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DOC. MIE11110 Rev. 5

Page 57 of 110

1.2:

V

OLTAGE

T

RANSFORMERS TESTS

With the selection VOLTAGE TRANFORMERS TEST the following
screen is opened.

It is possible to select the tap number: this selection is reported in
the available tests.

1.2.1: VT tests: ratio and polarity

When this test is selected, the following menu is displayed.

Purpose of the test is to measure the actual VT ratio, and to
verify its polarity. This test is performed applying voltage to the
primary side, and measuring the secondary voltage and phase
angle. The connection to the loads can be open or closed, in order
to verify the accuracy error caused by the burden.

Test parameters are:

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Summary of Contents for T2000

Page 1: ...DATE 18 11 2009 DOC MIE11110 REV 5 T 2000 APPLICATION GUIDE ...

Page 2: ... 1 All 25 04 2006 Issued Lodi 2 42 62 65 24 11 2006 Added the line impedance test notes to PT ratio test Lodi 3 48 52 23 04 2007 Modified the dynamic TAP changer test Lodi 4 23 27 31 7 2007 Added the very high current booster Lodi 5 All 18 11 09 Minor corrections Lodi ...

Page 3: ... 54 1 2 VOLTAGE TRANSFORMERS TESTS 57 1 2 1 VT tests ratio and polarity 57 1 2 2 VT tests burden secondary side 61 1 2 3 VT tests ratio electronic transformers 63 1 2 4 VT tests voltage withstand 64 1 2 5 VT tests secondary over current protection 66 1 3 POWER TRANSFORMERS TESTS 68 1 3 1 PT tests ratio per TAP 68 1 3 2 PT tests resistance of LTC contacts 72 1 3 3 PT tests dynamic LTC test 76 1 3 4...

Page 4: ...o waste to find it So either the manual is actually of help or I ignore it This is why I decided to split the T 2000 manual in three specification with all performance details application manual with instructions about how to use it one its operation is understood introductory guide with the device description and basic information The idea is that you may read once the device description while yo...

Page 5: ...ulties arising from unknown technical problems The Seller declines also any responsibility in case of modification of the Product or of any intervention not authorized by the Seller in writing The warranty includes the repair time and the materials necessary to restore the complete efficiency of the Product so it does not include other burdens such as the transport and customs fee Under no circums...

Page 6: ...olation degree at least equal to the one of the product To this respect the following symbols are used to alert the operator about dangerous outputs The symbols and are related to the HV generation up to 3000 V the first one is located close to the output connectors the second one is located close to the generation button that must be pressed during HV generation The symbol is related to dangerous...

Page 7: ...during the test In this situation very high currents or voltages could be applied to the test set that could be severely damaged also the operator would be exposed to an high risk Disconnecting the transformer during the test A very high voltage can be generated by the inductance of the transformer under test Filtered mains The AC voltage can be a squared waveform rather than sinusoidal the test s...

Page 8: ... while T 2000 is connected to the transformer to be tested there must be no connection of the transformer itself to a voltage or current source T 2000 outputs are protected against transient spikes but not against such a situation In case of doubt please contact your Seller The Seller and Manufacturer declines any and all responsibility due to improper usage or any usage outside the specified limi...

Page 9: ...age transformers At power on there is a message asking to wait for the self diagnosis is completed After this the following menu is displayed The desired operation is accessed by the multi function wheel The following chapters explain how to operate with the above selections NOTE WINDOWS is a trademark of MICROSOFT inc ...

Page 10: ...l information related to the test As a consequence there could be some repetition passing from one test to the next however we preferred to arrange the manual so that it was not necessary to read other paragraphs than the relevant one There are three types of tests available CT s VT s PT s At power on the following screen is opened The selection is accessed by the multi function knob 22 On all tes...

Page 11: ...election is reported in the available tests 1 1 1 CT tests ratio polarity voltage mode When this test is selected the following menu is displayed Purpose of the test is to measure the actual CT ratio and to verify its polarity This test is called voltage mode because these parameters are verified by connecting the main AC voltage output high or low to the CT secondary and measuring the correspondi...

Page 12: ...ltage so that we keep away from saturation and the related errors Note that at the saturation there is usually 1 V per turn more rarely 0 5 V per turn The test voltage range is the following VSM 2 80 V 80 TO 220 V 220 V V RANGE 90 V 250 V 3000 V The voltage input range is also selected as a function of the test voltage and of the CT ratio Given KCT CT ratio VP voltage at primary Then compute VP VS...

