INSTALLATION AND OPERATION LOAD SHARING MODULE Caterpillar


Chapter 3 - Setup and Calibration

Usage:

Introduction

Use this calibration procedure after a Load Sharing Module is installed on a generator set, to obtain the needed operating characteristics during load sharing.

1. Check that the proper voltage is connected to terminals 15(+) and 16(-). Proper polarity must be maintained. See the plant wiring diagram, Figure 1-3.
2. Remove wires from load sharing line terminals 10 and 11, and from the SPM-A Synchronizer (if used) at terminals 24 and 25.
3. Select isochronous operation by shorting terminals 13 and 14.
4. If a speed setting potentiometer is used, set it to mid position 50%.

------ WARNING! ------

WARNING - START-UP

Be prepared to make an emergency shutdown when starting the engine, turbine, or other type of prime mover, to protect against runaway or overspeed with possible personal injury, loss of life, or property damage.

--------WARNING!------
5. Start the engine according to the engine manufacturer's instructions. Adjust the engine for rated speed. Apply full load to the generator set.

NOTE: NOTE

The most accurate calibration is made at full load. However, if it is not possible to run the generator set at full load, run it at less than full lad, and reduce the voltage readings given in this calibration procedure proportionally. For example: run a 200 kW generator set at 100 kW and divide all voltages given in this calibration procedure by 2. If you reduce the load in this manner, be sure to reduce it by the same amount throughout the calibration procedure.

6. Set the LOAD GAIN potentiometer fully clockwise.
7. Check the load signal voltage between terminals 22 and 23. Adjust the LOAD GAIN potentiometer for 6.0 Vdc signal. If this voltage is not obtainable, set the load signal as close as possible to 6 Vdc.
8. Remove the load from the generator set.
9. Check the voltage between terminals 22 and 23. This voltage should be 0.0 ± 0.25 Vdc. If this voltage is not correct, the Load Sharing Module unit is faulty or there may still be load on the generator.

WARNING - HIGH VOLTAGEA high voltage across open CTs (current transformers) can cause death or serious injury. Do not disconnect a CT from the Load Sharing Module while the engine is running. The CTs can develop dangerously high voltages and may explode if open circuited while the engine is running.

For this check, the generator set must be running isochronously, not paralleled, and with a power factor greater than 0.8.

10. Check that the potential connections are made as follows and correct them if they are not.
* Phase A to terminal 1
* Phase B to terminal 2
* Phase C to terminal 3

NOTE: NOTE

The most accurate calibration is made at full load. However, if it is not possible to run the generator set at full load, run it at less than full load, and reduce the voltage readings given in this calibration procedure proportionally. For example: run a 200 kW generator set at 100 kW and divide all voltages given in this calibration procedure by 2. If you reduce the load in this manner, be sure to reduce it by the same amount throughout the calibration procedure.

11. Start the engine and apply full load to the generator set.
12. Using a dc voltmeter, measure the load signal at terminals 22 and 23. Adjust the load gain potentiometer to give a 6 Vdc load signal. If 6 Vdc is not obtainable, set the load signal as close as possible to 6 Vdc. Record this voltage.
13.Shut down the generator set.

WARNING - HIGH VOLTAGEA high voltage across open CTs (current transformers) can cause death or serious injury. Do not disconnect a CT from the Load Sharing Module while the engine is running. The CTs can develop dangerously high voltages and may explode if open circuited while the engine is running.

14. Disconnect the wire from terminal 5 that comes from the phase "A" CT and connect both wires from this CT to terminal 4.
15. Start the generator set and apply full load.
16. Measure the load signal at terminals 22 and 23. If the phase "B" and "C" current transformers are connected correctly, this voltage will be 1/3 lower than the voltage recorded in Step 13. For example: if the reading was 6 volts in step 13, the reading in this step should be approximately 4 bolts.
17. Shut down the generator set.
18. Reconnect the phase "A" CT wire to terminal 5.
19. If the reading in step 16 was correct, proceed to Load Gain Adjustment later in this chapter. Otherwise, perform the following Phase Correction Procedure.

Phase Correction Procedure

If this procedure is followed, the correct connection of the current transformers is assured; the correct CT will be connected to the correct input on the Load Sharing Module with the correct polarity. Use this procedure only if the Phasing Check indicates that the phasing is incorrect.

