Gen Parallel Operation

7/27/2019 Gen Parallel Operation

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PRODUCT TRAINING

Parallel Operation


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PRODUCT TRAINING


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PRODUCT TRAINING

Parallel Operation - When is it Required?

1. To increase the capacity of available power without loss of

supply to the customers distribution system.

2. To allow the Generator to be connected to a live system ( e.g ;

the Mains, (Grid, Utility,), Multiple Generator systems, C.H.P, etc.

3. To allow shutdown of individual Generators for Maintenance or

repair purposes.

4. To economise operating costs by running multiple generators

according to load demand.

5. To provide an emergency back-up to critical supplies without

loosing power, ( e.g ; Hospitals, Ships, Computer data systems, etc).


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PRODUCT TRAINING

Parallel Operation - Essential Requirements

1. All Generators must have the same voltage.

2. All Generators must have the same phase rotation.

3. All Generators must have the same frequency.

4. All Generators and Prime Movers (Engines), must have similar no

load, to full load, voltage and frequency characteristics.

5. Generator installation must be provided with Synchronising

equipment.

6. Essential protection should include Reverse power, Over-current ,

Over-temperature, Generator Over/Under excitation.

7. Generator of dissimilar design or manufacturer, should have

similar waveform characteristics (harmonics), if Neutrals are joined.


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PRODUCT TRAINING

Parallel Operation - Synchronising AC Generators

Synchronisation is carried out in order to parallel a Generator onto a

live Bus-bar, either in Island mode ( with multiple Generator sets as the

only supply), or to the Utility..

Synchronisation can be achieved Manually, Semi-Automatic with

Check-sync, or by fully automatic P.L.C systems.

Why is Synchronisation of AC Generators necessary ?


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PRODUCT TRAINING


GEN 2

GEN 1

Consider a simple installation with two Identical Gen-sets, (breakers open circuit).

Normally, one (or more), generators will already be connected to the load, and

supplying power. (GEN 2 is now closed onto the Bus-bar).

DROOP CTAVR

It is also normal that the Generator on line (GEN2) will be running at nominal

frequency (50 or 60 HZ), while the incoming generator (GEN1), can be running at a

higher (NO LOAD), frequency of about 52 or 62 HZ.

AVR DROOP CT

MCB

LOAD

BUS-BARCB1

CB2


7/36PRODUCT TRAINING


GEN 2

GEN 1

When the relative Engine speeds are different, the Generator waveforms will be

rapidly going in and out of phase with each other.

DROOP CTAVR

AVR DROOP CT

MCB

LOAD

BUS-BARCB1

CB2

Synchronising equipment is required to monitor the Bus Frequency and the

Incoming Generator frequency, to ensure that the Generators are in Synchronism.

Synchronising

Equipment

To correctly Synchronise A.C. Generators, the frequencies must be ALMOST identical.

Frequency (HZ), is the Electrical equivalent of Speed (RPM), which means that the

engine SPEEDS must be ALMOST identical.



EXAMPLE : In this analogy two trucks represent two Generator sets, to be paralleled .

However, if the REAR truck is A FEW RPM FASTER than the FRONT truck, it will

VERY SLOWLY catch up with the truck in front.

SYNCHRONISING is exactly the same process, the RATE OF CHANGE in speed must

be SLOW ENOUGH to allow the BREAKER to close when the Generators are IN PHASE .

If both trucks are travelling at EXACTLY THE SAME SPEED, they will ALWAYS

remain the SAME DISTANCE APART, ( IRRESPECTIVE OF SPEED).


On-line Generator SetIncoming Generator Set On-line Generator SetIncoming Generator Set

SYNCHRONISED




GEN 1

GEN 2

Example :- GEN 2 is supplying load and is running at 50HZ (1500 RPM).

GEN 1 is INCOMING, and the engine speed has been adjusted down slightly to

almost 1500 RPM (for example 50.1 HZ).

As there is a SMALL RELATIVE DIFFERENCE between speeds, the Synchronising

equipment should be indicating that the Generators are moving IN and OUT of phase

SLOWLY enough to ALLOW TIME to close the breaker.

50 HZ

(1500 RPM)

50.1 HZ(1503 RPM)

IN PHASE




GEN 1

GEN 2

50 HZ

50.1 HZ

What will happen if the circuit breaker is closed in the final condition above ?

