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PRESENTATION ON
REACTIVE POWER
CONTROL
S.K.SOONEE
GM,SRLDC
BANGALORE
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POWER IS PLEASURE---ASK THOSE
WHO ARE SEEKING IT
POWER IS PAIN
---ASK THOSE
WHO HAVE IT
REAL POWER IS PAIN
IMAGINARY POWER PLEASURE
SOURCES OF REACTIVE POWER
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SYNCHRONOUS GENERATORS
SYNCHRONOUS CONDENSORS
SHUNT CAPACITORS
STATIC THYRISTOR BASED DEVICES
TRANSMISSION LINES
REACTIVE POWER SINKS
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LOADS
INDUCTION MOTORS(PUMPS,FANS ETC)
 INDUCTIVE LOADS (CHOKES ETC)
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TRANSFORMERS
TRANSMISSION LINES
REACTORS
STATIC THYRISTOR BASED DEVICES
SHYNCHRONOUS MACHINES
SYNCHRONOUS
MACHINES
SYNCHRONOUS MACHINE
MODES OF OPERATION
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UNDER-EXCITED OR LEADING PF
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CONSUMES REACTIVE POWER
OVER-EXCITED OR LAGGING PF
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PRODUCES REACTIVE POWER
SYNCHRONOUS GENERATORS
VECTOR DIAGRAM
E
OVER-EXCITED
jIXd
δ
V
θ
I
E
UNDER-EXCITED
δ
θ
jIXd
I
V
CAPABILITY CURVE
Q=MVAR, REACTIVE POWER
U2=P2+Q2
LEAD
MOTORING
GENERATING
P=MW, ACTIVE POWER
LAG
LEAD/UNDER EXCITED(+) LAG/OVER EXCITED(+)
LIMITATIONS
TRANSMISSION
LINES
TRANSMISSION LINES
SIL
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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:

100 KM OF 400 KV LINE(MOOSE) CAUSES 55 MVAR
OF CHARGING CURRENT
OVERVOLTAGE PROBLEMS
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Generator self-excitation
Insulation breakdown
Flashover
Customer equipment damage
Excessive heating of overexcited
transformers
UNDERVOLTAGE CAUSES
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Heavy line loading
Disturbances
High customer demand
Induction motor heating
Dim lights - more lights
Less heat - more heaters
Voltage collapse
SOME FACTS
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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
TO CORRECT LOW VOLTAGE
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Remove shunt Reactors
Insert shunt capacitors
Energize open lines
Raise LTC set points
Raise voltage regulator set points
Use generator reactive overload capability
Curtail interruptible loads
Shed firm load
TO CORRECT HIGH VOLTAGE
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Remove shunt capacitors
Insert shunt reactors
Lower voltage set points
Close open-ended lines or remove from
service altogether
Buck with generators
Remove transmission lines from service
POINTS TO REMEMBER
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VAR control is the key to voltage control
Use voltage control equipment early
Avoid voltage collapse/High Voltage by
smart operating
Permissible Voltage Limits
Voltage Under Normal
Condition
Nominal
(kV)
Max permissible Voltage
at the far end of lines
normally kept energized
from one end
Max
Min
kV
220
145
245
120
200
148
245
400
420
360
420
735/765
800
700
800
132
REQUIREMENTS & METHODS
LOAD ANGLE
ITS IMPLICATION IN POWER
SYSTEM OPERATION
LOAD ANGLE
VOLTAGE
vs
FREQUENCY
Frequency and Voltage
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“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=P0(F/F0)
2
2. Q=Q0(V/V0)
IEEE MODEL: COMPOSITE LOADS
P(V,F)=(A1Vn1Fm1+A2Vn2fm2+A3Vn3Fm3)P0
Q(V,F)=(A4Vn4Fm4+A5Vn5Fm5+A6Vn6Fm6)Q0
CO-EFFICIENTS A1 TO A6 ARE ASSOCIATED WITH LOAD
CATEGORIES
A1+A2+A3=1
A4+A5+A6=1
LOAD REPRESENTATION
TYPE OF LOAD PF
∆P/∆V
(%)
∆P/∆F
(%)
∆Q/∆V
(%)
∆Q/∆F
(%)
INCANDESENT LAMP
1.6
1
0.5
0.8
0.3
-0.1
1.7
2.4
0.8
0
1
0.6
0.5
0.1
0
46
2.5
2.5
1.8
1.1
3
1.6
0
-65
-2.8
-1.3
-1.6
FLOURESCENT LAMP
AIR CONDITIONER WINDOW
TYPE
REFRIGERATOR
1
1.00
0.82
0.79
HOME APPLIANCE WITH
MOTOR
150 HP INDUCTION MOTOR
LARGE US TOWN
ALUMINIUM PLANT
AGRICULTURAL IN
WINTER(US)
0.88
0.89
0.91
1.9
0.4
0.7
TRANSFORMERS
AND
TAP CHANGING
ICT TAPS
ON LOAD TAP CHANGER
1.25% OR 5 KV PER TAP±10% RANGE
NOMINAL TAP AT 9
TAP NO 1=440/220
400 KV SIDE
220 KV SIDE
TAP NO 17=360/220
V
V
ICT TAP CHANGING EXAMPLE
TAP NO 1=440/220
100 MW
50 MVAR
9
210 KV
400 KV
TAP NO 17=360/220
V
BASE CONDITION
V
ICT TAP CHANGING EXAMPLE
100 MW
3
TAP NO 1=440/220
10 MVAR
208 KV
408 KV
TAP NO 17=360/220
V
V
TAP IS MOVED FROM 9 TO 3 SAY
MVAR FLOW AND RESULTANT VOLTAGES ARE
DEPENDANT ON GRID AND STRENGTH OF BUS
TAP CHANGING
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REARRANGES MVAR FLOW
TO BE DONE CONSIDERING VOLTAGES
ON BOTH SIDES
CO-ORDINATED ACROSS THE SYSTEM
TAP CHANGING SCHEDULES
GT TAP CHANGING
400 KV
BASE CASE
21 KV
TAP 9
~
INFINITE BUS
500 MW
30 MVAR
400 KV
TAP
CHANGED
21.3 KV
TAP 12
~
INFINITE BUS
500 MW
5 MVAR
REACTIVE LOAD STRATA
LOADED LINES
REACTORS
TRANSFORMERS
LOAD SHEDDING
REACTORS REMOVAL
BASE LOAD MET BY
1. CAPACITORS
LOAD
LAGGING
LEADING 1.SWITCH OFF CAPACITORS
2. GENERATORS
/LINES BELOW SIL
SUPPLYING VAR
CAPACITORS
2.GENERATORS ABSORBING VARS
3.SWITCH OFF LIGHTLY LOADED
LINES
4.TAP STAGGERING
DURATION
LIGHTLY LOADED LINES
VOLTAGE
CONTROL
WHAT THE IEGC SAYS……..
IEGC SECTION 4.9
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4.9 Reactive 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.
IEGC SECTION 6.9
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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 NorthEastern 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
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(q) All regional constituents shall make all
possible efforts to ensure that the grid voltage
always remains within the following operating
range. NOMINAL MAXIMUM MINIMUM
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400
420
360
220
245
200
132
145
120
IEGC SECTION 6.4
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6.4 Demand Control
6.4.1
Introduction:
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 6.8
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6.8 Recovery Procedures
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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 7.6
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1.
-
2.
3.
7.6 Reactive Power and Voltage Control:
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%.
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).
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….
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7.6.4In 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.
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
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VA METERING
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ACCURACY CLASS
DIFFICULTY IN CALIBRATION AND
CHECKING
DIFFICULTY IN MEASURING BAD
POWER FACTOR
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