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Products At Work: TDM Case Study

The following internal analysis was received from a major western utility company. The company has to date installed temperature differential monitoring on 15% of operating LTC's. The analysis covers the 6-month time period from 1/1/97 through 6/30/97. The vast majority of LTC troubles were identified as shown with TDM system technology. Ignoring the worst case scenario where a rewind would be required, the material and labor cost savings are still significant.

The customer outage information reflects a 4.5% reduction for the six-month time period. Projecting this percentage to include a TDM installation on all LTC's results in an annual outage reduction of 29.97%.

TRANSFORMER SAVES

Below is a list of transformers that were removed from service before they failed. Problems were detected by infrared, TDM's, and DGA tests. If left in service, at a minimum, customer outages would have occurred for each failure. Worst case scenario would include a total transformer rewind. On average for a typical 45MVA transformer winding failure, the total costs incurred would be approximately $500K. These costs would include removal and installation of the transformer.

1997:

1. Substation #1

TDM
Found hot connection due to loose bolts on low voltage bushing.
FPE
115/12KV
27MVA
LTC TC-546
Potential Customers Impacted = 758 Approximate Cost To Rebuild Only = $389K

2. Substation #2

TDM
LTC - Poor contact pressure caused contact burning which generated heat.
FPE
115/12KV
12.5 MVA
LTC TC-546
Potential Customers Impacted = 4572 Approximate Cost To Rebuild Only = $294K

3. Substation #3

TDM
LTC - Poor contact pressure caused contact burning which generated heat.
Maloney
115/12KV
12.5 MVA
LTC MB-2
Potential Customers Impacted = 2257 Approximate Cost To Rebuild Only = $294K

4. Substation #4

TDM
LTC - Poor contact pressure caused contact burning which generated heat.
Westinghouse
115/12KV
12.5 MVA
LTC UTT
Potential Customers Impacted = 10748 Approximate Cost To Rebuild Only = 294K

5. Substation #5

Infrared Inspection
Found hot 230KV bushing
Westinghouse
230/21KV
45MVA
LTC UZE
Potential Customers Impacted = 2516 Approximate Cost To Rebuild Only = $675K

6. Substation #7

TDM
LTC - Poor contact pressure caused contact burning which generated heat.
Westinghouse
4KV
2MVA
LTC URS
Potential Customers Impacted = 682 Approximate Cost To Rebuild Only = $83K

7. Substation #8

TDM
LTC - Poor contact pressure caused contact burning which generated heat.
FPE
115/21KV
13.5MVA
LTC 525
Potential Customers Impacted = 6536 Approximate Cost To Rebuild Only = $294K

8. Substation #9

TDM/DGA
LTC - Found loose bolt and burnt shunt.
FPE
230/34.5KV
115MVA
LTC UVT
Potential Customers Impacted = N/A Approximate Cost To Rebuild Only = $986K

OUTAGE INFORMATION

Total Customers = 28,069 customers
System Average Restoration Time = 105 minutes
Estimated Customer Minutes Saved = 2,947,245
Customers in System = 4,756,717
AIDI Saved = 0.62 minutes = 4.5 %
1997 YTD AIDI = 13.11 minutes
Potential AIDI W/O AIDI Saved = 13.73 minutes

Barrington Consultants, Inc.
2239 Valdes Court, Santa Rosa, CA 95403
Tel 707-527-8254 · Fax 707-542-9730 · Email ghb@barringtoninc.com

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