Page 13: ...tion to 3000 V and the input connection to 10 V For the connection use the following cables A Output connection 3000 V N 2 High voltage connection cables 4 m long 5 kV with earth screen Terminated on both sides with HV connectors N 2 Clamps for the HV connection RED S1 S2 RED ...

Page 14: ...o to avoid discharges during operation After connections the area around the HV clamps shall be isolated so that no accidental contact can occur If something goes wrong for any reason power off T 2000 before getting close to HV connections Input in the screen the primary and secondary current and the selected output voltage range and input measurement range the screen displays the nominal ratio If...

Page 15: ...table VOLTAGE OUTPUT VOLTAGE OUTPUT CURRENT OUTPUT A OUTPUT POWER VA LOAD TIME Min RECOVERY TIME min 3000 2500 0 2 0 6 600 1500 STEADY 1 8 The one minute duration at 0 6 A is more than enough for the test so it is no practical limitation However for higher currents the duration could not be sufficient for the test If when the test START button 56 is pressed the HV key is already ON the following m...

Page 16: ...slowly decrease to zero NOTE if CT s are located on the primary side and on the secondary side of a power transformer the test of the CT ratio can be performed with the voltage mode as follows Connect the CT secondary to the test set voltage output Connect the PT winding on which the CT is inserted to the low voltage measurement input The PT winding is not crossed by any current so the secondary v...

Page 17: ...DOC MIE11110 Rev 5 Page 17 of 110 test to the primary side and measuring the secondary current and voltage The connection diagram is the following For the connection use the following cables ...

Page 18: ... Clamps In alternative if desired N 1 Clip on transformer plus N 2 measurement cables to the clip on transformer N 2 measurement cables to the 600 V measurement or N 1 cable for low voltage measurement connection shielded 4 m long for the 10 V measurement shown in the circuit diagram plus N 2 Clamps to connect the voltage measurement Primary clamps shall be well tightened on a clean surface so tha...

Page 19: ...easurement input BEFORE STARTING THE TEST VERIFY THAT THE SECONDARY CIRCUIT IS CLOSED THE CT GENERATES H IGH VOLTAGE IF THE PRIMARY CURRENT IS INJECTED AND THE SECONDARY IS OPEN Press test start button 56 and adjust the primary current to the desired value by the adjustment knob 6 There are two tabs to select the measurement of ratio and polarity or burden With the selection RATIO the screen shows...

Page 20: ...ave a limited duration as per the following table CURRENT OUTPUT A OUTPUT POWER VA LOAD TIME s RECOVERY TIME min I SUPPLY AT MAX VA A 100 600 STEADY 2 8 150 800 15 min 30 4 2 200 1000 4 min 15 5 6 400 1600 15 5 11 3 600 2000 5 3 17 800 2000 1 2 22 6 Keep the test duration as short as possible if you exceed the above table the test set stops automatically the test and you have to wait until the rec...

Page 21: ...TION IF EITHER IS HIGH CONNECTION CLAMPS CAN BE VERY HOT USE PROTECTION GLOVES 1 1 3 CT tests ratio polarity with booster There are two types of booster High current booster primary tests up to 2000 A Very high current booster primary tests up to 4000 A 1 1 3 1 High current booster NOTE this type of booster is selected setting OFF the switch n 4 of the CONV board PWA21401 When this test is selecte...

Page 22: ...lows to get up to 2000 A Note that with this test it is impossible to measure the burden as it is in the former test This test is performed applying current to the primary side the test current generated by the booster is measured as voltage connecting the booster output to the 10 V measurement input the secondary current is measured connecting the CT secondary to the current metering input The co...

Page 23: ...high current output There are two inputs on the booster according to the desired test current 1000 A or 2000 A Even if 1000 A are not much more than the 800 A that T 2000 can generate the test duration with the booster is much longer than with T 2000 The following table summarizes the situation ...

Page 24: ...nection to the test object use the two high current vices C Input connection N 2 measurement cables for the secondary current plus N 2 Clamps In alternative if desired N 1 Clip on transformer plus N 2 measurement cables to the clip on transformer N 1 cable for low voltage measurement connection shielded 4 m long for the 10 V measurement shown in the circuit diagram going to the current booster Vic...

