EZCT S2TM DIGITAL CURRENT-TRANSFORMER TESTER USER’S MANUAL Vanguard Instruments Company, Inc. 1520 S. Hellman Ave.
EZCT S2 USER’S MANUAL REV 3 SAFETY SUMMARY FOLLOW EXACT OPERATING PROCEDURES Any deviation from the procedures described in this User’s Manual may create one or more safety hazards, may damage the EZCT S2, or cause errors in the test results. Vanguard Instruments Company, Inc. assumes no liability for unsafe or improper use of the EZCT S2.
REV 3 EZCT S2 USER’S MANUAL TABLE OF CONTENTS CONVENTIONS USED IN THIS DOCUMENT ....................................................................... 1 1.0 INTRODUCTION .................................................................................................................... 2 1.1 General Description and Features ................................................................................... 2 1.2 Furnished Accessories .......................................................................
EZCT S2 USER’S MANUAL REV 3 LIST OF TABLES Table 1. EZCT S2 Technical Specifications ....................................................................................... 4 Table 2. Functional Descriptions of EZCT S2 Controls and Indicators ............................................ 6 Table 3. Descriptions of Tabulated Test Results Elements ........................................................... 20 Table 4. Description of Test Plan Elements .........................................................
REV 3 EZCT S2 USER’S MANUAL CONVENTIONS USED IN THIS DOCUMENT This document uses the following conventions: • A key or switch on the EZCT S2 is indicated as [KEY] and [SWITCH]. • Menu options are referenced as (MENU OPTION). • Screen and menu names are referenced as “SCREEN/MENU NAME”. • The terms “test record” and “test shot” are used interchangeably. • EZCT S2 LCD screen output is shown as: 1. OPTION 2. OPTION 3. OPTION 4.
EZCT S2 USER’S MANUAL 1.0 INTRODUCTION 1.1 General Description and Features REV 3 The EZCT S2 is Vanguard’s second-generation, microprocessor-based, current transformer test set. The EZCT S2 can perform the current transformer (CT) excitation, CT current-ratio, and winding polarity tests automatically. The EZCT S2 automatically raises and lowers the excitation test voltage without any operator intervention.
REV 3 EZCT S2 USER’S MANUAL Test Record Header Information The test record header information can include the company name, substation name, circuit ID, manufacturer, CT serial number, operator’s name, and test record comments. In addition to the test record header, a 20-character test description for each test in the record can also be entered. Internal Test Record Storage Capacity The EZCT S2 can store up to 140 test records in Flash EEPROM.
EZCT S2 USER’S MANUAL 1.3 REV 3 Technical Specifications Table 1. EZCT S2 Technical Specifications TYPE Portable current transformer test set PHYSICAL SPECIFICATIONS 16.8”W x 12.6”H x 12”D (42.7 cm x 32 cm x 26.9 cm); Weight: 55 lbs (25 kg) INPUT POWER 100 – 120 Vac or 200 – 240 Vac (factory pre-set), 50 Hz/60 Hz MEASUREMENT METHOD ANSI/IEEE C57.12.90, IEC 60044-1 and ANSI/IEEE C57.13.1 standards TEST OUTPUT VOLTAGES 0 – 50 Vac @ 10A max, 0 – 250 Vac @ 10A max 0 – 500 Vac @ 5A max, 0 – 1500 Vac @ 1.
REV 3 1.4 EZCT S2 USER’S MANUAL EZCT S2 Controls and Indicators The EZCT S2’s controls and indicators are shown in Figure 1 below. A leader line with an index number points to each control and indicator, which is cross-referenced to a functional description in Table 2. The table describes the function of each item on the control panel. The purpose of the controls and indicators may seem obvious, but users should become familiar with them before using the EZCT S2.
EZCT S2 USER’S MANUAL REV 3 Table 2. Functional Descriptions of EZCT S2 Controls and Indicators Item Number Panel Markings 1 X Current transformer excitation voltage connector. The EZCT S2’s X output terminal is rated to 1500 Vac working voltage. Any voltage above 1500 Vac will damage the input circuitry. 2 H Current transformer primary input test cable connector. 3 4 Built-in 4.5-inch wide thermal printer.
