R8‑17     STANDARD VOLTAGE

(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)           In order to promote standardization of service 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

 

 

 

 

 

240

 

480

  600**

2400

4160

4800

6900

 

 

 

 

1380

 

23000

 

34500

 

208Y/120

240/120

 

480Y/277

 

 

 

4160Y/2400

 

 

8320Y/4800

12000Y/6930

12470Y/7200

13200Y/7620

13800Y/7970

20780Y/12000

 22860Y13200

24940Y/14400

34500Y/19920

 

*see (a)(2) below

** This classification covers the range of nominal voltages from 550 to 600 volts.

(2)           Each electric supplier operating within the State of North Carolina under the jurisdiction of the Commission shall offer 120/240 volt, single‑phase service. No electric supplier shall offer 115/230 volt single‑phase service or other such similar variant of 120/240 volt single‑phase service except upon specific authorization of the Commission.

(b)  In order to promote harmony between the service of electric suppliers and the utilization 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 which 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 caused by the addition of customer equipment without proper notification to the electric supplier, by the operation of customer's equipment, by the action of the elements, by infrequent and unavoidable fluctuations of short duration due to system operations, by conditions which are part of practical operations and are of limited extent, frequency, and duration, or by emergency operations shall not be construed a violation of this rule.

(f)  Consumers 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 installation which permit greater variations than those required above may be allowed upon specific authorization by this Commission.

(NCUC Docket No. E‑100, Sub 9, 4/25/72.)