Set up for Multi-unit Paralleling
For island paralleling mode, all units must be interconnected with control wiring for proper load sharing and control functions. All connections are made in the customer connection box.
Review what type of control system is used in each unit that will be paralleled together. Reviewing the control system is the first step in determining how to interconnect units.
Using 24 Pin Interconnect Harness
Install the factory-supplied 24 pin interconnect harness beginning at connector B (lower) on the first unit to connector A (upper) of the next unit. Continue in this fashion until all Units are connected together. No other interconnect control wiring is required.
Dead bus arbitration - When starting the group of units, the first unit up to rated voltage and frequency will close to the dead bus. Remaining units synchronize to the live bus.
Load sense/load demand - Automatically regulates which units to be running and paralleled on the common bus based on the load level. Higher load levels will require more units to run, lower load levels will require fewer units to run. To use this feature, each unit must be configured uniquely. Refer to Special Instruction, LEBE0007, "EMCP 4.4 Application and Installation Guide". This feature is disabled as factory default.
Group start - Allows for starting the entire group of units by wiring the remote start contact to a single unit within the group. In order to use this feature, connect a remote run request contact to terminals GRR+ and GRR- on any one unit.
Real power (kW) sharing - Automatically shares the load (kW) proportionally among all paralleled units.
Reactive power (kVAr) sharing - Automatically shares reactive load (VAr) proportionally among all paralleled units. Uses a 0-10V analog signal which is not designed to interface to any devices other than EMCP 4.4.
Manual Operation
The power module can be used in parallel with other units to provide power for an isolated load. Manual operation refers to manually closing the generator breaker using the circuit breaker switch. The following information describes the steps for manual operation.
- Ensure that all load cable connections have been correctly made.
- Verify that the unit can be safely started.
- Verify that power can be applied to the load.
Start Up Procedure for the First Unit
The following procedure applies to the first or primary unit that will be closing to a dead bus.
- Press the "RUN" button that is on the EMCP 4.4.
Note: The engine will begin to start immediately.
- Use the EMCP 4.4 display to observe the generator voltage and the frequency once the engine is running at the rated speed.
Note: The sync mode setting in the EMCP 4.4 will automatically change to "Check" mode when the EMCP 4.4 powers up. Additionally, the sync mode setting will automatically change to "Check" mode whenever the EMCP 4.4 "STOP" button is pressed. "Check"mode causes automatic generator-to-bus synchronization (not applicable in "Single Unit Mode") but requires manual closing of the generator breaker using the circuit breaker switch.
Note: If the manual voltage and/or frequency adjustment (prior to breaker closing) is desired, then change the EMCP 4.4 sync mode to "manual".
- If the EMCP 4.4 sync mode switch has been changed to "Manual Mode", make necessary voltage and/or frequency adjustments. Use the EMCP 4.4 control screen interface to make the adjustments, otherwise go to Step 4
- Use the circuit breaker switch to close the generator breaker at the desired time. Rotate the handle clockwise until the breaker closes, then release the handle. After the handle is released, the generator unit will be providing power for 100 percent of the load.
Start Up Procedure for All Other Units
The following procedures apply to the other units that are paralleling to a live bus.
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| Illustration 1 | g02314673 |
Sync mode switch | |
Sync mode switch (SMS) determines generator breaker control (manual or automatic close) and generator-to-bus synchronization control. Use function keys F1-F4 to change selection if desired.
Note: Always verify sync mode before startup. To verify sync mode, press CONTROL button on the EMCP 4.4 then select "PARALLELING" then select "SYNC MODE SWITCH".
Note: The sync mode setting in the EMCP 4.4 will automatically change to "Check" whenever the EMCP 4.4 is put in "STOP" mode. "STOP" mode happens when either upon boot-up or when pressing the "STOP" button on the EMCP 4.4. "Check" mode causes automatic generator-to-bus synchronization but requires the operator to close the generator breaker manually using the circuit breaker switch.
The Sync Overview screen shows the status of the generator and bus with the generator on the left-hand side of the screen.
