McKinney J.D., Warnick C.C. Microhydropower Handbook Volume 1

‘,.’

. . :

,_ :..,,

‘. . . . .

~ ‘<,

,..:

,, . ..’

.,_:

. a:.

5.2.3.4 Equipment Checkout. The turbine-generator must be checked

out before it is energized. Auxiliary turbine-generator systems, such as

cooling or lubrication systems, should be checked out first to ensure that

they function in accordance with the manufacturer's instructions.

The turbine-generator can now be checked for rotation and vibration.

With the penstock purge valve open and the valve to the turbine closed, the

penstock headgate can be opened slowly. Allow water to fill the penstock

until it flows freely through the penstock purge valve, and then slowly shut

the purge valve.

Check to be sure that the generator is not connected

el ectizi' Cal ly

to the system, and then partially open the turbine inlet valve.

Because the generator is unloaded, the inlet valve should not be fully

opened under any circumstances or the turbine will quickly reach runaway

speed.

.Once the equipment is rotating near design speed, a check for vibration

and shaft speeds can be made. A hand-held tachometer is useful to determine

speed. Accessable shafts and bearings should be checked for quietness of

operation.

.A screwdriver or metal rod firmly pressed against the bearing

housing will indicate rumbling or uneven operation that may be due to dirt.

A whistling sound is attributable to improper lubrication or insufficient

interna. clearance.

Unusual. noises should be investigated immediately.

The temperature rise caused by bearing operation may make the bearing

housing too hot to touch.

Bearings can operate to temperatures of ZOOOF and

greater without failure.

If you suspect that the temperature is too hot,

con.sul,t the bearing manufacturer. Operating temperatures can be predicted

from the operating parameters of your site.

Make a manual check of the emergency shutdown system at this time to

ensure that it operates reliably.

Once all checks have been made, the system can be shut down: slowly

shut the turbine inlet valve, and then slowly open the penstock purge valve

and close the intake headgate.

.

5-32

5.2.4 Electrical

CAUTION:

Electricity is Hazardous.

As stated in Subsection 4.8.l, J

qualified electrician should help install the electrical system.

Before the electrical system is energized for the first time, it should

be inspected by an electrical inspector.

In many localities, this inspec-

tion will be a state or county requirement.

The electrical system can be constructed concurrently with ot::?? plJ;.

tions of the microhydropower system.

The final connections to the g+,'~:'+i-

tor, however, cannot be made until the generator is permanently insr.?1'~;

Some rules for the electrical installations are:

e

All conductors must be mechanically protected, or else routed at

such a height that they are not a hazb?d. Mechanical protection

can be conduit, metal raceway, or burial in the earth.

Minimum

heights ,for overhead lines should be as specified by the National

Electric Code (NEC).

e

All conduits, boxes, equipment enclosures, and other electrical

equipment must be securely supported and anchored.

Standard

installation procedures are to support all boxes and enclosures

independently.

Conduits should be anchored every.8 feet on center

and within 3 feet of every bend or enclosure and as specified by

NEC.

e All wire splices must be properly made and properly insulated as

defined by NEC.

0

All wiring connections to equipment must be made up tight.

CAUTION: Do not energize the system until all protective

equipment for that specified portion is installed.

5-33

_..

I

The electrical installation consists of connecting the generator

to the load through the overcurrent protective devices. These

pieces of equipment will be interconnected by the system wiring

and made ready for service.

.

0

If the power system has a load control system, this system must

be set up, connected, and made ready for operation.

0

If the power system

interconnect

s to a utility system;the step-up

transformer and its protection equipment must be installed and

made ready for service.

This work will usually be done by the

utility company and the cost billed to the developer.

Even if the

utility does not perform this installation, close coordination

',

with them is required.

CAUTION:

Do not connect to the utility's power line.

.

0

When the generator has been permanently set and aligned, the

electrical system can be connected to the generator.

The'coils

of the generator will have to be interconnected to provide the

required voltage in accordance with the supplier's recommenda-

tions.

After the generator has been connected to provide the

voltage desired,

it can then be interconnected to the rest of the

system.

‘.

. ..:;.

. .-

.'.,

..

,.: '.....

0

All system connections must be verified before the system is

. .

energized for the first time.

This should be done on a point-to-

point basis. Any wiring diagrams that have been produced will be

helpful in this final checkout.

