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Power Quality Engineers
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Character of Service
The Utility's System
Hawaiian Electric produces and delivers electricity using a vast network of generators, transformers, switches, and thousands of miles of power lines. Although this system is very complex, Hawaiian Electric's objective is to deliver electricity where and when it is needed more than 99.95 percent of the time. At 99.95 percent, electricity would be available for all of the year except for 4.4 hours. This measure of service quality is called reliability.
Since a continuous supply of electricity is what most customers demand, Hawaiian Electric has processes in place that maintain service reliability. Regular trimming of trees around overhead power lines, infrared scanning to pinpoint trouble spots, routine preventative maintenance of equipment, and system upgrades are just a few of the steps that Hawaiian Electric takes to provide reliable service.
Unfortunately, there are circumstances beyond Hawaiian Electric's control that can and will interrupt electric service. Events like severe weather, accidents involving electric lines, unforeseen equipment failure, and vandalism may cause short circuits or faults that lead to a power outage. Power outages typically occur when Hawaiian Electric's protective equipment detects a fault and attempts to isolate the problem area by automatically disconnecting lines. Depending on the severity of the fault, the faulted line is usually not reconnected until Hawaiian Electric's trouble personnel can visually inspect the system for the cause of the fault. This visual inspection is to ensure that the public and Hawaiian Electric personnel are safe from any electrical hazards.
Once the trouble spot has been located, Hawaiian Electric's trouble personnel reconnect the healthy sections of the line to restore power to as many customers as possible. As soon as Hawaiian Electric's line crew can repair the fault, customers without power will be reconnected. Hawaiian Electric realizes that outages are inconvenient for our customers but electrical safety for both the public and Hawaiian Electric personnel is always our first priority.
Character of Service
Hawaiian Electric's activities are governed by a set of rules and rate schedules set forth by the Public Utilities Commission of the State of Hawaii. This set of definitions, rules, and rate schedules is known as the Hawaiian Electric Tariff. The portion of the tariff applicable to power quality is Rule No. 2, Character of Service. A few excerpts specifically related to power quality issues are listed below:
- Frequency (Sec. A.2): Alternating current service of approximately 60-cycle frequency will be supplied.
- Voltages (Sec. A.3): Voltages referred to in the tariff are nominal and may vary within the limits set forth in Sec. B.3 of this rule.
- Voltage Limits (Sec. B.3): Voltage variations will normally be within the range specified in paragraphs a, b, and c below.
- Secondary Voltages: For all service, except power service, the voltage variation will normally be no more than 5 percent above or below the nominal voltage. For power service, the voltage variation will normally be no more than 7-1/2 percent above or below the nominal voltage. Where 3-phase service is provided the Company shall exercise reasonable care to assure that the phase voltages are in balance.
- Primary Voltages: For service rendered at a primary voltage the voltage variation will normally be no more than 5 percent above or below the nominal voltage.
- Transmission Voltages: For service rendered at a transmission voltage the voltage variation will normally be no more than 10 percent above or below the nominal voltage.
- Exceptions to Voltage Requirements:
Voltage outside the limits specified above may be furnished when:
- The customer, by contract, agrees to accept service with unregulated voltage.
- The variations arise from the action of the elements.
- The variations are infrequent fluctuations not exceeding 5 minutes in duration.
- The variations arise from service interruptions.
- The variations arise from temporary separation from parts of the system from the main system.
- The variations are from causes beyond the control of the Company.
- Such fluctuations are caused solely by the load of one particular customer which does not affect the voltage of other customers in the vicinity.
Usage of Service Detrimental to Other Customers (Sec. E): The Company shall have the right to refuse to supply loads of a character that may impair service to other customers. In the case of motor starting, welding machines, x-ray machines, arc furnaces and other installations of like character where the use of electricity is intermittent or subject to substantial fluctuation, the customer shall provide at his/her own expense suitable equipment to reasonably limit such fluctuation or the Company shall alter its facilities to correct such fluctuations and the customer shall make a contribution in the amount of the cost of such alteration.
Due to the dynamic nature of its customer load, Hawaiian Electric utilizes voltage regulators, which operate to maintain the voltage delivered to its customers within the limits set forth in the tariff. Normally, the variations to the service voltage are within these limits.