Electricpoints -Recharge yourself: April 2014

Thursday, April 17, 2014

Control Cable Required For 33/11KV Sub-Station

Control Cable Required For 33/11KV Sub-Station

10 Core Cable:

Used for Wiring from Control Room To Breaker.

a. Within Breaker (4 X 6M) = 24 M
b. LV Breaker to Control Room (1 X 25M) = 25 M
c. Feeder Breakers to Control Room (3 X 40M) = 120 M
(35m+37m+40m) arrox 40m
d. One Length for Group Control (1 X 40M) = 40 M

Total 210 M (250 M Approx).

4 Core Cable:

a. CTs to Breaker (3 X 10M) = 30 M
b. 1 LV Breaker + 3 Feeder Breakers (4 X 30M) = 120 M
c. LV to PTR (1 X 10M) = 10 M
d. LV To Control Room(Voltmeter) (1 X 25M) = 25 M
e. PT Supply - AC, PT Section Box to Breakers (1 X 60M) = 60 M
(10m+15m+20m+15m)

Total 200 M (250 M Approx).

2 Core Cable:

a. Chargers to Breaker (4 X 20M) = 80 M
b. Station DTR Junction Box to Each Charge
and Charger to Breaker (5m+5m+10m+10m) = 30 M

Total 110 M.

All above Calculations were done by assuming that the control room will be constructed on 33 KV Side.

Capacitor Bank Sizing

9 Tips To Save Electricity

11 KV Polymer Disc and MP

11 KV Guy Insulator

11 KV Pin Insulator (Polymer Type)

Stay Set Bow and I Bolt

NSF Sub Station

Stay Rod

DTR Structure Mounting Channel & H X Arm

DTR Structure Mounting Angle

LT 3 Ph X Arm

Stay Set
Base Plat

Stay Wire

11 KV Top Cleat

11 KV X Arm

Sunday, April 6, 2014

Calculate % Voltage Regulation of Distribution Line - Method-2 (Load Base)

Method-2 (Load Base)

% Voltage Regulation =(I x (RcosǾ+XsinǾ)x Length ) / No of Cond.per Phase xV (P-N))x100

Voltage drop at Load A

Load Current at Point A (I) = KW / 1.732xVoltxP.F
Load Current at Point A (I) =1500 / 1.732x11000x0.8 = 98 Amp.
Distance from source= 1.500 Km.
Required No of conductor / Phase =98 / 205 =0.47 Amp =1 No
Voltage Drop at Point A = (I x (RcosǾ+XsinǾ)x Length ) / V (Phase-Neutral))x100
Voltage Drop at Point A =((98x(0.272×0.8+0×0.6)x1.5) / 1×6351) = 0.52%
% Voltage Regulation at Point A =0.52 %

Voltage drop at Load B

Load Current at Point B (I) = KW / 1.732xVoltxP.F
Load Current at Point B (I) =1800 / 1.732x11000x0.8 = 118 Amp.
Distance from source= 1500+1800=3.3Km.
Required No of conductor / Phase =118 / 205 =0.57 Amp =1 No
Voltage Drop at Point B = (I x (RcosǾ+XsinǾ)x Length ) / V (Phase-Neutral))x100
Voltage Drop at Point B =((118x(0.272×0.8+0×0.6)x3.3)/1×6351) = 1.36%
% Voltage Regulation at Point A =1.36 %

Voltage drop at Load C

Load Current at Point C (I) = KW / 1.732xVoltxP.F
Load Current at Point C (I) =2000 / 1.732x11000x0.8 = 131Amp.
Distance from source= 1500+1800+2000=5.3Km.
Required No of conductor / Phase =131/205 =0.64 Amp =1 No
Voltage Drop at Point C = (I x (RcosǾ+XsinǾ)x Length ) / V (Phase-Neutral))x100
Voltage Drop at Point C =((131x(0.272×0.8+0×0.6)x5.3)/1×6351) = 2.44%
% Voltage Regulation at Point A =2.44 %

Here Trail end Point % Voltage Regulation is 2.44% which is in permissible limit.

Calculate % Voltage Regulation of Distribution Line - Method-1 (Distance Base)

Calculate % Voltage Regulation of Distribution Line

Calculate Voltage drop and % Voltage Regulation at Trail end of following 11 KV Distribution system:

System have ACSR DOG Conductor (AI 6/4.72, GI7/1.57)
Current Capacity of ACSR Conductor = 205Amp,
Resistance = 0.2792Ω and Reactance = 0 Ω,

Permissible limit of % Voltage Regulation at Trail end is 5%.

Calculate percentage of Voltage Regulation of Distribution Line

Method-1 (Distance Base)

Voltage Drop = ( (√3x(RCosΦ+XSinΦ)x I ) / (No of Conductor/Phase x1000))x Length of Line

Voltage drop at Load A

Load Current at Point A (I) = KW / 1.732xVoltxP.F
Load Current at Point A (I) =1500 / 1.732x11000x0.8 = 98 Amp.
Required No of conductor / Phase =98 / 205 =0.47 Amp =1 No
Voltage Drop at Point A = ( (√3x(RCosΦ+XSinΦ)xI ) / (No of Conductor/Phase x1000))x Length of Line
Voltage Drop at Point A =((1.732x (0.272×0.8+0×0.6)x98) / 1×1000)x1500) = 57 Volt
Receiving end Voltage at Point A = Sending end Volt-Voltage Drop= (1100-57) = 10943 Volt.
% Voltage Regulation at Point A = ((Sending end Volt-Receiving end Volt) / Receiving end Volt) x100
% Voltage Regulation at Point A = ((11000-10943) / 10943 )x100 = 0.52%
% Voltage Regulation at Point A =0.52 %

