ME 31-POWER PLANT ENGINEERING: VARIABLE LOAD PROBLEM

Flashcards covering the fundamentals of variable load problems in power plant engineering, including definitions of demand factors, load curves, and hydroelectric specific terminology.

Variable Load

The variation in demand on a power station that occurs because consumers' power demands change in accordance with their activities, meaning the load is never constant.

Electric Power System

A system designed to connect the power station to the consumers’ loads through transmission and distribution networks.

Load Curve

A curve showing the variation of load on the power station with respect to (w.r.t) time.

Daily Load Curve

A graph where load variations during a day (24 hours) are recorded half-hourly or hourly and plotted against time.

Monthly Load Curve

A curve obtained from the daily load curves of a month by calculating and plotting average values of power at different times of the day.

Yearly Load Curve

A curve obtained by considering the monthly load curves of a particular year, generally used to determine the annual load factor.

Units generated/day formula

$$\text{Units generated/day} = \text{Area (in kWh) under daily load curve}$$

Average load formula

$$\text{Average load} = \frac{\text{Area (in kWh) under daily load curve}}{24\,\text{hours}}$$

Load Factor formula

$$\text{Load Factor} = \frac{\text{Average Load}}{\text{Max. demand}}$$

Ideal Load Curve

A curve representing constant power generation for the entire 24 hours of the day from the standpoint of the industrial plant or central station.

Connected Load

The sum of the continuous ratings of all the equipment connected to the supply system at the consumers' premises.

Maximum Demand

The greatest demand of load on the power station during a given period, such as a day.

Demand Factor

The ratio of maximum demand on the power station to its connected load; the value is usually less than 1.

Demand Factor formula

$$\text{Demand Factor} = \frac{\text{Maximum Demand}}{\text{Connected Load}}$$

Average Load

The average of loads occurring on a power station in a given period, such as a day, month, or year.

Yearly Average Load formula

$$\text{Yearly Average Load} = \frac{\text{No. of Units (kWh) generated in a Year}}{8760\,\text{hours}}$$

Diversity Factor

The ratio of the sum of individual maximum demands to the maximum demand on the power station, which is always greater than 1.

Diversity Factor formula

$$\text{Diversity Factor} = \frac{\text{Sum of individual max. demands}}{\text{Max. demand on power station}}$$

Plant Capacity Factor

The ratio of actual energy produced to the maximum possible energy that could have been produced during a given period.

Plant Capacity Factor formula

$$\text{Plant Capacity Factor} = \frac{\text{Average Demand}}{\text{Plant Capacity}}$$

Annual Plant Capacity Factor formula

$$\text{Annual Plant Capacity Factor} = \frac{\text{Annual kWh output}}{\text{Plant Capacity} \times 8760}$$

Reserved Capacity

The difference between the installed plant capacity and the maximum demand on the plant: $\text{Reserved Capacity} = \text{Plant Capacity} - \text{Max. Demand}$

Plant Use Factor

The ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation.

Plant Use Factor formula

$$\text{Plant Use Factor} = \frac{\text{Station output in kWh}}{\text{Plant Capacity} \times \text{Hours of use}}$$

Load Duration Curve

A curve showing the total time within a specified period during which the load equaled or exceeded power values, obtained by arranging load elements in descending magnitude.

Dump Power

Hydropower in excess of load requirements that is made available by surplus power.

Firm Power

Power intended to be always available even under emergency conditions.

Prime Power

The maximum potential power (chemical, mechanical, or hydraulic) constantly available for transformation into electric power.

Cold Reserve

Generating capacity that is available for service but not currently in operation.

Hot Reserve

Generating capacity that is in operation but not currently in service.

Reserve Equipment

The installed equipment in excess of that required to carry a peak load; if not in operation, it is sometimes called standby equipment.

Spinning Reserve

Reserve generating capacity that is connected to the bus and ready to take load.

System Reserve

The capacity in conductors and equipment installed on the system in excess of that required to carry the peak load.

Run-of-River Station

A hydroelectric generating station which utilizes stream flow without storage.

Spare Equipment

Complete equipment or parts kept on hand for repair or replacement.

Generating Station Auxiliary Power

The power required for the operation of the generating station auxiliaries.

House Turbine

A turbine installed specifically to provide a source of auxiliary power.