opened, the no-load speed would be 4 percent above synchronous speed. This governor would be defined as having 4 percent speed droop. Paralleling an isochronous governor to an infinite bus  would  be  impractical  because  any  difference  in speed setting would cause the generator load to change constantly. A speed setting slightly higher than the bus frequency would cause the engine to go to full-load position. Similarly, if the speed setting were slightly below synchronous speed, the engine would go to no- load position. Setting speed droop on hydraulic governors is accomplished  by  adjusting  the  speed-droop  knob located on the governor body. Setting the knob to position No. 5 does not mean 5 percent droop. Each of the settings on the knob represents a percentage of the total governor droop. If the governor has a maximum of 4 percent droop. the No. 5 position would be 50 percent of 4 percent droop. Setting speed droops on solid-state  electronic  governors  is  accomplished  by placing   the   UNIT-PARALLEL   switch   in   the PARALLEL  position.  The  governor  speed  droop  is factory set, and no further adjustments are necessary. ISOLATED  BUS  OPERATION.—In the following  discussion,  assume  that  one  generator,  called the master machine, is operating and that a second generator,  called  the  slave  machine,  is  being synchronized to the master machine. Governor con- trols on the master ernogenerator should be set to the ISOCHRONOUS or UNIT position. The governor setting  on  the  slave  generator  must  be  set  to  the PARALLEL  position. NOTE:  The  hydraulic  governor  droop  setting  is  an approximate value. Setting the knob to position No. 5 will allow you to parallel and load the generator set. Minor adjustments may be necessary to prevent load swings after the unit is operational. When you are paralleling in the droop mode with other generator sets, the governor of only one set may be in the isochronous position; all others are in the droop  position.  The  isochronous  set  (usually  the largest  capacity  set)  controls  system  frequency  and immediately  responds  to  system  load  changes.  The droop generator sets carry only the load placed on them by the setting of their individual speed controls. Both voltage  regulators  should  be  set  for  parallel  and automatic  operation. The slave machine is brought up to the desired frequency by operating the governor controls. It is preferable to have the frequency of the slave machine slightly higher than that of the master machine to assure that the slave machine will assume a small amount of load when the main circuit breaker is closed. Adjust the voltage controls on the slave machine until the voltage is identical to that of the master machine. Thus two of the requirements for synchronizing have been met: ‘frequencies are equal and terminal voltages are equal. There  are  several  methods  to  check  generator phase sequence. Some generator sets are equipped with phase sequence indicator lights and a selector switch labeled “GEN” and “BUS.” Set the PHASE SEQUENCE  SELECTOR  SWITCH  in  the  BUS position,  and  the  “1-2-3”  phase  sequence  indicating light should light. (The same light must light in either GEN or BUS position.) If “3-2-1” phase sequence is indicated, the slave machine has to be shut down, the load  cables  isolated,  and  two  of  the  load  cables interchanged at their connection to the load terminals. Another method to verify correct phase sequence is  by  using  the  synchronizing  lights.  When  the synchronizing switch is turned on, the synchronizing lights  will  start  blinking.  If  the  synchronizing  lights blink  on  simultaneously  and  off  simultaneously,  the voltage sequences of the two machines are in phase. The frequency at which the synchronizing lights blink on and off together indicates the different frequency output between the two machines. Raise or lower the speed of the slave machine until the lights blink on together and offtogether at the slowest possible rate. If the synchronizing lights are alternately blinking (one on while the other is off), the voltage sequence of the two machines is not in phase. Correct this condition by interchanging  any  two  of  the  three  load  cables connected to the slave machine. Some  of  the  portable  generators  being  placed  in the NMCB Table of Allowances (TOA) are equipped with a permissive paralleling relay. This relay, wired into the main breaker control circuit, prevents the operator from paralleling the generator until all three conditions have been met. Now  that  all  three  paralleling  requirements  have been met, the slave machine can be paralleled and loaded. If a synchroscope is used, adjust the frequency of the  slave  machine  until  the  synchroscope  pointer rotates  clockwise  slowly  through  the  ZERO  position (twelve  o’clock).  Close  the  main  circuit  breaker  just before the pointer passes through the ZERO position. To  parallel  using  synchronizing  lights,  wait  until  the 3-9