How to calculate Voltage Regulation of 11 KV line

 Voltage Regulation:It is a measure of change in the voltage magnitude between sending end and receiving end of a component, such as Transmission or Distribution line.

Voltage regulation Formula:

%VR=Vs-Vr    x  100 
               Vs

Permissible Voltage Regulation in distrDistrib System:

Permissible Voltage Regulation as per REC:

Part of Distribution System	Urban Area (%)	Suburban Area (%)	Rural Area (%)
Up to Transformer	2.5	2,5	2.5
Up to Service Main	3	2	0.0
Up to Service Drop	0.5	0.5	0.5
Total	6.0	5.0	3.0

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%

Sometimes it can be difficult to achieve the required voltage, especially in rural areas . Part of the reason for the high voltage drop in rural areas it due to the fact that these areas are usually further was from the electricity supplies. Therefore, the power lines have to be extended over long distances, resulting in higher line losses. Power theft is a further factor which can contribute to voltage drops in rural areas. In these cases, 11/0.433 kV may be used in place of normal 11/0.4 kV distribution transformers .

Method to calculate % Voltage Regulation:

Method -1(Distance base )

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

Method-2(Load base):

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

P-phase

N-neutral

Explained:

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%.

Method 1:

Voltge 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+0x0.6)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) / Sending end Volt) x100
• % Voltage Regulation at Point A = ((11000-10943) / 11000)x100 = 0.51%
• % Voltage Regulation at Point A =0.51 %

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+0x0.6)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) / Sending end Volt) x100
• % Voltage Regulation at Point B= ((11000-10734) / 11000)x100 = 2.41%
• % Voltage Regulation at Point B =2.41 %

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+0x0.6)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) / Sending  end Volt) x100
• % Voltage Regulation at Point C= ((11000-10731) / 11000)x100 = 2.44%
• % Voltage Regulation at Point C =2.44 %

Here Trail end Point % Voltage Regulation is 2.41% which is in permissible limit.

Method-2

• 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+0x0.6)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+0x0.6)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+0x0.6)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.

Simple and practical method to measure Voltage Regulation in a distribution system:

1St measure staring end voltage of a DTR as Vs and then trail end voltage of a DTR as Vr then Voltage Regulation easily calculated.

For Vs=(Vry+Vyb+Vrb)/3

          Vr=(Vry+Vyb+Vrb)/3

  Vry:-Phase voltage between r and y phase

How to improve Voltage Regulation in a distribution line:

1.Use of generator voltage regulators

2. Application of voltage-regulating equipment in the distribution substations;

3. Application of capacitors in the distribution substation

4. Balancing of the loads on the primary feeders

5. Increasing of feeder conductor size

6. Changing of feeder sections from single-phase to multiphase

7. Transferring of loads to new feeders

8. Installing of new substations and primary feeders

9. Increase of primary voltage level

10. Application of voltage regulators on the primary feeders

11. Application of shunt capacitors on the primary feeders

12. Application of series capacitors on the primary feeders.

13.By preventing theft Voltage Regulation can be impoved and theft can be minimized by using of insulation on Conductor.

14.Now many projects like HVDS ,IPDS running for volatage regulation improvement.

15. In these cases, 11/0.433 kV may be used in place of normal 11/0.4 kV distribution transformers .