2022 International Conference on Computational Intelligence and Sustainable Engineering Solutions (CISES) | 978-1-6654-8004-8/22/$31.00 ©2022 IEEE | DOI: 10.1109/CISES54857.2022.9844359
1st International Conference on Computational Intelligence and Sustainable Engineering Solution(CISES2022)
Transient Switching Study for 120 MVAr Variable
Shunt Reactor at 220 kV Substation
Ayyaj Maner
Project Engineering
Adani Electricity Mumbai
Mumbai, India
ayyaj.maner@adani.com
Sonu Karekar
In-charge Netwotk Development
Adani Electricity Mumbai
Mumbai, India
sonu.karekar@adani.com
Amol Salunkhe
Testing and Protection
Adani Electricity Mumbai
Mumbai, India
amol.salunkhe@adani.com
Raiju Hassan
Network Development
Adani Electricity Mumbai
Mumbai, Inida
raiju.hassan@adani.com
Mahesh Ambardekar
Head Project and Engineering
Adani Electricity Mumbai
Mumbai, Inida
mahesh.ambardekar@adani.com
Arvindkumar Sharma
COO, Transmission
Adani Electricity Mumbai
Mumbai, India
arvind.kumar.sharma@adani.com
Abstract— This paper describes transients switching study
carried out for variable shunt reactor (VSR) connected to 220
kV Grid at 220/33 kV Adani Electricity Mumbai Ltd (AEML)
Gorai substation. The study model developed in the PSCAD. It
includes a model for VSR, Sf6 CB, other substation
equipments. Inrush currents due to uncontrolled switching and
transient recovery voltage peak due to forced 5A current
chopping corresponding to lowest 48 MVAr (40%) and highest
120 MVAr (100%) reactive power were determined. Based on
the analysis, controlled switching device (CSD) was proposed
for point on wave switching strategy for 120 MVAr VSR and
operational methodology is devised.
Reactive shunt compensation (bus reactors) were placed at
various locations in study model and the effect on system
voltages were observed. Further, the possibility of physical
installation of bus reactors, i.e. space availability at substation, was also explored.
Keywords — variable shunt reactor, inrush current,
controlled switching, transient recovery voltage.
A single VSR is always advantageous compared to,
traditional fixed type shunt reactor for stabilizing the voltage
for a range of loading conditions in the system. 31 Steps are
considered for VSR where 1st tap provides 40% reactive
power of rated one and 29th tap provides the 100% reactive
power. Taps can be changed remotely to meet continuous
compensation of reactive power as load varies and therefore
securing voltage stability of grid. Some other key benefits
are elimination of voltage jumps resulting from switching of
traditional fixed type reactors, flexible for load pattern,
reduced footprint of substation etc [1].
I. INTRODUCTION
Mumbai Metropolitan Region (MMR), the financial
capital of the country, having a mix of diversified electrical
requirements ranging from households to commercial
complexes, corporate Offices, data /IT Centers to industrial
establishments like refineries, BARC, Port, Airport, etc.
Presently the average demand of MMR is around 3500 MW.
Considering importance of the region, it is necessary to
provide 24x7 quality power supply to all the consumers.
However, there has been consistent complaints with
respect to voltage dips in and around interconnected substations of the 400/220/100 kV Kalwa S/s. by various
utilities viz. M/s. HPCL, M/s. TATA, M/s. AEML & other
consumers. To identify the reasons and remedial measures,
the Director (Operations), MSETCL, formulated a working
group comprising of members from various utilities under
his leadership. A series of meetings of the working group
were conducted for identifying the reasons and remedial
measures thereof.
It noted the reasons for frequent high magnitude voltage
dips that consumer being affected was due to number of
system fault occurrences in network associated with high
fault currents; failure of switchgear & protection system to
clear the fault instantly. Remedial measures were proposed
by working group to reduce the fault current.
Further group study also revealed that during winter
MMR demand was lowest and system voltages were highest.