REV 3 EZCT S2 USER’S MANUAL 2.0 PRE-TEST SETUP 2.1 Operating Voltages The EZCT S2’s operating voltage is preset at the factory for 100-120 Vac, 50/60 Hz or 200-240 Vac, 50/60 Hz. 2.2 LCD Screen Contrast Control To increase the LCD screen contrast, press and hold the [PAPER ∧ Contrast] key for two seconds. Release the button when the desired contrast level has been reached. To decrease the LCD screen contrast, press and hold the [PAPER ∨ Contrast] key for two seconds.
EZCT S2 USER’S MANUAL 2.5 REV 3 Replacing the Thermal Printer Paper The roll of thermal paper is housed inside a dispenser underneath the printer cover. To replace the paper, follow the steps below: • • • • • • • Unscrew the two large printer cover screws and remove the printer cover. Remove the leftover thermal paper roll from the paper holder. Unroll the new thermal paper roll. Feed the thermal paper into the slot between the paper pocket and the rubber roller.
REV 3 EZCT S2 USER’S MANUAL 3.0 OPERATING PROCEDURES 3.1 EZCT S2 Cable Connections Always connect the EZCT S2 to the substation ground before connecting any test cables. The X cable connections are required to run the current transformer excitation test. The H and X cable connections are required to run the transformer turns-ratio test. A typical excitation and ratio test connection is shown in Figure 2.
EZCT S2 USER’S MANUAL REV 3 Figure 3. Bushing CT Connection on Delta Transformer Figure 4.
REV 3 3.2 EZCT S2 USER’S MANUAL Performing Tests 3.2.1. Entering Test Record Header Information You can enter the test record header information before performing tests. The record header includes identifying information such as the company, station, circuit, model number, etc. Once the header information has been entered, it will apply to all subsequent test records. To enter the header information: a.
EZCT S2 USER’S MANUAL REV 3 d. The following screen will be displayed: STATION: ↑/↓ TO POSITION “ENTER” TO ACCEPT Type the station name using the alpha-numeric keypad and then press the [ENTER] key. e. The following screen will be displayed: CIRCUIT: ↑/↓ TO POSITION “ENTER” TO ACCEPT Type the circuit information using the alpha-numeric keypad and then press the [ENTER] key. f.
REV 3 i. EZCT S2 USER’S MANUAL The following screen will be displayed: COMMENTS: ↑/↓ TO POSITION “ENTER” TO ACCEPT Enter any relevant comments using the alpha-numeric keypad and then press the [ENTER] key. j. The following screen will be displayed: OPERATOR: ↑/↓ TO POSITION “ENTER” TO ACCEPT Type the operator’s name using the alpha-numeric keypad and then press the [ENTER] key. All header information will be saved, and you will be returned to the “START-UP” menu.
EZCT S2 USER’S MANUAL REV 3 3.2.2. Performing Excitation and Ratio Tests The following procedure describes the general steps for performing excitation and ratio tests. a. When the EZCT S2 is turned on, it will first go through a start-up cycle and load the firmware. Then the “START-UP” menu will be displayed as shown below: 1. RUN TEST 12/01/09 2. SETUP 08:20:19 3. TEST PLANS 4. DIAGNOSTIC Press the [1] key (RUN TEST) to start a test. b. The following screen will be displayed: 1. EXCITATION & RATIO 2.
REV 3 EZCT S2 USER’S MANUAL e. If the selected test included an excitation test, the following screen will be displayed: SELECT VOLTAGE RANGE 1. 50V 3. 500V 2. 250V 4. 1500V Select the test voltage range by pressing the corresponding key ([1] - [4]). f. If the selected test included an excitation test, the following screen will be displayed: SET TEST CURRENT: 1. 0.2A 2. 0.5A 3. 1A 4. 2A 5. 5A 6. 10A Select the maximum test current for the excitation test by pressing the corresponding key ([1] - [6]).