A CT for any phase (A, B, or C) will produce the most positive load signal voltage when it is connected, in the proper polarity, to the terminals on the Load Sharing Module which corresponds to the same phase. Any other connections of the CT will produce a less positive signal voltage. This procedure makes trial connections of the first CT to all three CT inputs on the Load Sharing Module, polarized both ways on each CT input. The load signal voltage is recorded for each connection, and the CT is then connected to the CT input terminals that produced the most positive load signal voltage and with the polarity that produced the most positive load signal voltage.

In alike manner, the second CT is tried on each of the two remaining CT input terminals in each polarity, then connected, in the correct polarity, to the terminals which produced the most positive load signal voltage.

The remaining CT is then connected to the remaining CT input and the load signal checked for each polarity. This CT is then connected to the CT input, polarized so that it produces the most positive load signal voltage.

When the procedure is completed, all three CTS are connected to the proper CT inputs on the Load Sharing Module, with the correct polarity, and are now labeled with their correct destinations.

The procedure for correcting phase wiring requires that the generator set be shut down and the current transformers disconnected many times. For convenience during the phasing check, the temporary method of connecting the current transformers shown in Figure 3-1 is recommended. By connecting a burden resistor (a 0.5 ohm, 20 W resistor), across each current transformer, that current transformer can be disconnected from the Load Sharing Module after removing all load. The connections between the terminal strip and the Load Sharing Module can be changed with the generator set running; however, remove all load before any changes in connections are made. Do not disconnect a wire from a current transformer with load on the system. After completion of the procedure remove the terminal strip and the resistors.

WARNING - HIGH VOLTAGEA high voltage across open CTs (current transformers) can cause death or serious injury. Do not disconnect a CT from the Load Sharing Module while the engine is running. The CTs can develop dangerously high voltages and may explode if open circuited while the engine is running.

For this procedure, the generator set must be running isochronously, not paralleled, and with a power factor greater than 0.8.

1. Start with the generator shut down.
2. Label each CT wire with the phase and polarity that you think it should be. Even though this identification may prove to be wrong during this procedure, this step is necessary so that the individual wires may be identified during the description of the procedure.


Figure 3-1. Temporary CT Connections

3. Disconnect the phase "B" CT wires from terminals 6 and 7 and connect these two wires together. Use a small screw and nut and tape the connection.
4. Disconnect the phase "C" CT wires from terminals 8 and 9 and connect these two wires together. Use a small screw and nut and tape the connection.
5. Connect the two wires from the phase "A" CT to phase "A" input terminals 4 and 5.

------ WARNING! ------

WARNING - START-UP

Be prepared to make an emergency shutdown when starting the engine, turbine, or other type of prime mover, to protect against runaway or overspeed with possible personal injury, loss of life, or property damage.

--------WARNING!------
6. Start the engine and apply full load.
7. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
8. Shut the generator set down and reverse the phase "A" wires on terminals 4 and 5.
9. Start the engine and apply full load.
10. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
11. Shut the generator set down.
12. Remove the phase "A" CT wires from terminals 4 and 5 and connect the phase "A" CT wires to phase "B" input terminals 6 and 7.
13. Start the engine and apply full load.
14. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
15. Shut the generator set down and reverse the phase "A" CT wires on terminals 6 and 7.
16. Start the engine and apply full load.
17. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
18. Shut the generator set down.
19. Remove the phase "A" CT wires from terminals 6 and 7 and connect the phase "A" CT wires to phase "C" input terminals 8 and 9.
20. Start the engine and apply full load.
21. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
22. Shut the generator set down and reverse the phase "A" wires on terminals 8 and 9.
23. Start the engine and apply full load.
24. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
25. Shut down the generator set.
26. Remove the phase "A" CT wires from terminals 8 and 9 and connect the wires to the pair of terminals, in the same polarity, that produced the most positive load signal voltage.
27. Untape and disconnect the Phase "B" CT wires. Connect the phase "B" CT wires to one pair of the two of the two remaining CT input terminals on the Load Sharing Module.
28. Start the generator set and apply full load.
29. Measure the load signal voltage at terminals 22 and 23 and record this voltage.
30. Shut the generator set down and reverse the phase "B" wires on the CT input terminals.
31. Start the engine and apply full load.
32. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
33. Shut down the generator set.
34. Remove the phase "B" CT wires from the terminals they are connected to and connect them to the remaining pair of CT input terminals on the Load Sharing Module.
35. Start the generator set and apply full load.
36. Measure the load signal at terminals 22 and 23 and record this voltage.
37. Shut the generator set down and reverse the phase "B" wires on the CT input terminals.
38. Start the engine and apply full load.
39. Measure the load signal voltage between terminals 22 and 23 and record this voltage.
40. Shut down the generator set.
41. Remove the phase "B" CT wires from the CT input terminals and connect the wires to the pair of terminals in the same polarity, that produced the most positive load signal voltage.
42. Untape and disconnect the Phase "C" CT wires. Connect the phase "C" CT wires to remaining pair of CT input terminals on the Load Sharing Module.
43. Start the generator set and apply full load.
44. Measure the load signal at terminals 22 and 23 and record this voltage.
45. Shut the generator set down and reverse the phase "C" wires on the CT input terminals.
46. Start the engine and apply full load.
47. Measure the load signal at terminals 22 and 23 and record this voltage.
48. Shut down the generator set.
49. Remove the phase "C" CT wires from the CT input terminals and connect the wires to the pair of terminals, in the same polarity, that produced the most positive load signal voltage.
50. Label each wire with the designation of the terminal to which it is now connected. Be sure and remove the original designations to avoid future confusion.

