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Core and Frame Insulation

This document discusses checking the insulation between the core, frame, and tank of a power transformer. It outlines: 1) The purpose is to check that the transformer core is insulated from the tank and core frame. 2) Earthing links are removed from the core, core frame, and tank. Insulation resistance is measured between various combinations, including core to frame, core to tank, and core/frame to tank. 3) The measurement is performed using an insulation resistance meter applying 500-2500V DC for at least 1 minute until resistance stabilizes. Measured values must be above 50 MΩ and are documented in the test report.

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2K views7 pages

Core and Frame Insulation

This document discusses checking the insulation between the core, frame, and tank of a power transformer. It outlines: 1) The purpose is to check that the transformer core is insulated from the tank and core frame. 2) Earthing links are removed from the core, core frame, and tank. Insulation resistance is measured between various combinations, including core to frame, core to tank, and core/frame to tank. 3) The measurement is performed using an insulation resistance meter applying 500-2500V DC for at least 1 minute until resistance stabilizes. Measured values must be above 50 MΩ and are documented in the test report.

Uploaded by

karnatisharath
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 PPTX, PDF, TXT or read online on Scribd
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Check of Core and Frame Insulation

References/Standards

IEC 60076-1, Cl. 11.12 Power transformers:


General

Purpose of the test


• The purpose of the measurement is
to check and prove that the
transformer core is insulated from
the tank and core frame.
PERFORMANCE OF THE MEASUREMENT
• Earthing links from core to earth and from core frame to
earth (if the latter one exists) are removed (disconnected)
in earthing connection box (terminal box).
• Several combinations of measurement of insulation
resistance are possible depending upon the performance of
core and frame earthing:
 Core to Frame;
 Core to Tank;
 Core Frame to Tank;
 Core to (Tank + Core frame);
 (Core + Core Frame) to Tank.
….Contd.
Core and Frame Connection
Click icon
to add pic
ture

In Power Transformers these connections are brought out on transformer


tank.
PERFORMANCE OF THE MEASUREMENT

• The measurement is performed by means of an


insulation resistance meter.
• For each measurement a DC voltage of at least 500 V
(but not greater than 2500 V) is applied between pair
of terminal bushings in earthing terminal box for a
measuring period ≥ 1 min. or until the measuring
insulation resistance become stable.
 At least combination core to (tank + core frame) or core to tank is
to be measured. In all measurements tank is assumed as earth
potential.
 Measured values for each combination shall be above 50 MΩ.
TEST REPORT
Measured values with indication of measured
combination are documented in transformer
routine test report.
Data Presentation

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