EZCT S2 USER’S MANUAL REV 3 ENTER PLATE RATIO: 80 : 1.0 Press the [ENTER] key. Continue to step h. 2. NO Press the [2] key if you do not want to enter the CT nameplate values. Continue to step h. h. The following screen will be displayed: ENTER TEST 1 NOTE: ↑/↓ TO POSITION “ENTER” TO ACCEPT Use the alpha-numeric keys on the keypad to enter a test note. The test note field is 20 characters long. One test note can be saved for each test.
REV 3 EZCT S2 USER’S MANUAL The “HIGH VOLTAGE PRESENT” light will be illuminated to indicate that high voltage is present. NOTE k. If the selected test included a ratio test, the following screen will be displayed: RATIO TEST Vx= 39.9 Vh= 0.4984 I=0.1324 RAT=+80.058 When the ratio test is complete, the final results will be displayed: ANY KEY TO CONTINUE Vx= 39.9 Vh= 0.4984 I=0.1324 RAT=+80.058 Press any key on the keypad to continue. l. The following screen will be displayed: PRINT TEST RESULTS? 1.
EZCT S2 USER’S MANUAL REV 3 n. The following screen will be displayed: TEST 1 SAVED Press any key to continue. o. The following screen will be displayed: RUN ANOTHER TEST? 1. YES 2. NO Press the [2] key (NO). p. The following screen will be displayed: SAVE THIS RECORD? 1. YES 2. NO Press the [1] key (YES) to save the record. The following screen will be displayed momentarily: SAVING RECORD... PLEASE WAIT... q.
REV 3 EZCT S2 USER’S MANUAL Figure 5.
EZCT S2 USER’S MANUAL REV 3 Table 3. Descriptions of Tabulated Test Results Elements Item Number Description 1 Test record header information. 2 The X terminals (taps) that were selected for this test. 3 Test note for this particular test. The test note can be up to 20-characters long. 4 Recorded excitation current readings on the CT secondary winding. 5 Recorded excitation test voltages applied to the CT secondary winding. 6 Impedance calculated at each data point.
REV 3 EZCT S2 USER’S MANUAL Knee Point Marker Figure 6.
EZCT S2 USER’S MANUAL 3.3 REV 3 Working With Test Records 3.3.1. Restoring and Printing a Test Record From Flash EEPROM You can restore a test record from the EZCT S2’s Flash EEPROM to the working memory. You can then print the restored test record on the unit’s built-in thermal printer. To restore a test record: a. Start from the “START-UP” menu: 1. RUN TEST 12/01/09 2. SETUP 14:52:19 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2.
REV 3 EZCT S2 USER’S MANUAL If you do not want to print the test record, press the [2] key (NO). The test record will be restored to the working memory, and you will be returned to the “STARTUP” menu. If you would like to print the test record, press the [1] key (YES). Continue to step d. 2. SCROLL TO SELECT Press the [2] key if you would like to scroll through a directory of the stored test records.
EZCT S2 USER’S MANUAL REV 3 d. The following screen will be displayed: PRINT OPTIONS: 1. FULL DATA 2. ABBREVIATED DATA Press the [1] key to print the tabulated data and graphics results on the thermal printer. The test record will be restored to the working memory and will be printed on the thermal printer, and then you will be returned to the “START-UP” menu. Press the [2] key to print the test report and graphic results on the thermal printer, without the excitation voltage and current data points.
REV 3 EZCT S2 USER’S MANUAL 3.3.2. Printing a Restored Test Record You can print a test record at the time that it is restored from the Flash EEPROM (see section 3.3.1), or you can restore it to the working memory and print it later. To print the current test record in the working memory: a. Start from the “START-UP” menu: 1. RUN TEST 09/24/09 2. SETUP 08:20:19 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2. PRINT RECORD 3.
