Is your plant well protected?

In recent years protection of electrical systems has developed considerably with the advent of programmable electronic protection devices which provide the scope for much closer protection and monitoring of electrical equipment. However, is this sophisticated equipment being used correctly to provide the protection required and are our systems as well protected as they should be? The protection is only effective if it is set correctly and co-ordinated with other devices on the network and with the mechanical capabilities of motors and driven equipment. This requires protection studies to be carried out to ensure co-ordination of protection, monitoring of equipment and ensuring that settings are correct to protect the equipment whilst eliminating nuisance tripping. The experience of the authors is that many systems are not as well protected as they could be and that the capabilities of the relays are not being fully utilised. The paper considers the requirements of a system study to determine correct protection settings and the parameters which need to be considered to ensure this is done thoroughly. The needs to have full revision control on the relay settings is then considered before looking at the consequences of the settings not being correctly set. This could result in components exceeding their switching capability with consequent results or unnecessary damage to equipment with subsequent loss of availability of electrical systems.