0 Final connection to a utility line must be made by the utility.

The utility should be contacted and asked to proceed with any work

they have to perform. All disconnects must be left open at this

time.

_, ;:-

,. -..._

6.

STARTUP, OPERATION, AND MAINTENANCE

i

, up, equipment calibration, and

concern.

After the system has

maintenance system must be imp

give trouble.free operation.

Once the completed microhydropower system has been checked

O!.ii, ;:;--1..

steady-state operation are the next freer;,: ~,

been placed in steady-state operation,

t: ~Oc?cl

lemented to ensure that the equipment w ill

6.1 Initial System Startup

Starting up the completed system for calibration and then steaay, : :t;

operation requires the following test instruments:

0

Fuse tester

l

Hand-held tachometer

0

Volt-ohm-ammeter

I

Clamp-on ammeter

a Pressure gage with an air purge valve.

6.1.1 Synchronous Generator Startup

If the no-load test run of Section 5 checks out as expected, then

startup and operation of the generator with a small amount of connected

electrical load can begin. The generator should not initially be started

fully loaded; it should be started with about 10% load and then incremental

loads added if smooth operation continues. Resistance loads that produce

heat will work best because they are steady and can be easily controlled in

small increments.

If a load controller is being used in the system, you

should analyze it to determine what resistance can be used.

If motor loads

exist, they should be disconnected during the low output testing of the gen-

erator since sufficient power may not exist to operate them at their design

6-1

.-- .-I--- --. ..__. __. - ._...___ ._._- .._ _ _ _

. _ .

. .

_

_ . . _. .- ._ _

-

---. .~ .-

--.

condition.

This can be done by throwing the breaker in the panel. If you

are using a governor, review the manufacturer's data to determine at what

minimum load it will operate, and start there.

.:

Slowly open the turbine isolation valve a small amount to generate the

10% load.

The generator is loaded, and the system should run at its design

speed.

The amperage meter should reflect the power being generated, and

both frequency and voltage should be right on specification.

.._

Two or three frequency cycles either side of 60 Hz is acceptable, but

any more than that will require adjustment of the governor. A 10% system ,(

. . :

load will depend on the size of the system. For a lo-kW plant, 10% will be

1 kW, or 1000 watts (about the load rating of one small baseboard heating

unit or a hand-held hair dryer).

Larger plants will require correspondingly

greater converted loads to get to the 10% load level. Many homes powered

by microhydropower plants use electric heat, and these systems can be oper-

ated so that the loads are connected in increments for testing purposes.

Once the system is operating well at the 10% load level, the load can

be increased. . The power output will increase, but the frequency should stay

right at 60 Hz.

There may be a momentary blip in frequency when the addi-

tional load comes on, but that should last only a second or two until the

U governor system compensates.

The frequency is a function of generator speed, and the governor or

electronic load controller will control either the power supplied by the

turbine or the electrical load on the generator so that generator speed and

:'

frequency are maintained.

Both hydraulic and electronic systems may require

.._.' . .._.

some. adjustment before they operate.properly.

Specific operating instructions

for governors should come from the

operation manuals for those units.

Each has its own sequence for making

adjustments and fine tuning the system.

Once the right set points are

found, mark the panel faces so they can be reset if moved.

6-2

.

Let the unit run at part load for l/2 hour or more. Monitor ~.s..:EF~

tures

of the generator and bearings for abnormal heat buildup.

; i St',: f;.

any

vibration that is more than a common type hum, and be aware of rl",

abnormal

smells that could indicate excessive heat buildup or eltct.rlti

insulation

problems.

Increase the electrical load on the generator gradually. The frequency

meter should remain at CD 2 1 Hz, indicating that the governor is c!~.:~ci':‘ .r.

Properly.

Heat and vibration levels should not change. As the 1 ad6 u;i :’ _

generator changes,

the speed of the turbine and generator should remair :n,:

same.

You can check this function by varying the load. The fre<;ie. __ I_- :

will show any problems by varying more than 1 Hz from the 60-Hz r,a:?ir,ji.

When you have the system operating at full output, note the way it

sounds and feels.

Later,

any

change in those characteristics may indicare

that something is wrong.

An intuitive sense of when it is running woil will

be very helpful.

