Statutes, codes, and regulations
Maine Administrative Code
Department 65 - DEPARTMENT OF PUBLIC UTILITIES COMMISSIONDivision 407 - PUBLIC UTILITIES COMMISSION
Chapter 320 - ELECTRIC TRANSMISSION AND DISTRIBUTION UTILITY SERVICE STANDARDS
Section 407-320-4 - QUALITY OF SERVICE

65-407-320 Me. Code R. § 4

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Current through 2024-51, December 18, 2024
Section 407-320-4 - QUALITY OF SERVICE
A.Frequency

Each T&D Utility shall design and operate its T&D system such that alternating current service shall be supplied at 60 cycles per second (Hertz or Hz) under normal, steady state conditions and shall vary only in accordance with Applicable Codes, Standards, and Requirements. The system shall operate within a +/-0.5 Hertz limit.

B.Voltage
1.Nominal System and Service Voltages

Each T&D Utility shall establish and maintain Nominal System and Service Voltages as may be required by the design of its T&D System and the service to be provided to its Customers. The Nominal System and Service Voltages shall conform with the standard nominal system voltages established by ANSI C84.1.

2.Voltage Variation; Limits
a. Each T&D Utility shall maintain and operate its system to conform to the voltage variation ranges established by ANSI C84.1 for Voltage Range A and Voltage Range B. Figure IV.B.2.a and Figure IV.B.2.b below set forth the voltage variation limit requirements specified by the current version of ANSI C84.1 (ANSI C84.1-2016), Range A and Range B.
b. T&D Systems shall be designed, maintained, and operated so that Service Voltages will generally be within the Range A limits. Infrequent and limited periods during which Service Voltages are outside of the Range A limits but are within the Range B limits are acceptable. When Service Voltages occur that are outside of Range B, T&D Utilities shall take prompt corrective action to restore the Service Voltages to acceptable levels.

Figure IV.B.2.a (Range A)

Established Standard Service Voltage

Minimum Voltage

Maximum Voltage

Type of Service

120

114

126

Single Phase

120/240

114/228

126/252

Single or Polyphase

208Y/120

197Y/114

218Y/126

Single or Polyphase

240

228

252

Single or Polyphase

480Y/277

456Y/263

504Y/291

Single or Polyphase

480

456

504

Single or Polyphase

600

570

630

Single or Polyphase

2400

2340

2520

Single or Polyphase

4160Y/2400

4050Y/2340

4370Y/2520

Single or Polyphase

12470Y/7200

12160Y/7020

13090Y/7560

Single or Polyphase

Figure IV.B.2.b (Range B)

Established Standard Service Voltage

Minimum Voltage

Maximum Voltage

Type of Service

120

110

127

Single Phase

120/240

110/220

127/254

Single or Polyphase

208Y/120

191Y/110

220Y/127

Single or Polyphase

240

220

254

Single or Polyphase

480Y/277

440Y/254

508Y/293

Single or Polyphase

480

440

508

Single or Polyphase

600

550

635

Single or Polyphase

2400

2280

2540

Single or Polyphase

4160Y/2400

3950Y/2280

4400Y/2540

Single or Polyphase

12470Y/7200

11850Y/6840

13200Y/7620

Single or Polyphase

3.Voltage Testing and Records

Each T&D Utility shall sufficiently test voltage levels within its service territory to assess and ensure compliance with voltage requirements set forth in this Rule. The voltage testing protocols shall be specified in the T&D Utility's Terms and Conditions, subject to Commission review and approval. Test results shall be maintained and made accessible in accordance with Section III.D of this Rule.

4.Harmonics

Each T&D Utility shall maintain and operate its system in a manner consistent with the IEEE 519 Standard: Recommended Practice and Requirements for Harmonic Control in Electric Power Systems. In accordance with the IEEE 519 recommendations, current distortion limits are determined by the short-circuit ratio, or the ratio of short-circuit current at the point of common coupling (PCC) to the maximum load or demand current.

5.Flicker

T&D Utilities shall limit the frequency and magnitude of Flicker events in accordance with IEEE Recommended Practice 1453.

65-407 C.M.R. ch. 320, § 4