10. Conclusion

Network protection plans have gone through three technological stages:

• robust electromechanical relays with very limited capabilities ;

• electronic relays offering more or less the same possibilities as electromechanical relays, but also capable of providing new services such as automatic adjustment of compensation coils on neutral-compensated networks;

• digital relays with a large number of pre-programmed functions, plus the ability to implement custom functions.

The use of digital relays improves the performance of protection schemes, by enabling functions that were not possible with other levels of protection technology. One example among many: in the past, protection settings had to be determined for the most unfavorable cases of operating...