Fixed Series Capacitors for Increased Power Transmission Load Ability of 400 KV Raipur

IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 01, 2014 | ISSN (online): 2321-0613

Fixed Series Capacitors for Increased Power Transmission Load ability of 400 KV Raipur – Wardha Corridor Piyush M. Khadke1 Aditya S.Tohare2 Dr. N. R. Patne3 G. A. Shinde 4 1,2P.G. Student 3Asst. Professor 4Sr. Engineer (Testing) 1,2,3 Department of Electrical & Electronics Engineering 1, 2, 3 VNIT, Nagpur, India. 4 Wardha S/s, POWERGRID, WR-I, India.

Abstract— This paper highlights a practical case study of 6) R1 = 0.0146 Ω/km, X1 = 0.2530 Ω/km, B1 = 4.5777 Fixed Series Compensation (FSC) at 1200/765/400/220 KV micro-mho/km Wardha Substation, POWERGRID, WR-I (Western Region 7) √(L/C) = 235 – I), India for increasing the power load ability and meeting 8) SIL – 680 MW the rising power demands, implemented on 400 KV D/C Name of the line -: 400 KV D/C Wardha – Akola Line (Double Circuit) Raipur – Wardha Line. This FACTS device was commissioned at Wardha Substation in January 2013. 1) Line Length – 162 km (approximately) This paper will give an overview of FSC and its components 2) Conductor Type – Twin Moose with effects of FSC on the specified line and also on one of 3) Xl = 49.734Ω (line reactance) the adjacent line based on simulated data and real time data. 4) R1 = 0.0288 Ω/km, X1 = 0.3070 Ω/km, B1 = 3.7687 micro-mho/km Key words: FSC, Flexible AC Transmission Systems 5) √(L/C) = 285 (FACTS), Power Transmission System, POWERGRID, 6) SIL = 560 MW MOV.

III. BASIC CONCEPT I. INTRODUCTION Power Transmitted without series compensation Modern power systems with their complexity and increasing Vs ∗ Vr ∗ sinδ power demands require power with acceptable standards of = ⁄X (1.1) quality and economical costs. A proposition of new line l comes with its own constraints related to environment and Where, crowding with the other existing lines. Flexible Alternate δ = Angle between voltage buses Current Transmission Systems (FACTS) is one of the Vs = Sending end Voltage solutions for optimization of given corridor’s transmission capacity. FACTS are well known because it provides lot of Vr = Receiving end Voltage benefits to improve the power load ability in transmission Xl = Line Reactance lines, as well as power system stability. In the given To Increase Transmission Capacity of the Line purview, FSC is the simplest and cost-effective solution. following parameters are to be looked upon. Series capacitors have been used extensively since 1950 as a very effective means of increasing the power transfer 1) Increase in Voltage: Higher Transmission Voltages capability of a power system that has long (250 kms or will boost the power transmission capacity of a given more) transmission lines. In consideration with the future line. plan of evacuation of huge power from Eastern part of India 2) Increase in the Angle: It can be used to increase power which is having great potential of Power Generation to transfer; but it has limitation due to stability problems. Western part of India through Wardha Mega power corridor, 3) Decrease in: By reducing the reactance also we can it was necessary to step up the power transmission capability achieve the increment in power transfer. of Raipur – Wardha Corridor. This paper will deal with the detailed aspects of FSC in 400 KV D/C Raipur – Wardha Line placed at 1200/765/400/220 KV Wardha Substation, POWERGRID, WR-I.

