EEP303: Experiment 2c
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This document summarizes experiments measuring the sequence impedances of transformers: (1) A three-phase, two-winding transformer's zero sequence impedance was measured under different connection types and ranged from 0.613 to 2.227 Ohms. (2) A three-phase, three-winding transformer's positive, negative, and zero sequence impedances were directly measured. The positive sequence impedance between the primary and secondary (Zps) was 0.475 Ohms. The positive sequence impedance between the primary and tertiary (Zpt) was 0.43 Ohms. The positive sequence impedance between the secondary and tertiary (Zst) was 0.47 Ohms.
EEP303: Experiment 2c
- 1. INDIAN INSTITUTE OF TECHNOLOGY DELHI Power Engineering Experiment 4: Measurement of Sequence Impedances Of Transformer Report Submitted By: CIDDHI JAIN-2010EE50011 INDRA BHUSHAN-2010EE50548 MEHUL MITTAL-2010EE50553 SHRISTI MAHAJAN-2010EE50561 UMANG GUPTA-2010EE50564 VIVEK MANGAL2010EE50566
- 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. Nameplate Ratings: 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 Circuit Diagram:
- 3. Observations: (A) Three-phase two winding 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(neutral is 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. (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
- 4. 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: