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Reliability Data for 2011


Choptank's reliability indices for 2011:

Choptank Electric Cooperative's system-wide reliability indices for 2011 are listed below. These figures include all interruptions including planned construction outages as well as power supplier and major storm outages. The outages from August 27-29th, 2011 are coded as "Major Storm" and are associated Hurricane Irene that swept through the State of Maryland.

SAIDI
(System Average Interruption Duration Index) - average outage duration for each member served; calculated as sum of duration of all member interruptions for year divided by total number of members served.
System Total: 181.22 minutes

SAIFI
(System Average Interruption Frequency Index) - average number or frequency of interruptions that a member would experience; calculated as total number of member interruptions divided by total number of members served.
System Total: 2.04 interruptions

CAIDI
(Customer Average Interruption Duration Index) - average outage duration any given member would experience; calculated by dividing SAIDI by SAIFI.
System Total: 88.62 minutes

The indices with only "major storm" removed are as follows:

SAIDI
System Total: 177.04 minutes
SAIFI
System Total: 2.01 interruptions
CAIDI
System Total: 88.11 minutes

These indices give a value of the reliability performance of the Choptank portion of its system as a whole.

Choptank experienced approximately 2,262 outages in 2011: 445 caused due to equipment failure (67 underground primary cable, 152 underground service cable, 74 overhead transformers, 34 underground transformers). Note: transformer failures may or may not have been lightning related. 242 outages were lightning related; 77 vehicular outages, 41 dig-ins; 512 right of way outages with 29 caused by trees beyond the limits of the R/W; 29 power supplier outages; 352 outages caused by Hurricane Irene and coded as "major storm"; 564 outages caused by reasons such as animals, wind, ice, snow and unknown.

In 2012, Choptank will continue to replace old underground cable. Choptank's current underground cable design, which has been installed since the late 1980s, has been found to be extremely reliable. Choptank does not know of a single failure from the newer style cable. Choptank plans to continue the system-wide replacement of old primary underground cable.

In 2012, Choptank will bring a new substation on line in the Salisbury district to improve reliability, improve load transfer capability and reduce system losses. The co-op will also begin work on a substation in the Cambridge district that is designed to achieve similar results.

Choptank has several other feeder improvement projects that are being selectively undergrounded to improve reliability. When a feeder is selected to be rebuilt, its geography is examined to determine which portions should be constructed overhead and which ones should be constructed underground in order to reduce outages and increase operability of the feeder.

In order to address the endemic lightning problem found on the Eastern Shore, Choptank continues to install additional lightning arresters. Sectional ground rods are also being installed systemwide.

Choptank experienced 41 substation outages in 2011. In some cases, a single transmission outage is counted in Choptank's outage system as multiple outages when more than one substation is affected. 29 of these outages were power supplier outages that amounted to 19.7% of the customer-hours of outages experienced by Choptank's member- owners.

Choptank Electric continues to believe in the necessity of maintaining and enhancing the reliability of Choptank's service to its members. Choptank has begun a program of selectively undergrounding portions of its system to increase reliability.


Choptank Electric Cooperative, Inc., P.O. Box 430, Denton MD 21629 Toll Free: 877-892-0001


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