It may be helpful in developing that sense to sit and

watch

the unit run for several hours.

When one or more of the various protective devices such as governors

or

load

controllers (see Subsection 4.8.12) are included,

they should be

activated to be certain

that

they work properly.

Be certain that all oper--

ators understand the operation of these devices and know how to reset them

if

necessary.

The tachometer can be used to verify generator or turbine speed if

problems are encountered with speed control and frequency output. The

electrical instruments

should

be used to help adjust over current relays,

emergency shut down relays and circuit protective devices included in the

electrical control

systenb.

6.1.2 Connecting Synchronous Generators to Utility Powerlines.

The utility's representatives should be present during initial startup

and

synchronization of

the

generator to the powerline.

Syncronous

generators are connected to active utility powerlines only after the gener-

ator

has been brought up go the frequency and voltage of the powerline.

6-3

._‘__... ^ ._. .

Making a smooth connection to the powerline requires that certain prerequi-

site conditions be met. The output voltage of the generator must be the

same as the powerline, the speed of the generator must correspond to the

,

frequency of the powerline,

and the generator voltage must be in phase with

.

_. . .

the powerline. In actual practice, there is some tolerance in these condi-

tions.

A slightly higher generator voltage when connecting to the powerline

does not cause any serious problem. At the instant the connection is made,

the two voltages are forced to be the same. Minor differences in voitage

w

are neutralized by the internal impedance of the generator, which will seek

a phase angle with respect to the powerline that brings the voltages

together.

, ..'

Some minor difference in generator speed with respect to the powerline

is tolerable at the instant the connection is made, but immediately follow-

ing closure, the generator speed becomes locked to that of the powerline.

Any appreciable difference in speed at the instant of closure will result

in a corresponding mechanical and electrical jolt to the system.

When the individual cycles of the powerline are exactly in step with

those of the generator, then the generator and the powerline are said to be

"in phase." It is only when the generator and powerline are in phase that

the generator can be smoothly connected to the powerline. This is roughly

equivalent to engaging two rotating mechanical gears.

It is not sufficient

that the gears be rotating at the same speed to make a smooth engagement.

It is also necessary that the gear teeth be properly aligned at the instant

'i

,

,. .'

of engagement. If the generator and powerline are out of phase, the gener-

.'

,. . .

ator i's operated either faster or slower than the powerline until the two

systems are in phase. In actual practice, the speed of the generator is

adjusted until it is as near the frequency of the powerline as Possible.

The speed of the generator, however,'rarely remains precisely the same as

the powerline for more than a few seconds at one time. With this slight

difference in speed, the two systems will slowly wander into and out of

phase.

it is necessary to observe the phase relationship and close the

connection to the powerline only at the instant when the two systems are in

phase.

6-4

The typical power plant has voltmeters to compare voltages

11: ~7~. ’

systems and a synchroscope to determine the relative speed of ~iie ',

1, r( \I 5,' j ^

terns.

A synchroscope is a round dial with a single pointer. The ?oi.::??r

rotates at a speed which is the difference between the frequency cf t::

powerline and the generator. The pointer comes to a halt when tne ~2rIc~ra-,;tr.

is operating at the speed of the powerline;

and the pointer points up when

the systems are in phase. In a typical plant, the pointer on the synct~-

scope will not come to a complete halt until the generator is connec'.x :o

the powerline. After the connection is closed, the pointer will re;na;ji

fixed pointing upward.

Counterclockwise rotation of the pointer IPL~..~~;:L

that the generator is rotating more slowly than the poweriine freqluc T,_\J &'.c;

clockwise rotation indicates that the generator is rotating faster +.!a(~ t,I‘e

powerline frequency.

It is generally accepted that closure to toe poti,e~.i,~;e

is best made with the pointer moving slowly clockwise and with the needie

slightly past the straight up position.

This, however, is somewhat

dependent on the characteristics of the plant.

If the voltage,

speed, and phase are correct, the,generator is said to

be synchronized with the powerline,

and connection to the powerline can'be

made with no noticeable mechanical or electrical reaction.

A mismatch of

voltage, speed, or phase when connection to the powerline is made will *cause

a mechanical reaction and an electrical surge in the connecting lines.

