Power Research

K. S. Meera ¹, M. Kanyakumari ²

Affiliations
1 Additional Director, Power System, Division, Central Power Research Systems, Banglore, IN
2 Additional Director, High Voltage Division, Central Power Research Systems, Banglore, IN

Abstract

The reliability of power supply provided by an electric power systemis judged by the frequency and duration ofsupply interruptions to its customers. Althoughthere are many causes of interruptions, breakdown of insulation is one of the most frequent.The insulation provided to the equipment has to withstand a variety of stresses(overvoltages) with varying shapes, magnitudes and duration during its service period.We cannot prevent these overvoltages in an electric network,so we need to protect against them. The main objective of Insulation coordination is to ‘Design the system insulation of all power system components to minimize power interruptions and damage resulting from steady-state, dynamic and transient overvoltages in an economic fashion’.To keep interruptions to a minimum, the insulation of various equipments of the system must be so graded that flashovers occur only at intended points.

The magnitudes of over-voltages are usually limited to a desiredprotective level by protective devices. Thus the insulation level of the equipment has to be above the protective level by a safe margin. This paper attempts to give an overview of concepts of insulation coordination and the different methodologies of insulation co-ordination studies.

Keywords

Insulation coordination, overvoltages, transients, Basic Impulse Insulation Level

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J. Sreedevi ¹, P. Noorcheshma ², N. Ashwin ², K. S. Meera ³

Affiliations
1 Joint Director, PSD, Central Power Research Institute, Bengaluru, Karnataka, 560080, IN
2 Senior Research Fellow, PSD, Central Power Research Institute, Bengaluru, Karnataka, 560080, IN
3 Additional Director, PSD, Central Power Research Institute, Bengaluru, Karnataka, 560080, IN

Abstract

Various sophisticated technologies have been deployed in the modern power system to facilitate the notion of smart grid, integrating the power system, associated IT infrastructure and the communication network into a Cyber-Physical System (CPS). The increasing coupling between a physical power system and its communication network necessitates a Cyber-Physical test environment to investigate and guarantee the grid’s stability and reliability. A Cyber-Physical Testbed consists of four components – a Physical power systems layer, a power systems monitoring layer, a Communication Network layer and an Energy Management Systems layer. In this paper, the need of a Cyber Security testbed is detailed along with an architecture of a typical Cyber Security Testbed and the role of a Real Time Simulator in the Testbed.

Keywords

Cyber-Physical System (CPS), Cyber-Physical Testbed, Phasor Measurement Units (PMU), Real Time Digital Simulator

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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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K. S. Meera ¹, Santosh Kumar Patro ²

Affiliations
1 Joint Director, Power Systems Division, Central Power Research Institute, Bangalore - 560080, IN
2 SRF, Power Systems Division, Central Power Research Institute, Bangalore 560080, IN

Abstract

Overvoltages caused by transients are important in a power system as they cause stresses on electrical equipment. Majority of power system failures are directly or indirectly related to transient problems rather than steady state operation. The insulation level of each element in a power system is governed by the transient voltages originating as a result of lightning, short circuits and switching actions. In contrast to lightning, switching overvoltages originates on the system and is inherently measured in terms of the system voltage.

With the adoption of 400 kV voltages and above, it was clear that switching surges created in the system would determine the cost and strength of the major insulations to ground. This paper gives an insight to the electromagnetic transient phenomenon - switching and power frequency overvoltages and case study results of simulation for these overvoltages for a typical Indian 765 kV system.

Keywords

Electromagnetic Transients, Overvoltages, EMTP (electromagnetic transients program)

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K. S. Meera ¹, Kaliappan Perumal ¹

Affiliations
1 CPRI, Bangalore, Karnataka, IN

Abstract

Phasor Measurement Units (PMUs) and Phasor Data Concentrators (PDCs) are the fundamental components of Wide Area Measurement Systems (WAMS) and Wide Area Monitoring Protection and Control Systems (WAMPACS). PMUs provide fast time-stamped measurement of system parameters such as voltage, current and frequency. They have communication features which help in exchange of large quantities of data quickly. As these measurements are very useful in power system support applications such as system parameter analysis, online voltage stability calculations, adaptive protective algorithms etc. they must always function reliably and accurately. This necessitates that the PMUs be calibrated so that their data is consistent, accurate, and credible, and that the models from different manufacturers are interoperable. The 6135A PMUCAL of fluke make is a unique tool which carries out manual/ automated tests that certify a PMU configuration for meeting the latest performance standards of the IEEE Standard for Synchrophasor Measurements for Power Systems (IEEE C37.118.1:2011, IEEE C37.118.1:2014 and IEEE C37.242). This paper discusses the 6135A PMUCAL – a unique test facility set up at the Power Systems Division of CPRI and also results of typical PMUs tested using this facility.

Keywords

Global Positioning System (GPS), Phasor Measurement Unit, Rate-of-change-of-Frequency Error (RFE), Synchrophasor, Total Vector Error (TVE)

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Puneeth Bhurat ¹, K. S. Meera ², N. Vasudev ³

Affiliations
1 Vijaya Sales Corporation, #49, 4th Cross Small Scale Industrial Area, Rajajinagar, Bengaluru – 560010, Karnataka, IN
2 Power Systems Division, Central Power Research Institute, Bengaluru – 560080, Karnataka, IN
3 Manobhu Technologies, Bengaluru – 560010, Karnataka, IN

Abstract

Switching Overvoltages (SOV) are critical for systems operating at Ultra High Voltage (UHV) level. Pre-insertion resistors (PIR) are usually used to suppress the switching overvoltages in UHV systems. PIR are effective in suppressing SOV’s, but their shortcomings prompt utilities to explore other protection schemes. In this paper, the application of Line Surge Arresters (LSA) to suppress switching over voltages is studied. The statistical overvoltage analysis is carried out for a typical UHV system to compute the highest overvoltage magnitudes. The location and number of LSA’s to be placed along the transmission line are decided based on the overvoltage profile along the line, observed during switching operations. The switching impulse withstand values of the equipment are calculated for proposed non-gapped line arrester arrangements and also compared with the withstand values for conventional system. The energy absorbed by the LSA’s when placed along the transmission line is also observed. The simulations are performed using Electro-Magnetic Transient Program for the 1200 kV Indian transmission system. The results of this study show that the LSA’s can be considered an alternate protection measure to suppress SOV’s in a UHV system.

Keywords

Co-Ordinations, EMTP, Insulation, Switching Over-voltage, Transient, Ultra High Voltage.

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