II. LINE PARAMETERS In this paper, we are considering following two lines to Fig. 1: Series compensated Transmission Line. study the effects of FSC using Matlab® control system Power Transmitted after Series Compensation toolbox. Vs ∗ Vr ∗ sinδ = ⁄(X − Xc) (1.2) Name of line with FSC – 400KV D/C Raipur-Wardha l 1) Percentage of Series Compensation – 40% Where, 2) Line Length – 375 km (approximately) δ = angle between voltages, 3) Conductor Type – Quad Moose Vs = Sending end Voltage, 4) Thermal Limit of Quad Moose – 3 KA Vr = Receiving end Voltage, 5) Xl = 91.85 Ω (line reactance)

Sr. Xl = Line Reactance, Description Rating No. Xc = Series Capacitor Reactance E = 25MJ/phase

IV. COMPONENTS OF FSC 3 Spark Gap FOV** = 330 KVp to 420 KVp 12 Ohms, 60 A, 1400 A for 1 1) Capacitor banks 4 Damping Resistor 2) Metal Oxide Varistor (MOV) sec 3) Spark Gap 5 Damping Reactor 700 micro Henry, 3000 A 4) Damping Circuit 400 KV, 3 phase, SF6, 3150 6 By-pass Circuit Breaker 5) By-pass Circuit Breaker (BPCB) A, 40 KA for 1 sec 6) By-pass Isolator Table. 1: RATINGS OF VARIOUS COMPONENTS OF 7) CT’s FSC *MCOV = Max. Continuous Operating Voltage **FOV = Flash Over Voltage

VI. PROTECTION OF SERIES CAPACITOR BANK The series capacitor banks are protected with MOV and forced triggered spark gap protection. In case if there is a fault in the transmission line, short circuit current will flow also through the capacitor bank. The high short circuit current will increase the voltage across the capacitors. It is not economical to design the capacitors to withstand very high voltages. Therefore there is a metal-oxide varistor (MOV) connected in parallel with the capacitors. MOV has highly nonlinear Voltage vs. Current characteristics, which is almost like a step function. When the voltage will reach Fig. 2: Single-line scheme of Wardha S/s FSC. protective voltage level (in Wardha protective voltage level = 2.2pu) MOV will limit (cut) the voltage to this value. The capacitor units have been designed to withstand this voltage for a certain time, which is determined by the line protection requirements. In case of external fault (fault outside the line section, where the series capacitor is located) the MOV will limit the voltage to protective voltage level until the line circuit breakers in the external line will clear the fault. In case of internal fault (fault inside the same line section, where the series capacitor bank is located) the forced triggered spark gap will bypass the MOV and the Fig. 3: Layout arrangement of Wardha S/s FSC. capacitor bank thus protecting them. At the same time the closing command is given to the bypass breaker in order to protect and extinguish the spark gap. After the successful reclosure of the line by the line circuit breakers, the series capacitor bank will be automatically reinserted. The damping circuit will limit and dampen the discharge current of the bank in case the spark gap operates or the bypass breaker is closed. Current transformers are provided at different locations to measure the current for different protection system. The two Isolators (the platform disconnections) are used to connect the platform & platform equipment’s to the line or to isolate the platform & platform equipment’s from Fig. 4: FSC installation at Wardha S/s. the line. The earth switches are used for earthing the V. RATINGS OF COMPONENTS (FSC) platform & platform equipment’s as soon as the platform is Sr. Description Rating completely isolated from the line. No. Fixed Compensation 36.74 Ohm, 86.66 μF, 3KA, Capacitor Bank Arrangement and Details 1 Capacitor Bank 330.66 MVAR/phase Capacitor units are composed of several capacitor elements, MOV for Capacitor MCOV* = 116KV rms, 2 which are connected in series and parallel between Bank PL = 350 KVp at 30KAp, themselves. Thus, desired reactance (and further reactive

All rights reserved by www.ijsrd.com 179 Fixed Series Capacitors for Increased Power Transmission Load ability of 400 KV Raipur – Wardha Corridor (IJSRD/Vol. 2/Issue 01/2014/045) power) of the one unit and whole bank, is achieved. The Spark Gap capacitor unit is protected by internal fuses. In case a The forced triggered spark gap is an overvoltage protector capacitor element fails, the internal fuse will disconnect the connected in parallel to capacitor bank and MOV. It will failed element. protect the Metal Oxide Varistors (MOV) in case it reaches its design limits. Following are the parameters for Spark Gap. Operating time = 2-3 ms FOV = 330KVp to 420KVp Three Spark Gap units in series Gap = 68.4mm

