sebu7789-00 - operation & maintenance,service information

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Product: GENERATOR SET

Model: 3516B GENERATOR SET ZAP

Configuration: 3516B Generator Set ZAP00001-UP

Operation and Maintenance Manual 3500 Generator Sets Media Number -SEBU7789-06 Publication Date -01/08/2011 Date Updated -08/08/2011

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Parallel Operation

SMCS - 4450

Initial Start-Up

Preparing a generator for parallel operation requires special attention. Before you attempt to parallelunits for the first time, check all the units for the following three conditions.

same phase rotation•

same alternating current frequency•

same voltage adjustment•

Check the phase rotation.1.

Units that operate in parallel must have the same phase rotation. There are two methods thatmay be used in order to determine if the incoming unit and the unit that is on-line have the same phase rotation. These methods are listed below:

using a phase rotation meter ◦

using a set of three light bulbs◦

Use the procedure below to determine the proper phase rotation by using three light bulbs.

Page 1 of 53516B Generator Set ZAP00001-UP(SEBP4057 - 11)/Basic Search

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Illustration 1 g00695380

When servicing or repairing electric power generation equipment:

Make sure the unit is off-line (disconnected from utility and/or othergenerators power service), and either locked out or tagged DO NOT

OPERATE. Remove all fuses.

Connect the light bulbs with rated voltage between the generator leads and thecorresponding line phase. For example, connect terminal 1 to line 1 across the opencircuit breaker.

a.

Start the units that will be in operating in parallel. Bring the units up to speed. As theunits approach the same speed, the lights will start to blink.

b.

If the lights blink in sequence, one of the units is connected backward. In order tocorrect the problem, stop the units. Remove generator leads 1 and 3 at the circuit breaker. Exchange these generator leads. This reverses the direction of phaserotation. Terminal 2 should always be connected to line 2. Go to 5.

■

Both generators have the same phase rotation when the lights blink in unison. Thefirst condition of "Initial Start-Up" has been met.

■

Adjust the frequency.2.




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The units that will be operating in parallel must operate at the same speed. Speed is proportional to the alternating current frequency.

Allow each electric set to run under load for about 30 minutes.a.

Adjust the control in order to give the rated frequency at full load. b.

Remove the load and check the high idle speed. The high idle speed should beapproximately 2 to 5 percent above full load speed for generators that are equipped withdroop. If these speeds can not be obtained, contact your Caterpillar dealer.

c.

For the most consistent results, repeat 2.b and 2.c until the second condition of "InitialStart-Up" has been met.

d.

Adjust the voltage.The potentiometers should be at the initial settings. Refer to Operationand Maintenance Manual, "Voltage Regulators".

3.

Note: Make sure that the speed droop is identical for all of the engines beforeadjustments are made to the generator.

Preset the unit for parallel operation by connecting the current transformer to S1 and S2of the connector J2. Set potentiometer P1 for quadrature droop in the center position.Apply the rated load. The voltage should drop for 2% to 3%. Switch the positions of thetwo incoming secondary wires of the current transformer if the voltage increases.

a.

The no-load voltages should be identical for all the generators that are operating in parallel. Connect the generators in parallel. Try to obtain a 0 kW power exchange byadjusting the speed of the generator. Try to minimize the circulating currents betweengenerators by altering the voltage setting with potentiometer P2 or Rhe on one of thegenerators.

b.

Note: Do not change the voltage settings after this step.

Apply the available load. The setting is correct only if a reactive load is available.Equalize the Kilowatts or divide the rated power of the units proportionally by alteringthe speed. Alter the quadrature droop potentiometer (P1) in order to equalize the currentsor divide the currents.

c.

Starting Multiple Units

Use the procedure for starting single units in order to start multiple units. Refer to Operation Section,"Single Unit Operation".

Paralleling Multiple Units

Units may be paralleled at no load. Units may also be paralleled with units under load. After the initialconditions for start-up are satisfied, verify for the following requirements:

Generators must have voltage droop compensation or cross current compensation.•

Start the unit which will be paralleled.1.




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Turn on the synchronizer lights.2.

After the engine has run a few minutes, bring the engine up to synchronous speed. This meansthat the frequency of the incoming unit will be the same frequency as the unit that is on-line.The synchronizing lights will begin to blink.

3.

Note: The frequency of the incoming unit should be slightly greater than the line frequency.

This will allow the incoming unit to assume some of the load instead of adding to the systemload.

By using the control, adjust the engine speed until the lights blink very slowly.4.

The lights are off when the voltages of the two units are in-phase. At this point, very quicklyclose the breaker while the lights are out.

5.

Use the controls in order to share kW load between engines.6.

Generator temperature will be stabilized in approximately one hour. After the generatortemperature has been stabilized, adjust the voltage droop rheostat of each generator. This will

share the reactive load and this will limit the circulating currents. Less droop increases thereactive current that is carried by the generator. Adjusting the voltage droop rheostat in acounterclockwise direction will decrease the droop. Adjusting the voltage droop rheostat in aclockwise direction will increase droop.

7.

Load Division and Speed Droop (If Equipped)

Once two units have been paralleled, the unit's share of the kW load is determined by the controlsetting. If two units of the same capacity and the same characteristics have the same control settings,the units will share the load equally. The total load must not exceed the capacity of the one engine.

In order to transfer the load from one engine to another engine, use the following procedure:

Increase the speed control of one unit in order to increase the load.1.

Reduce the speed control of the other unit in order to decrease the load on that unit.2.

Raise the speed control or lower the speed control of both units in order to change systemfrequency.

3.

Stopping

In order to remove a generator from the line, perform the following procedure.

Check the load. The load must be less than the rated capacity of the remaining units.1.

Be sure that the neutral of one of the remaining units is grounded.2.

Remove the load from the outgoing unit. See the Parallel Operation, "Load Division - SpeedDroop". The amperage may never go to zero due to circulating currents.

3.

Open the circuit breaker.4.




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Allow the engine to cool for five minutes.5.

Stop the engine.6.

Circulating Current

s

Understanding the circulating currents becomes very important when you parallel the units. Thesecirculating currents are flowing between generators in parallel operation. The circulating currents arecaused by voltage differences between the generators. The circulating currents are not doing usefulwork. The amount of the circulating current can be determined by subtracting the amperage which isgoing to the load from the total generator amperage.

The circulating current may be as high as 25 percent of rated amperes with cold generator sets. Suchcurrent may not even be considered harmful. The total generator current should not exceed theamperage rating.

As the generators warm, the circulating currents will decrease. The ammeter readings should decreaseslightly, but the voltage meter readings should remain constant.

Copyright 1993 - 2012 Caterpillar Inc.

All Rights Reserved.

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Tue Jun 12 12:39:33 UTC+0500 2012


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