Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Protection guidelines

Two possible options had been investigated to overcome the absence of high short circuit levels required for conventional over current sensing in a MicroGrid.
- Increasing the fault current contribution from converters at a reasonable cost

- Finding alternate means of detecting an event within an isolated MicroGrid

A detailed analysis of the probable protection schemes for the MicroGrid was performed.
- For a fault on the distribution system, the MicroGrid will continue to operate in an island by opening the circuit breaker upstream of the main distribution transformer.

- For a fault on the MicroGrid network, the whole MicroGrid will discontinue its operation. Sectionalising of a general MicroGrid is not advised as the cost involved could not be justified for the benefits gained. The decision would be mainly dependent on the identified needs of the MicroGrid users.

- For a fault at a residential consumer, the relevant consumer would be disconnected from the MicroGrid, and normal operation would continue.

Over current protection relay, distance protection relay, Residual Current Device (RCD) and Short Circuit Protection Devices (MCCB or fuse) have been identified as the possible solutions to be used in the protection of a MicroGrid.

INESC have carried out a study to evaluate the discriminating capability of zero sequence protection to be used in the MicroGrid. The fault analysis had been performed assuming grid-connected operation of the MicroGrid. In the near future, fault analysis during islanding operation of the study case MicroGrid will be performed.

Reported by

University of Manchester
B9, Ferranti Building, PO Box 88
M60 1QD Manchester
United Kingdom