Page 25: ...ustment knob 6 The screen shows The primary current The secondary current The transformer s ratio The ratio percentage error with respect to the nominal The polarity as OK or KO You will notice that the error does not change very much as a function of the test current Keep the test duration as short as possible if you exceed the above table the test set stops automatically the test and you have to...

Page 26: ...t from the current booster this means that you have over heated the module and the thermal protection is intervened cutting the measurement output All you have to do is to wait until the booster is cooled down and the measurement comes back 1 1 3 2 Very high current booster NOTE this type of booster is selected setting ON the switch n 4 of the CONV board PWA21401 When this test is selected the fol...

Page 27: ...easurement Te test is performed applying current to one or more transformers the adjustment is performed by the test set adjustment knob fine adjustment and or by the interposing module coarse adjustment by means of the selection switch marked 1 to 4 NOTE the test current generated by the booster is measured as voltage connecting the measurement transformer output to the 10 V measurement input the...

Page 28: ...rents and or cause an huge temperature increase Connections from the test set to the Interposing module IM2000are The variable AC voltage output not isolated from the mains that performs the fine current adjustment The TEST START command coming from the auxiliary output The test set mains supply When the time delay is to be measured also the TIMER START contact The secondary current can be measure...

Page 29: ...DOC MIE11110 Rev 5 Page 29 of 110 The following is the connection s chematic for the case of four transformers and two turns ...

Page 30: ...DOC MIE11110 Rev 5 Page 30 of 110 The following picture shows the option components in the case of a transformer only ...

Page 31: ...he following picture shows the detail of the connection of the two cables to the clamp The following picture shows the connection of the option to T 3000 and to the transformer under test in the picture there is an aluminium bar on a CT ...

Page 32: ...otection will open at test start Select the position 1 all counter clockwise on the interposing module IM2000selector Connect the interposing module IM2000to the transformers via cables provided NOTE always connect ALL transformers the impedance of a not connected transformer does not allow the current to flow Connect the interposing module IM2000to the mains with the supply cable provided Connect...

Page 33: ... the START test set input to the corresponding interposing module IM2000output Connect the CT secondary winding to the high AC current input of T 3000 or use the current metering clamp see above Select the CT test mode with the booster For time measurement select the relay mode then program timer start External auxiliary contact close Input in the screen the nominal primary and secondary current I...

Page 34: ...he desired current stop the test adjust back to zero the test set current adjustment knob and switch to position 2 the selection switch of the coarse adjustment box As soon as you start the test again a little less than the current that you had adjusted will be generated into the CT and the light of the second transformer turns on You can now further increase this value up to the desired current I...

Page 35: ... 2000 6 21 2 2 1000 900 5 2000 27 20 3000 6 45 4 1 1000 INFINITE 4 5 2000 900 18 3000 100 40 2 1000 900 6 2000 27 24 3000 6 54 4000 2 96 NOTE with the supply of 115 V the following table summarizes maximum currents and test durations N OF TRANS INTERP MODUL E CODE WEIGHT N OF TURNS TEST CURRENT A ON DURATION s 1 NO PII57102 19 5 3 500 100 1000 30 2 YES PII58102 29 5 2 500 900 1000 100 2000 30 4 YE...

Page 36: ...LES PLEASE CONSIDER THE TEST DURATION IF IT WAS LONG CONNECTION VICES AND CABLE CAN BE VERY HOT USE PROTECTION GLOVES 1 1 4 CT tests burden secondary side When this test is selected the following menu is displayed Purpose of the test is to measure the CT burden in terms of VA This test is performed applying current to the CT secondary connections and not current to the primary side as in the forme...

Page 37: ...CT secondary is disconnected and the selected T 2000 current output connected For the connection use the following cables A Output connection N 2 Low current connection cables 10 sq mm 4 m long Terminated on one side with the current clamp ...

Page 38: ...VA VA rating compute VS VA IN If VS 10 V connect to the 10 V input that has a better resolution else connect to the 600 V input Now input in the screen The CT nominal secondary current IN The test current output 10 A or 40 A The secondary voltage measurement input 10 V or 600 V Press test start button 56 and adjust the secondary current to the desired value by the adjustment knob 6 the screen show...

Page 39: ... to gapless CT s ANSI2 In a log log diagram the knee point is the one where the curve has a tangent at 30 This refers to gapped CT s IEC the knee is the point of the curve where a 10 increase of the voltage causes a 50 increase of the current Input the other parameters of the CT under test From these data the test set computes and displays the nominal knee voltage and current according to the sele...

