ANGLE ASSEM. 5M8485 - Caterpillar

that are operated in parallel must share real power requirements and reactive power requirements for the electrical load of the system. The governor for the generator engine controls sharing of the real power requirements. Real power requirements are expressed in kilowatts (kW). The voltage regulator controls sharing of the reactive power requirements. The reactive power requirements are expressed in Kilovolt Amperes Reactive (kVAR). If the voltage output of a generator, that is operated in parallel with other generators, is slightly higher than the voltage output of the other generators, a lagging reactive current will flow to the other generators that are connected in parallel. The reactive current will circulate between the generators. This will increase the heat in the generators and may cause protective relaying nuisance trips. One method of minimizing circulating reactive current is by reducing the voltage output of the generator proportionally to the amount of lagging reactive current. This method of reducing voltage in order to control the lagging reactive current is called droop. For proper reactive load sharing, the regulator must regulate based on the following: the rated generator output current, the current feedback from generator output and the allowable percentage of droop on the output voltage of the generatorAs reactive lagging current increases, the regulator will cause the output voltage to droop proportionally. If the reactive output current is leading, the output voltage will rise proportionally. In either case, this action will tend to reduce the reactive current for better sharing of kVAR with other units. The percentage of droop is adjustable with the potentiometer "P1". "P1" controls the percentage of change in the voltage that will occur on output of the generatorwhen reactive current is present. It is important that the polarity of the Current Transformer (CT) is correct. If the polarity is not correct the voltage droop will not occur with a lagging reactive current flow. The CT must be installed on B phase of the generator output. It is also important that the polarity of the connections for voltage sensing are correct. The voltage sensing wires must be connected the same way to each AVR for each generator operating in parallel. Refer to Service Manual, KENR9009, "Reactive droop adjust" for instructions in order to adjust Reactive droop .Note: The optional external CT is connected to the terminals of the Automatic Voltage Regulator (AVR) next to the jumper ST4. The may also be connected next ot the optional remote voltage adjust pot if it is present.