Instantaneous relay- is a type of rely that will be energized as soon as it is signaled. Time Delay Relay- is a type of relay that pauses before it energizes. Differential relay- is a relay that is a back up for another relay in the case that one does not energize properly. Over current relay- this relay only works when current coming in is higher than the allotted amount. Helpful when you are dealing with extremly high currents. Under current relay- is a relay that works when a current is coming in at a higher rate than it is allotted amount. Helpful in preventing damage to any system it is applied to. Protective relay- is a relay that measures all elements of electrical current in a system. It is also a self diagnostic tool and can be set to run by it’s self when programmed.