Registered Public Utility Engineer - Power key terms

A utility planning document comparing supply-side and demand-side options over a multi-year horizon to meet forecast load at least cost, subject to reliability and policy constraints, and typically filed for regulatory review.

The percentage of expected peak demand held as additional firm capacity to cover forecast error, forced outages, and weather extremes. It is a deterministic adequacy screen, distinct from probabilistic loss-of-load metrics.

The expected number of days or hours per year in which available generation cannot meet demand, computed by convolving unit outage probabilities with load. Common planning targets are about one day in ten years.

The amount of perfectly reliable capacity a variable or energy-limited resource can be credited with while holding system reliability constant. It varies with portfolio mix, load shape, and penetration level.

A projection of future electricity demand by hour, season, and year, built from weather normalization, economic and demographic drivers, and historical usage. Accuracy directly affects capacity procurement and rate design.

Adjusting historical sales or peak data to reflect typical rather than actual weather, usually through heating and cooling degree-day regression, so that forecasts and rate comparisons are not distorted by abnormal years.

A customer class's demand measured at the moment the whole system reaches its maximum. It drives transmission and capacity cost allocation because it reflects each class's contribution to shared peak-driven investment.

Average load divided by peak load over a period, expressed as a percentage or fraction. Higher load factors spread fixed costs over more energy and generally lower average cost per kilowatt-hour.

A normalization in which voltages, currents, powers, and impedances are divided by chosen base values so that transformer ratios disappear and quantities across voltage levels compare directly. Fault and load-flow calculations are normally performed in per unit.

A method that resolves unbalanced three-phase voltages or currents into positive-, negative-, and zero-sequence sets. It underlies unbalanced fault analysis and relay settings for ground faults and phase imbalances.

A calculation of fault currents at each bus under defined contingencies, used to select interrupting ratings, size grounding equipment, and set protection. Results must be updated when the network or generation changes materially.

The process of choosing pickup values and time delays so that the device nearest a fault clears it first, with backup devices operating only if primary protection fails. Coordination must respect equipment damage curves.

A reliability standard requiring the system to remain stable and within limits after the loss of any single element, such as a generator, transformer, or line. Violations trigger corrective operating or transmission plans.

A systematic simulation of credible element outages to identify overloads, voltage violations, and islanding risk. Results feed operating limits, remedial action schemes, and transmission planning studies.

A thermal, voltage, or stability limit that restricts power flow on a facility or interface. Binding constraints raise congestion costs and can force out-of-merit dispatch of generation.

The allocation of generation output among available units to meet load at minimum total variable cost, subject to ramp rates, minimum run levels, and network limits. In markets it appears as economic merit order.

The marginal cost of serving one additional megawatt-hour at a specific bus, composed of system energy cost plus congestion and loss components. It signals where new generation or transmission has the greatest value.

The total revenue a utility must collect to recover prudently incurred operating expenses, depreciation, taxes, and a fair return on rate base. It is the starting point for allocating costs among customer classes.

The net investment on which a utility is authorized to earn a return, typically plant in service plus working capital, less accumulated depreciation and deferred taxes. Its valuation and inclusion are contested in rate cases.

An analysis allocating a utility's revenue requirement to customer classes based on their responsibility for costs, using methods such as coincident peak, average demand, or minimum-system approaches for different cost components.

The structure of charges, such as fixed customer charges, volumetric energy rates, demand charges, and time-of-use periods, that recovers the allocated revenue while pursuing efficiency, equity, and policy goals.

A rate component billed on a customer's maximum measured demand, often coincident with system peak, intended to recover capacity and transmission costs that vary with peak contribution rather than energy use.

An energy rate structure in which the price per kilowatt-hour rises in successive consumption blocks, commonly used to encourage conservation and to shield low-volume customers from high fixed-cost recovery.

A regulatory mechanism that separates a utility's authorized revenue from its actual sales volume, so that lost revenue from efficiency or distributed generation does not penalize the utility financially.

A state or national requirement that a minimum share of retail electricity sales come from qualifying renewable resources, enforced through tradable credits and compliance filings with penalties for shortfalls.

A tradable certificate representing the environmental and compliance attributes of one megawatt-hour of renewable generation, tracked through a registry and used to demonstrate RPS compliance.

A contract between a generating facility owner and a transmission or distribution provider setting technical requirements, protection settings, metering, operating obligations, and cost responsibility for connecting to the grid.

A sequence of feasibility, system impact, and facilities studies that identifies thermal, voltage, protection, and stability impacts of a proposed generator and the network upgrades needed to accommodate it.

The amount of distributed generation a feeder or area can accommodate without adverse voltage, thermal, or protection effects under existing settings and without major upgrades. It informs siting and screening.

A protection function that detects and disconnects distributed generation when the utility source is lost, preventing an unintentional island that could endanger line workers and damage equipment.

The method assigning firm capacity credit to each resource type for resource adequacy purposes, increasingly based on marginal reliability contribution rather than nameplate rating, especially for variable and storage resources.

A short-duration reduction in RMS voltage, typically lasting from a few cycles to a few seconds, caused by faults or motor starting. It is a power quality concern distinct from a sustained undervoltage condition.

The ratio of the root-sum-square of harmonic components to the fundamental component of a voltage or current waveform, expressed as a percentage. High THD can overheat transformers and misoperate controls.

The set of characteristics describing voltage and current quality at a delivery point, including magnitude, frequency, waveform distortion, transients, and interruptions, judged against recognized standards and customer needs.

Planned clearing and inspection of rights-of-way to maintain required clearances from conductors. It is a leading driver of wildfire risk reduction and a major component of distribution operating budgets.

A structured process that identifies asset failure modes and consequences to target maintenance at the functions that matter most, balancing preventive and run-to-failure strategies against cost and risk.

Using sensors such as dissolved-gas analysis, thermography, vibration, or partial-discharge detection to trigger maintenance when measured indicators show degradation, rather than on fixed calendar intervals.

Total customer-minutes of interruption divided by total customers served, usually reported annually and excluding major-event days. It is a standard reliability performance measure used in regulation and benchmarking.

A regulator's examination of whether a utility's incurred costs and management decisions were reasonable given information available at the time, determining whether those costs may be recovered from customers.

A private communication with a decision-maker about a contested proceeding outside the formal record. It is generally prohibited or must be disclosed so all parties can respond, protecting due process.