The

severity of the reaction will depend on the degree of mismatch. Closure of

the connection when the generator is 180 degrees out of phase is the worst

case situation. Such an event may result in an electrical surge that is

worse than short circuit and could do considerable damage to the generator.

A properly designed system will have protective equipment that should pre-

vent damage from such an event by disconnecting the generator from the line.

,

Use of a synchroscope is one of several ways that can be used to syn-

chronize the generator with the powerline.

There is a very unsophisticated

method that uses lamps connected between the powerline and generator to

indicate phase and frequency and in a crude way voltage also.

The lamps

blink on and off at a rate that corresponds to the difference between the

speed of the generator and the frequency of the powerline.

When the !aaps

stop blinking, the generator speed is matched to the powerline.

Depending

6-5

‘.

on tne connection, the lamps will be full bright or totally dark when phase

and voltage are correct. Similarly, voltmeters can be connected so

as

to

react with the same pattern as the lamps.

Combinations of lamps and volt-

meters can also be used. A problem with this method is that both lamps and

vcltmeters have reaction patterns that lag behind the true

voltage

being

indicated. However, such systems have been used very successfully.

.

Some equipment suppliers are supplying microhydropower developers with

solid-state equipment that senses when conditions are correct for. closing

the connection to the powerline and automatically closes the switch.

In

these installations, the operator adjusts speed and voltage.

When condi-

tions are correct, the system automatically makes the

connection without

the need for a

synchroscope.

With the generator connected to the powerline, load can be added by

increasing water flow to.the turbine.

As load is increased,

it may be nec-

essary to add excitation current if the generator

has an external exciter,

but most small plants begin operation with an excess of exciter current,

which permits a wide range in generator load without need for adjusting the

exciter current. Self-excited generators are usually

self adjusting. If

the.exciter current is run too low, the power factor

of the generator will

be low and the generator may pull out of synchronism.

For this type of installation there is little need for automatic speed

regulating equipment unless there are periods when the plant is to run

stand-alone.

Before three-phase generators are connected to a powerline, it is cus-

tomary to check the phase rotation of the generator.

It is possible to

make

an error'in the wire connections so that phase rotation is opposite that of

the powerline.

Checking. the phase rotation is usually done with a special

meter with leads that clip onto the three output leads

of the generator.

The generator should come with sufficient wiring information

to be able to

make the connections without error.

However,

it is a good idea to check

the phase rotation from the actual output voltages of the generator because .

.

6-6

an error could cause damage to the generator.

If a synchroscope is .Y~G Q,:

the plant, incorrect phase rotation would be shown by the fact t3a+. j'.

would not function.

6.1.3 Induction Generator Startup

The startup of an induction generator differs somewhat from a ~*~qr:hro,-

nous generator.

An induction generator is always connected to a ui.;- lJ

powerline, and so a utility representative should be present for 7n-i :,:-I

startup. The induction generator should be energized momentarily tr: -h+p~

for correct rotation acting as a motor. Any reverse current relays rig ;-

have to be switched out of the control circuitry. If rotation is "R~-.:,*YY;,

then a reconnection of the wires at the generator will correct the pr~~l~rr:.

Once the generator has been wired to rotate correctly acting as a motor,

then it can be energized again to run as a motor.

While the generator is running as a motor, make calibration checks to

determine what the incoming power characterisitcs are on all phases. Look

for an imbalance in voltage between phases. A difference of 15 to ?8% is

probably not abnormal, but more than 10% could indicate a problem on the

utility line.

Check the shutdown circuitry to ensure that it functions properly for

over- and undervoltage tripout, over- and underfrequency shutdown, reverse

current trip, etc.

After the shutdown circuitry has been checked and the relays have been

properly adjusted, the generator can then be energized again as a motor.

Once the unit is running smoothly, open the turbine inlet valve slowly while

monitoring the system ammeter.

Remember, reverse current relays will be

switched out of the control circuit at this time.

As additional water is

allowed to flow through the turbine,

the ammeter will slowly decrease mtil

the synchronous speed of the generator is reached (no motor slip exists).

Once the synchronous speed is exceeded, the generator begins to function not

as a motor but as a generator,

and the ammeter now reads output instead of

input.

The turbine inlet valve can be set for maximum generator output, and

\

L-- ’

6-7

McKinney J.D., Warnick C.C. Microhydropower Handbook Volume 1

Подождите немного. Документ загружается.