EZCT S2 USER’S MANUAL REV 3 3.3.3. Printing a Directory of Test Records Stored in the EZCT S2’s Memory You can print a directory of all the test records stored in the EZCT S2’s Flash EEPROM using the steps below: a. Start from the “START-UP” menu: 1. RUN TEST 09/24/09 2. SETUP 08:20:19 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2. PRINT RECORD 3. RESTORE RECORD 4. NEXT PAGE Press the [4] key (NEXT PAGE). c.
REV 3 EZCT S2 USER’S MANUAL Figure 7.
EZCT S2 USER’S MANUAL REV 3 3.3.4. Erasing Test Records From the Flash EEPROM You can erase individual or all test records stored in the EZCT S2’s Flash EEPROM. To erase a test record: a. Start from the “START-UP” menu: 1. RUN TEST 09/24/09 2. SETUP 08:20:19 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2. PRINT RECORD 3. RESTORE RECORD 4. NEXT PAGE Press the [4] key (NEXT PAGE). c. The following screen will be displayed: 1.
REV 3 EZCT S2 USER’S MANUAL • You can press the [STOP] key to cancel the process. NOTES • If you do not know the record number, you can first print a test record directory using the instructions in section 3.3.3. The following screen will be displayed momentarily: ERASING RECORD NUMBER: 01 PLEASE WAIT... Then the following confirmation screen will be displayed: RECORD NUMBER 1 ERASED! Press any key to return to the “START-UP” menu. 2.
EZCT S2 USER’S MANUAL 3.4 REV 3 Working With Test Plans A test plan is comprised of the saturation test voltage, current range selection, CT nameplate ratios, and CT winding terminal combinations (X1 to X5) for each test. Up to 10 test definitions can be stored per test plan, and up to 128 CT test plans can be stored in the EZCT S2’s Flash EEPROM. The ability to use test plans makes CT testing an extremely simple process.
REV 3 EZCT S2 USER’S MANUAL Press any key to return to the “START-UP” menu. You must first restore a test record to the working memory before a test plan can be extracted. Please see section 3.3.1 e. The following screen will be displayed: TEST PLAN NUMBER 1 HAS BEEN SAVED! The test plan will be extracted from the test record in the working memory and will be saved to the EZCT S2’s Flash EEPROM as a new test plan. The test plan number will be automatically incremented by the EZCT S2.
EZCT S2 USER’S MANUAL REV 3 3.4.2. Printing a Directory of Test Plans Stored in the EZCT S2’s Memory You can print a directory of all the test plans stored in the EZCT S2’s Flash EEPROM using the steps below: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 08:39:17 3. TEST PLANS 4. DIAGNOSTIC Press the [3] key (TEST PLANS). b. The following screen will be displayed: 1. LOAD TEST PLAN 2. UNLOAD TEST PLAN 3. PLAN DIRECTORY 4. NEXT PAGE Press the [3] key (PLAN DIRECTORY). c.
REV 3 EZCT S2 USER’S MANUAL Figure 8.
EZCT S2 USER’S MANUAL REV 3 3.4.3. Printing a Test Plan To print a test plan: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 09:15:25 3. TEST PLANS 4. DIAGNOSTIC Press the [3] key (TEST PLANS). b. The following screen will be displayed: 1. LOAD TEST PLAN 2. UNLOAD TEST PLAN 3. PLAN DIRECTORY 4. NEXT PAGE Press the [4] key (NEXT PAGE). c. The following screen will be displayed: 1. EXTRACT TEST PLAN 2. PRINT TEST PLAN 3. ERASE TEST PLAN Press the [2] key (PRINT TEST PLAN). d.
REV 3 EZCT S2 USER’S MANUAL Figure 9. Typical Test Plan Printout Table 4. Description of Test Plan Elements Item Number 35 Description 1 Number of tests in test plan (2) 2 Tests to be performed (Excitation and Turns Ratio) 3 Terminals used for excitation test (X2-X3) 4 Maximum excitation voltage (300 V) 5 Maximum excitation current (2.
