(a) Each electric
supplier shall adopt and file with the Commission standard average service
voltages available from its distribution class facilities. The filing shall
contain the nominal voltage, base voltage, lower limit, and upper limit. The
voltage maintained at the point of delivery shall be reasonably constant and
variations therein should not normally exceed the limits set forth in this
rule.
(1) The standard nominal voltage
adopted by the electric supplier shall be a voltage indicated by the version of
ANSI Standard C84.1, Electric Power Systems and Equipment-Voltage Ratings (60
Hz), or equivalent ANSI standard as later amended, in effect at the time of
adoption of nominal voltages. The following standard nominal service voltages
are hereby adopted by the Commission as the preferred standard nominal service
voltages:
|
NOMINAL SYSTEM VOLTAGE****
|
|
Two-wire
|
Three-wire
|
Four-wire
|
|
Single-Phase Systems
|
|
120*
|
120/240*
|
|
Three-Phase Systems
|
|
208Y/120***
|
|
240/120
|
|
240
|
|
480Y/277
|
|
480
|
|
600**
|
|
2400
|
|
4160
|
4160Y/2400
|
|
4800
|
|
6900
|
|
8320Y/4800
|
|
12000Y/6930
|
|
12470Y/7200
|
|
13200Y/7620
|
|
13800
|
13800Y/7970
|
|
20780Y/12000
|
|
23000
|
22860Y/13200
|
|
24940Y/14400
|
|
34500
|
34500Y/19920
|
*see (a)(2) below
**This classification covers the range of nominal voltages
from 550 to 600 volts.
***A modification of this three-phase, four-wire system is
available as a 120/208YV service for single-phase, three-wire, open-wye
applications.
****Preferred system voltages are in bold-face type.
(2) An electric supplier may adopt
different nominal voltages to serve specific customers if such action does not
compromise prudent transmission and distribution system operation.
(b) In order to promote harmony
between the service of electric suppliers and the utilization of voltage
requirements of presently manufactured equipment, the following service voltage
variations are permitted:
(1) For service
rendered for individual residential use or specifically for lighting purposes,
the voltage variations shall not exceed five percent (5%) above or below the
standard base voltage.
(2) For
other service the voltage variations shall not exceed ten percent (10%) above
or below the standard base voltage.
(c) An electric supplier may elect to deliver
service at a nominal voltage that is not standard on its system. The variation
in the nonstandard voltage shall not exceed the limits set forth above for the
type of service being rendered.
(d)
Upon approval of the Commission and proper notification to its customers a
utility may cease to deliver a particular voltage.
(e) Variations in voltage in excess of those
specified that are caused by the following shall not be construed a violation
of this rule:
(1) Addition of customer
equipment without proper notification to the electric supplier.
(2) Operation of customer's
equipment.
(3) The action of the
elements.
(4) Infrequent and
unavoidable fluctuations of short duration due to system operations.
(5) Conditions that are part of practical
operations and are of limited extent, frequency, and duration.
(6) Emergency operations.
(f) Customers shall select,
install, maintain and operate their electrical equipment so as to cause the
least interference with the regulation of the electric supply system. Three
phase motors in excess of 20 horsepower, single phase motors in excess of five
horsepower and other apparatus with high starting or fluctuating currents must
be installed in accordance with the supplier's filed tariffs and rules and
regulations.
(g) Greater variations
in voltage for service to installations that permit greater variations than
those required above may be allowed upon specific authorization by the
Commission.
Notes
04
N.C. Admin. Code 11 R08-17
NCUC Docket No. E-100,
Sub 9, 4/25/72; NCUC Docket No. E-100, Sub 153,
11/27/2019.
NCUC Docket No. E-100,
Sub 9, 4/25/72.
