Code of Maine Rules › 65 - DEPARTMENT OF PUBLIC UTILITIES COMMISSION › 407 - PUBLIC UTILITIES COMMISSION › Chapter 320 - ELECTRIC TRANSMISSION AND DISTRIBUTION UTILITY SERVICE STANDARDS › Section 407-320-4 - QUALITY OF SERVICE

Current through 2024-29, July 17, 2024
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.