Fig. 5: Capacitor arrangement of FSC. Note: C = 86.66 μF, Xc = 36.74 Ohm i.e. 40% of Raipur – Wardha Line Reactance. Rated Parameters of Each Capacitor Bank Sr. Description Parameters No. 1 Rated Capacitance (μF) 38.99 2 Rated Output (KVAR) 459.3 A B 3 Rated Voltage (KV) 6.13 4 Rated Frequency (Hz) 50 Fig. 7: (a) MOV installation and (b) Spark Gap inner view. Max. withstand capacity Transient Voltage of 5 between terminals 22.8 KV Damping Circuit 6 Type of Dielectric All PP film It is basically air cored reactor in parallel with the resistors. 7 Foil material Aluminum The purpose of the damping circuit is to limit and damp the 8 Make Nokian Capacitors capacitor bank discharge current in case the bank is by- Table. 2: RATED PARAMETERS OF EACH passed in fault condition. The inductance of the reactor and CAPACITOR BANK the resistance of the resistor are so chosen that the dampening meets the standard requirements. By-Pass Circuit Breaker (BPCB) It is used to by-pass the capacitor bank in different kinds of fault situations. Also it extinguishes the spark and thus protects the spark gap electrodes from destruction. In case of FSC Wardha S/s BPCB, Closing Time = 84-90 ms Opening Time = 20 ms

Fig. 6: Capacitor bank installation of FSC. Metal Oxide Varistor (MOV) The purpose of the MOVs is to limit the voltage across the capacitor bank during external fault conditions. They are placed in parallel with the capacitor bank. When series capacitor bank is operating on its normal load current, the leakage current through MOV is very small (only few mA). MOVs are very non-linear resistors, so in case of the over voltage fault situation across the bank (and MOV), they become conductive and limit the voltage over the bank. MOVs are chosen so that they withstand the maximum energy accumulation during the worst external fault conditions (in this case 0.9x25 MJ of energy). In a case of A B internal fault, the MOVs are allowed to bypass quickly by means of a triggered spark gap. Fig. 8: (a) Damping circuit and (b) By-pass circuit breaker (BPCB).

VII. RESULTS Fig. 11: Power flow results in 400KV Wardha-Akola line without Effect of FSC on 400KV Raipur – Wardha line Actual Real Time Data Simulation Data Power Flow in 400 KV Power Flow in 400 KV Raipur – Wardha Line Raipur – Wardha Line without FSC without FSC = 289 MW = 287 MW Power Flow in 400 KV Power Flow in 400 KV Raipur – Wardha Line with Raipur – Wardha Line with FSC FSC = 462 MW = 453 MW Table. 3: COMPARISON OF ACTUAL DATA V/S SIMULATED DATA FOR RAIPUR – WARDHA LINE Fig. 12: with FSC in 400KV Raipur-Wardha line respectively.

VIII. CONCLUSIONS In this paper a 400KV FSC at Wardha S/s is considered which is designed for 40% compensation. The changes in power load ability for the specified line and one of the adjacent lines is studied with and without the presence of FSC. This system was simulated and the results were compared and analyzed with real-time data available. As a consequence of implementation of FSC in 400 Fig. 9: Power flow results in 400KV Raipur-Wardha line KV D/C Raipur – Wardha Line placed at 1200/765/400/220 without KV Wardha Substation, POWERGRID, and WR-I, considerable increase of the power transmission capacity over the corridor has been attained.

ACKNOWLEDGEMENTS The authors would like to thank EEE Dept., VNIT Nagpur for providing required research infrastructure for this project and POWERGRID WR-I for providing the necessary data as well as technical expertise for the same.

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