Practical protection coordination study for electrical substation 154kV / 34.5kV

Protection coordination analysis

Adequate protection system which detects faults and disconnects elements of the power system during a fault is an essential design subject of the power system. The protection system cannot prevent the occurrence of the fault, but they should act immediately after the occurrence of the fault.

The protection system is an arrangement between protection equipment (like relays, fuses, etc.) and other devices (like transformers, circuit breakers, batteries, etc.) which are vital to accomplishing a specified function depending on the protection principles applied.

This paper is concerned with the protection coordination (ProC) study of Siddik Kardesler Substation (SKS) which is an AIS type. The protection study is planned to be presented in two parts (Part-1 and Part-2).

The overcurrent coordination study of SKS with necessary procedures will be discussed in section-5. Finally, the EFP will be discussed in section-6.

Substation Components

The SKS consists of 154 kV and 34.5 kV components that serve numerous purposes. Components like circuit breakers, isolators, current transformers (CTs), surge arrestors, power transformers, meters, control, relay equipment and etc. are shown symbolically upon the substation’s single line diagram as shown in Figure 1.

Based on the single line diagram shown in Figure 1, the protection arrangements for the SKS are as follow:

1. For the 154 kV incoming transmission lines, distance protection (21/21N), directional OCP (67/67N) and frequency protection (25) are implemented.
2. Differential protection (87T), overcurrent and earth fault protections (50/51/50N/51N) are implemented for the power transformer.
3. For the MV outgoing feeders, overcurrent and earth fault protections (50/51/50N/51N) are implemented.
4. Auxiliary Transformer is protected by MV fuse.

ABB relay RED 615 is used in this project and the setting parameters for differential relay are determined in this work. Furthermore, the transmission line which transfers energy from one place to another is protected by distance relay which is placed in the electrical substation.

In this project, MiCOMho P443 relay is used and settings are calculated. The results from the coordination study are implemented to the substation protection relays. After the necessary test and commissioning of the protection system, the SKS is successfully energized.