EXAMPLE 2 – COGENERATOR CONTROL

Given that a co-generation system has automatic

engine controls, auto synchronizer, and automatic kW

and kVar controls, the system will virtually operate by

itself. The only functions not readily apparent are the

start/stop signals to the generators. Two system con

figurations using a Power Relay may be utilized to

generate contact closures for start and/or stop signals.

The first configuration (Figure 2) shows a power relay

connected to the utility to sense kW. The pickup point of

the relay is set at the maximum desired utility power

level. If the power relay contact closes, the generator

will be started and automatically paralleled with the

utility system. A time delay of 15 seconds or more is

generally included in the start circuit to ignore

transient overload conditions.