Generator Fundamentals Transcript

7/25/2019 Generator Fundamentals Transcript

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Generator Fundamentals P a g e | 1

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Generator Fundamentals

Transcript

Slide 1

Welcome to the Data Center UniversityTMcourse on Generator Fundamentals.

Slide 2: Welcome

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normal play of the course. Click the Notes tab to read a transcript of the narration.

Slide 3: Learning Objectives

At the end of this course you will be able to:

Identify the main components of a standby generator

Explain the functions of a standby generators prime mover, the alternator and governor

Describe the various fuel types utilized by standby generators

Identify resources for on-site power technology guidelines

Slide 4: Introduction

Consider these statistics. According to Contingency Planning Research power related events such as

blackouts and surges account for 31% of computer downtime episodes lasting more than 12 hours, power

failure and surges account for 45.3% of data loss, and according to IDC power disturbances account for

about 33% of all server failures. A standby generator is one critical equipment component that will keep you

from becoming one of these statistics. Understanding the basic functions and concepts of standby

generator systems helps provide a solid foundation allowing IT professionals to successfully specify, install,

and operate critical facilities. This course is an introduction to standby generators and the subsystems that

power a facilitys critical electrical loads when the utility cannot.


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Slide 5: Standby GeneratorsA standby generator system is a combination of an electrical generator and a mechanical engine mounted

together to form a single piece of equipment. The components of a generator include the prime mover, the

alternator, the governor, and the distribution system. The distribution system is made up of several

subcomponents which include the Automatic Transfer Switch (ATS) and associated switchgear and

distribution. In many instances, generators also include a fuel tank and are equipped with a battery and

electric starter.

As we begin the course let us first focus on the internal combustion engine or the prime mover.

Slide 6: Internal Combustion Engine: The Prime Mover

The internal combustion engine is the well-respected workhorse of the latter half of the 20th century, and

has carried this role into the new millennium. In basic terms, an internal combustion engine converts its fuel

source into mechanical motion via its internal moving parts. As outside air mixes with the fuel inside the

engine these moving parts ignite the air/fuel mixture to create a controlled internal explosion (combustion)

within the cavities known as cylinders.

Slide 7: Internal Combustion Engine: The Prime Mover

Although there are numerous variations of the internal combustion engine, the most commonly used for

standby generator systems is the 4-stroke engine.

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It is referred to as a 4-stroke engine because of the four distinct stages that occur in the combustion cycle.

These stages include intake of the air/fuel mixture, compression of that mixture, combustion or explosion,

and exhaust. When referring to generators, the 4-stroke engine is generally referred as the prime mover.

The following slide describes the core attributes of the prime mover.

Slide 8: Fuel

There are four main fuels used to power generators. These include diesel, natural gas, liquid petroleum

(LP), and gasoline. The selection of a fuel type depends on variables such as storage, cost, and

accessibility. Generator systems with diesel or natural gas engines are the most common standby power

generators utilized to support data centers. Fuel availability generally dictates the type of standby generator

selected. For example, if a generator is located in an isolated area where public utilities are not available, LP

or diesel fuel are logical choices. Additionally, the generators fuel type, as well as the magnitude of potential

step-load changes, or whether the generator will be expected to support an instantaneous change in load

current, from zero to full load for example, will influence the selection of the governor. Because these

factors contribute to the accuracy and stability of the prime movers speed, they must be considered in the

overall design.

Lets review some of the advantages and disadvantages of the different fuel types.


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Slide 9: DieselDiesel fuel is often chosen in many applications because of easy onsite storage, fewer problems with long

term storage, reduced fire hazard, and more operating hours between overhauls. Disadvantages to using

diesel fuel are its low volatility at low ambient temperatures and diesel does not burn as cleanly as natural

gas or liquid petroleum and therefore it has potential harmful affects on the environment.

Slide 10: Natural Gas

Natural gas is used quite often due to its numerous advantages. Natural gas is a clean burning fuel with less

exhaust emissions and the exhaust is less harmful to the environment than diesel. Because natural gas is acleaner fuel there is minimum carbon build up and cleaner crankcase oil. Additionally, there are no fuel

storage problems, and there is less engine maintenance then diesel or gasoline generators. The

disadvantages of using natural gas are the high cost. Gas generators tend to cost more that other generator

types and you are also limited in the size of the generator. Natural gas is provided by a single source, its

regulated by the pipeline it is connected to. Subsequently, during emergencies, gas lines can get sucked dry

by other consumers and if you're towards the end of the line, you might not be able to get supply. Safety is

also another factor. If there are leaks it has a high explosive capability. Lastly, energy content of natural gas

is lower than most other fuel sources, so you need more of it to generate electricity for you generator.