978-1-6654-8004-8/22/$31.00 ©2022 IEEE
Committee report recommends the installation of bus
reactors in Adani Electricity 220kV Network at Gorai S/s,
will result in significant reduction in high system voltages
during off peak condition. In view of installation of 120
MVAr reactor at 220 kV level; transient switching study of
reactor is carried out in PSCAD and presented in this paper.
Mainly there are two concerns seen while switching the
reactor, which are briefly elaborated. First is the inrush
current is relatively dependent on the CB pole closing instant
and
linearity characteristics of the reactor core [2].
Uncontrolled switching of shunt reactor may cause high
magnitude inrush current [3]. It may lead to serious damages
if not appropriately managed.
Second is current chopping phenomena, observe while
interrupting the small inductive current that leads to
overvoltage across the circuit breaker terminals and shunt
reactor [2]. It is due to trapped energy in the reactor. The
voltage appears across the circuit breaker is termed as
transient recovery voltage (TRV) which can be dangerous
and risk of reignition if the peak value exceeds the rated one
[4].
Controlled
switching
device
(CSD)
normally
recommended to use alongwith circuit breaker for extending
closing or opening command at optimum time instant on
voltage or current waveform to eliminate the harmful
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1st International Conference on Computational Intelligence and Sustainable Engineering Solution(CISES-2022)
transients produced due to uncontrolled random switching
[5].
1500.0
II. MODEL IN PSCAD
1000.0
geographic information systems
A. Model for VSR
For switching study, 220 kV Gorai Substation is modeled
alongwith its connectivity with external network represented
one bus away from substation [6]. Gorai is the GIS
substation with two bus system configuration with 10 bays
which includes two underground cables of 9.1 km each,
hybrid transmission line-1 (OH 11.6 km + Cable 0.055 km),
hybrid transmission line-2 (OH 9.17 km + Cable 0.055 km),
two 125 MVA transformer, one 120 MVAr VSR (proposed),
two Bus PT and B/C.
500.0
Ln=1.284H
0.0
0
cross linked polyethylene
220 kV
3000.0
Frequency
50 Hz
Core Type
Three limb
Reactive Power
120 MVAr
(Tap position 29)
Ψ (V.s)
Voltage Rating
48 MVAr
(Tap position 1)
126 A
Total losses ( at 220 kV)
190 kW
78 kW
Lair=0.3H
2000.0
1000.0
Ln=3.21H
0.0
0
Per phase Capacitance
(winding to ground)
Reactor Bushing
Capacitance
500
1000
1500
i (Amp)
3.2 ηF
Fig. 2. Instantaneous flux-current saturation curve of 48 MVAr shunt
reactor
250 pF
853660.7 [ohm]
Ia
0.0032 [uF]
3Iph2Rcu = PTot - Pfe
0.000250 [uF]
Variable shunt reactor model is represented by RLC
circuit shown in Fig. 3 [6]. Copper losses (Pcu) and iron
losses (Pfe) are determined using equation (1) considering
two scenarios first, PTot 190 kW at 314.9 A and second, PTot
78 kW at 126 A. Pfe as a constant.
0.4480 [ohm]
853660.7 [ohm]
------ equation (1)
and
3Vph2 / Rfe = Pfe = PTot - Pcu
Per phase copper resistance (Rcu) is calculated initially
using equation (1) then iron loss (Pfe) & hence iron resistance
(Rfe) is calculated using phase voltage (Vph).
Ib
0.0032 [uF]
0.000250 [uF]
Pcu = 3Iph2Rcu
1500
Fig. 1. Instantaneous flux-current saturation curve of 120 MVAr shunt
reactor
4000.0
314.9 A
1000
i (Amp)
TECHNICAL DATA OF VSR
Nominal Current
500
To study the inrush current of reactor during energization
requires an instantaneous flux–current saturation curves (Fig.
1 and Fig. 2) of reactor iron core [7]. Typical values provided
by manufacturer are converted in to pu and then it used in
nonlinear inductance element in PSCAD. It is approximated
into two segments.
VSR bay is modelled in detail includes 55 meter 220kV
XLPE cable portion from GIS Bay to VSR, circuit breaker,
transformer bushing and other high voltage equipment.