Load Gain Adjustment

For this procedure, the generator set must be running isochronously, not paralleled, and with a power factor greater than 0.8.

1. Start the generator set and run at full load.
2. Measure the load signal voltage and adjust the LOAD GAIN potentiometer for 6 ± 0.1 Vdc.

If the load signal voltage cannot be raised to 6 volts, and the phasing has been checked and is correct, it will be necessary to use a lower load signal voltage. Set the full load signal voltages to all generator sets in the system to the same voltage.

When paralleled, adjustment of a generator set's LOAD GAIN potentiometer clockwise will cause that generator set to carry less load. If stability problems occur when paralleled at a particular load signal voltage, reduce the load signal voltage by adjusting the LOAD GAIN potentiometer counterclockwise and set all the load signal voltage of all other generator sets in the system to the same voltage (NOTE-Adjust the LOAD GAIN with the generator running isochronously and not paralleled). When the load signal voltages of all generator sets in a system are reduced, the load sharing gain will be reduced. This may result in some loss of load-sharing sensitivity but will increase load sharing stability. It may be necessary to reduce the load signal voltage of each unit in the system to as low as three volts in cases of extremely poor system dynamics.

Droop Adjustment

Droop is usually expressed as a percentage. Droop percentage is calculated by dividing the difference between the no load speed and the full load speed by the rated speed.

The DROOP potentiometer only needs to be adjusted when the generator set is to be operated in droop mode. The method of setting droop depends on whether the load on the generator set is an isolated load or an infinite bus. Once adjusted, the droop potentiometer will not have to be readjusted unless a different droop percentage is desired.

Setting Droop For an Isolated Load

1. Open the OPEN FOR DROOP switch (or disconnect the wires from terminals 13 and 14).
2. Start the engine and adjust the speed for rated with no load.
3. Apply full load.
4. Adjust the DROOP potentiometer to give the desired speed. Example: Operating at 60 Hz, 57 Hz at full load indicates 5 percent droop. If only 50 percent loading is possible, 58.5 Hz would indicate 5 percent droop (see figure 3-2).


Figure 3-2. Droop Adjustment

Setting Droop For an Infinite Bus

1. With the generator not paralleled, adjust the speed above rated frequency by the percent droop required (set engine at 63 Hz for 5 percent droop on a 60 Hz system).
2. Mark the speed setting potentiometer position or measure dc voltage on TB27(+) and TB26(-), and re-adjust the engine speed for rated frequency.
3. Turn the DROOP potentiometer fully clockwise for maximum droop.
4. Synchronize the generator with the bus and parallel it with the bus.
5. Increase the speed setting potentiometer to the position marked in step 2, increasing load.
6. Slowly adjust the DROOP potentiometer counterclockwise, decreasing droop, until 100 percent load is obtained.

If it is necessary to set droop without pulling 100 percent load, set the engine speed accordingly for the desired percent of droop at the load to be pulled. For example: Five percent droop at 50 percent load will require a no load rated speed of 61.5 Hz, not 63 Hz, on a 60 Hz system.

Caterpillar Information System:

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