Abstract
According to NEC 240.101 regulations each and every component of a power system distribution network has to have an over-current protective device (OCPD) for its protection. The OCPDs must coordinate with other devices both upstream and downstream for a reliable operation and protection of the power systems distribution network. There are four equipment/components for the IEEE 13 node radial test feeder each modelled in this paper to be protected by fuses. These components are namely the nodes, the underground cables, the overhead distribution lines and the transformers. Equipment protection is an important and necessary exercise of performing power systems protection coordination processes. The equipment and their over-current protective device’s time-current characteristic (TCC) curves are important tools used to show and to indicate the protection requirements, landmark points and damage curves for all power systems equipment. Individual equipment protection requirements and limitations are described and identified by use of their various landmarks and damage curves. These damage curves and the landmark points are all superimposed with the Time-Current Characteristic curves of the Over-Current Protective Devices used in protecting the equipment on one composite TCC graph. Equipment damage curves which fall to the right and above the Over-Current Protective Device’s TCC curves with sufficient margins are considered to be protected by the OCPDs. Equipment damage curves which fall to the left and below the OCPD’s TCC curves are considered not to be protected by the OCPDs. IEEE Standard 241 states that on all power systems, the OCPDs should be selected and set to open before the Ampacity mark, the short circuit damage curves, and both the thermal and the mechanical damage curves limits of the protected components are exceeded. This paper presents a detailed Fuse-Fuse protection scheme for the IEEE 13 node radial test feeder as modeled on the Electrical Transients Analysis Program (ETAP).
Highlights
According to NEC 240.101 regulations each and every component of a power system distribution network has to have an over-current protective device (OCPD) for its protection
Transformers having percentage impedance less than 10% the primary/source side protection must have an upstream fuse rated at 300% of the transformer full load currents
Transformers rated over 1000V on the secondary/load side and having percentage impedance less than 6% the load side protection must have a downstream fuse rated at 250% of the transformer full load currents
Summary
IEEE 13 node radial test feeder was modeled using ETAP electrical simulation software. The TCC Curve for the overhead distribution line and its protective fuses is shown in Fig 12.The TCC curve shows the overhead phase conductors ampacity of 730A at the upper decade at the 1000seconds mark of the TCC curve and the line’s short circuit damage curve located at the bottom three decades starting at the 0.01seconds mark up to the 10seconds mark. The TCC Curve for the overhead distribution line phase conductor and its protective fuses is shown in Fig 15.The TCC curve shows the overhead line’s ampacity of 230A at the upper decade at the 1000seconds mark of the TCC curve and the line’s short circuit damage curve located at the bottom three decades starting from the 0.01seconds mark to the 10seconds mark.
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