Technical details of variable shunt rector are given in Table
1.
TABLE I.
Ψ (V.s)
Lair=0.77H
0.4480 [ohm]
853660.7 [ohm]
0.0032 [uF]
0.000250 [uF]
Ic
0.4480 [ohm]
Fig. 3. VSR Model
A bay is a power line within an electrical substation which connects a circuit (such as a power line
or transformer) to a busbar Each bay typically includes circuit breakers, disconnectors, instrument
transformers and surge arresters. It is suggested not to tag all these individual components.
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1st International Conference on Computational Intelligence and Sustainable Engineering Solution(CISES-2022)
B. Model for CB and Bay Equipment
P = 1.29
Q = 15.68
P is in Watt
Q is in MVAr
V is in kV
0.5 [ohm]
0.001 [mH]
Bus
0.0005 [uF]
BRKA
A
V
1.18 [ohm]
P = -0.6945
Q = 15.82
A
V
A
V
BRK
3.21 [H]
Ia
P = 0.07962
Q = 47.96
V = 220
2079430 [ohm]
3.21 [H]
Ib
1.18 [ohm]
P = -0.5166
Q = 15.78
Fig. 4. Model of circuit breaker
A
V
Electric arc model [2] is considered for circuit breaker.
Reactor switching produces transients of high frequency, bay
equipments were represented by capacitance with respect to
ground (Table II). For three phases in one bus GIS,
manufacturer provided the capacitance 62pF per meter for
the bus. The capacitance of disconnecting switches and
circuit breakers does not vary greatly from the values per
meter for the bus [8].
TABLE II.
2079430 [ohm]
2079430 [ohm]
3.21 [H]
Ic
1.18 [ohm]
Fig. 6. Steady State load flow of 48 MVAr Reactor
B. Uncontrolled energization
Current waveforms during uncontrolled energization of
VSR with 100% capacity i.e. 120 MVAr reactive power at
time instants ta =120 ms, tb=119 ms, tc = 121 ms are
presented in Fig. 7.
CAPACITANCE TO GROUND [8]
Reactor Current (kA)
GIS equipment
Ia
Capacitance (pF)
Ib
Ic
1.00
Disconnector
62
Current Transfomer
200
Potential Transformer
80
0.50
0.00
-0.50
III. SIMULATIONS OF SWITCHING TRANSIENTS
-1.00
Switching transient is simulated on 100% rating of
reactor (120 MVAr at highest tap) and 40% rating of reactor
(48 MVAR at lowest tap).
Fig. 7. Reactor Current Iamax = 969.5A , Ibmax= 841.4A , Icmax= 837.4A
A. Steady State load flow
Initially load flow is carried out to confirm the steady
state losses and measurands, results of load flow shown in
Fig. 5 and Fig. 6.
Current waveforms during uncontrolled energization of
with 40% capacity i.e. 48 MVAr reactive power at time
instants ta =120 ms, tb=119 ms, tc = 121 ms are presented in
Fig. 8. Magnitude of Inrush current are lower in case with 48
MVAr compared to 120 MVAr.
P = 3.226
Q = 39.23
P is in Watt
Q is in MVAr
V is in kV
A
V
x
0.150
1.283 [H]
0.448 [ohm]
A
V
P = -1.74
Q = 39.57
BRK
A
V
0.250
Ib
Ic
0.40
853660.7 [ohm]
Ib
0.200
Reactor Current (kA)
Ia
P = 0.1915
Bus Q = 120
V = 220
t (sec)
Simulation shows that transient inrush current with
amplitude of 3.07 p.u. and high DC component can last up to
4 seconds (Fig. 9)
853660.7 [ohm]
Ia
0.100
0.30
1.283 [H]
0.20
0.10
0.448 [ohm]
0.00
P = -1.295
Q = 39.48
A
V
Ic
-0.10
853660.7 [ohm]
-0.20
1.283 [H]
-0.30
-0.40
0.448 [ohm]
x
Fig. 5. Steady State load flow of 120 MVAr Reactor
0.100
0.150
t (sec)
0.200
0.250
Fig. 8. Reactor Current Iamax = 391.7 A, Ibmax=340.5 A, Icmax= 338.7 A
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1st International Conference on Computational Intelligence and Sustainable Engineering Solution(CISES-2022)
Reactor Current (kA)
1.00
Ia
Ib
Ct is total capacitance parallel with the breaker (F)
Ic
For the SF6 breaker , λ ϵ [ 4 - 17×104 ],
0.75
0.50
Modern SF6 breakers have a relatively low arc voltage and
do not tend to significantly chop current [5].
