Northern Natural Gas Company
Fifth Revised Volume No. 1
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Effective Date: 11/01/2007, Docket: RP08- 67-000, Status: Effective
Fifth Revised Sheet No. 206A Fifth Revised Sheet No. 206A : Effective
Superseding: 1 Revised 2 Revised Sheet No. 206A
GENERAL TERMS AND CONDITIONS
Tolling Agreement. A tolling agreement or arrangement means that the owner of the
electric generator has agreed with an LDC to convert natural gas owned and provided by
the LDC to electricity owned by the LDC.
Total or Gross Heating Value. The term "total or gross heating value" means the total
calorific value, expressed in Btus when one cubic foot of anhydrous gas at sixty
degrees Fahrenheit (60 F) is combusted with dry air at the same temperature and the
products of combustion are cooled to sixty degrees Fahrenheit (60 F). The Btu
specified is on a higher heating value (HHV) basis. A conversion factor is required
to convert lower heating value to a higher heating value basis to correctly calculate
the expected fuel usage of certain equipment. For estimating purposes, the higher
heating value of natural gas is approximately 10 percent more than the lower heating
Town Border Station (TBS). The term "Town Border Station" ("TBS") shall mean the
physical location where the LDC receives gas from Northern. The TBS generally
consists of facilities to regulate gas pressure and measure gas quality and volumes.
Unauthorized Gas. "Unauthorized Gas" shall mean any volumes delivered to Northern
from receipt points which have not been nominated in any amount by any Shipper for
that month and which have not been scheduled by Northern.
Valid Request. Any reference in this Tariff to a "valid request" used in conjunction
with Section 26 "Requests for Service" shall also include any requests submitted
electronically through Northern's Internet website.
Wobbe Index - The term "Wobbe Index" shall mean a number which indicates the
interchangeability of gas. The Wobbe Index is determined by dividing the higher
heating value of the gas in Btu per standard cubic foot by the square root of its
specific gravity with the respect to air. Wobbe Index is used as an indicator of the
heat release rate of combustion equipment employing fixed orifices such as boilers,
stoves, water heaters, and furnaces.