EEP 303 lab report

1. INDIAN INSTITUTE OF TECHNOLOGY DELHI
Power Engineering
Experiment 4: Measurement of Sequence
Impedances
CIDDHI JAIN
INDRA BHUSHAN-2010EE50548
MEHUL MITTAL-2010EE50553
SHRISTI MAHAJAN-2010EE505
UMANG GUPTA-2010EE50564
VIVEK MANGAL2010EE50565

2. Aim:
(i) To measure the positive and negative sequence impedance of a three phase three winding
transformer.
(ii) To measure the zero sequence impedance of a three phase two winding transformer.
NameplateRatings:
Rated KVA : 10 KVA
Rated Voltage : 200 V per phase per winding
Rated Current per phase per winding = (10 * 1000)/(200 * 3 *2) = 8.33 A
Observations:
(A) Three-phase twowinding Transformer:
Connection Excitation Voltage E
(Volts)
Input Current I
(Amps)
Zero Sequence Impedance
(Ohms)
Star-delta 2.9 14.2 0.613
Star-star(open) 10.84 14.6 2.227
Star-star(closed) 10.81 14.6 2.221
Star-star(neutral
connected)
3.6 15.2 0.71
In all cases,primary is star connected with neutral connected to the ground.
There is zero sequence current in star-delta connection as the secondary is delta, so there is path for
zero current to flow in the secondary.
There is also zero sequence current in stat-star(neutralis connected) ,there is path for zero current to
flow in the secondary.
In case 2 and 3, the zero sequence impedance is high. The current which is observed is just the
magnetising current and not due to the leakage reactance.

3. (B) Three phase three winding transformer
Measurement 1:
For Zps
Measured in Primary Secondary: Short Circuited Tertiary: Open
Excitation Voltage E
(Volts)
Input Current I
(Amps)
(Ohms)
3.75 7.9 0.475
Zps =E/I= 0.475 Ω
Measurement 2:
For Zpt
Measured in Primary Secondary: Open Tertiary: Short Circuited
Excitation Voltage E
(Volts)
Input Current I
(Amps)
(Ohms)
3.3 7.7 0.43
Zpt = E/I=0.43 Ω
Measurement 3:
For Zst
Measured in Secondary Primary: Open Tertiary: Short Circuited
Excitation Voltage E
(Volts)
Input Current I
(Amps)
(Ohms)
3.78 8.1 0.47
Zst = 0.47 Ω
Calculations: