PRESENTATION ON REACTIVE POWER CONTROL S.K.SOONEEGM,SRLDCBANGALORE

POWER IS PLEASURE---ASK THOSE WHO ARE SEEKING IT POWER IS PLEASURE---ASK THOSE WHO ARE SEEKING IT POWER IS PAIN ---ASK THOSE WHO HAVE IT POWER IS PAIN ---ASK THOSE WHO HAVE IT REAL POWER IS PAIN IMAGINARY POWER PLEASURE REAL POWER IS PAIN IMAGINARY POWER PLEASURE

SOURCES OF REACTIVE POWER SYNCHRONOUS GENERATORS SYNCHRONOUS GENERATORS SYNCHRONOUS CONDENSORS SYNCHRONOUS CONDENSORS SHUNT CAPACITORS SHUNT CAPACITORS STATIC THYRISTOR BASED DEVICES STATIC THYRISTOR BASED DEVICES TRANSMISSION LINES TRANSMISSION LINES

REACTIVE POWER SINKS LOADS LOADS INDUCTION MOTORS(PUMPS,FANS ETC) INDUCTION MOTORS(PUMPS,FANS ETC) INDUCTIVE LOADS (CHOKES ETC) INDUCTIVE LOADS (CHOKES ETC) TRANSFORMERS TRANSFORMERS TRANSMISSION LINES TRANSMISSION LINES REACTORS REACTORS STATIC THYRISTOR BASED DEVICES STATIC THYRISTOR BASED DEVICES SHYNCHRONOUS MACHINES SHYNCHRONOUS MACHINES

SYNCHRONOUS MACHINES

SYNCHRONOUS MACHINE MODES OF OPERATION UNDER-EXCITED OR LEADING PF UNDER-EXCITED OR LEADING PF CONSUMES REACTIVE POWER CONSUMES REACTIVE POWER OVER-EXCITED OR LAGGING PF OVER-EXCITED OR LAGGING PF PRODUCES REACTIVE POWER PRODUCES REACTIVE POWER

SYNCHRONOUS GENERATORS VECTOR DIAGRAM E I θ δ V jIX d I θ δ V E OVER-EXCITED UNDER-EXCITED

CAPABILITY CURVE U 2 =P 2 +Q 2 LEAD LAG MOTORINGGENERATING Q=MVAR, REACTIVE POWER P=MW, ACTIVE POWER

LIMITATIONS LAG/OVER EXCITED(+) LEAD/UNDER EXCITED(+)

TRANSMISSION LINES

TRANSMISSION LINES SIL SURGE IMPEDANCE LOADING:-The SIL is the loading level where the reactive VARs generated by the line capacitance equal the VARs required by the line inductance. SURGE IMPEDANCE LOADING:-The SIL is the loading level where the reactive VARs generated by the line capacitance equal the VARs required by the line inductance. QUICK FACT: QUICK FACT: 100 KM OF 400 KV LINE(MOOSE) CAUSES 55 MVAR OF CHARGING CURRENT 100 KM OF 400 KV LINE(MOOSE) CAUSES 55 MVAR OF CHARGING CURRENT

OVERVOLTAGE PROBLEMS Generator self-excitation Generator self-excitation Insulation breakdown Insulation breakdown Flashover Flashover Customer equipment damage Customer equipment damage Excessive heating of overexcited transformers Excessive heating of overexcited transformers

UNDERVOLTAGE CAUSES Heavy line loading Heavy line loading Disturbances Disturbances High customer demand High customer demand Induction motor heating Induction motor heating Dim lights - more lights Dim lights - more lights Less heat - more heaters Less heat - more heaters Voltage collapse Voltage collapse

SOME FACTS A 10 percent voltage drop cuts light output by 30 percent. A 10 percent voltage drop cuts light output by 30 percent. A 10 percent voltage drop cuts heat output by 20 percent. The user response, in many such cases, is to turn on more lights A 10 percent voltage drop cuts heat output by 20 percent. The user response, in many such cases, is to turn on more lights

TO CORRECT LOW VOLTAGE Remove shunt Reactors Remove shunt Reactors Insert shunt capacitors Insert shunt capacitors Energize open lines Energize open lines Raise LTC set points Raise LTC set points Raise voltage regulator set points Raise voltage regulator set points Use generator reactive overload capability Use generator reactive overload capability Curtail interruptible loads Curtail interruptible loads Shed firm load Shed firm load

TO CORRECT HIGH VOLTAGE Remove shunt capacitors Remove shunt capacitors Insert shunt reactors Insert shunt reactors Lower voltage set points Lower voltage set points Close open-ended lines or remove from service altogether Close open-ended lines or remove from service altogether Buck with generators Buck with generators Remove transmission lines from service Remove transmission lines from service

POINTS TO REMEMBER VAR control is the key to voltage control VAR control is the key to voltage control Use voltage control equipment early Use voltage control equipment early Avoid voltage collapse/High Voltage by smart operating Avoid voltage collapse/High Voltage by smart operating

