Delta 4000 Instruction Manual download pdf (Page 90)

81331 Rev 01 Nov 2010

Tests 20, 21, 22, and 23 are C1 measurements for the low side (L) bushings.

Test 23 is used only if the high winding has a neutral bushing with a test tap.

Test mode is UST-R.

Tests 24, 25, 26, and 27 are C1 measurements for the Tertiary (T) bushings.

Test 27 is used only if the high winding has a neutral bushing with a test tap.

Test mode is UST-R.

NOTE: Many condenser bushings will have factory values for C1 stamped on

their nameplates, both for power factor and capacitance. The test results

for C1 on each bushing can be compared directly to its respective

nameplate values.

Oil Tests

The 94500 test form includes a single test line (Test 28) for capturing the results

of one power factor test on insulating oil. This is generally done on a sample of

oil drawn from the main tank of the transformer under test. The test requires an

oil test cell designed for field use. The test cell should be a three-terminal cell

where connections for high voltage, measurement lead, and ground can be safely

made.

As with the other insulation tests on this test form, the test sequence is initiated

by right-clicking on the blue highlighted test number (28) at the bottom of the

Bushing C1 Tests table. The test mode used is UST-R.

Bushing C2 Tests

Bushings with test taps may also be tested to obtain a C2 insulation

measurement. The C2 insulation is the insulation between the test tap

connection and the bushing mounting flange. To perform a C2 test, the HV lead

is carefully connected to the bushing test tap and the Red lead is connected to

the bushing center conductor. Care should be taken not to cause physical

damage to the test tap, as the tap connection point may be a small pin or a

flexible spring. If this is the case, use a small insulated jumper wire or a specially

designed test tap adapter to make the HV lead connection.

CAUTION

Bushing test taps have very limited insulation and should

generally be energized at reduced voltage levels. If the bushing

manufacturer does not specify a test voltage level use no more

than 500 volts (0.5kV).

Tests 29 to 40 are measurements of the individual bushings C2 insulation. All

are performed with test mode GSTg-R. All phase and neutral bushings may be

tested providing they have test taps.

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Delta 4000 Instruction Manual Page 90