1	Improving IEEE 693 Test Procedures, Retrofitting Transformer Bushing to Improve Seismic Performance, and MCEER-EUC Anshel J. Schiff Precision Measurement Instruments 27750 Edgerton Rd. Los Altos Hills, CA 94022
2	Key Power Systems Issues Discussed Correct IEEE 693 procedures for the qualification of transformer bushings Correct IEEE 693 procedures for the qualification of hollow-core composite insulators Need for a technical review of IEEE 693 testing methods Need to test an improved retainer ring for retrofitting transformer bushings and evaluating it on a 500 kV bushing MCEER establishing Electric Utility Consortium
3	Correct IEEE 693 Procedures for the Qualification of Transformer Bushings IEEE 693 qualification tests on a 1980 vintage, GE Type U 230 kV transformer bushing did not cause oil leaks, porcelain slipping, or porcelain cracks Additional tests above IEEE 693 to the full capacity of the PEER (Richmond Test Facility) shake table could not cause failure In the 1994 Northridge earthquake about 25 of these bushings slipped and developed permanent oil leaks so that they had to be replaced
4	IEEE 693 Transformer Bushing Qualification Bushings are qualified by testing without being mounted on a transformer Bushings are attached to a stiff support structure for qualification Qualification base motions are doubled to account for the amplification introduced by the transformer Qualification base motions are doubled again to account for uncertainties in the failure mode (Tested to the Performance Level) These tests have not captured the influence of the transformer on bushing performance
5	Correct IEEE 693 Procedures for the Qualification of Hollow-Core Composite Insulators EPRI Consortium of Utilities have done research on composite CVTs IEEE 693 requires a pull test to 1/2 the SML load and measures the top deflection The top deflection forms the acceptance criterion for dynamic tests Damage to the composite assembly can increase damping and reduce stiffness of the unit The standard assumes that the increased flexibility will cause damaged units to exceed the acceptance criterion Post-vibration pull test show that units that pass IEEE 693 criterion would be considered to have failed
6	Need for a Technical Review of IEEE 693 Testing Methods Based on three qualification test that I have been involved with (the two above and one for disconnect switches) all have had flawed qualification methods IEEE 693 has been deficient in allowing the use of flawed measuring methods IEEE 693 has acceptance criteria that do not adequately evaluate the earthquake performance of tested equipment Commercial test laboratories uncritically follow the standard There is a need for a detailed review of IEEE 693 by individuals who are familiar with testing to monitor the qualification of equipment at commercial testing laboratories
7	Overall Assessment of IEEE 693 Good Uniform seismic input criteria established - facilitates manufacturers to incorporate seismic design as part of normal design process of new equipment Test and analysis methods standardized for qualification Uniform acceptance criteria are established Procedures are tailored to each type of equipment so that past earthquake performance and unique characteristics of the equipment can be taken into account
8	Need to Test an Improved Retainer Ring for Retrofitting Transformer Bushings Slipping between the transformer bushing flange and porcelain can cause permanent oil leak after an earthquake This requires that the bushing be changed and puts the transformer out of service Tests have shown that a retainer ring can prevent this on 230 kV bushings An improved ring needs to be evaluated and tested on a 500 kV bushing
9	MCEER Establishing Electrical Utilities Consortium MCEER and its predecessor (NCEER) have had a focus area on lifeline systems since their inception To improve the opportunity for utilities to guide the program for electrical power systems the Electric Utilities Consortium is being formed Participating utilities will have Flagship Partner membership in the center Participating utilities will have seats on the center's Industry Advisory Board and the MCEER-EUC Technical Oversight Committee