ES&H Alert - Defective Load Break Switches

The following is a heads-up notice that we received from Mr. Victor Gutierrez, Brookhaven National Lab. BNL had a serious discovery of defective load break switches in 300kVA transformers. The announcement states that they plan to submit the following announcement to the DOE Electrical Safety Advisory Committee's Bulletinboard by Friday 10/3/97. They are also looking into submitting an OR as a near miss with possible fatal results. We will post supplemental information as it becomes available. For additional questions or comments, please contact Mary Grace or Greg Mitchell.

POTENTIAL DANGER

Introduction

A potentially serious condition has been identified with a RTE type loadmake/loadbreak switch which was installed in two separate 300kVA transformers at Brookhaven National Laboratory . These oil immersed switches, operated at 13.8kV, are designed to use a hook-stick to charge and activate a spring assembly ensuring quick loadmake/loadbreak operation while under full load. During a loadbreak operation, these switches seemed to charge the spring assembly as designed during normal hook-stick travel; but, the release mechanism never activated to de-energize the circuit. This defect left the transformer's 13.8kV primary energized, when it should have opened the circuit. This is compounded by the fact that the commercial interlock is configured to sense the hook-stick handle position and not whether the circuit is actually de-energized, allowing personnel access to the "live" 13.8kV components, including the non-load-break-rated overcurrent fuses. Access to these "live" components presents a lethal hazard potential for unfamiliar personnel.

Background

During late 1996, two new 13.8kV to 480V transformers purchased through Avon Electric were installed to provide power for an environmental remediation project on the BNL site. These transformers manufactured by Pennsylvania Transformer were supplied with load-break switches manufactured by RTE. The switches were labeled RTE item number 2238000C03M, which during a troubleshooting operation were found to be defective as stated above. Avon Electric, Pennsylvania Transformer and RTE have all been notified by BNL of this identified defect. Personnel from Pennsylvania Transformer investigated BNL's report of a failed switch. They replaced the two identified defective switches and took the failed parts for evaluation.

Conclusion

These loadmake/loadbreak switches are widely used in the transformer industry. Similar transformers on the BNL site are in the process of being evaluated for this defect. This notice is meant to provide an alert for all DOE sites and other facilities relying on similar switches that an evaluation of these units may be warranted.