushing waveforms for the transformer as the SF6 LS PCB picks up load (176 MW, 37MV, 740A on 138kV). The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the X3 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 10

Zoom-in on second burst from left upper waveform set. Blue = H3 bushing tap. Red = X3 bushing tap (bushing input max.approx. 5kV). Green = Neutral bushing & represents pulse travel through X3 transformer winding / insulation combination from X3 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 11

Opening a 345 kV energized air disconnect switch todrop short bus & bushing capacitive load

The top trace is the magnitude vs. time overlay of the H1 bushing tap, the X1 bushing tap, & the Neutral bushing waveforms for the transformer as a 345kV disconnect switch is opened to obtain a working clearance for 345kV line CCVTs. The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the H1 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 12

Zoom-in on first burst from left upper waveform set. Blue = H1 bushing tap (bushing max. input approx. 5kV). Red = X1 bushing tap. Green = Neutral bushing & represents pulse travel through H1 transformer winding / insulation combination from H1 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 13

Pre-strike of the 230kV Air Disconnect Switch onEnergizing 230kV Transformer from High Side

The top trace is the magnitude vs. time overlay of the H1 bushing tap, the X1 bushing tap, & the Neutral bushing waveforms for the 230kV Air Disconnect Transients on energizing the transformer . The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the H1 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 14

Zoom-in on highest burst from left upper waveform set. 2 uSec. / big division. Blue = H1 bushing tap. (Bushing input max. approx. 30kV pk.) Red = X1 bushing tap. Green = Neutral bushing & represents pulse travel through H1 transformer winding / insulation combination from H1 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 15

230/115kV, 300MVA, Auto with 230kVHigh Side Air Disconnect Switch

230kV High Side Air Disconnect Switch

OLFRA & OLRPF Equipment

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 16

Fast transient currents entering top of bushing see an inductivedraw lead in series with a large capacitance at winding to case with most all initial voltage drop across the bushing draw lead.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 17

Opening a 115kV, 58.5MVAR,Capacitor Bank OCB

The top trace is the magnitude vs. time overlay of the H2 bushing tap, the X2 bushing tap, & the Neutral bushing waveforms for the transformer as a 115kV cap. bank OCB is opened. The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the X2 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 18

Zoom-in on first burst from left upper waveform set. Blue = H2 bushing tap Red = X2 bushing tap (bushing max. input approx. 6kV). Green = Neutral bushing & represents pulse travel through H2 transformer winding / insulation combination from H2 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 19

115kV, 58.5MVAR, Capacitor Bank

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 20

Pre-strike of 230kV SF6 PCB onEnergizing 230kV, 180MVAR Capacitor Bank

The top trace is the magnitude vs. time overlay of the H2 bushing tap, the X2 bushing tap, & the Neutral bushing waveforms for the 230kV SF6 PCB prestrike transients on energizing the cap bank . The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the H2 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 21

Zoom-in on highest burst from left upper waveform set. 2 uSec. / big division. Blue = H2 bushing tap. (Bushing input max. approx. 7kV pk.) Red = X2 bushing tap. Green = Neutral bushing & represents pulse travel through H2 transformer winding / insulation combination from H2 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 22

230kV, 180MVAR, Capacitor Bank

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 23

Opening a 230kV Energized Air Disconnect Switchto Clear Up 230kV, 180MVAR

Capacitor Bank for MaintenanceThe top trace is the magnitude vs. time overlay of the H3 bushing tap, the X3 bushing tap, & the Neutral bushing waveforms for the transformer as a 230kV disconnect switch is opened to obtain a working clearance for 230kV cap bank after the SF6 cap breaker is opened. The waveforms are sampled at 12 bit, 20MHz w/ 64K records. The 60 Hz is filtered out to increase transient dynamic range of measurement. The bottom purple graph is the FFT of the H3 tap waveform that indicates frequency energy well into the MHz range. The FFT full scale is 5MHz.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 24

Zoom-in on first burst from left upper waveform set. Blue = H3 bushing tap (bushing max. input approx. 2.5kV). Red = X3 bushing tap. Green = Neutral bushing & represents pulse travel through H3 transformer winding / insulation combination from H3 to neutral.

Progress Report on Failures of High Voltage Bushings with Draw Leads

By Jim McBride and Larry Coffeen, JMX Services / NEETRAC 7/26/2010

7/26/2010 IEEE PES July 26, 2010 25

Summary1. Air disconnect switches and power circuit breakers are examples of

devices that produce a significant number of medium voltage and/or current, fast transients as a result of normal switching operations.

2. These fast transients have rise times in the sub-microsecond range with frequencies well into the megahertz region.

3. The fast transients are characterized as they reach the high side, low side, and neutral bushings of the auto-transformer using the NEETRAC OLFRA equipment built by JMX Services, Inc.