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| Illustration 2 | g02314354 |
Sync overview screen | |
The arrows on the graphs of voltage, frequency, or phase show the value of that generator parameter relative to the corresponding bus value. The black bar on the graph represents the sync window for that parameter. When the arrow lines up to the black portion of the graph, then this parameter is close to the value of the same bus parameter. The width of the black bar is representative of the size of the programmed window for that parameter.
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| Illustration 3 | g02140727 |
Voltage/frequency control screen | |
- Determine sync mode. Sync mode should be in "CHECK".
- Press the "RUN" button that is on the EMCP 4.4.
The engine will begin to start immediately.
- Use the EMCP 4.4 display to observe the generator voltage and the frequency once the engine is running at the rated speed.
- Observe the synchroscope on the EMCP 4.4 refer to Illustration 2.
- If the EMCP 4.4 sync mode switch has been changed to "Manual" mode, then make necessary voltage and/or frequency adjustments. Use the EMCP 4.4 voltage/frequency control screen interface refer to Illustration 3, otherwise go to Step 6 .
Note: Voltage or frequency adjustments can only be made prior to closing the breaker and only when the sync switch is in "Manual" mode.
- Use the circuit breaker switch to close the generator breaker at the desired time. Close the breaker when the sync overview screen indicates that the generator is in-sync with the bus. The generator is in-sync with the bus when all arrows are within the black bars. Rotate the handle clockwise until the breaker closes, then release the handle.
The paralleled units are now powering the load, sharing load proportionally.
Shut Down Procedure for Each Unit
- Verify load level permits unit shutdown without overburdening the remaining paralleled units.
- Press "STOP" button that is on the EMCP 4.4.
Note: Pressing "STOP" begins ramping down generator output. At the programmed kW trip level, the breaker will automatically trip open and engine will go into cooldown.
Automatic Operation
The power module can be used in parallel with other units to provide power for an isolated load. Automatic operation refers to the use of the on-board control system to close the generator breaker automatically. The following information describes the steps for automatic operation.
- Ensure that all load cable connections have been correctly made.
- Verify that the unit can be safely started.
- Verify that power can be applied to the load.
Pre-startup Procedures
- Install wiring from the remote run request contact.
Note: The remote run request contact is controlled by the automatic transfer switch or by other customer supplied controls.
- Press the EMCP 4.4 "AUTO" key in each unit so that all units are in "AUTO" mode.
Note: The sync mode setting in the EMCP 4.4 will automatically change to "AUTO" whenever the EMCP 4.4 is put in "AUTO" mode
Note: For automatic breaker close control, the generator breaker control switch must be in the normal position (not in trip).
Startup Procedure
All units can be started simultaneously using a remote run request contact.
- After the lead unit is running at rated speed, then the generator breaker will close automatically to a dead bus.
- All of the other units will automatically synchronize and then close to the live bus.
Note: Alternatively, each unit can be started individually, beginning with the lead unit, first placing the EMCP 4.4 sync mode switch in "auto" mode. After placing the EMCP 4.4 sync mode switch in "auto" mode, press the "RUN" button on the EMCP 4.4. The generator breaker will close automatically once the unit is up to rated voltage and frequency and synchronized with the bus.
The paralleled units now power the load and share the load proportionally.
Shutdown Procedure
Any of the methods below will initiate a normal shutdown:
- If a remote run request contact is used to start the units, then open the contact in order to put all units in stop/cooldown.
- Press the "STOP" button that is on the EMCP 4.4 in each unit to put all units in stop/cooldown.
Note: First, verify load level permits unit shutdown without over-burdening the remaining paralleled units.
Note: Pressing "STOP" begins ramping down generator output. At the programmed kW trip level, the breaker will automatically trip open and engine will go into cooldown.
Generator Circuit Breaker
The generator circuit breaker is a 100% rated universal power circuit breaker. The generator circuit breaker is designed to protect electrical systems from damage caused by overloads, short circuits, and equipment ground faults. The circuit breaker is designed to open and close a circuit electrically. The circuit breaker is designed to open the circuit automatically at a predetermined over current setting.
The generator circuit breaker is operated via a stored energy mechanism. The stored energy mechanism can be charged manually or charged by using a motor. The closing time is less than five cycles. Closing and opening operations can be initiated by electrical signals.
