Comments opened with the suggestion that the Working Group name be changed to "Network Enclosure Fires" to imply that all network facilities are to be considered. Also, the suggestion was made to use the term "secondary network" when describing network applications to eliminate confusion.
Shayne Wright gave a presentation on HL&P’s activities to reduce network incidents. Actions included cost-effective modifications of vaults to allow remote switching, for example. Others include tying protector operation into heat detectors.
Bob Cunningham of Seattle City Light presented a video showing the effects of methane gas build up in manholes and meter cans. This issue has been of occasional concern where organic matter decomposition generates methane.
Joe Groeger of Altran Materials Engineering presented summaries of three utilities’ experience after network equipment failures with both Fire Department and eventual legal issues. Materials discussed included off-gassing propensity of various cable and vault equipment materials. It was noted that many utilities and vendors have misconceptions regarding "low smoke" cable performance with respect to manhole secondary network incidents. Jack Lasky of Okonite cautioned that low smoke insulations were developed with escape visibility in mind. The net burning of material and total smoke may be the same, if not more, than standard insulating materials. Most agreed that high fire point insulating materials warranted consideration for new secondary network applications.
Bill Thue suggested that an EEI study from approximately 20 years ago may provide meaningful information for a review of network limiter operations. The working group was not sure if secondary fuses are covered by ICC or T&D. This issue will be resolved by the next ICC meeting in November 1995.
Mr. Thue also suggested that litigation matters may be avoided by using examples of events which are beyond statutory time imitations.
In discussions as to developing a Guide for reducing the risk of secondary network incidents, concerns were expressed that 7-40 may be crossing over into equipment areas which are addressed by IEEE/PES T&D working groups and are beyond the scope of ICC. However, the point was made that not all of the items listed in the scope of 7-40 are addressed by T&D and the operational and maintenance issues of the total underground network system warrant discussion and possible inclusion in a Guide. The suggestion was made that T&D working groups be included in the review of any document and possibly have the T&D Transformer working group address ICC 7-40 concerns with respect to equipment within their scope. This issue was not finalized. Further discussion with the T&D working group members and ICC officers are planned and hopefully a more clear mission statement for 7-40 will be agreed upon by November 1995.
Collection of forensic evidence during and after a secondary network incident was an issue which everyone present agreed warranted more study and inclusion into a future guide. The subject of a Didactic on networks was discussed. Scheduling options for upcoming ICC meetings were significantly limited, as noted by Greg Mastoras. Options were discussed for extending the duration of the 7-40 meeting to include a 30-40 series of tutorials.
Support for developing a Guide was met with heated discussion. While the majority supported this venture enthusiastically, others cautioned that litigation matters should be carefully considered prior to considering such an effort. Topics for consideration in the Guide were presented by the Chair. Ensuing discussion ranged from caution against being prescriptive to dropping the entire concept of a Guide, for fear of litigation against the ICC or this subcommittee. The Chair noted, in principal, their use is elective. The Chair further noted that discussions had already been held with the legal staff of IEEE in this regard and it was noted that a founding principal of IEEE is the fostering and dissemination of knowledge. A Guide is consistent with these principals. It was agreed by the majority that the Guide concept would be pursued, but incrementally, beginning with a section of post-event evidence preservation.
A working group will carry on the activities of 7-40 between sessions, through mailings and phone meetings.
The meeting opened with Joe Groeger, Chairman of 7-40, who explained IEEE's reluctance to the development of a Guide because of legal concerns. He reiterated the scope of the Guide and emphasized its usefulness in the areas of basis forensic evidence collection and analysis. (For the purposes of continuity of the minutes, the SC- 7-40 group decided, collectively, to develop a Guide that would be incrementally developed, using a root cause Guide as the first step. Alternatives were discussed, including system design reviews, load flow analyses, and others, but these were determined to be very cumbersome given the tremendous variety between installed systems.)
Ralph Samm gave an update on EPRI's "Evaluation of Explosive Gases in Distribution Cable Systems." He explained that Bruce Bernstein of EPRI is manager of the project and UL Laboratories is the prime contractor. Test facilities in Lennox, MA are near completion. This site features full-sized manholes and below grade duct banks, using designs from Consolidated Edison of New York, the co-funding utility on this project. Experiments should begin in 1996. Manufactured explosions will be used to develop mitigation procedures in the construction of the underground systems. UL has determined that sustained high impedance arcing is possible at 120 volts ac and some of the by-products of several duct materials evaluated include carbon monoxide, carbon dioxide, methane and acetylene.
Joe Groeger presented a draft copy of the guide written by himself, Harry Thomas (Northeast Utilities, retired) and George Bolden (Eastern Utilities Associates). It was noted that George was unable to attend due to travel restrictions imposed by his employer. The focus of the Guide is on the need to preserve, then properly analyze evidence after a significant failure. Long-term preservation is stressed in the event that subsequent events or facts shed new light on a previous event. The benefits of following the basic methodology established in the Guide could be realized in the determination of the cause of failure, identifying failure characteristics that may exist in other areas and help justify a proactive approach to address potential problems. The Guide is expected to be developed to provide basic, elective suggestions in the areas of personnel safety, elimination of hazards to the public, secondary failures which could be caused by the initial event and the prevention of the spread of fire.
Joe Groeger recommended the current textbook Fires and Explosions by Randall Noon as a good source of information for understanding and mitigating fires and explosions. The reference was cited as being very practical and broad.
Mr. Groeger also gave a slide presentation illustrating a recent explosion in the vault of a hospital. Initially, the explosion was thought to have originated in an oil-filled switch. However, a detailed investigation revealed evidence of a bomb having been strategically placed in the vault. Joe explained how knowledge of structural members in the switchgear components and blast characteristics proved the origin of the blast. Jim Carey of United Illuminating Company gave a summary presentation on the work that they have conducted on a network cable condition assessment project, co-sponsored by EPRI and conducted at the University of Connecticut. In this project, a number of field-aged cables were removed from service for condition assessment using in-situ and laboratory methods with an emphasis on determining active aging mechanisms. In most cases, non-aged samples were not available for reference, though indoor sections of selected cables could be used as a partial basis for comparison. In other cases, manufacturing data was available for comparison. All cables tested were used for 120/208 volt applications and were aged for as long as 40 years. In summary, the program has found that these cables have sustained little, if any insulation degradation as a result of normal aging.
In the general discussion session, one utility inquired about personnel risks when traditional gas "sniffing" units are used prior to entering network manholes. It was noted that this type of device is best suited for detecting oxygen-depleted work environments and/or those high in carbon dioxide or carbon monoxide concentration. These are not effective for monitoring potentially explosive or combustible gases, though such devices are available. If combustible gases are present, though, the corresponding oxygen level could be expected to be reduced.
Potential plans for the next meeting were discussed. These include an invitation to OSHA and the National Fire Protection Association (NFPA). Attendance by the former would be limited to a presentation and follow-up questions, not to the general business session. It is anticipated that a hard copy of the draft Guide will have been developed to the circulation level by the time of the April meeting.
