(b) An 11 kV, 50 Hz radial system is shown in Figure 6. Assume a CO-7 overcurrent protective relay with characteristic given in Figure 7. By using different power factor for all loads (in the range of 0.8 ~ 0.9), design suitable relay settings (current tap setting, time dial setting) and coordination design to protect the system with time interval of 0.3 seconds. 2 I32, 1 I21, 11 kV C.T.R=400/5 C.T.R=200/5 C.T.R=200/5 Figure 6: Simple radial network Load at bus 3 :7 MW, Short circuit rating at bus 3 (Isc3) = 4kA : 3 MW, Short circuit rating at bus 2 (Isc2) = 3kA :4 MW, Short circuit rating at bus 1 (Isc1) = 2kA Load at bus 2 Load at bus 1 Typical time curves Тype CO-7 over current relay 50-60 cycles 6. Current tap settings: 4,5,6,7,8,10,12 amperes Time dial setting 1 1/2 5 6 7 8 9 10 12 14 16 18 20 Current as a multiple of tap setting Figure 7: CO-7 Overcurrent Protective Relay Time vs Current Curve Operating time in seconds 2.
Protection System
A system that protects electrical systems from faults by isolating the problematic part from the remainder of the system, preventing power from being cut from healthy elements, improving system dependability and efficiency is the protection system. Protection devices are the equipment that are utilized to implement the protection system.
Predictive Maintenance System
Predictive maintenance technologies are designed to assist in determining the state of in-service equipment so that maintenance can be scheduled. Predictive maintenance is the application of information; proactive maintenance approaches examine the condition of equipment and anticipate when it should maintain. The purpose of predictive maintenance is to forecast when equipment will fail (depending on a variety of parameters), then prevent the failure through routine and corrective maintenance.Condition monitoring is the continual monitoring of machines during process conditions to maintain optimal machine use, which is necessary for predictive maintenance. There are three types of condition monitoring: online, periodic, and remote. Finally, remote condition monitoring allows the equipment observed from a small place and data supplied for analysis.
Preventive Maintenance System
To maintain the equipment and materials on a regular basis in order to maintain those running conditions and reduce unnecessary shutdowns due to unexpected equipment failure is called Preventive Maintenance (PM).
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