EZCT S2 USER’S MANUAL REV 3 3.4.4. Erasing Test Plans From the Flash EEPROM To erase one or all test plans from the EZCT S2’s Flash EEPROM: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 09:39:19 3. TEST PLANS 4. DIAGNOSTIC Press the [3] key (TEST PLANS). b. The following screen will be displayed: 1. LOAD TEST PLAN 2. UNLOAD TEST PLAN 3. PLAN DIRECTORY 4. NEXT PAGE Press the [4] key (NEXT PAGE). c. The following screen will be displayed: 1. EXTRACT TEST PLAN 2. PRINT TEST PLAN 3.
REV 3 EZCT S2 USER’S MANUAL NOTES • You can press the [STOP] key to cancel the process. • If you do not know the test plan number, you can print a test plan directory using the instructions in section 3.4.2. The selected test plan will be erased and the following screen will be displayed: TEST PLAN NUMBER 1 ERASED! Press any key to return to the “START-UP” menu. 2. ERASE ALL PLANS Press the [2] key if you would like to erase all test plans.
EZCT S2 USER’S MANUAL REV 3 3.4.5. Loading a Test Plan from the EZCT S2’s Flash EEPROM To use a test plan for running a test, it must first be loaded into the working memory. To load a test plan from the EZCT S2’s Flash EEPROM into the working memory: a. Start from the “START-UP” menu: 1. RUN TEST 09/24/09 2. SETUP 08:20:19 3. TEST PLANS 4. DIAGNOSTIC Press the [3] key (TEST PLANS). b. The following screen will be displayed: 1. LOAD TEST PLAN 2. UNLOAD TEST PLAN 3. PLAN DIRECTORY 4.
REV 3 EZCT S2 USER’S MANUAL 3.4.6. Running a Test Using a Loaded Test Plan Once a test plan has been loaded into the working memory (see section 3.4.5 for directions), it can be used to run a test. To run a test using a loaded test plan: a. Make sure a test plan has been loaded into the working memory and then start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 10:20:30 3. TEST PLANS 4. DIAGNOSTIC Press the [1] key (RUN TEST). b.
EZCT S2 USER’S MANUAL REV 3 When the test has finished, the following screen will be displayed: SAVE THIS RECORD? 1.YES 2.NO Press the [1] key (YES) to save the record. The following screen will be displayed momentarily: SAVING RECORD... PLEASE WAIT... Then the following confirmation screen will be displayed: RECORD NUMBER 2 HAS BEEN SAVED! Press any key to return to the “START-UP” menu. 3. UNLOAD TEST PLAN Press the [3] key to unload the test plan and run a test without a test plan.
REV 3 EZCT S2 USER’S MANUAL TEST 1 PARAMETERS: 1500V 1.0A X1-X2 “START” TO BEGIN Press the [START] key to begin the test. f. The EZCT S2 will start performing the test per the test plan parameters. When the test has finished, the following screen will be displayed: ANY KEY TO CONTINUE Vx=77.6 I=0.0522 Vh=0.3876 RAT=+200.08 Press any key to continue. g. The following screen will be displayed: PRINT TEST RESULTS? 1.YES 2.NO Press the [1] key (YES) if you would like to print the test results.
EZCT S2 USER’S MANUAL REV 3 Press the [1] key (YES) to save the record. The following screen will be displayed momentarily: SAVING RECORD... PLEASE WAIT... The following confirmation screen will then be displayed: RECORD NUMBER 2 HAS BEEN SAVED! Press any key to return to the “START-UP” menu.
REV 3 EZCT S2 USER’S MANUAL 3.4.7. Unloading a Test Plan from the Working Memory To unload the test plan from the working memory and clear all the test plan parameters: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 10:25:35 3. TEST PLANS 4. DIAGNOSTIC Press the [3] key (TEST PLANS). b. The following screen will be displayed: 1. LOAD TEST PLAN 2. UNLOAD TEST PLAN 3. PLAN DIRECTORY 4. NEXT PAGE Press the [2] key (UNLOAD TEST PLAN). c.
