Registered Public Utility Engineer - Power flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Planning reserve margin

Installed capacity minus peak demand, divided by peak demand. It measures capacity above forecast peak and is set by the balancing authority or state commission, commonly 15–20% for summer-peaking systems.

LOLE

Loss of Load Expectation, the expected number of days per year in which available generation cannot meet demand. A common planning target is 0.1 day per year, one event in ten years.

ELCC

Effective load-carrying capability: the additional peak load a resource can reliably serve. It credits variable resources below nameplate and is typically lower for solar than wind in summer-peaking systems.

Weather normalization

Adjusting historical load to remove the effect of actual weather, usually by regressing load against heating and cooling degree days, so forecast trend reflects non-weather drivers rather than anomalous years.

Per-unit impedance conversion

Z_pu,new = Z_pu,old × (S_new/S_old) × (V_old/V_new)². It rebases an impedance from one MVA and voltage base to another, required whenever combining equipment data on a common base.

Surge impedance loading

SIL = V_LL² / Z_c, where Z_c is the line surge impedance. A line loaded near SIL has an approximately flat voltage profile and requires little reactive support.

SAIDI

System Average Interruption Duration Index: total customer-minutes interrupted divided by total customers served, usually reported per year. It measures average outage duration experienced by a customer.

SAIFI

System Average Interruption Frequency Index: total customer interruptions divided by total customers served. It measures how often the average customer experiences a sustained interruption.

Slack bus

The power flow bus where voltage magnitude and angle are fixed. It supplies the mismatch between scheduled generation and load plus losses, and its angle is the reference for all others.

Zero-sequence network

The symmetrical-component network carrying ground-fault current. It exists only where a ground path is present, so delta windings and ungrounded systems block zero-sequence current flow.

Zone 1 distance reach

The first, instantaneous distance-relay zone, typically set to about 80% of the protected line impedance so it does not overreach past the remote bus for faults on adjacent lines.

Critical clearing time

The longest fault duration for which the system remains transiently stable. Beyond it the accelerating area exceeds the decelerating area under the equal-area criterion and the generator slips poles.

Revenue requirement

The total annual revenue a utility must collect: operating expenses plus depreciation, taxes, and the authorized return applied to rate base. It is the starting point for rate design.

Rate base

Net plant in service plus working capital and other allowed items, less accumulated depreciation. The authorized rate of return is applied to it to compute the return component of revenue requirement.

Coincident peak allocator

A cost-of-service method assigning demand cost by each class's contribution at the time of system peak. It favors classes whose peaks do not coincide with the system peak.

Decoupling mechanism

A ratemaking adjustment that separates utility revenue from sales volume, removing the incentive to oppose efficiency. Revenue shortfalls or surpluses from forecast sales differences are trued up.

Filed tariff

The schedule of rates, terms, and conditions on file with the commission. A utility may not charge outside it, and exceptions require commission approval or an authorized tariff provision.

Fuel adjustment clause

A tariff rider passing variable fuel and purchased-power costs to customers between rate cases, subject to a reasonableness review that can disallow imprudent costs.

Just and reasonable standard

The statutory ratemaking test requiring rates to recover prudently incurred costs and to avoid undue discrimination among similarly situated customers. It anchors both federal and state rate review.

ANSI Range A voltage

Service voltage within plus or minus 5% of nominal, the normal steady-state limit. Range B permits wider excursions of limited duration and frequency at the service point.

IEEE 519 harmonic limits

Standards limiting voltage distortion at the point of common coupling, commonly 5% total harmonic distortion, and current distortion scaled by customer size relative to short-circuit ratio.

Arc flash boundary

The distance at which incident energy equals the threshold for second-degree burn. Work inside it requires arc-rated PPE, and energized work needs a permit when de-energizing is infeasible.

Cluster interconnection study

A process that studies many interconnection requests together rather than serially, reducing queue backlog and assigning network upgrade costs across the cluster.

Certificate of public convenience

The state siting approval a utility must obtain before building generation or transmission. It typically requires need demonstration, environmental review, and public hearings.

NEPA environmental assessment

A federal review document determining whether a major federal action significantly affects the environment. A finding of significance triggers a full environmental impact statement.

Hosting capacity

The amount of distributed generation a feeder location can accept without violating voltage, thermal, or protection limits. It is computed per feeder and varies along the circuit.

Smart inverter volt-var

A DER control function that injects or absorbs reactive power in response to local voltage, supporting feeder voltage and reducing the need for conventional regulation equipment.

Duck curve

The net-load shape created by midday solar production: a deep midday trough followed by a steep evening ramp, making ramping capability rather than total energy the binding constraint.

Grid-forming inverter

An inverter that establishes voltage and frequency reference rather than following the grid, providing synthetic inertia and short-circuit strength as synchronous generation retires.

Asset health index

A composite score from condition, age, loading, and failure history used to rank assets for repair, refurbishment, or replacement before reliability degrades.

Dissolved gas analysis

A transformer diagnostic sampling insulating oil for gases generated by thermal or electrical faults. Gas type and ratio patterns indicate arcing, overheating, or partial discharge.

Professional seal obligation

An engineer seals only work they prepared or directly supervised. Sealing another's unreviewed work is misconduct regardless of employment relationship or client pressure.