Closing the Breaker
The generator circuit breaker can be closed automatically when running in the "AUTO" mode or manually with the circuit breaker switch in the "RUN" mode. All of the following conditions must exist to close automatically or manually:
- Engine running
- Voltage/frequency normal
- Circuit breaker switch is in the normal position (red or green flagged) for automatic operation OR is in the close position for manual operation
- UMR sync check is active (if UMR is installed and the utility circuit breaker is closed)
- 86 lockout device not tripped (if UMR is installed)
- Primary unit jumper installed (when dead bus closing only)
- No shutdown alarm is active
- Customer connection box door is closed
Opening the Breaker
The generator circuit breaker can be opened manually by rotating the handle of the circuit breaker switch to the left. The breaker can be held open indefinitely by rotating the handle of the circuit breaker switch to the left. Then pull the switch handle toward the operator. The circuit breaker will open automatically in the event of any of the following reasons:
- Over current fault condition
- Circuit breaker trip unit protection setting
- Emergency stop activated
- Any EMCP, ADEM, or Cat DVR commanded emergency shutdown
- 86 Lockout activated (if UMR installed)
- DC power failure
- Engine not running
- "STOP" on the EMCP is pressed
Function of The Engine Governor
This section describes the function of the engine governor in relation to load division between parallel electric sets. For detailed information on governor controls and adjustments, refer to the Service Manual for additional information.
Understanding two basic facts about load division between generator sets which are operating in parallel is important.
- The power which is supplied to the generator and, thus, to the load is a function of the engine. The engine governor settings and the positions of the governor controls determine the amount of power that is delivered by the engine. Therefore, the engine governor settings and the positions of the governor controls determine the kW load which is carried by the generator. If the governor control setting is advanced, the engine and generator will assume more kW load. Likewise, decreasing the governor control setting will result in a reduction of load on the unit. Any other units on the line will, conversely, either reduce load or gain load at the same time. These other units will assume that no change in total load or no change in the governor settings of the other units has taken place.
- The division of power is not determined by generator excitation or terminal voltage. The power factor at which a generator will operate when paralleled with other generators is determined by the excitation.
Governors that are used with Caterpillar powered electric sets can be of two types: governors with fixed speed droop or governors with adjustable speed droop. The values of speed droop which are commonly used are 3 percent and 0 percent. Governors with adjustable speed droop can be adjusted so the characteristics match closely the characteristics of governors with fixed speed droop. If the governor is adjusted for 0 percent speed droop (isochronous) operation, then the same speed from no load to full load can be obtained.
Summary on Governor Operation
The preceding discussion of governor operation can be summarized below
- The simplest governor combination for parallel generator sets is to have approximately 3 percent speed droop characteristics for each governor. If a constant frequency from no load to full load is required, one governor can be adjusted for isochronous operation. This isochronous unit will be called a "lead unit".
- In order for all paralleled units to accept full share of the load, the following governor adjustments are required. The governors should have the same full load speed. The governors should have the same high idle (no load) speed in the case of governors which are adjusted for speed droop operation. Governor controls should be set to the high idle position so that the full governor range is available.
- Operation of an isochronous governor in parallel with speed droop governors requires special techniques.
- Any number of electric sets can be operated in parallel. However, only one governor of the group can be adjusted for isochronous operation. The exception will be some special cases of electronic governors with automatic load sharing.
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.
- Be sure that the neutral of one of the remaining units is grounded.
- Remove the load from the outgoing unit. Refer to the Parallel Operation, "Load Division - Speed Droop". The amperage may never go to zero due to circulating currents.
- Open the circuit breaker.
- Allow the engine to cool for 5 minutes.
- Stop the engine.
Circulating Currents
important when you parallel the units. These circulating currents are flowing between paralleled generators. The circulating currents are caused by voltage differences between the generators and are not doing useful work. The amount of the circulating current can be determined by subtracting the amperage which is going 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. Such current may not even be considered harmful. The total generator current should not exceed the amperage rating.
As the generators warm, the circulating currents will decrease. The ammeter readings should decrease slightly, but the voltage meter readings should remain constant.