Slide 11: Liquid Petroleum

The advantages of using a generator powered by liquid petroleum are similar to those of natural gas. Its a

clean burning fuel with less environmental impact than diesel, and the exhaust is less harmful to the

environment. Additionally, there are no fuel storage problems, and there is less engine maintenance then

diesel or gasoline generators. The biggest disadvantage to using a liquid petroleum powered generator is

that Liquid petroleum presents the greatest hazard. If any liquid petroleum vapors are leaked or released,

being heavier than air, the liquid petroleum will flow to low areas such as basements and potentially create

an explosion hazard.


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Slide 12: GasolineGasoline is often used in smaller engine generator sets due to the fact that it is readily available and that

gasoline powered engines start easier than diesel engines in cold temperatures. The disadvantages are

that the storage of gasoline is a fire hazard and that long term storage and usage of old gasoline can be

detrimental to the performance of the generator engine. Lastly, there is the option of using duel fuel engines.

For example, if a generator is capable of using both natural gas or liquid petroleum it offers that much more

flexibility when considering environmental safety needs and also the need for redundant power.

Now that we have examined fuel types lets look at another important aspect of generator function, cooling.

Slide 13: Cooling

The majority of prime movers for generator applications are cooled with a radiator cooling system much like

the cooling system in an automobile. A fan is used to move sufficient air over the radiator to maintain

moderate engine temperature. The waste heat is drawn off the radiator to the outside, with ductwork of the

same cross-sectional area as the radiator face. The intake air opening like, louvers into the room, is

typically 25-50% larger than its ductwork. Rigorous maintenance of the cooling system is needed for

reliable operation. Coolant hoses, coolant level, water pump operation, and antifreeze protection must bediligently reviewed for acceptable performance.

Slide 14: Lubrication

Next is lubrication. Modern 4-stroke engines utilize full-flow filter systems, which pump the lube oil through

externally mounted filters to prevent harmful particles and contaminants from damaging the moving parts or

bearings. Make-up oil reservoirs are used to maintain proper oil level, and external oil coolers assist in

preventing lubrication breakdown due to high temperatures.

Slide 15: Filters: Air & Fuel

Air and fuel filters are critical elements for the reliable operation of the prime mover. Like the other

components previously mentioned, it is essential that a proper maintenance schedule be followed. A system

that includes dual redundant fuel lines and filters is a significant benefit in mission-critical applications where


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long runtime must be supported. This is because fuel lines and filters can be isolated and changed whilethe engine remains running. Not having spare parts for filters and other "consumables" can result in

downtime. Proactive monitoring of these filters is done with Differential Pressure Indicators. They show the

pressure difference across a filter or between two fuel lines during engine operation. When applied to air

filters, these proactive monitoring devices are known as Air Restrict Indicators. These provide a visual

indication of the need to replace a dry-type intake air filter while the generator engine runs.

Slide 16: Starter motor

The last component of the prime mover that we will be discussing is the starter motor. As shown in thisillustration, the starter motor system is one of the most critical elements to the successful use of a generator.

The majority of generator systems use a battery-operated starter motor, as in automotive applications,

although pneumatic or hydraulic alternatives are sometimes found on the heaviest prime movers. The

critical element in the conventional starter is clearly the battery system. For example, the battery-charging

alternator present on some engines does nothing to prevent battery discharge during the unused periods.

Providing a separate, automatic charging system with remote alarm is considered a "best practice. It is

also essential to keep the battery warm and corrosion-free.


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Engine block heaters also contribute to the startup success rate by reducing the frictional forces that thestarter motor must work against when energized. Numerous studies have found startup failures to be the

leading cause of generator system failures.

Slide 17: Starter motor

When considering a standby generator, the minimum time to detect a power problem, start the prime mover,

establish stable output frequency and voltage, and connect to loads is usually at least 10-15 seconds.

However, many systems in use today do not reliably perform to this very quick deployment due to such

factors as uncharged or stolen batteries. Other factors include improper maintenance and human error.

Conscientious maintenance and design of a starter motor is absolutely critical to achieving a respectable

success rate for generator startup systems.

Slide 18: The Alternator: The Electrical Generation Component

The alternator is another critical component of the generator. The main function of the alternator is to

convert mechanical energy from the prime mover into alternating current. This is similar to the alternator in

an automobile, however in an automobile it is usually driven by a belt, whereas in a generator it is driven bythe main drive shaft of the prime mover. Through the years, certain characteristics of alternator components

have been improved to increase the efficiency, capacity and reliability of the alternator.