IN PHASE

Consider above condition:-

The Generator is IN PHASE, , but is now about to go OUT OF PHASE.

180o

OUT OF PHASE


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PRODUCT TRAINING


GEN 1

GEN 2

The Generator waveforms are 180 OUT OF PHASEwith each other.

180

The transient forces created are both Electrically and Mechanically DESTRUCTIVE

As the breaker closes, GEN 1 will instantly try to reverse the rotation of GEN 2.

This is IMPOSSIBLE, because of the inertia in the Engine/Generator moving parts.The Generators will be INSTANTLY CRASHED into synchronism. .

CR SHEDINTO PH SE

Electrical damage can occur to Diodes, Varistors, and Main Stator windings.

Mechanical damage may also occur to Couplings, Bearings, and Shaft.


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PRODUCT TRAINING


GEN 1

GEN 2

Example 2 :- GEN 2 is supplying load and is running at 50HZ (1500 RPM).

GEN 1 engine speed has been adjusted to almost 1500 RPM (50.1 HZ).

The Generator waveforms are SLOWLY moving IN and OUT of phase.

50 HZ1500 RPM

50.1 HZ1503 RPM

The circuit breaker can be SAFELY closed in the above condition.

IN PHASE

The Synchronising equipment indicates that the Generator are IN PHASE.


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PRODUCT TRAINING

MCB

LOAD


GEN 2

GEN 1

The INCOMING Generator should ALWAYS be slightly FASTER than the loaded

Generator. This ensure that the incoming Generator ALWAYS takes a small proportion of

load when the breaker is closed. This will prevent REVERSE POWER protection tripping.

DROOP CTAVR

AVR DROOP CT

BUS-BARCB1

CB2

The Generators are now IN PARALLEL, the next step is LOAD SHARING.

Synchronising

Equipment

When the Synchronising equipment indicates that the incoming Generator (GEN 1) is

IN PHASE with the Bus-bar frequency, the circuit breaker can be safely closed.

OK !


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PRODUCT TRAINING

POWER ( kW )

REACTIVE (kVAr)LEADING

REACTIVE kVArLAGGING

90

ACTIVE CURRENT is the USEFUL CURRENT , which is IN PHASE with the Voltage, and

provides the POWER, or kWATT component of the load.

INDUCTIVE CURRENT is WASTED or WATTLESS CURRENT, which is LAGGING the

Voltage by 90. This is the kVAr component, (POWER FACTOR 0).

ACTIVE CURRENT

p.f 1 (kW)

VOLTAGE

(50 OR 60HZ)

REACTIVE CURRENTLAGGING p.f 0

REACTIVE CURRENTLEADING p.f 0

TIME

VOLTAGE

(50 OR 60HZ)

The VECTORIAL RESULTANT is the kVA , ( APPARENT POWER).

The COSINE of the RESULTANT ANGLE is called the POWER FACTOR ( COS ).

90

CAPACITIVE CURRENT LEADS the Voltage by 90.

COS

COS

Parallel Operation - Load Sharing

REACTIVE CURRENT SHARING is controlled by the GENERATORS, (AVR & DROOP).


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PRODUCT TRAINING

The Brushless AVR controlled Generator has a natural linear voltage DROOPING

characteristic from NO LOAD to FULL LOAD.

0.5% Voltage Regulation for AVR Types MX321, MA325, MA327

1.0% Voltage Regulation for AVR Types MX341

REACTIVE (WATTLESS) CURRENT SHARING

409V

415V

VOLTS

0%

0.5%

1.0%

0% 50% 100%PERCENTAGE LOAD

TO AUTOMATICALLY SHARE REACTIVE LOAD CURRENT, GENERATORS

MUST HAVE SIMILAR NO LOAD TO FULL LOAD VOLTAGE CHARACTERISTICS.



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PRODUCT TRAINING

The PARALLEL DROOP CIRCUIT, provides a signal which allows the AVR to

sense WATTLESS REACTIVE CURRENT, ( ZERO POWER FACTOR ).

At full load 0.8 power factor the voltage DROOP required (single running), is 3%.

This is in addition to the normal (natural) voltage regulation of the AVR, and

allows the DROOP CIRCUIT to automatically control a % of the voltage.

The DROOP SETTING is adjusted on the AVR DROOP CIRCUIT.