EZCT S2 USER’S MANUAL 4.0 CHANGING SETUP PARAMETERS 4.1 Setting the Knee Point Marker REV 3 Use the steps below to change the knee point marker for the excitation graph: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 10:47:17 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2. PRINT RECORD 3. RESTORE RECORD 4. NEXT PAGE Press the [4] key (NEXT PAGE). c. The following screen will be displayed: 1. RECORD DIRECTORY 2.
REV 3 EZCT S2 USER’S MANUAL If a test record is loaded in the current working memory, the following screen will be displayed: NOTE KNEE TYPE CHANGED SAVE RECORD? 1. YES 2. NO Press the [1] key (YES) to save the test record with the updated knee point marker setting. Press the [2] key (NO) if you do not want to update the saved test record. Knee Point Marker Knee Point Marker Type Figure 10.
EZCT S2 USER’S MANUAL 4.2 REV 3 Selecting the Buried CT in Transformer Delta Option The EZCT S2 can be used to measure the turns ratio of a CT buried in the transformer Delta windings (see Figure 11 and Figure 12 for further information). However, in order for the unit to correctly calculate the turns ratio of a CT buried in the transformer Delta windings, the “CT Buried in Delta” option must first be selected. Use the steps below to set the “Buried CT in Delta” option: a.
REV 3 EZCT S2 USER’S MANUAL The “Buried CT in Delta” option will stay active for all subsequent tests performed. Turning off the EZCT S2 will reset this option. NOTE Figure 11. Buried CT in a Delta Transformer Illustration 1 Figure 12.
EZCT S2 USER’S MANUAL • NOTES • • • REV 3 Vx . Vh Since the induced voltage (V) is sensed through the H1-H2 terminals of 2 the Delta winding, this induced voltage is measured as V = ( ) Vh. 3 Vx 3 Vx The CT turns ratio is now measured as Ratio = or Ratio = ( )( V 2 Vh 3 ). This measured turns ratio is higher than the actual turns ratio. 2 The EZCT S2 will display the correct CT turns ratio by adjusting the 2 measured turns ratio by .
REV 3 4.3 EZCT S2 USER’S MANUAL Setting the Clock To set the EZCT S2’s internal clock: a. Start from the “START-UP” menu: 1. RUN TEST 12/04/09 2. SETUP 11:11:11 3. TEST PLANS 4. DIAGNOSTIC Press the [2] key (SETUP). b. The following screen will be displayed: 1. RECORD ID 2. PRINT RECORD 3. RESTORE RECORD 4. NEXT PAGE Press the [4] key (NEXT PAGE). c. The following screen will be displayed: 1. RECORD DIRECTORY 2. ERASE RECORD 3. KNEE POINT MARKER 4. NEXT PAGE Press the [4] key (NEXT PAGE). d.
EZCT S2 USER’S MANUAL 5.0 DIAGNOSTICS, VERIFICATION, AND TROUBLESHOOTING 5.1 Performing a Diagnostics Test REV 3 The Diagnostics test mode displays the output voltage at the X leads (Vx), the voltage sensed by the H leads (Vh), and the X voltage excitation current (Ix). These values can then be verified using an external volt meter and ampere meter. The Diagnostic Test mode uses the X1-X2 taps. To perform a diagnostic test: a. Start from the “START-UP” menu: 1. RUN TEST 09/24/09 2. SETUP 08:20:19 3.
REV 3 5.2 EZCT S2 USER’S MANUAL Verifying the EZCT S2’s Vx Sense Circuit Using an External Meter The excitation voltage (Vx) sensed by the EZCT S2 can be verified using an external RMS volt meter. Follow the steps below to verify the EZCT S2’s Vx sense circuit: a. Connect the X cables to an RMS volt meter as shown in Figure 13. b. Select the EZCT S2’s Diagnostics mode (see section 5.1). c. Press the [PAPER ∧ Contrast] key to raise the Vx voltage. d.
