International Journal of Advances in Electronics and Computer Science, ISSN: 2393-2835 Volume-2, Issue-9, Sept.-2015

Design And Implementation Of Quadrilateral Relay On TLS Using NRDE

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DESIGN AND IMPLEMENTATION OF QUADRILATERAL RELAY ON TLS USING NRDE

1REVATI GODSE, 2PRAGYA MISHRA, 3ANIL P. VAIDYA

1,2PG Student, 3Professor E-mail: 1revagodse72@gmail.com, 2pragyajpmishra@gmail.com, 3anil.vaidya@walchandsangli.ac.in

Abstract— Distance relay scheme is widely used for the protection of transmission lines. It has many characteristics such as impedance, reactance, mho and quadrilateral characteristics. Quadrilateral characteristics provide better protection for transmission line as compared to others. This paper presents the development of quadrilateral relay characteristics in Numerical Relay Development Environment (NRDE) using MPLAB software and its implementation on Transmission Line Simulator (TLS). Characteristics of quadrilateral relay are realized by measuring the values of voltage and current. The analog voltage and current signals from TLS are given to NRDE through interfacing hardware. This hardware interface samples the input analog signals acquired from TLS and convert them into suitable form for NRDE. MPLAB software is used to program the relay. Program code is written in ‘C’ language. Quadrilateral relay algorithm is developed using NRDE and its performance under different fault condition is evaluated on TLS. Index Terms— Distance Relay, Distance Protection, Quadrilateral Relay Characteristics, Transmission Line Protection.

I. INTRODUCTION Transmission lines are a vital part of the electrical distribution system, as they provide the path to transfer power between generation and load. Transmission lines are among the power system components with the highest fault incidence rate, since they are exposed to the environment. Line faults due to lightning, storms, vegetation fall, fog and salt spray on dirty insulators are beyond the control of man. The balanced faults in a transmission line are three phase shunt and three phases to ground circuits. Single line-to-ground, line-to-line and double line-to-ground faults are unbalanced in nature [1]. On a transmission system the protective relaying system is incorporated to detect the abnormal signals indicating faults and isolate the faulted part from the rest of the system with minimal disturbance and equipment damage. The key challenge to the transmission line protection lies in reliably detecting and isolating faults compromising the security of the system. There are different types of protective schemes used for the protection of transmission line like overcurrent protection, distance protection, pilot protection. Out of all these schemes, distance protection is widely used protective scheme for the protection of high voltage (HV) and extra high voltage (EHV) transmission and sub-transmission lines. Distance protection is comparatively simple to apply and it can be fast in operation for faults located along most of a protected circuit. It can also provide both primary and remote back-up functions in a single scheme. On the other hand distance relay being actuated by two quantities, comparatively gives much better performance by taking care of various factors like line resistance, source impedance, types of faults, fault location etc. Distance relays are available in a wide variety of

characteristics too like impedance relay, mho relay, quadrilateral relay, reactance relay, which is an advantage when seeking the best device for a given application [2]. This paper presents the implementation of Quadrilateral relay characteristics on TLS. The present set-up of TLS is provided with overcurrent protection only. Also, NRDE kit has some real field limitation, as the data of faulted as well as normal conditions has to be fed. Hence, the analog voltage and current signals from TLS under both healthy and faulted condition are given to NRDE through hardware interface and Quadrilateral relay characteristics developed using NRDE are implemented on TLS. II. TRANSMISSION LINE SIMULATOR Transmission Line Simulator is a sophisticated module developed with the purpose of understanding of some basic concepts in power systems [3]. The block diagram of TLS is as shown in Fig. 1.

Fig. 1. Block diagram of TLS

International Journal of Advances in Electronics and Computer Science, ISSN: 2393-2835 Volume-2, Issue-9, Sept.-2015

Design And Implementation Of Quadrilateral Relay On TLS Using NRDE

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The entire system of TLS works on three phase AC supply of 415 V. The block diagram consists of four different blocks namely input control panel, pi-section box, series compensation box and output control panel. The real world transmission line can be simulated with help of TLS software [3]. III. NUMERICAL RELAY DEVELOPMENT ENVIRONMENT This hardware is a replica of an actual relay. This relay is self-sufficient with 3 voltage channels and 3 current channels. Additional digital inputs and outputs are provided along with a trip contact and an alarm contact. All the inputs and outputs are programmable. The top view of NRDE is as seen in Fig. 2. This hardware can be programmed using programming MPLAB IDE software. Any algorithm can be coded and can be tested for its characteristics and response. Code can be written in ‘C’ and can be downloaded to this relay. Once the algorithm is coded and downloaded to this relay, the system behaves as per the algorithm developed [4].