Permissible Voltage Limits Voltage Under Normal Condition Max permissible Voltage at the far end of lines normally kept energized from one end Nominal (kV) MaxMin kV /

REQUIREMENTS & METHODS

LOAD ANGLE ITS IMPLICATION IN POWER SYSTEM OPERATION

LOAD ANGLE

VOLTAGE vs FREQUENCY

Frequency and Voltage “The general synchronous machine equations show that voltage levels are directly proportional to the frequency and for godd voltage control extremes of system frequency are to be avoided” “The general synchronous machine equations show that voltage levels are directly proportional to the frequency and for godd voltage control extremes of system frequency are to be avoided” ………Excerpts from Chapter on Reactive Power and Voltage control. System operators Manual L

Impact of freq on Voltage E=4.44фfN Where E is the EMF Generated,f is the Frequency, ф the flux

Transmission Planning criteria 1. P=P 0 (F/F 0 ) 2. Q=Q 0 (V/V 0 ) 2

IEEE MODEL: COMPOSITE LOADS P(V,F)=(A 1 V n1 F m1 +A 2 V n2 f m2 +A 3 V n3 F m3 )P 0 Q(V,F)=(A 4 V n4 F m4 +A 5 V n5 F m5 +A 6 V n6 F m6 )Q 0 CO-EFFICIENTS A1 TO A6 ARE ASSOCIATED WITH LOAD CATEGORIES A 1 +A 2 +A 3 =1 A 4 +A 5 +A 6 =1

LOAD REPRESENTATION TYPE OF LOAD PF∆P/∆V(%)∆P/∆F(%)∆Q/∆V(%)∆Q/∆F(%) INCANDESENT LAMP FLOURESCENT LAMP AIR CONDITIONER WINDOW TYPE REFRIGERATOR HOME APPLIANCE WITH MOTOR HP INDUCTION MOTOR LARGE US TOWN ALUMINIUM PLANT AGRICULTURAL IN WINTER(US) 0.8

TRANSFORMERS AND TAP CHANGING

ICT TAPS 400 KV SIDE 220 KV SIDETAP NO 17=360/220 TAP NO 1=440/220 VV ON LOAD TAP CHANGER 1.25% OR 5 KV PER TAP±10% RANGE NOMINAL TAP AT 9

ICT TAP CHANGING EXAMPLE 400 KV 210 KVTAP NO 17=360/220 TAP NO 1=440/220 VV BASE CONDITION MW 50 MVAR

ICT TAP CHANGING EXAMPLE 408 KV 208 KVTAP NO 17=360/220 TAP NO 1=440/220 VV TAP IS MOVED FROM 9 TO 3 SAY MVAR FLOW AND RESULTANT VOLTAGES ARE DEPENDANT ON GRID AND STRENGTH OF BUS 3100 MW 10 MVAR

TAP CHANGING REARRANGES MVAR FLOW REARRANGES MVAR FLOW TO BE DONE CONSIDERING VOLTAGES ON BOTH SIDES TO BE DONE CONSIDERING VOLTAGES ON BOTH SIDES CO-ORDINATED ACROSS THE SYSTEM CO-ORDINATED ACROSS THE SYSTEM TAP CHANGING SCHEDULES TAP CHANGING SCHEDULES

GT TAP CHANGING ~ INFINITE BUS400 KV 21 KV TAP MW 30 MVAR BASE CASE ~ INFINITE BUS 400 KV 21.3 KV TAP MW 5 MVAR TAP CHANGED

REACTIVE LOAD STRATA LEADING LAGGING LOAD TRANSFORMERS LOADED LINES REACTORS CAPACITORS LIGHTLY LOADED LINES DURATION LOAD SHEDDING BASE LOAD MET BY 1.CAPACITORS 2.GENERATORS /LINES BELOW SIL SUPPLYING VAR REACTORS REMOVAL 1.SWITCH OFF CAPACITORS 2.GENERATORS ABSORBING VARS 3.SWITCH OFF LIGHTLY LOADED LINES 4.TAP STAGGERING

VOLTAGE CONTROL WHAT THE IEGC SAYS……..

IEGC SECTION Reactive Power Compensation 4.9Reactive Power Compensation (a)Reactive Power compensation and/or other facilities, should be provided by SEBs/STUs or distributing agencies as far as possible in the low voltage systems close to the load points thereby avoiding the need for exchange of Reactive Power to/from ISTS and to maintain ISTS voltage within the specified range. (a)Reactive Power compensation and/or other facilities, should be provided by SEBs/STUs or distributing agencies as far as possible in the low voltage systems close to the load points thereby avoiding the need for exchange of Reactive Power to/from ISTS and to maintain ISTS voltage within the specified range.