Lets start by looking at some of these improvements used in todays data center generators.

Slide 19: Brushless and Self Excited Alternators

The following diagram illustrates a cross sectional view of a self excited, externally regulated, brushless

alternator.



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The brushless designation refers to the fact that this design requires no contacts be placed against any

revolving parts to transfer electrical energy to or from the components. Brushes in motors and very small

generators may still be an acceptable design, but predictably the brushes wear out with use, and are

impossible to inspect in a proactive manner. A large generator design that relies on brushes is not up to the

reliability standards needed for mission-critical operation. When a generator is described as self excited it

means that the electricity used to create the electromagnetic field is created within the alternator itself

thereby allowing the alternator to produce large amounts of electricity with no other energy then what is

provided by the prime mover.

Slide 20: Main Stator/ Armature Windings

The Main Stator or Armature Windings are the stationary coils of wire where the electricity for the critical

loads begins to be generated. The characteristics of the alternating current produced are related to the

quantity and geometry of the coil windings. A large variety of configurations are available to deliver

combinations of ampacity and voltage requirements.


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Slide 21: The Governor

The next component we will be discussing is the governor. The governor maintains constant RPM of the

prime mover under a variety of conditions by adjusting the fuel that feeds the prime mover. A stable AC

frequency is required and is directly proportional to the accuracy and response time of the governor. This

item is a key component in determining the AC output power quality. Frequency variation and its impact on

power quality is not a problem that users must contend with when connected to a stable utility grid.

However, sensitive electronics are vulnerable to disruption due to abrupt changes in frequency under the

influence of generator power. The generators capability to produce a constant frequency is directly

proportional to the RPM speed of the prime mover which is controlled by the governor. Many system

designs exist, from simple spring-types to complex hydraulics and electronic systems that dynamically

adjust the fuel throttle to keep the engine at constant RPM. Simply adding or removing loads, or cycling

those loads on and off, creates conditions to which the governor must respond.


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Slide 22: The GovernorAn isochronous (same speed) governor design maintains constant speed regardless of load level. Small

variations on the speed of the prime mover still occur and their extent is a measure of the governors

stability. Today governor technology exists to maintain frequency regulation to within 0.25% with

response times to changing loads on the order of 1 to 3 seconds. Modern electronic solid-state designs

deliver high reliability and the needed frequency regulation for sensitive loads.

Slide 23: The Governor

Sophisticated electronic governor systems for paralleling have recently been developed that providesuperior coordination and frequency stability under a variety of conditions. When two or more generators are

paralleled for capacity or redundancy they must all be governed at the same speed using either the utility or

another generator as the primary frequency reference. This is because if the two sources are out of synch,

one of them will carry a larger fraction of the load, which will result in a needed correction. These advances

are a welcome enhancement to the high availability requirements of todays data centers, due to their

reliability, reduced maintenance, and coordination efforts.

Now lets review the voltage regulator.


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Slide 24: Voltage RegulatorThe basic function of a voltage regulator is simply to control the voltage produced at the output of the

alternator. The operation of the voltage regulator is vital to critical loads dependent on computer grade

power. The goal is to configure a system with an appropriate response time to minimize sags and surges

that occur as the load changes. Another issue to be aware of is the behavior of the regulator when

subjected to non-linear loads such as older switch-mode power supplies. Non-linear loads draw current in a

manner that is inconsistent with the voltage waveform, while resistive loads (like a light bulb) draw current in

synch with the voltage waveform. Non-linear loads can interact negatively with a generator system thereby

jeopardizing the availability of the critical load during standby operation.

Slide 25: Switchgear & Distribution

This diagram illustrates how the Automatic Transfer Switch ATS monitors the utility source and initiate

engine starting and transfer of the load from the utility to the generator as soon as the generator is available

and stable.

The ATS also re-transfers the load to utility when normal conditions are restored. Other common features of

ATS related equipment includes automatic generator test scheduling and monitoring of important cool-down


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cycles for the generator after the utility is restored. Traditionally this hardware is sourced from a variety ofvendors, including the generator manufacturers, distribution switchgear manufacturers, and specialists in

ATS design.

Slide 26: Grounding

When considering the best practices for a generator proper grounding should be first on the list. Grounding

is a necessity when it comes to both safety and the reliability of a generator. Grounding performs such

critical functions as:

Preventing the shock or electrocution of maintenance or repair techniciansEnsuring that circuit breakers trip before electrical malfunctions develop into fires and

Provide a low-impedance path for internal processing signals

Slide 27: Air & Noise Pollution

One key issue when discussing generators is that of air and noise pollution. Environmental laws, building

permits, and duration of generator use vary considerably by locale. For example, if the facility is located in a

stringent area, the generator system declarations on emissions may be required when applying for permits.