Fig. 2. Top view of NRDE

IV. QUADRILATERAL RELAY The quadrilateral distance relay characteristic consists of four straight lines as shown in Fig. 3. The positive torque region is the region covered by all the four lines i.e. quadrilateral ABCDA. If the impedance seen by the relay is inside the operating region, then relay trips.

Fig. 3. Quadrilateral relay characteristics

Each of these lines can be defined by an equation given by;

Line AB: X = m1*R (1) Line BC: X = constant (k) (2) Line CD: X = m2*R+C (3) Line DA: X = 0 (4)

Where, m1 is the slope of the line AD; m2 is the slope of the line BC and C is the constant. Hence, during fault if reactance and resistance (X and R) up to the fault point are known, the trip condition can be decided. In this paper, simple algebraic equations as given below are used for calculating the impedance, resistance and reactance of the line which is required for the development of relay characteristic.

A. Algorithm The algorithm to obtain quadrilateral characteristics is as given below:

(i) Read the values of voltage and current of each phase

(ii) Compute the value of R and X (iii) Check whether X >= m1*R (iv) Check whether X <= K (v) Check whether X <= m2*R+C (vi) Check whether X >= 0 (vii) If all four conditions are satisfied then issue

a trip signal otherwise repeat all the steps from start to end.

B. Flowchart

International Journal of Advances in Electronics and Computer Science, ISSN: 2393-2835 Volume-2, Issue-9, Sept.-2015

Design And Implementation Of Quadrilateral Relay On TLS Using NRDE

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V. ALGORITHM IMPLEMENTATION A. Simulation of line parameters For hardware testing 200 km long transmission line is simulated on TLS. Line data is given below (Fig. 4.):

Type of conductor - Twin moose Voltage level – 400 kV No. of Pi-sections - 8 Line length (L) – 200 km Resistance per km (R) – 0.0328 Ω/km Reactance per km (X) – 0.3319 Ω/km Per pi-section length (l) – 25 km Per pi-section R – 0.82 Ω Per pi-section X – 8.299

Fig. 4. Simulation of line parameters

Here, zone protection is also considered, while developing a relay algorithm. Zone 1 provides the protection up to 80% of total line length i.e. 160 km. Zone 2 protection is set for the protection of remaining portion of line length. B. Results Quadrilateral relay algorithm is developed using IDE MPLAB software. ‘C’ language is used for programming. Zone protection is also considered while developing relay characteristics. The results of algorithm implementation for different fault conditions and for 1st zone protection are given below.

a) LG fault (Phase R-Zone 1)

TABLE 1 TLS METER READINGS (RG FAULT)

TABLE 2 NRDE READINGS (RG FAULT)

b) LL fault (Phase RY-Zone 1)

TABLE 3 TLS METER READINGS (RY FAULT)

TABLE 4 NRDE READINGS (RY FAULT)

c) LLLG fault (Zone 1) TABLE 5 TLS METER READINGS (LLLG FAULT)

TABLE 6 NRDE READINGS (LLG FAULT)

The results of algorithm implementation for different fault conditions and for 2nd zone protection are given below.

a) LG fault (Phase R-Zone 2) TABLE 7 TLS METER READINGS (RG FAULT)

TABLE 8 NRDE READINGS (RG FAULT)

b) LL fault (Phase RY-Zone 2) TABLE 9 TLS METER READINGS (RY FAULT)

TABLE 10 NRDE READINGS (RY FAULT)

International Journal of Advances in Electronics and Computer Science, ISSN: 2393-2835 Volume-2, Issue-9, Sept.-2015

Design And Implementation Of Quadrilateral Relay On TLS Using NRDE

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c) LLLG fault (Zone 2) TABLE 11 TLS METER READINGS (LLLG FAULT)

TABLE 12 NRDE READINGS (LLG FAULT)

CONCLUSION This paper presents the implementation of Quadrilateral relay on TLS. A 200km long transmission line is simulated on TLS. The voltage and current signals acquired from TLS are given to NRDE. Quadrilateral relay algorithm is developed using NRDE. While developing relay algorithm zone protection is also considered. Different types of faults are created on TLS and the performance of developed Quadrilateral relay algorithm during various fault conditions is evaluated successfully. The developed relay algorithm work successfully during different fault conditions. Zone protection is also implemented successfully.

REFERENCES

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[4] NRDE Lab Manual, Power Research & Development Consultants Pvt.Ltd.

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