IEGC SECTION (J)All generating units shall normally have their automatic voltage regulators (AVRs) in operation, with appropriate settings. In particular, if a generating unit of over fifty (50) MW (10 MW in case of North-Eastern region) size is required to be operated without its AVR in service, the RLDC shall be immediately intimated about the reason and duration, and its permission obtained. Power System Stabilisers (PSS) in AVRs of generating units (wherever provided), shall be properly tuned as per a plan prepared for the purpose by the CTU from time to time. CTU will be allowed to carry out tuning/checking of PSS wherever considered necessary. 6.9 (J)All generating units shall normally have their automatic voltage regulators (AVRs) in operation, with appropriate settings. In particular, if a generating unit of over fifty (50) MW (10 MW in case of North-Eastern region) size is required to be operated without its AVR in service, the RLDC shall be immediately intimated about the reason and duration, and its permission obtained. Power System Stabilisers (PSS) in AVRs of generating units (wherever provided), shall be properly tuned as per a plan prepared for the purpose by the CTU from time to time. CTU will be allowed to carry out tuning/checking of PSS wherever considered necessary.

IEGC SECTION 6.9 (q)All regional constituents shall make all possible efforts to ensure that the grid voltage always remains within the following operating range. (q)All regional constituents shall make all possible efforts to ensure that the grid voltage always remains within the following operating range.NOMINALMAXIMUMMINIMUM

IEGC SECTION Demand Control 6.4Demand Control 6.4.1Introduction: 6.4.1Introduction: This section is concerned with the provisions to be made by SLDC's to permit the reduction of demand in the event of insufficient generating capacity, and transfers from external interconnections being not available to meet demand, or in the event of breakdown or operating problems (such as frequency, voltage levels or thermal overloads) on any part of the grid. This section is concerned with the provisions to be made by SLDC's to permit the reduction of demand in the event of insufficient generating capacity, and transfers from external interconnections being not available to meet demand, or in the event of breakdown or operating problems (such as frequency, voltage levels or thermal overloads) on any part of the grid.

IEGC SECTION Recovery Procedures 6.8Recovery Procedures d)The RLDC is authorised during the restoration process following a black out, to operate with reduced security standards for voltage and frequency as necessary in order to achieve the fastest possible recovery of the grid. d)The RLDC is authorised during the restoration process following a black out, to operate with reduced security standards for voltage and frequency as necessary in order to achieve the fastest possible recovery of the grid.

IEGC SECTION Reactive Power and Voltage Control: 7.6Reactive Power and Voltage Control: 1.The Beneficiaries are expected to provide local VAR compensation/generation such that they do not draw VARs from the EHV grid. However, considering the present limitations, this is not being insisted upon. Instead, VAR drawals by Beneficiaries (except on their lines emanating from ISGS) are to be priced as follows:- -The Beneficiary pays for VAR drawal when voltage at the metering point is below 97%. -The Beneficiary gets paid for VAR return when voltage is below 97%. -The Beneficiary gets paid for VAR drawal when voltage is above 103%. -The Beneficiary pays for VAR return when voltage is above 103%. 2.The charge/payment for VARs, shall be at a nominal paise/kVARh rate as may be approved by CERC from time to time, and will be between the beneficiary and the Pool Account (for VAR interchanges with ISTS), and between two beneficiaries (for VAR interchanges on ties between their systems). 3.Notwithstanding the above, RLDC may direct a beneficiary to curtail its VAR drawal/injection in case the security of grid or safety of any equipment is endangered.

IEGC SECTION 7.6 CONTD… In general, the Beneficiaries shall endeavour to minimise the VAR drawal at an interchange point when the voltage at that point is below 95% of rated, and shall not return VARs when the voltage is above 105%. ICT taps at the respective drawals points may be changed to control the VAR interchange as per a beneficiary's request to the RLDC, but only at reasonable intervals In general, the Beneficiaries shall endeavour to minimise the VAR drawal at an interchange point when the voltage at that point is below 95% of rated, and shall not return VARs when the voltage is above 105%. ICT taps at the respective drawals points may be changed to control the VAR interchange as per a beneficiary's request to the RLDC, but only at reasonable intervals. 5.Switching in/out of all 400 KV bus and line Reactors throughout the grid shall be carried out as per instructions of RLDC. Tap changing on all 400/220 KV ICTs shall also be done as per RLDC's instructions only. 5.Switching in/out of all 400 KV bus and line Reactors throughout the grid shall be carried out as per instructions of RLDC. Tap changing on all 400/220 KV ICTs shall also be done as per RLDC's instructions only. 6.The ISGS shall generate/absorb reactive power as per instructions of RLDC, within capability limits of the respective generating units, that is without sacrificing on the active generation required at that time. No payments shall be made to the generating companies for such VAR generation/absorption. 6.The ISGS shall generate/absorb reactive power as per instructions of RLDC, within capability limits of the respective generating units, that is without sacrificing on the active generation required at that time. No payments shall be made to the generating companies for such VAR generation/absorption.

VA Metering VA METERING VA METERING ACCURACY CLASS ACCURACY CLASS DIFFICULTY IN CALIBRATION AND CHECKING DIFFICULTY IN CALIBRATION AND CHECKING DIFFICULTY IN MEASURING BAD POWER FACTOR DIFFICULTY IN MEASURING BAD POWER FACTOR