Generator Set Load Sensor Caterpillar

Note: Before you start this procedure, be sure that the phasing check has been completed. Refer to Testing And Adjusting, "Phasing - Check" for the instructions.

Most problems with paralleling are caused by the improper wiring of the three-phase current and the potential inputs. Common errors are listed below.

• Wiring the voltage of one phase with the current of another phase

• Wiring the transformers backward

1. Initial procedure

   1. Be sure that the engine is stopped. Label each current transformer (CT) lead with the phase and the polarity that you think it should be.

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   Never disconnect current transformers from the Generator Set Load Sensor when the engine is running. The current transformers can develop very high voltages when open circuited with the unit loaded. This can result in serious injury or death to personnel.

   Note: Terminals 4 through 9 of the generator set load sensor are the input terminals from the current transformers.

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   All current transformer lead ends must be connected to the Generator Set Load Sensor, or be taped as noted. If load is applied to the generator with leads not fastened together after they are disconnected from the Generator Load Sensor, extremely high voltages will be generated at lead ends. This can result in serious injury or death to personnel.

   Note: The CT leads can be taped together as follows: CT4 to CT5, CT6 to CT7, CT8 to CT9.

   2. Disconnect phase B CT input leads from T6 and T7. Tape these two lead ends together.

   3. Disconnect phase C CT input leads from T8 and T9. Tape these two lead ends together.

   4. Connect phase A CT input leads to T4 and T5.

2. Determine the phasing for phase A CT input leads.

   1. Start the engine. Apply a full load. Connect a DC voltmeter across terminals T21 and T22 on the generator set load sensor. T21 is a positive terminal. T22 is a negative terminal. Leave the voltmeter connected for the remainder of this procedure. Measure the load signal. Record this voltage.

   2. Unload the system. Stop the engine. Reverse the phase A CT input leads T4 and T5. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   3. Unload the system. Stop the engine. Remove phase A CT input leads from T4 and T5. Connect phase A CT input leads to T6 and T7. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   4. Unload the system. Stop the engine. Reverse the phase A CT input leads T6 and T7. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   5. Unload the system. Stop the engine. Remove phase A CT input leads from T6 and T7. Connect phase A CT input leads to T8 and T9. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   6. Unload the system. Stop the engine. Reverse the phase A CT input leads T8 and T9. Restart the engine. Apply a full load. Measure the load signal voltage and record this voltage.

   7. Unload the system. Stop the engine. Compare the six voltage readings that were taken in 2.a through 2.f.

      Expected Result: One of the voltage readings is higher than the rest.

      Results:

      • YES: Remove the phase A CT input leads from T8 and T9. Connect the phase A CT input leads to the pair of terminals that produced the highest positive load signal voltage and in the polarity that produced the highest positive load signal voltage. Go to 3.

      • NO: Check the voltmeter. Go to 2.a.

3. Determine the phasing for phase B CT input leads.

   1. Be sure that the engine is stopped. Untape the phase B CT input leads. Connect these leads to one of the two remaining pairs of CT input terminals.

   2. Start the engine. Apply a full load. Measure the load signal and record this voltage.

   3. Unload the system. Stop the engine. Reverse the phase B CT input leads. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   4. Unload the system. Stop the engine. Remove phase B CT input leads. Connect these leads to the other pair of terminals. Restart the engine and apply a full load. Measure the load signal and record this voltage.

   5. Unload the system. Stop the engine. Reverse the phase B CT input leads. Restart the engine and apply a full load. Measure the load signal and record this voltage.

   6. Unload the system. Stop the engine. Compare the four voltage readings that were taken in 3.b through 3.e.

      Expected Result: One of the voltage readings is higher than the rest.

      Results:

      • YES: Remove the phase B CT input leads. Connect the phase B CT input leads to the pair of terminals that produced the highest positive load signal voltage and in the polarity that produced the highest positive load signal voltage. Go to 4.

4. Determine the phasing for phase C CT input leads.

   1. Be sure that the engine is stopped. Untape the phase C CT input leads. Connect these leads to the remaining pair of CT input terminals.

   2. Start the engine. Apply a full load. Measure the load signal and record this voltage.

   3. Unload the system. Stop the engine. Reverse the phase C CT input leads. Restart the engine. Apply a full load. Measure the load signal and record this voltage.

   4. Unload the system. Stop the engine. Compare the two voltage readings that were taken in 4.b and 4.c.

      Expected Result: One of the voltage readings is higher than the rest.

      Results:

      • YES: Connect the phase C CT input leads to the pair of terminals that produced the highest positive load signal voltage and in the polarity that produced the highest positive load signal voltage. Relabel each input lead with the phase designation of the input terminal it is connected to. STOP.