Voltage drop at Load B

Load Current at Point B (I) = KW / 1.732xVoltxP.F
Load Current at Point B (I) =1800 / 1.732x11000x0.8 = 118 Amp.
Distance from source= 1500+1800=3300 Meter.
Voltage Drop at Point B = ( (√3x(RCosΦ+XSinΦ)xI ) / (No of Conductor/Phase x1000))x Length of Line
Voltage Drop at Point B =((1.732x (0.272×0.8+0×0.6)x98) / 1×1000)x3300) = 266 Volt
Receiving end Voltage at Point B = Sending end Volt-Voltage Drop= (1100-266) = 10734 Volt.
% Voltage Regulation at Point B= ((Sending end Volt-Receiving end Volt) / Receiving end Volt) x100
% Voltage Regulation at Point B= ((11000-10734) / 10734 )x100 = 2.48%
% Voltage Regulation at Point B =2.48 %

Voltage drop at Load C

Load Current at Point C (I) = KW / 1.732xVoltxP.F
Load Current at Point C (I) =2000 / 1.732x11000x0.8 = 131 Amp
Distance from source= 1500+1800+2000=5300 Meter.
Voltage Drop at Point C = ( (√3x(RCosΦ+XSinΦ)xI ) / (No of Conductor/Phase x1000))x Length of Line
Voltage Drop at Point C =((1.732x (0.272×0.8+0×0.6)x98) / 1×1000)x5300) = 269 Volt
Receiving end Voltage at Point C = Sending end Volt-Voltage Drop= (1100-269) = 10731 Volt.
% Voltage Regulation at Point C= ((Sending end Volt-Receiving end Volt) / Receiving end Volt) x100
% Voltage Regulation at Point C= ((11000-10731) / 10731 )x100 = 2.51%
% Voltage Regulation at Point C =2.51 %

Here Trail end Point % Voltage Regulation is 2.51% which is in permissible limit.

Required Size of Capacitor

Size of capacitor for improvement of the Power Factor from Cos ø1 to Cos ø2 is:

Required size of Capacitor (Kvar) = KVA1 (Sin ø1 – [Cos ø1 / Cos ø2] x Sin ø2)

Where KVA1 is Original KVA.

Optimum location of capacitors

L = [1 – (KVARC / 2 KVARL) x (2n - 1)]

Where:

L – distance in per unit along the line from sub-station.
KVARC – Size of capacitor bank
KVARL – KVAR loading of line
n – relative position of capacitor bank along the feeder from sub-station if the total capacitance is to be divided into more than one Bank along the line. If all capacitance is put in one Bank than values of n=1.

Voltage Rise due to Capacitor installation:

% Voltage Rise = (KVAR(Cap) x Lx X) / 10 x Vx2

Where:

KVAR (Cap) – Capacitor KVAR
X – Reactance per phase
L – Length of Line (mile)
V – Phase to phase voltage in kilovolts

How to calculate Voltage Regulation for 11KV, 33KV Overhead Line

Voltage Regulation for 11KV, 33KV Overhead Line

% Voltage Regulation = (1.06 x P x L x PF) / (LDF x RC x DF)

Where:

P – Total Power in KVA
L – Total Length of Line from Power Sending to Power Receiving in KM.
PF – Power Factor in p.u
RC – Regulation Constant (KVA-KM) per 1% drop.

RC = (KV x KV x 10) / ( RCosΦ + XSinΦ)

LDF – Load Distribution Factor.
LDF = 2 for uniformly distributed Load on Feeder.
LDF > 2 If Load is skewed toward the Power Transformer.
LDF = 1 To 2 If Load is skewed toward the Tail end of Feeder.

DF – Diversity Factor in p.u

Permissible Voltage Regulation (As per REC)

Maximum Voltage Regulation at any Point of Distribution Line
Part of Distribution System	Urban Area (%)	Suburban Area (%)	Rural Area (%)
Up to Transformer	2.5	2.5	2.5
Up to Secondary Main	3	2	0.0
Up to Service Drop	0.5	0.5	0.5
Total	6.0	5.0	3.0

Voltage Regulation Values

The voltage variations in 33 kV and 11kV feeders should not exceed the following limits at the farthest end under peak load conditions and normal system operation regime.

Above 33kV (-) 12.5% to (+) 10%.
Up to 33kV (-) 9.0% to (+) 6.0%.
Low voltage (-) 6.0% to (+) 6.0%

In case it is difficult to achieve the desired voltage especially in Rural areas, then 11/0.433 kV distribution transformers(in place of normal 11/0.4 kV DT’s) may be used in these areas.

What is FSA or Fuel Surcharge Adjustment?

FSA or Fuel surcharge adjustment is the additional fuel cost that was not collected from consumers by DISCOMs like APCPDCL, APEPDCL, APSPDCL and APNPDCL in the previous years. The monthly electricity bills of consumers that year did not cover the actual cost of fuel that distribution companies paid to generators to buy power. So, to make up for the loss that discoms suffered, sometimes it is allowed if the government and court allows to collect this money in coming years. Usually their is a lot of political involvement as they do not want to raise the price frequently so that they do not loose the vote bank but due to heavy losses by the discoms lead them to take tough decisions and implement the policy.