Reliability Of The Transmission Line Through Distance Relay Protection By Using Matlab/Simulink: Transmission Development Research Paper, UoS, Singapore

Reliability Of The Transmission Line Through Distance Relay Protection By Using Matlab/Simulink

ABSTRACT:

Protection of transmission lines has been the utmost concern in a typical power system network nowadays. This work depicts the fault identification and protection of the transmission lines through a distance relay protection scheme. Here the symmetrical and asymmetrical faults are analyzed for the particular transmission line.

An algorithm has been applied to develop the model for transmission lines fed from one end by the evaluation of impedances using analysis of symmetrical components. This paper assists us in determining the faults in transmission lines and thereby increases the reliability of the complex network.

The suggested algorithm is tested through MATLAB/SIMULINK software, considering LLL and LLLG faults at distinct zones with variations in impedance, area of fault occurrence, and short circuit current tolerance of the source.

INTRODUCTION:                   

“A customary force framework is a perplexing organization included generators, engines, transformers, transmission, and dissemination lines alongside their switchgear security”. The most bothering problem is short circuit currents that occur in the network due to which would damage the apparatus or appliances of the power system; these would lead to a blackout of the system.

During a circumstance of short circuit, a large amount of short circuit current flows into the system beyond its rating; this has an adverse impact on the entire network. The majority of the equipment is costly, and the catastrophe of these would be unaffordable. In the event of fault occurrence, a protective system is required to safeguard the whole power system, and several protection schemes have been developed to do so.

The protection devices include several components such as transducers, protective relays, and circuit breakers, among which circuit breakers protect the equipment as soon the fault has occurred by isolating the system from the fault location. The protective relays have a significant role in the protection system as they send the signal to the circuit breaker for tripping the circuit instantly after sensing the fault.

Due to this characteristic of relays, they are being used for both primary and backup protection. There are many relay protection schemes, among which the best is the distance relay protection which exhibits an excellent mode of operation in detecting the faults and thereby initiating the tripping process by the circuit breaker across a specific range of distance[1].

This work aims to analyze the symmetrical faults determination, impedance evaluation, and protection in non-identical zones with variations in the system’s parameters. Ultimately, the viability of the suggested design is tested through MATLAB/SIMULINK software.

MODELLING OF THE SYSTEM

The propounded simulation design for the evaluation of faults and protection of the line at distinct zones is depicted in Fig. 1. The prototype comprises of generating station, transmission line, and load centre. Power line protection is the most significant problem in the electrical network as 85-89% of faults occur in overhead transmission lines[2].

The most severe faults in the electric power system are the symmetrical faults that are uneconomical and reduce reliability. Most of the faults in a power system were caused by apparatus break down such as transformers, pivoting engines, generators, and other electric-powered equipment. Both the forced, unforced error of humans and atmospheric conditions are accountable for the occurrence of faults in the power system.

In order to establish a robust and durable supply of power, it is mandatory to scrutinize the cause of fault in transmission lines for a specific zone and implement the required protection scheme contrary to faults. Conventional distance relay consists of three measuring units, can be three separate units or one unit for the first and second zone with time delay and a second unit for the third zone.

The first and second unit act as primary protection units whereas second and third zone provides remote back up protection for adjacent lines[3].  The impedance value is proportional to transmission line

length[4]. We have considered voltage, current, and impedance conditions prior to and subsequent to the fault for designing the logical circuit of the relay in our suggested prototype. We have distinguished the entire transmission line into three zones.

At zone one, the impedance of the line is under 25 ohms. Assuming the deficiency impedance estimated by the transfer is fewer than 25 ohms, the hand-off will convey a message to the electrical switch that an issue has happened at zone 1. At zone two, the impedance is between 25 ohms to 55 ohms. In the event that the issue impedance estimated by the transfer is between 25 ohms to 55 ohms, then, at that point, the hand-off will convey a message that the shortcoming has happened at zone 2.

At zone three, the impedance is over 55 ohms[2]. Additionally, assuming the issue impedance estimated by the transfer is over 55 ohms, the hand-off will convey a message that the shortcoming has happened at zone3.