This document describes test procedures for determining the knee point voltage and verifying the current transformation ratio of a current transformer (CT). The knee point test involves gradually increasing the voltage source connected to the primary winding while the other windings are open, and recording the voltage and current readings. The primary current injection test involves injecting current into the primary winding with the secondary winding shorted, and recording the actual and calculated current ratios. Both tests are intended to check specifications listed on the CT nameplate.

1. PT. TRAFOINDO PRIMA PERKASA
KNEE POINT TEST
1. Purpose
This test is intended to obtain the knee point voltage of current transformer (CT).
2. Test equipment
2.1.Slide regulator, 5 A, 230 V. Use step up transformer to raise up output voltage.
2.2.Voltmeter
2.3.Amperemeter
2.4.Cable connection 2.5 mm2
3. Test circuit
Figure 1: Connection diagram of knee point test
4. Test procedure
4.1.Connect the circuit as shown as figure 1.
4.2.Primary winding and other(s) secondary winding is left opened.
4.3.Raise the voltage source step by step and record the voltage and current as table 1.
CT Specification:
Ratio :
Serial no :
Test core no :
No. Voltage (V) Current (A) Remarks
1.
2.
3.
4.
5.
6.
Table 1: Voltage and current of test
4.4.If current already reached to the nominal secondary current, the test is stopped.
4.5.For evaluation of test, send the record to: trafo@trafoindonesia.com/FAX: +6221-3850702
A
V
1S1
1S2
~ Adjustable
Voltage source

2. PT. TRAFOINDO PRIMA PERKASA
PRIMARY CURRENT INJECTION TEST
1. Purpose
This test is intended to verify that current transformation ratio as shown on the name
plate is correct. Primary current injection test is not accuracy test, therefore the result
of this test to calculate ratio error is not acceptable.
2. Test Circuit
Note: Ensure to short-circuited secondary terminal prior to conduct primary current
injection. Fail to do so will cause damage to current transformer.
3. Test procedure
3.1.Check the name plate ratio and primary current
3.2.Check the current source is able to raise up to nominal current of CT.
3.3.Check the size of primary cable
3.4.Check the terminal on secondary CT either core I, core II and or core III are short-
circuited.
3.5.Start to raise up the current and record with below simple table.
CT Specification:
Ratio :
Serial no :
Test core no :
No. Actual primary current
(A)
Actual secondary
current (A)
Actual ratio Calculated
ratio
1.
2.
3.
4.
5.
6.
A P1
P2
~ Adjustable
Current source
1S1
1S2
A