A long-neglected but simple means to control the load tapchangers (LTC) of transformers connected in parallel is coming into vogue again. The increased use of capacitors in substations and on distribution feeders has improved the load power on many circuits to near unity.

Digital products, which are now the norm for LTC control, enable accuracies with less that 1% error. These improvements equate to nearly an order of magnitude improvement relative to the conditions experienced 50 years ago in the overall accuracy of the “Negative Reactance” method of controlling LTC transformers in parallel.

The Negative Reactance method requires no intercontrol wiring or recognition of substation circuit breaker status. It is forgiving of mismatched transformers and involves no paralleling balancer hardware. This method can be applied to any number of transformers in parallel using standard LTC transformer controls.
Circle 177 on Reader Service Card