Question

1. Discuss in detail the main technical considerations necessary when installing generation within the distribution system.

2. Explain why short circuit fault level is generally specified in MVA and not in Amperes.

Answer 1

1. Distribution System:
An electrical system which distributes the power supply from the supply mains to the consumer end.

The supply to the distribution system is fed from the substation with the help of the transmission lines which is further distributed to the consumers.

While installing generation within the system, the main technical factors to be considered are as follows:
a. All performance standards must be satisfied at the point of common coupling, i.e., the point at which the generation equipment and the distributed system are interconnected electrically.

b. Ground Grid is required ion order to provide proper grounding of all the metallic framework, equipment and this should be able to limit the potential gradient in order to ensure safety of the personnel and the  equipment.

c. The equipment required for installation should be of the appropriate rating and as per the standards.

d. Fault interruption, load flow and load interruption should be given due consideration.

e. Protective Relaying schemes should be checked in order to ensure maintenance and timely clearance of the faults and regular supply.

2. Short circuit fault level should be specified in MVA as it is used for the determination of the fault at different points in a power system where line to line voltage is considered and 3 phase fault current is taken into consideration for the calculation.

Short Circuit MVA is given by the formula:

Since, the short circuit currents are of very high magnitude and are rated in kVA and the line to line voltage in kV.

Thus the rating is in MVA and not in Amperes.