t
800 Cabin Hill Dr.
Greensburg, PA 15601
John L. Munsch
Attorney
724-838-62 IO
Fax: 724-830-7737
November 22,201 1
FEDEX NEXT DAY
Ms. Sandra Squire
Executive Secretary
Public Service Commission of West Virginia
201 Brooks St.
PO Box 812
Charleston, WV 25323
Re:
Rodney E. Steorts v.
Monongahela Power Company
Case No. 11-0442-E-C
Dear Ms. Squire:
Monongahela Power Company (“Mon Power”) responds to the Final Joint Staff
Memorandum dated July 29, 201 1 in the above-captioned proceeding concerning inspection of
surge arrestors.
Mon Power believes that its inspection methods and intervals for surge arrestors comport
with industry standards. In addition, Mon Power submits the attached report to the Commission
Staff on the sufficiency of these practices.
Sincerely,
I,
Attorney
WV State Bar No. 9933
JLM:jss
Attachment
cc:
Certificate of Service
Rodney Steorts v. MP
NO, 1 I-0442-E-C
Surge Arrester Report
Mon Power will submit a report to the Commission Staff on the sufficiency of these
practices [inspection methods and intervals for surge arresters] by November 23, 201 1.
Mon Power installs surge arresters on distribution circuits routinely to protect equipment
from lightning or similar overvoltage events. Surge arresters are installed on distribution
transformers, reclosers, regulators and other major pieces of distribution equipment.
Mon Power’s practice of using surge arresters to protect utility equipment is consistent
with the rest of the utility industry.
Surge arresters are very simple devices; traditionally they were a set of spark gaps and a
non-linear resistor inside a porcelain housing. Modern designs use varistor materials
housed in a polymer housing. Both designs basically operate by diverting the surge
current from a lightning strike to ground thereby protecting the piece of distribution
equipment on which they are installed. Surge arresters are designed with an isolator on
the bottom of the housing. If the arrester fails, the isolator will operate to clear the
ground lead from the base of the arrester.
Surge arrester maintenance is limited to visual inspection as part of the overhead and
circuit inspection process. Surge arresters are very reliable devices and they are either
fully operational or failed. A distribution arrester in the failed mode can usually be
identified during a visual inspection by identifying the arrester’s ground lead is
disconnected or the housing is damaged. Industry standards such as The Institute of
Electrical and Electronics Engineers (IEEE) and Doble have recognized that there are
really no effective maintenance practices that can be performed on distribution class
surge arresters other than performing a visual inspection.
Mon Power’s practice of performing overhead circuit and equipment inspections on a six
year cycle is based on accepted electric utility practices and the experience of the
FirstEnergy operating companies. National Electrical Safety Code (NESC) Rule
12. I2 I .A states, “lines and equipment shall be inspected at such intervals as experience
has shown to be necessary.’’ Overhead circuit and equipment inspections have proven to
be successful in addressing emergent problems in a timely manner, allowing for proper
planning and remediation prior to the emergent problem having a negative impact on
personal safety, equipment integrity or service reliability.
Mon Power has experienced a very low failure rate of arresters when compared to the
number of surge arresters on distribution circuits. The Company does not have
abnormally high equipment failure that can be attributed to high voltage and the arresters
appear to be very effective at preventing distribution transformer failures during lightning
storms with out failure themselves. Therefore the Company’s experience indicates that
arresters are a very reliable piece of equipment and are relatively maintenance free.
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1
Re: Case No. 11-0442-E-C
CERTIFICATE OF SERVICE
I hereby certify that on this 22nd day of November', 20 1 1, a copy of the foregoing
Rporte was sent by U.S. Mail, First Class, to:
Rodney E. Steorts
249 Steorts Rd
Sutton, WV 26601
John Auville, Staff Attorney
Public Service Commission of WV
201 Brooks Street
P.O. Box 812
Charleston, WV 25323