A SHORTING SWITCH may be fitted across the DROOP CT for single running.

1.0% (SINGLE)


REACTIVE (WATTLESS) CURRENT SHARING

DROOP kWATT

403 V

415 V

VOLTS

0%

3.0%

0% 50% 100%LOAD AT 0.8 POWER FACTOR
http://localhost/var/www/apps/conversion/tmp/scratch_6/NPT39%20AVR%20DROOP%20CONTROL.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_6/NPT39%20AVR%20DROOP%20CONTROL.ppt


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PRODUCT TRAINING

Parallel Operation - Circulating Current

GEN 2

GEN 1

CB1

CB2

EXAMPLE: Two similar 400V Generators are required to operate in parallel

Generator 2 isincorrectlyadjusted to406V (at no load).

GEN 2 is connected to the Bus by closing circuit breaker CB2

400V

406V

MCB

LOADBUS

WHY IS DROOP IS REQUIRED FOR GENERATORS IN PARALLEL ?

AVR 1

AVR 2

SYNCHRONISING

EQUIPMENT

GEN 1 is synchronised with GEN 2, and breaker CB1 is closed

0 LOAD

CB2

CB1

The resultant Bus-Bar Voltage will be approximately average of the two Generators.

403V

403V

403V


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PRODUCT TRAINING


GEN 2

GEN 1

CB1

CB2

MCB

LOAD

GEN 1 EXCITATION SYSTEM is trying to PULL the voltage DOWN to 400 V.

This PRESSURE DIFFERENCE (VOLTS), forces CIRCULATING CURRENT into GEN 1.

AVR

AVR

403V

BUS-BAR

403 V

400V

406V

GEN 2 EXCITATION SYSTEM is trying to PUSH the voltage UP to 406 V.

CIRCULATING CURRENT

The RESULTANT VOLTAGE will be approximately. AVERAGE of the two Generators

CIRCULATING CURRENT is WATTLESS, (POWER FACTOR 0).

WHY IS DROOP IS REQUIRED FOR GENERATORS IN PARALLEL ?


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PRODUCT TRAINING


GEN 2

GEN 1

MCB

LOAD

HIGH LEADING CURRENT ( CAPACITIVE, power factor 0 ) is now flowing INTO GEN 1.

The DROOP CONTROL must REDUCE circulating current to ACCEPTABLE limits.

BUS-BAR

403 V

HIGH LAGGING CURRENT ( INDUCTIVE, power factor 0 ) is now flowing OUT of GEN 2.

CIRCULATING CURRENT

PF

LAG

1 LEADLEAD

PF

LAG

1 LEAD

PF

LAG

LEAD1

PF

LAG

LEAD1PF

LAG

1LEAD

PF

LAG

LEAD1

AVR 1

AVR 2

DROOP CT

DROOP CT

POWER

FACTOR

METERS

CB1

CB2

The MAXIMUM acceptable limit for circulating current is normally 8 %.


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PRODUCT TRAINING


PF

LAG

LEAD1PF

LAG

LEAD1

PF

LAG

LEAD1

GEN 2

GEN 1

MCB

LOAD

AVR 1 receives a signal proportional to the circulating current (LEADING p.f),

which INCREASESthe Generator D.C EXCITATION VOLTAGE.

AVR 1 DROOP CT

BUS-BAR

403 V

CIRCULATING CURRENT

AVR 2 DROOP CT

CB1

CB2

DROOP CT

AVR 2 receives a signal proportional to the circulating current (LAGGING p.f)

which DROOPS (DECREASES), the Generator D.C EXCITATION VOLTAGE.

DROOP CT

AVR 1

AVR 2

POWER

FACTOR

METERS

LEAD

PF

LAG

1 LEAD

PF

LAG

1LEAD


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PRODUCT TRAINING


GEN 2

GEN 1

MCB

LOAD

VR 1 DROOP CT

BUS-BAR

PF

LAG

LEAD1

VR 2 DROOP CT

CB1

CB2

PF

LAG

LEAD1

POWER

FACTOR

METERS

When the MCB is closed, the DROOP CONTROL must also assist in SHARING the

REACTIVE, ( power factor 0 ), component of the LOAD CURRENT.