Industry professionals are usually experienced with the approval process in the locations they serve. As wehad discussed earlier, generators are very similar to automobiles engines. Just as automobile noise and

exhaust is a significant issue, so is the noise and air pollution caused by a generator. While the concept of

minimizing noise and ducting exhaust air is straightforward, the environmental and regulatory issues are not.

Slide 28: Noise Pollution

Local ordinances on noise pollution typically dictate the highest recordable background noise allowed in a

24-hour period. Exhaust mufflers are generally categorized as industrial, residential, or critical. Critical

offers the highest level of sound reduction. To spare the expense of a retrofit design, one should considerthe noise rating of the system prior to purchase and have these numbers qualified by the zoning authority in

the planning stages. Mechanical vibration also contributes to the overall noise level and the perception of

noise for occupants in the surrounding area. Mounting and isolation techniques exist to minimize this

concern.


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Now that we have explored the topic of environmental pollution lets a take a closer look at a feworganizations that set the regulatory standards for standby generators.

Slide 29: Regulations

In the United States, the Federal Environmental Protection Agency (EPA) has delegated to each state the

jurisdictional authority and discretion on how to achieve air quality goals established on the national level.

Other countries have similar regulatory bodies that set limits on generator emissions. For instance, Defra

(Department for Environment Food and Rural Affairs) sets policies for environmental protection in the United

Kingdom. And in India, the Ministry of Environment and Forests (MoEF) plays this role. In addition, thereare worldwide organizations that offer a wealth of information about emissions and other standby generator

considerations. One such organization is the EGSA (Electrical Generating Systems Association). EGSA

serves as a source of information, education, and training and develops performance standards for on-site

power technology.

Slide 30: Aesthetics

Another important consideration for generators is that of aesthetics. Some municipalities have requirements

in terms of placement of the generator, including that it be housed within concrete block walls that match themain buildings appearance. This keeps the generator from being noticed and keeps it aesthetically neutral

to the surrounding neighborhood. Now that we have discussed some of the regulatory issues of standby

generators, lets look more closely at some key maintenance measures that ensure optimal performance.

Slide 31: Maintenance Measures

Maintenance is the key to ensuring the seamless operation of your generator. As we have mentioned

throughout the course there are many different way in which you can optimize your standby generator.

When you consider the fact that malfunctions can be almost completely eliminated, with the proper

preventative maintenance, the importance of such preventative steps hits home.


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Here are a few steps to take to ensure that your generator is ready when you need it.

Its important to note that a good preventative maintenance program is going to require shutting off

all power for approximately 10-20 hours once a year. This will help to check the tightness of all

medium voltage (MV) and switchgear terminations

If a total shut down is not a possibility, thermal imaging can be used to detect any hot spots caused

by electrical terminations and connections

The trip setting of major circuit breakers should be tested

Transformers and cables should be tested, and lastly

Coolant samples should be taken for signs of insulation deterioration

Slide 32: Maintenance Measures

Additionally, a management system that monitors all generator subsystems and provides early warning

through preventative maintenance reminders is a great way to ensure reliability. Here are a few key

preventative maintenance initiatives that can be taken to ensure reliability of your generator:

Coolant hoses, coolant level, water pump operation, and antifreeze protection must be diligently

reviewed for acceptable performance.

Real time remote and local monitoring system that provides critical information and alarms at every

interface

Battery monitoring and weak battery detection

An automatic alarm that is sent whenever the controller is not set to automatic, the emergency stop

is engaged, or the generator output breaker is not closed

Block temperature and coolant level monitoring and alarms

Fuel level and load power measurements, available even when the generator is in standby

Oil level monitoring so that oil can be added or leaks repaired, rather than waiting for the generator

to start and shutdown due to low pressure


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Slide 33: SummaryTo summarize lets review some of the information that we have covered throughout the course:

A standby generator system is a combination of an electrical generator and an engine mounted

together to form a single piece of equipment.

The most commonly used engine for a standby generator system is the four stroke engine also

known as the prime mover.

There are four main fuels used to power generators, these include: diesel, natural gas, liquid

petroleum (LP), and gasoline.

In order to ensure reliability of your generator, it is advised that a detailed maintenance schedule is

maintained.

Slide 35: Thank You!

Thank you for participating in this course.

Generator Fundamentals Transcript

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