Subject of Previous Article 
Article

Glossary of Generators – Part One


Glossary of Generators – Part Two


First: Reasons
for having onsite generators
Second: Applicable performance standards for generator sets Third: Selection Factors Used For Generators Sizing Calculations


Third: Selection Factors Used For
Generators Sizing Calculations
3 Location Considerations, 4 Fuel Selection Considerations, 5 Site Considerations, 

Third: Selection Factors Used For
Generators Sizing Calculations
6 Environmental Considerations, 7 System Voltage and Phase, 

Third: Selection Factors Used For
Generators Sizing Calculations
8 Acceptable percent of voltage & frequency dip, 9 Acceptable duration of the voltage & frequency dip, 

Third: Selection Factors Used For
Generators Sizing Calculations
10 Percent And Type Of Loads To Be Connected – Part One 

10
Percent And Type Of Loads To Be Connected – Part Two


Third: Selection Factors Used For Generators
Sizing Calculations

Here
we will describe preliminary factors for selecting a generator for certain
project, which will be as follows:

11 Load
Step Sequencing

Loads Control Methods
There are many decisions, related to the
method of loads control, must be taken by the designer which will affect the
generator sizing process. The designer may select on or more loads control
method from the following:
Using
the one or more order from the above loads control methods will result in
smaller size generators than a fullload system, and will have a significant
savings in purchase price of the generators.

1 The
Load Prioritization Order
Prioritization Definition:
It is the process by which
the customer identifies what electrical loads are needed and in what
priority.

2 Load
Acceptance Order
Block
Load definition:
A block load refers to the percentage of
rated power at rated power factor instantaneously added to the generator.
For
example, if a generator is rated 1000 kW at 0.8 pf and a 250 kW load at 0.8
pf is applied to the generator, a block load of 25% [(power applied/rated
power) x 100%] is applied.
Load
Steps definition:
Load steps refer to the amount of load
that will be placed on a generator at one time.
Notes:
Block
Load & NFPA
Standards
Block
Load And Transient Capability For Gas Engine Generators

3 The
Load Shedding Order

4 The
Unit Starting Order

5 The
Unit Shut Down Order, and/or Redundancy
Fig.1:
Redundancy order

How To Calculate The
Required Load Steps/ Starting Sequence
Fig.1:
BMEP Curve from TMI
For example, Using Figure.1, the number of load steps needed for
desired power can be determined as follows:

12 Future
Needs

The customers’ future needs are to be
taken into account when sizing the generator set. If the customer anticipates
growth in their application due to increased volume or expanded needs, one of
two design solutions can be applied:
However, the projected load growth for
any application should never be less than 10%.
Table1
shows typical load growth
over a period of 10 years for various applications.
Table1: Load Growth over 10 Years for various
applications

In the next article, we will start
explaining the Applicable Procedures for Generators Sizing Calculations. So,
please keep following.
Back To 