LOAD CURRENT

DROOP CTVR 1

DROOP CTVR 2

LEAD

PF

LAG

1 LEAD

PF

LAG

1LEAD

PF

LAG

LEAD1

PF

LAG

LEAD1

LOAD403 V


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PRODUCT TRAINING

GEN 2

GEN 1

MCB

LOAD

AVR 1 DROOP CT

BUS-BAR

AVR 2 DROOP CT

kWATT

METER

ACTIVE CURRENT (power factor 1) is the kWATT component of the load, and is

CONTROLLED and SHARED by the PRIME MOVERS (ENGINES).

ENG 2

ENG 1

LEADkW

LEADkW

Parallel Operation - kW Load Sharing

kWATT

METER

LEADkW

LEADkW

The PRIME MOVERS (ENGINES), must have similar NO LOAD to FULL LOAD

GOVERNOR CHARACTERISTICS, in order to share the ACTIVE CURRENT, (PF1).

ACTIVE CURRENT or kW

LOAD


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PRODUCT TRAINING

1500 RPM

1560 RPMSPEED

0%

4.0%


A MECHANICAL ENGINE GOVERNOR REQUIRES A MINIMUM OF 4% SPEED

DROOP IN ORDER TO SHARE THE ACTIVE CURRENT (KW), WHEN IN PARALLEL.

1 HORSE POWER = 746 WATTS , ( OR 0.746 kWATTS .)

HORSE POWER is the mechanical equivalent of kWATTS, (ELECTRICAL POWER).

kWATTS = CURRENT X VOLTAGE X POWER FACTOR ( X 1.732 for 3 phase ).

ACTIVE LOAD CURRENT SHARING, is controlled by the ENGINE GOVERNORS.


ACTIVE CURRENT ( kWATT) LOAD SHARING


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PRODUCT TRAINING

ENGINE 2/ 500 H.P

ENGINE 1/ 500 H.P

EXAMPLE : Two Generator Sets are required to run in parallel, both sets have

equal size 500 H.P Engines, with mechanical ENGINE GOVERNORS.

How will ENGINE 1 and 2 share the load AUTOMATICALLY, throughout all load

variations, from NO LOAD to FULL LOAD ?

MCB

LOAD

BUS-BARCB1

CB2



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PRODUCT TRAINING

ENGINE GOVERNING

EXAMPLE : In this analogy the truck ENGINE represents the GENSET DIESEL

ENGINE, and the TRUCK represents the GENERATOR.

EngineA.C Generator



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PRODUCT TRAINING

ENGINE GOVERNING

LOAD LOAD

EXAMPLE : In this analogy the truck ENGINE represents the GENSET DIESEL

ENGINE, and the TRUCK represents the GENERATOR.

When the truck is UNLOADED, the engine is powering the LOSSES only.

When the truck is LOADED, the engine must provide extra power, and the truck

speed will fall (for example 4% SPEED DROOP), because the ENGINE GOVERNOR is

fixed at constant speed.

What will happen if the trucks are NOW JOINED SOLIDLY TOGETHER??

As with a Genset, the truck engine speed is FIXED, at a constant speed ie.,1500 RPM.



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PRODUCT TRAINING


ENGINE GOVERNING

The trucks are now JOINED TOGETHER, similar to two GENERATOR SETS when they

are in PARALLEL.

1) Both ENGINES have SIMILAR LOAD CHARACTERISTICS from no load to full load ?

How will the engines SHARE THE LOAD in the following situations ?...

LOAD LOAD

ANSWER - THEY WILL AUTOMATICALLY SHARE THE LOAD - EQUALLY


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PRODUCT TRAINING


ENGINE GOVERNING

2) THE TRUCK IN FRONT HAS A STRONGER ENGINE THAN THE ONE AT THE BACK.?

LOADLOAD

ANSWER- THE FRONT ENGINE WILL TAKE LOAD AWAY FROM THE REAR ENGINE.


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PRODUCT TRAINING

Parallel Operation - kW Load SharingENGINE GOVERNING

3) The TRUCK AT THE BACK develops an ENGINE FAULT, and LOOSES POWER ?

LOAD

ANSWER - THE FRONT TRUCK TAKES ALL OF THE LOAD, AND MOTORS

THE REAR TRUCK.

MOTORSMOTORSMOTORSMOTORSMOTORSMOTORSMOTORSMOTORSMOTORS


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PRODUCT TRAINING

ENGINE 2500 H.P

When BOTH Engines have similar GOVERNOR CHARACTERISTICS, they will share

the kW load in parallel, AUTOMATICALLY, from NO LOAD to FULL LOAD.