0.25
0.00
Note: 5 A max chopping current is assumed to study the
TRV peak in this study model.
-0.25
-0.50
-0.75
-1.00
x
0.0
1.0
2.0
t (sec)
3.0
4.0
Transient Recovery Voltage (kV)
5.0
400
TRVA
TRVB
TRVC
300
Fig. 9. Uncontrolled Switching of VSR
200
100
C. Controlled energization
Switching of reactor at voltage peak time instant using
control switching device (CSD) significantly reduces the
inrush currents in each phase. Current waveform at optimum
switching instant is shown in Fig.10 for 120 MVAr reactive
power and in Fig.11 for 48 MVAr reactive power.
0
-100
-200
-300
-400
x
0.120
0.130
0.140
t (sec)
0.150
Reactor Current (kA)
0.50
Ia
Ib
Fig. 12. Voltage across circuit breaker (TRV) at 120 MVAr Reactive Power
Ic
Transient Recovery Voltage (kV)
0.40
0.30
400
0.20
TRVB
TRVC
300
0.10
0.00
200
-0.10
100
-0.20
0
-0.30
-100
-0.40
-200
-0.50
x
TRVA
0.110
0.120
0.130
0.140
0.150
-300
t (sec)
-400
x
Fig. 10. Reactor Current Iamax=466.8 A, Ibmax=467.5 A, Icmax= 468.8 A
0.120
0.130
t (sec)
0.140
0.150
Reactor Current (kA)
0.40
Ia
Ib
Fig. 13. Voltage across circuit breaker (TRV) at 48 MVAr Reactive Power
Ic
0.30
0.20
TABLE III.
PEAK TRANSIENT RECOVERY VOLTAGE ACROSS CICUIT
BREAKER (KV)
0.10
0.00
Reacti
ve
Power
(MVA
r)
-0.10
-0.20
-0.30
-0.40
x
0.110
0.120
0.130
0.140
0.150
t (sec)
Fig. 11. Reactor Current Iamax=190.3 A, Ibmax=190.1 A, Icmax= 191.1 A
D. Deenergization of VSR
Current chopping phenomena can be seen while
interrupting the small reactor current that leads overvoltage
across the circuit breaker terminals and shunt reactor [2].
Phase B
U1max
U1max
(Ich =
(Ich =
0A)
5A)
Phase C
U1max
U1max
(Ich =
(Ich =
0A)
5A)
120
351.2
360.4
347.5
356.8
351.4
360.7
48
346.1
366.8
341.0
362.3
347.3
368.1
IV. RESULT
Simulation Results are summarized below.
A.
Voltage appears across the circuit breaker immediate
after current interruption is termed as transient recovery
voltage which may result in damages of interrupter and
nearby connected equipments. Magnitude of Transient
recovery voltage peak largely depends on the magnitude of
chopping current which described in equation (2) [9].
Ich = λ * √ Ct
Peak TRV across Circuit Breaker (kV)
Phase A
U1max(
U1max
Ich =
(Ich =
0A)
5A)
Inrush Current Peak
Table IV shows the magnitude of inrush current which is
recorded during uncontrolled switching and controlled
switching of reactor at 40% and 100% reactive power. It can
be understood that magnitude of inrush current significantly
reduced with controlled switching compared to uncontrolled
random switching.
------ equation (2)
Ich is chopping current (A)
TABLE IV.
λ is the chopping number (AF-0.5)
Reactive
Power
Identify applicable funding agency here. If none, delete this text box.
