2200 kvar Capacitor-Bank Relay Calculation (BEF/SP)
(I ) [DMT OVER CURRENT RELAY
Calculate the Capacitive Resituate at Ratted Voltage
XC= 40²X 1000/2200 =727.27Ω
Calculate the effective reactance of Complete Capacitor& reactor unit
XCI = 727.27-0.13X 727.27
= 632.72 Ω
Calculate the KVAR Capacity of bank at 25KV KV
KVAR = (25)² X1000/632.72
= 987.79 KVAR
Ratted Current of CAP-Bank at- system voltage 25KV
CAP- Bank Current AMP.ICAP =987.79/25
= 39.51 AMP
To recomandate the CT & relay error. The 10% higher value of above
calculated current is recommended for setting of relay
Current setting of IDMT relay in AMP (Irelay) =1.10x39.51/200/5
=1.0865AMP
Setting% = 1.0865/5x100= 21.73%
TMS Setting
Fault current = 27000/4.36+37.82 =640AMP
Plug setting multiplier =640X5/200/5.43=2.94=5.81
To archivethe operating time 500ms FR fault after shunt reactor, the
TMS=250/100=TMSX0.14/(33/5.43)0.02-1
250/100=TMSX0.14/1.0367-1
TMS= 0.0656 ie.=0.07
(2) Over voltage setting
in volt= 1.1 X 27500/27500/110=121V
Setting in % = 121/110X100=110%
Time Setting /Play setting multiplier = 121/110=1.1
From IDMT curve7sec at 1.5 times at 1.2 time of setting the operating time
is 17 sec at TMS .1 to achieve the operating time 1sec.
TMS setting= 1/17 = 0.058 ie 0.06
(3) UNDER VOLTAGE RELAY
Setting in volt (Vu/v)= 17500/27500/110
=70 volt
Setting in % = 70/110X 100
=63.64% ie 64%
Time setting
Play setting multiplier = 70/110 =0.64
From IDMT curve 5sec at 0 voltage.
At 0.64 times of setting the operating time is nearly 9sec at TMS 1. To
achieve the operating time 1sec.
TMS setting = 1/9
= 0.11
(4) Unbalance current Relay
Vender asking
Setting current in Amp = 0.863/211
= 0.4315Amp
5 sec % = 0.4315/ 1 X 100
= 43.15 = 43%
Time setting
200-400ms.
Settings guidelines 25 KV shunt cap Brake protection relay
1) 1 DMT over current relay.
a) Current setting
Capacitive reactance
XC= KV² X 1000/KVAR = Ω
KVAR = 25² X1000/ X CI
System voltage 25KV Cap-Box Current I.E
AMP I cap = KVAR/ Rated system voltage in ler.
Current setting 1 DMT relay in AMP (I relay)
= 1.10 X 1 cap / CT ratio
= AMP
Setting in% = I relay / CT secondary X 100\
5500 KVAR Relay Setting calculation for capacitor bank
1. Assumption The following assumptions are made for sample calculation:
a. Shunt capacitor bank rating = 5500 KVAr at 40 KV
b. NCT ratio = 5/1
c. PT ratio = 27500/110
d. Fault MVA = 10000 MVA at 132KV base voltage.
e. CT ratio = connected-100/5 (200-100/5)
2. IDMT Over current relay
a) Current setting Calculate the capacitive reactance at rated voltage
Xc = 40² * 1000/5500 = 290.91 Ω
Calculate the effective reactance of complete capacitor & reactor unit
Xc1 = 290.91-0.13 * 290.91 = 253.09 Ω
Calculate the KVAr capacity of bank at 25 kV KVAr =
(25)² * 1000/253.09 = 2469.47 KVAr
Rated current of capacitor bank at system, voltage 25 kV
2452.47/25
Capacitor bank current in amp, I cap = 98.77 amp
To accommodate the CT and relay errors, the 10% higher value of above calculated
current is recommended for setting of relay.
Current setting of IDMT relay in amp (lrelay) = 1.10 * 98.77/100/5 = 5.43Amp
Setting in % = 5.13 * 100/5 =108.65 i.e. 109%
b) TMS setting
Fault current = 27000/4.36 + 37.82 = 640Amp
= (Source and traction transformer impedance 4.36 ohm as calculated above for traction
transformer setting) Plug setting multiplier = 640 * 5 / 100/5.43 = 5.89
To achieve the operating time 500 ms for fault after shunt reactor, the TMS
250/1000 = TMS X 0.14/{(33/5.43)º·º²-1}
250 = TMS X 0.14
c) Over voltage setting
Setting in volt (Vo/v) = 1.1x27500 = 121Volt
27500/110
Setting in % = 121x100 = 110%
110
Time Setting
Plug Setting Multiplier = 121 =1.1
110
From IDMT curve 7sec at 1.5 times , at 1.2 times of setting the operating times is 17 sec at
TMS I . Achieve the operating time 1 sec .
TMS setting = 1/17 = 0.058 i.e. 0.06
© Under voltage relay
Setting in voltage (Vu/v)= 17500 =70 Volt
27500/110
Setting in % =70x100 = 63.64% =64%
110
Time setting
Plug Setting Multiplier = 70 = 0.64
110
From IDMT curve 5sec at 0 Voltage at 0.64 times of setting the operating time is nearly 9 sec
at TMS 1 . to Achieve the operating time 1 sec.