When the engines have DIFFERENT governor characteristics, (as single running

engines), load sharing will become UNEQUAL as kW load is INCREASED.

ENGINE 1500 H.P

1500 RPM

1560 RPM

ENGINE

SPEED


50% 0%

4.0% SPEED DROOP


In above example ENGINE 2 is the STRONGER ENGINE


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PRODUCT TRAINING

ENGINE 2/ 500 H.P

ENGINE 1/ 50 H.P

EXAMPLE: Two different sizes of Generator Sets are required to run in parallel,

Set 1 has a 50 H.P ENGINE, set 2 has a 500 H.P ENGINE.

How will ENGINE 1 know that it must take 10% of the total kW load,

AUTOMATICALLY, from NO LOAD to FULL LOAD ?

MCB

LOAD

BUS-BARCB1

CB2



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PRODUCT TRAINING

ENGINE 2500 H.P

When BOTH Engines have similar GOVERNOR CHARACTERISTICS, they will

PROPORTIONALLY share the kW load, AUTOMATICALLY, from NO LOAD to FULL LOAD.

ENGINE 1 should AUTOMATICALLY take 10% of the load throughout all load changes.

ENGINE 150 H.P

1500 RPM

1560 RPM

ENGINE

SPEED


50% 0%

4.0% SPEED DROOP


37 kW 370 kW

Parallel Operation kW Load Sharing


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PRODUCT TRAINING


ENGINE 2, 500 H.P

ENGINE 1, 50 H.P

Example : Engine 1 (50HP) develops a fault, which causes it to loose speed & power.

What will happen if Engine 1 is running in parallel with Engine 2?

MCB

LOAD

BUS-BARCB1

CB2

Answer; Engine 2 will be supplying ALL OF THE LOAD CURRENT, and feeding

back ACTIVE CURRENT (kWATTS) INTO GEN 1.

ACTIVE CURRENTGEN 2

GEN 1

GEN 1 has now become a MOTOR, DRIVING ENGINE 1.

REVERSE POWER.

WHAT IS REVERSE POWER ?

MOTOR

This is REVERSE POWER, and can severely DAMAGE the ENGINES.

Parallel Operation kW Load Sharing


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PRODUCT TRAINING

ENGINE 2, 500 H.P

ENGINE 1, 50 H.P

REVERSE POWER can occur :-

1. NO LOAD - following synchronisation, if the INCOMING Engine speed is lower than

the BUS BAR speed/frequency.2. ON LOAD - if a FAULT occurs on one of the Engines, causing it to LOOSE POWER,

or if the Governor is INCORRECTLY ADJUSTED relative to the other Generators.

MCB

LOAD

BUS-BARCB1

CB2

GEN 2

GEN 1

The Generator should be DISCONNECTED from the system to avoid damage.

ACTIVE CURRENT

REVERSE

POWER

PROTECTION

THIS IS ACHIEVED WITH REVERSE POWER PROTECTION

MOTOR


P ll l O ti kW L d Sh i


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PRODUCT TRAINING

How can kW Load sharing be achieved WITHOUT SPEED DROOP?, i.e., constant

speed from no load to full load?

Answer : The Engines must be fitted with ISOCHRONOUS ELECTRONIC GOVERNORS.

MCB

LOAD

BUS-BARCB1

CB2

ISOCHRONOUS

GOVERNOR kW FEEDBACK

ISOCHRONOUS


ACTIVE CURRENT

ISOCHRONOUS


ISOCHRONOUS


kW LOAD SHARING (kW), is achieved by GOVERNOR CONTROL from a kW feedback

signal, which automatically controls the kW LOAD SHARING.



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PRODUCT TRAINING

RETURN TO MAIN MENU

POWER FACTOR CONTROLLER PFC3

PARALLEL DROOP CIRCUIT
http://localhost/var/www/apps/conversion/tmp/scratch_6/NPT01%20MAIN%20MENU%20.ppshttp://localhost/var/www/apps/conversion/tmp/scratch_6/NPT39%20AVR%20DROOP%20CONTROL.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_6/NPT49%20PFC3%20+%20RCI.ppt

Documents

Gen Parallel Operation