Exam Question

### (a) Conditions for Paralleling an A.C. Generator
For an incoming A.C. generator (alternator) to be safely and successfully paralleled with live bus-bars, four critical conditions must be met. Failure to meet these conditions can result in severe electrical and mechanical damage to the generator, prime mover, and distribution system.
1. **Equal Voltages:** The terminal voltage of the incoming generator must be equal to, or very slightly higher than, the bus-bar voltage.
* **Reasoning:** If the incoming generator's voltage is significantly lower, upon closing the circuit breaker, it will draw a large reactive current from the bus-bars, acting as an inductive load (like a motor). This is known as 'motoring'. Conversely, if the voltage is significantly higher, it will supply a large reactive current to the system, potentially overloading its windings. A slightly higher voltage ensures that once connected, the generator immediately starts supplying reactive power (kVAr) to the grid, preventing it from drawing power and ensuring stable operation.