PEAK INRUSH CURRENT (AMP)
Peak Inrush Current (Amp)
Uncontrolled Switching
Controlled Switching
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1st International Conference on Computational Intelligence and Sustainable Engineering Solution(CISES-2022)
(MVAr)
Ia
Ib
Ic
Ia
Ib
Ic
120
969.5
841.4
837.4
466.8
467.5
468.8
48
391.7
340.5
338.7
190.3
190.1
191.1
seen increasing with increase in chopping current value.
Hence it is adviced to switch OFF the variable shunt reactor
at lowest tap position (1st tap – 48 MVAr reactive power) for
SF6 breakers (Modern) using CSD.
V. CONCLUSION
This paper describes transient switching study carried out
for 120 MVAr VSR connected to 220 kV Adani Electricity
Mumbai Network for voltage control. Simulation was
performed for steady state load flow, uncontrolled switching,
controlled switching for VSR at its 40% and 100% reactive
power. Study shows that the magnitude of inrush current is
considerably reduced to its nominal current level almost with
controlled switching. Further the magnitude of TRV peak
can be seen higher for forced 5A chopping current, compared
to zero current chopping. TRV peak mainly depends on
chopping current value. Pre-determined switching of VSR
using controlled switching device (CSD) significantly
reduces the inrush current, overvoltage and risk of reignition.
Operational methodology for switching of VSR is devised
and 220 kV grid voltage regulation at typical loading
conditions also studied.
B. Transient Recovery Voltage Peak
Table III shows the recorded value of transient recovery
voltage peak can be seen around 351 kV without chopping
and 360.7 kV with forced 5A current chopping. TRV peak
can be observed below the breaker’s maximum withstand
voltage 375 kV.
It can be seen that 55 meter 220kV XLPE cable portion
used to connect 220kV GIS and reactor contributes to limit
the TRV across CB and helps to reduce the shunt reactor
overvoltage from 1.12 p.u. to 1.04 p.u. for a 120 MVAr
capacity during deenergization.
C. Bus Voltage Control
Table IV shows the 220 kV Gorai bus voltage regulation
with and without VSR at typical off peak loading conditions
in AEML network.
Simulations shows that the bus voltage of Gorai
substation is reduced by 3.03 kV and 1.37 kV respectively to
120 MVAr and 48 MVAr reactive power compensation
using VSR.
TABLE V.
ACKNOWLEDGMENT
The authors like to mention special thanks to
engineering, testing & protection team of AEML-T for
providing data for the work presented in this paper, as well
as network team for their support and providing the access of
simulation software used in this paper.
220 KV VOLTAGE (KV) AT GORAI S/S
220 kV Grid Voltage (kV) at Gorai S/s
Reactive
Power
(MVAr)
Without VSR
(kV)
With VSR
(kV)
120
236.84
233.81
48
236.84
235.47
a.
REFERENCES
[1]
[2]
PSSE used for Voltage regulation study.
[3]
D. Point on Wave (PoW) Switch
1) PoW switch is used to extend the open or close
control command at a pre-determined point on voltage
waveform for preventing inrush current and overvoltage
transients. Command is extended to the phase for which
voltage peak either negative or positive occurring first, then
after command extend to remaining two phases with delay
of 60 deg (A-C-B) [5].
2) Further PoW helps to reduce the probability of
reignition by ensuring well separation of contacts of a
circuit breaker from each other before the current is
interrupted. It involves identifying right instant to open the
breaker so that its contacts will part just after a current zero;
an arc that will extinguish less than a half-cycle later at the
next current zero [5].
[4]
[5]
[6]
[7]
[8]
E. Operational methodology.
1) Inrush current magnitude is observed less at lowest
tap position therefore it is adviced to switch ON the variable
shunt reactor at lowest tap position (1st tap – 48 MVAr
reactive power). Fine tunned CSD further helps to reduce the
inrush current significantly.
2) Transient recovery voltage is observed less at lowest
tap position for low chopping current value and TRV can be
[9]
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