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Current Transformer Testing
Testing Procedures
Insulation Resistance test.
CT Resistance, Excitation curve, Ratio & Polarity test.
Current Transformer Loop test.
Primary Injection Test.
Download:
CT Test Format
Equipment Required
Insulation Resistance tester: Megger mit1020.
CT Analyzer
Multimeter.
Primary Injection Kit: ODEN AT
Insulation Tester
CT Analyzer
Multimeter
Insulation Resistance Test
Use Megger mit1020 to measure insulation resistance.
Insulation Resistance Tests to be done:
Primary
winding
- Ground (Apply 5000V for 1 minute)
Primary winding - Secondary
winding (Apply 2500V for 1 minute)
Secondary winding - Secondary winding (Apply 2500V for 1 minute)
Secondary - Ground (Apply 1000V for 1 minute)
CT Characteristics Test
Use CT Analyzer to test CT Characteristics.
Connection on CT Analyzer will be same as the shown figure.
Repeat the test for the other phases and the other secondary cores.
Refer to CT Analyzer
User Manual
to find how to use CT Analyzer & how to enter CT Data.
Connection Circuit
CT Loop Resistance Test
Measure CT resistance from CT terminal blocks
(CT Side)
.
Measure Loop resistance from CT terminal blocks
(Load Side)
.
Measure the Total Loop resistance
(CT resistance + Load resistance + wiring resistance)
.
CT Primary Injection Test
Core Identification Test:
In this test we confirm the CT secondary connection.
Inject low current (
for example:
50A).
Use small jumper to short the CT secondary from CT box, the measurement will be gone at panel.
Repeat this test for all phases and cores.
Short & Isolate Facility Test:
In this test we confirm the CT short & isolate facility for correct connection.
Inject low current (
for example:
50A).
Short
CT links then
Isolate
the external wiring to confirm CT circuit will not be opened.
Single Earth Point Test:
For all CT Loops, each loop must have only one earth point, otherwise secondary current will be divided.
Open all earth point in the loop, check with buzzer that there is no earth link is closed, then close only one point.
For all protection & measurement CTs, Close the earth point in the nearest point to the CT.
For High Impedance Differential Protection, Close the earth point in the nearest point to the Relay.
Primary Injection Test:
After confirming all previous steps, CT is ready now to the primary injection test.
Use the ODEN AT kit to inject high current (for example: 500A).
Measure the secondary current in all loop up to the end of this loop.
ODEN AT
CT Terminal Block
Home
Site Map
About Substations
Formats
Auxiliary Relays
Equipments Formats
Protection Formats
>
Energization Tests
Functional Test Format
Manuals
Software
Support
Testing & Commissioning
Test Procedures
Relays Calculations
Relays Configuration
Tutorials
References
Label Design
Blog
About Me