EZCT S2 USER’S MANUAL 5.3 REV 3 Verifying the EZCT S2’s Ix Sense Circuit Using an External Meter You can verify the excitation current (Ix) sensed by the EZCT S2 by using an external RMS ampere meter. Follow the steps below to verify the EZCT S2’s Ix sense circuit: a. Connect the X cables to a power resistor and an RMS ampere meter as shown in Figure 14. b. Select the EZCT S2’s Diagnostics mode (see section 5.1). c. Press the [PAPER ∧ Contrast] key to raise the Vx voltage. d.
REV 3 5.4 EZCT S2 USER’S MANUAL Quickly Verifying the EZCT S2’s Turns Ratio Circuit You can quickly verify the EZCT S2’s turns ratio circuit by performing the following ratio test: a. Connect the X1 test lead to the H1 test lead as shown in Figure 15. b. Connect the X2 test lead to the H2 test lead as shown in Figure 15. c. Run a turns ratio test (see section 3.2.2). d. Observe the turns ratio test on the LCD screen. The turns ratio should be 1.
EZCT S2 USER’S MANUAL 5.5 REV 3 Troubleshooting Guide PROBLEM DESCRIPTION Probable Cause Suggested Solution When running the excitation test, the Vx voltage is always zero. The excitation current can be raised during a test. • The EZCT S2 X cables are driving a • Check CT shorting screws. When running the excitation test, the Vx voltage can be raised but the excitation current is always zero during a test. • The EZCT S2 X cable is driving an opened circuit. • Check the CT terminal connection.
REV 3 6.0 EZCT S2 USER’S MANUAL Appendix A - Calculating Turns Ratio on a Shunt Reactor The Vanguard EZCT line of products use the voltage method to measure the turns-ratio on current transformers. A typical connection for a stand-alone CT is shown in Figure 16. Figure 16 The EZCT applies a test voltage (V1) to the CT secondary winding. The induced voltage (V2) is sensed through the CT primary winding. In this case a single conductor is used.
EZCT S2 USER’S MANUAL REV 3 Figure 17 shows a typical connection of a CT mounted on the primary bushing of a single phase transformer. When the voltage V1 is introduced to the CT's secondary winding, there is an induced voltage (V3) on the primary winding of this single phase transformer.
REV 3 EZCT S2 USER’S MANUAL Since this is a single phase transformer, and the transformer secondary winding is accessible, the user can apply a jumper to short out the transformer secondary winding as shown in Figure 18. By shorting out the transformer secondary winding, the user can eliminate most of the V3 voltage (V3=0V).
EZCT S2 USER’S MANUAL REV 3 Figure 19 show a CT mounted on a typical shunt reactor. This configuration is very similar to the CT mounted on a single phase transformer, the main difference being the lack of the secondary winding! The turns-ratio in this case will be: Ratio= ( ) Figure 19 Since there is no secondary winding on the shunt reactor, the turns-ratio measurement from using this method will always have some built-in error.
REV 3 EZCT S2 USER’S MANUAL Figure 20 show a CT with 5 taps. The turns-ratio of the CT can be measured by treating the CT secondary winding as an auto-transformer. When using this method, the effect of the shunt reactor winding is totally eliminated.
EZCT S2 USER’S MANUAL REV 3 A common practice for verifying the CT turns-ratio in the field is to apply an AC voltage to the CT secondary full winding (X1-X5). A volt meter can be used to verify the voltage drop across the CT terminals. For example, if a 120Vac voltage is applied to the X1-X5 of this CT, the voltage reading across X2-X5 shall be expected as follows: Voltage (X2-X5) = 120 V x ( ) = 100 V Figure 21 This method also eliminates the effect of the (reactor) winding on the H1 – H2 terminals.
REV 3 EZCT S2 USER’S MANUAL Figure 22 Figure 23 61
1520 S. Hellman Ave • Ontario, CA 91761 • USA Phone: 909-923-9390 • Fax: 909-923-9391 www.vanguard-instruments.com Copyright © 2014 by Vanguard Instruments Company, Inc. EZCT S2 User’s Manual • Revision 3.
