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K. S. Meera ¹, R. A. Deshpande ², R. S. Shivakumara Aradhya ³

Affiliations
1 Joint Director Power Systems Division,Central Power Research Institute, Bangalore - 560 080, IN
2 Joint Director Distribution Systems Division, Central Power Research Institute, Bangalore - 560 080, IN
3 Ex Director, Central Power Research Institute, Bangalore - 560 080, IN

Abstract

Circuit breakers are an important element in a substation, which is used for coupling of busbars, transformers, transmission lines, switching of shunt reactors, capacitor banks etc. The most important task of a circuit breaker is to interrupt fault currents and thereby protect various power system components. This task requires operation of the circuit breaker under different making and breaking conditions such as - faults in the vicinity of the circuit breaker, short-line faults, out-of-phase closing/ opening, switching of - capacitor /shunt reactor banks, no-load transformers/lines etc. During opening operation, after the arc extinction, the insulating medium between the breaker contacts has to withstand the rapidly increasing recovery voltage. This recovery voltage has a transient component (transient recovery voltage, TRV) caused by the system when current is interrupted. The TRV of the Circuit Breaker is a decisive parameter that limits the interrupting capability of the Circuit Breaker. The TRV to be adopted for system voltages of 1200 kV, towards which our country is migrating, needs to be estimated by transient studies as they cannot be extrapolated from lower voltage systems. This paper deals with the modeling and study results of TRV for typical 1200 kV networks and a sample 1200 kV Indian system using Electromagnetic Transient Programs (EMTP).

Keywords

Transient Recovery Voltage (trv ), Rate of Rise of Recovery Voltage (rrrv ), Electromagnetic Transient Program (EMTP), Circuit Breaker (cb).

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S. Ganga ¹, N. Vasudev ¹, V. Asai Thambi ¹, R. S. Shivakumara Aradhya ¹, A. Sudhindra ¹

Affiliations
1 Central Power Research Institute, Bangalore-560080, IN

Abstract

This paper presents experimental results obtained on tracking and erosion resistance of Silicone rubber (SIR) with and without pollutants. The IEC-60587 Inclined Plane Tracking and Erosion Test method combined with UV radiations of different intensities was employed to assess two different formulations with same base polymeric material (SIR). The hydrophobicity recovery property of silicone rubber formulations before and after inclined plane tracking test was studied besides the effect of corona. Some of the physical, thermal and electrical properties were compared before and after inclined plane tracking test. It is inferred from the analysis carried out on the experimental results that the intensity of UV radiation plays a major role in deteriorating the surface characteristics of the material. It is also found that the introduction of UV in the test method has helped in distinctly evaluating polymeric materials. The effect of two different pollutants was not the same on formulations considered for the study, which implies that the additives play a dominant role in the overall performance of the material than the base polymer. The study also revealed that a formulation with a better performance under a certain pollutant need not have to behave the same way under a different pollutant. Presently, CIGRE Working Group (WG D1.14) is active in standardization of material aspects besides developing suitable methodology for the testing of polymeric materials for outdoor insulation application; the inferences appear to be an useful input to both CIGRE working group and International Electro technical Committee (IEC TC 15 PT 2).

Keywords

Inclined plane tracking IEC 60587, UV radiation, Silicone rubber, Pollutant

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C. Ahalya ¹, R. S. Shivakumara Aradhya ¹

Affiliations
1 Central Power Research Institute (CPRI), Bengaluru, IN

Abstract

Fault classification is necessary for the rapid restoration of service to LT consumers after the occurrence of a fault. This paper presents a step by step procedure for the identification of ten different types of faults commonly occurring in the LT distribution system. Information on the distribution transformer secondary current for different faults at different load buses is used to define the input fuzzy variables. Fuzzy inference engine and the centroid de-fuzzifier are used to relate the input to the fuzzy rule base and to obtain crisp outputs respectively.

Keywords

Fault Classification Method, Fuzzy Logic, LT Feeder, MATLAB, RSCAD.

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M. Kanyakumari ¹, R. S. Shivakumara Aradhya ²

Affiliations
1 CPRI, Bangalore, IN
2 Lamco Industries Pvt. Ltd., Hyderabad, IN

Abstract

Zinc oxide (ZnO) surge arresters are being used extensively in high voltage power systems for providing protection to the transmission lines and the associated substation equipment from over voltages caused due to lightning and switching surges. It has been observed in practice that the voltage distribution in a tall multi-section arrester under normal operating conditions is quite non-uniform. As a result, the ZnO blocks at the top section share higher voltage and hence higher thermal stresses than the ZnO blocks at the bottom section. This leads to accelerated thermal aging of the blocks at the top if proper measures are not taken to make the voltage distribution uniform along the entire length of the arrester. Generally, provision of grading rings is a common method for achieving uniform voltage distribution through out the length of arrester. In this paper, the results of the optimization of the grading ring dimensions for a 765 kV system arrester with a rated voltage of 624 kV using Finite Element based 2D Elecnet software are presented.

Keywords

Grading ring, Zinc oxide surge arresters, Voltage distribution of arrester, Electric fi eld distribution.

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Pradeep M. Nirgude ¹, B. Gunasekaran ¹, R. S. Shivakumara Aradhya ¹

Affiliations
1 Central Power Research Institute, IN

Abstract

This paper presents the results of the study conducted on 400 kV, 800 kV and 1200 kV transmission line insulator strings and conductor–tower window geometries with an aim to optimize air insulation clearances. Laboratory investigations were carried out to evolve the switching impulse performance of phase–to–earth and conductor–window confi gurations in addition to the reference rod plane air gap lengths in EHV/UHV range. Tests were conducted on 400 kV, 800 kV and 1200 kV line confi gurations of I, Vee, double Vee, etc., by simulating the tower windows. The paper also presents results of the study on optimization of conductor-tower air insulation clearances for adoption in 1200 kV AC transmission lines using 8 bersimis conductor bundle carried out for establishment of 1200 kV Test Station at BINA, Madhya Pradesh, by Power Grid Corporation of India. Results of the tests and the data presented in the paper will be useful for design of phase-to-ground air insulation for adoption in EHV/UHV Transmission lines.

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J. Sreedevi ¹, V. Anuradha ², Premila Manohar ², R. S. Shivakumara Aradhya ³

Affiliations
1 Power Systems Division, Central Power Research Institute, Bengaluru – 560080, Karnataka, IN
2 Department of Electrical and Electrinics Engineering, Ramaiah Institute of Technology, Bengaluru – 560054, Karnataka, IN
3 Department of Electrical and Electronics Engineering, Acharya Institute of Technology, Bengaluru – 560107, Karnataka, IN

Abstract

Strength of the AC system is one of the important parameters that govern performance of HVDC systems. Even though VSC-HVDC is known to have fewer problems compared to LCC-HVDC at lower system strengths, it is still the topic of research. This paper presents a detailed analysis on the modelling and tuning of the control system of a VSC-HVDC system for varied AC system strengths. Emphasis has been on the tuning of control system parameters considering the effect of AC system strength to improve the transient response of the VSC-HVDC system. A combination of control schemes consisting of DC voltage and AC voltage control at the rectifier and inverter end have been considered. The control parameters are tuned with symmetrical and modulus optimum criteria and found that tuning method is working for weak systems. The VSC-HVDC system is modelled in RSCAD software of RTDS.

Keywords

AC Voltage Control, Active and Reactive Power Control, DC Voltage Control, Proportional Integral (PI), Short Circuit Ratio (SCR) Words, Source Impedance, VSC - HVDC

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