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Lab 2 Prem

The lab report details an experiment using a Megger for insulation testing of a transformer, highlighting the apparatus used and the procedure followed. It includes observations of insulation resistance measurements for both phase-ground and phase-phase connections, indicating that the transformer passed the insulation test due to high resistance values. The conclusion notes that phase-to-ground resistance is lower than phase-to-phase resistance, with overall resistance in mega ohms confirming the transformer's insulation integrity.

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18 views4 pages

Lab 2 Prem

The lab report details an experiment using a Megger for insulation testing of a transformer, highlighting the apparatus used and the procedure followed. It includes observations of insulation resistance measurements for both phase-ground and phase-phase connections, indicating that the transformer passed the insulation test due to high resistance values. The conclusion notes that phase-to-ground resistance is lower than phase-to-phase resistance, with overall resistance in mega ohms confirming the transformer's insulation integrity.

Uploaded by

hexev69272
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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KATHMANDU UNIVERSITY

SCHOOL OF ENGINEERING

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

INSTRUMENTATION LABORARTORY WORK EEEG 306

LAB REPORT: 2

Use of Megger for Insulation Testing of a Transformer

Submitted By: Submitted To:


Prem Kr Yadav Aayush Bista
EE-Power & Control DoEEE, KU
III/I
Roll.no: 31246

Date: 2025/05/15
Experiment-II
Title: Use of Megger for Insulation testing of a transformer
Apparatus
S. No. Equipment Range Type Quantity
1 Megger 230V, 1-phase 1
2 Connecting wires 3/22, 15A Few
3 Transformer 2

Theory

Megger is used for insulation testing. The insulation should be high in MΩ for good equipment and
will lie in Ω range for damaged equipment.

Circuit diagram:

Figure 1: (a). Transformer (b) Transformer insulation testing using megger

Procedure:
1. Remove completely external supply to transformer.
2. Connect leads to megger and set the megger voltage to 1000V.
3. Measure the insulation resistance

Theory:
A megger test, also known as insulation resistance testing, measures the resistance of insulation in
electrical equipment to identify potential faults or degradation. It's a critical safety check for
electrical systems, ensuring proper insulation and preventing issues like electrical failures, shorts,
or fires.

Megger testing measures resistance between the phase windings of the motor under test and ground.
If there is an insulation breakdown, the resistance is negatively impacted and there is a departure
between phases or between one measurement and a previous one and a determination of motor
health is made.

Figure 2: Megger

Observation Table:
Phase- Ground Insulation Check:

S. No. Connection Resistance (MΩ)

1 1.2-Ground 16

2 1.1 Ground 24

3 2.1 Ground 56

4 2.2 Ground 105

5 3.1 Ground 621


6 3.2 Ground 726

Table 1: Phase-ground insulation resistance check

Phase-Phase Insulation Check:


S. No. Connection Resistance (MΩ)

1 1.2-2.1 32 MΩ

2 1.2-2.2 59 MΩ

3 1.2-3.1 93 MΩ

4 1.2-3.2 129 MΩ

5 1.1-2.1 485 MΩ

6 1.2-2.2 636 MΩ

7 1.2-3.1 386 MΩ

8 1.2-3.2 698 MΩ

9 1.3-2.1 769 MΩ

10 1.3-2.2 465 MΩ

Table 2: Phase-phase insulation resistance check

Conclusion:
From the above experiment, the resistance for phase to ground is less than that for the phase-to-
phase connection. We can also observe that the resistance increases as the phase-to-phase voltage
increases. Since, the resistance is in mega ohms, the transformer passes the insulation test.

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