Paralleling Generators To Utility Substations Caterpillar

Paralleling Generators To Utility Substations

Usage:

ELECTRIC POWER GENERATIONSR4 (1MS, 2ED, 2GG, 2SM, 2WD, 3EF, 3KJ, 3MF, 3RD, 3WF, 4MD, 4SJ, 5AA, 5CA, 5DA, 5DD, 5EA, 5FA, 5GA, 5HA, 5NJ, 5RA, 5RF, 5SA, 5TA, 5TD, 5UA, 5VA, 5YA, 5ZA, 6AA, 6BA, 6CA, 6CG, 6DA, 6DG, 6EG, 6EJ, 6GA, 6GF, 6HA, 6JA, 6LA, 6MA, 6NA, 6NW, 6PA, 6RA, 6SA, 6TW, 6WA, 6WR, 6XA, 6YA, 6YR, 6ZA, 6ZW, 7AJ, 7BF, 7RS, 7SS, 7TS, 7WS, 7XS, 7YR, 7YS, 7ZS, 8DR, 8ER, 8FD, 8HG, 8JF, 8KF, 8LF, 8MM, 8SW, 8WW, 8ZD, 8ZL, 9AB, 9BB, 9CR, 9DR, 9DW, 9EF, 9FF, 9FG, 9GF, 9HW, 9LW, 9RW),
SR4B (1BN, 1HN, 2DM, 2DN, 2FN, 2GM, 2GN, 2GZ, 2HN, 2SN, 3BM, 3BZ, 3EN, 3FN, 3GN, 3HN, 4DM, 4EN, 4FN, 4GN, 4SZ, 4WN, 5CK, 5DM, 5JW, 5LF, 5SN, 5WN, 6DW, 6GM, 6PK, 6SN, 6ZZ, 7DN, 7GM, 7TN, 8DM, 8EZ, 8GK, 8GW, 8HM, 8LZ, 8NN, 8PZ, 8TZ, 8XS, 9AZ, 9CN, 9DZ, 9EN, 9GZ, 9MZ, 9RZ, 9WZ, 9XZ, AAD, AAJ, AAR, AAT),
SR4BHV (5HW, 5RW, 6CW, 8HS, 8JS, 8KS, 8LS, 8MS, AAL, ABA, ABE, ABG, ABT, ACB, ACG, ACK, ACR, ACW, ACZ, ADB, ADJ, ADT, AEA, AEG, AEL, AES, AEY, CAN) ELECTRIC POWER GENERATION

Problem:

Problems can occur when paralleling generator sets with utility substations.

Solution:

1.The best way to parallel a generator set to a public utility is by voltage matching. Voltage matching requires voltage matching paralleling equipment. Because many paralleling sites do not have access to voltage matching paralleling equipment, voltage matching is not always an option. When voltage matching is not an option, request a chart of the voltage fluctuation at the paralleling site and perform the calculations in Example 1.

Example 1If the minimum buss voltage is 460 VDC and the maximum buss voltage is 510 VDC, set the generator set voltage to 485 VDC.

510 - ((510 - 460) /2) = 485

This will minimize the voltage difference between the buss and the generator set and will place the maximum difference at 5.15% (25/485 = 5.15%). At 6% or less difference, the generator excitation system can make it through the transition and oscillations until the system stabilizes.

2.Upon start-up at a paralleling site, ensure that the droop circuit is operating satisfactorily. To ensure that the droop circuit is operating properly, set the power factor and test to ensure that the proper power factor can be maintained at full load. If the power factor does not track as expected, ensure that the droop circuit is sending a proper signal to the voltage regulator.

3.When the load peak is dropping off in the afternoon, utility substations can experience a "bucking" situation. A "bucking" situation occurs when station transformers experience an out-of-phase, momentary loss of synchronization with the grid. If generators are on-line when a "bucking" situation occurs, failure of the excitation system varisters may be experienced due to sudden phase shifts or voltage spikes. A "bucking" situation may also cause diodes and heat sinks to fail. To avoid repair costs and down time, units should be taken off line before the load peak begins to drop off in the afternoon. If diode/varister failures are experienced, monitor the site for incidents of phase reversal and/or voltage spikes during the paralleling operation.

4.When paralleling with utility substations, always ask if capacitive power factor control banks are being used. When capacitive power factor control banks are being used, paralleled generators should not be on line when the power factor is below 0.9 leading pf.