TMS setting = 1/9 = 0.11
d) Current unbalance relay
It is seen that with the failure of 8 elements resulting voltage appeared across healthy
elements parrel to failed elements is 1.76 times of ratted voltage, the unbalance current
above number of elements failure is 0.863 Amps. This is the sample results only; it may very
manufactures, therefore approach to capacitor bank manufacture for actual permitted
unbalance current.
Set current in amp. Iub = (0.863/5/1)= 0.1726 amp. (CTR=5/1A)
Setting in % =.01726x100 = 17.26% i.e.= 18%
1
Time setting
The time setting shall be kept at 200-400 ms
The basic parameter for designing of capacitor bank at -TSS
Sl.No. Description Rating
1 Nominal system voltage 25KV (Phase to Earth)
2 Possible variation in the traction supply 19.0 to 27.5KV
voltage sometime s touching
29KV)
3 Equipment voltage class 52KV
4 Ratted frequency 50 Hz +-
3%
5 Average power factor of the traction 0.8 lagging
system without capacitor bank
6 Desired power factor after installation of 0.97lagging
capacitor bank
7 Present capacitor bank 10800KVAR
8 Present monthly PF 0.96
9 Present CD of BSP-TSS 25.5MVA
Detail of Capacitor bank ratings
Capacity of Xc (Ω) Xl(Ω) Xc’(Ω) Capacity of I at 25 KV Rated
bank in bank in (in Amps) current of
KVArat 40 KVAr at 25 reactor (in
KV KV Amps)
In the KV2x 0.13xXc 0.87xXc KV2x1000/Xc’ KVArat Iat 25KVx
multiple of 1000/KVAr 25 /KV/25 1.3
220 KVAr
2200 727.27 94.55 632.73 988 39.51 51
3300 484.85 63.03 421.82 1482 58.27 77
4400 363.64 47.27 316.36 1976 79.02 103
5500 290.91 37.82 253.09 2469 96.78 128
6600 242.42 31.52 210.91 2963 118.53 154
7700 207.79 27.01 180.78 3457 138.29 180
8800 181.82 23.64 158.18 3951 158.05 205
9900 161.62 21.01 140.61 4445 177.80 231
11000 145.45 18.91 126.55 4939 197.56 257
Note- Losses of the reactor shall be guaranteed at the rated current ᶲ
Design of new Capacitor bank
a) Angles:
Cos ᶲ1= 0.96 (Existing capacitor bank).
Cosᶲ2= 0.98
ᶲ1 =16.26
ᶲ2= 11.47
Tan ᶲ1=0.29
Tanᶲ2=0.203
Tanᶲ1=KVAR1/KW, KVAR1=KW Tan ᶲ1
Tanᶲ2=KVAR2/KW, KVAR2=KW Tanᶲ2
Cos ᶲ1= KW/KVA1
Cosᶲ2=KW/KVA2
Rating of the shunt capacitorbank
Considering reasonably loaded of traction sub-station, the methodology for calculating changeable
power factor from 94% to 98% the optimum.
KVARc=KVAR1-KVAR2
=KW Tanᶲ1 –KW Tanᶲ2
=KW (Tan ᶲ1-Tanᶲ2)
= KVA1cosᶲ1(Tan ᶲ1-Tanᶲ2)
= CDx 0.96(0.29-0.203)
= -------- KVAR
Design for requirement of Capacitor bank at ------TSS for improvement of power factor from 96% to 98%
Ratting of fixed capacitor bank is ----- KVAR
Assuming 10% extra for the future growth of load .KVAR Capacity of the capacitior
bank at 25 KV= 1.1x--x-- KVAR
Capacitor reactance of –x---KVAR =1000xKV2 /KVAR 25x25x1000/---xKVAR= ----Ω
Series reactor rating in ohm
In order to avoid resonance at all odd harmonics the minimum value of series reactor
reactance (Xl) should to be 11.11% to 13% of the capacitive reactane (Xc) .
moreover , to keep the effective capacitive reactance same as 178 ohm. The
capacitive reactance of capacitor bank should be increased by the same amount of
the series reactor reactance.
The value of series reactor reactance Xl=0.13 Xc
And (Xc-Xl)= ------x---ohm
So, Xc = ----Ohm /(1-0.13) =------Ω
And Xl=0.13x----ohm = -----Ω
Actual rating of series reactor in capacitor bank
Taking into account the fluctuation of incoming supply voltage and the voltage rise
at no load due to capacitor , the voltage class of capacitor bank should be calculated
taking the bus voltage as 28 KV
Current drawn by capacitor –reactor
Circuit current at fundamental frequency =28000/(Xc-Xl)
= 28000/347-45
93 ohm
Voltage
Sl.No BEF/SP setting
1 Make –Alind
Model- ANC 214
SL.No-1210330
YOM-2021
2 General config, 200 Amp
Line CT Primary
3 Line Ct Secondary 5A
4 NCT Primary 2
5 NCT secondary 1
6 PT Primary 27500 V
7 PT Secondary 110 V
8 Trip Ckt Supervision EN
9 Trip CKT Rst Discard
10 Relay ID 1
11 Baud Rate 9600
IDMT OC protection set 30%
12 IDMT OC protection TMS 0.07
Relay setting mode OV Protection
13 Over Voltage Protection Trip Val. 110%
14 OV Protection TMS 0.06
Relay setting mode UV Protection
15 UV protection En
16 UV Protection Trip Val. 71%
17 UV Protection TMS 0.11
Relay setting mode current
unbalance
18 Current unbalance Trip Val. 43.5%
19 Current unbalance Trip Time 250 mSec
