3 CT PurposeTo accurately reduce the primary current to a value suitable for relays and meters. (5 or 1 amps).Provide isolation from the high voltage system.
4 Testing and Verification NETA -National Electrical Testing Association Recommendations:Perform polarity test.Perform ratio-verification test using voltage or current methodPerform an excitation test.Measure circuit burden.
5 Ratio and PolarityRatio must be verified so that relays and meters will operate and indicate correctly.Polarity must be correct if relays are to “look” in the correct direction, and for meters to indicate correctly.
6 Ratio and Polarity Errors Taps may have been connected to the wrong terminals or may have been labeled incorrectly.Wrong number of turns on CT secondary.Shorted turns.Wrong polarity markings.
7 Saturation VoltageExcitation characteristics and saturation voltage must be known to verify that the CT will perform as required by providing required output voltage during fault conditions.
9 Typical test circuit of variac volt and amp meters
10 Time StudyTime to test 5-tap CT (ten ratios and one excitation curve) with older style equipment for:RatioPolarity and phase-angleExcitation and SaturationWinding ResistanceInsulation resistanceTime=52 minutesWith DCT-2000x5, time < 5 minutes
11 Product available in two models: Adwel solutionThe DCT-2000 offers the most advanced features in automated multi-ratio CT testing.Product available in two models:DCT-2000x2DCT-2000x5 – Test Plan Driven
12 Automated testing of one winding of a CT for: Key Features of DCT-2000x2Automated testing of one winding of a CT for:RatioPolarity and phase-angleExcitation and SaturationWinding ResistanceInsulation resistance
15 Save test and go the next winding Testing Steps of x2Enter windings to be testedCheck-off tests to be preformedSet a voltage limitPress testObserve progressSave test and go the next winding
16 Test Screen for x2 Configured Note: x2 does not have test plan
17 Automatically tests up to 5 taps with operator intervention. Key Features of x5Same as x2 plus:Automatically tests up to 5 taps with operator intervention.Test plan driven.Provides the ultimate in CT testing productivity.
30 Other FeaturesSaturation voltage (knee point) is calculated.Winding resistance is measuredInsulation resistance is measuredFull 75 key keyboardStore 200 files.Store 140 test plans in x5.
31 Other FeaturesUp to 2000 Vac outputUp to 2 amps outputBurden output: voltsCircuit impedance measurement in burden mode.Transfer results to PC with USBTransfer results to memory stick
32 Results stored in database. PC Based SoftwareResults stored in database.Sort on twelve fields.Generate full report form including data and color graphs of all curves.Files compatible with word processing and spread sheets.
33 Modes of Operation Auto mode: Manual mode: Burden mode: Allows DCT to automatically complete a series of tests.Manual mode:Allows operator to manually raise and lower the voltage to make diagnosis.Burden mode:Current source for secondary injection
34 Comparison of modelsBoth models have identical features regarding tests, output, range, accuracy, keyboard, printer, memory capacity, memory stick, software and database.Differences are listed below.
35 Test AutomationX2:Check boxes on test screen are used to select the tests to be performed in automatic sequence.X5:A test plan conducts the required tests on up to ten ratios on a multi-ratio CT. Saves 140 plans.
36 Extent of Automation X2: X5 Completes all selected tests for one winding.X5Completes all selected tests for up to ten ratios.
37 ConclusionContact your local representative or Adwel International for questions or further information.