Page 40: ...ng the test is at least 2 VSM so that the saturation knee is well designed Then select the voltage input range as a function of the test voltage and of the CT ratio Given KCT CT ratio VP voltage at primary Then compute VP VSM 2 KCT The connection diagram is the following ...

Page 41: ...DOC MIE11110 Rev 5 Page 41 of 110 NOTE the drawing shows the output connection to 3000 V For the connection use the following cables A Output connection 3000 V ...

Page 42: ...s If the test is to be performed at 3000 V select TEST on the screen and then press test START button 56 the following message will be displayed The HV is generated only while the START button 56 is kept pressed this is an additional safety feature The operator will have both hands occupied one for the knob 6 the other for the button 56 however this is much safer than starting the HV generation an...

Page 43: ...ed the HV key is already ON the following message is displayed In this instance press the STOP button 55 turn OFF the HV key 28 then press test START button 56 Now select CURVE the screen shows you in real time the current versus voltage diagram Press ON and slowly increase the output voltage the suggested test time is 20 30 s As you increase the voltage voltage and current are displayed in the V ...

Page 44: ...he return to zero is too fast the CT saturation curve would be distorted The following pictures show the correct CT saturation curve the saturation curve of the same CT after the voltage has been decreased too fast the two curves superimposed 2 If your CT is rated at 50 Hz and your supply is at 60 Hz the nominal voltage knee is 1 2 times bigger than the one at 50 Hz ...

Page 45: ...DOC MIE11110 Rev 5 Page 45 of 110 ...

Page 46: ...magnetized If you return to the former screen it displays the computed V and I values for the knee point Select SAVE on the menu then slowly reduce the voltage the test can be stopped only after knob 6 is in its zero position This is because the transformer under test cannot be left with some remaining magnetization So if the test is broken during the generation and the output has not been adjuste...

Page 47: ...t is to measure the CT burden in terms of Ohm i e the active component of the VA burden measured in the former paragraph This test is performed applying DC current to the CT secondary connections and measuring the corresponding DC voltage drop With this test it is possible to apply the nominal current to the burden while in the previous test this current can be less or much less depending upon the...

Page 48: ... as shown or to the burden If the test is on the primary resistance both ends of the primary should be grounded this nulls the effect of the primary inductance For the connection use the following cables A Output connection N 2 Low current connection cables 10 sq mm 4 m long Terminated on one side with the current clamp ...

Page 49: ...onding voltage drop The ohm burden at the ambient temperature The ohm burden at reference temperature These measurements will not change very much with the test current When you are satisfied with the result press SAVE test result is saved Return to zero the adjustment knob 6 VERY IMPORTANT NOTICE during the current adjustment a current is induced into the primary loop that is short circuited the ...

Page 50: ... DISAPPEARS If you do the residual energy would cause an high voltage spark on the conductor you are removing 1 1 7 CT tests voltage withstand When this test is selected the following menu is displayed Purpose of the test is to verify the isolation of the CT secondary cabling and of the CT secondary itself and to measure the corresponding leakage current typically capacitive This test is performed...

Page 51: ...x I the current that should not be exceeded during the test If this occurs i e if the load sinks a current more than Max I the test is automatically interrupted and the operator alerted by a message Max T the test time measured from when the test voltage is more than Min V that should not be exceeded during the test If this occurs i e if the elapsed time is more than Max T the test is automaticall...

Page 52: ...nnected and the HV output is connected to the secondary and to the ground For the connection use the following cables N 2 High voltage connection cables 4 m long 5 kV with earth screen Terminated on both sides with HV connectors N 2 Clamps for the HV connection ...

Page 53: ...ore getting close to HV connections One of the two test leads will be connected to ground unfortunately this fact reduces the safety margin The contact to ground of the other lead causes a short circuit to the HV output with immediate disconnection of the test set Much worse the accidental contact of the operator with the other lead would submit him to the high voltage WITH NO PROTECTION FROM THE ...

Page 54: ...ment knob 6 During this test the isolation resistance should typically be more than 1 MOhm An higher resistance could mean that there is a connection error a lower resistance typically is caused by the presence of moisture it is advisable to clean and dry the transformer and to repeat the test 1 1 8 CT tests polarity by impulses When this test is selected the following menu is displayed Purpose of...

Page 55: ...ill be displayed on the screen so that you can decide in case of doubt A counter counts automatically the number of tests performed The connection diagram is the following The current impulse output is connected to the primary the secondary is connected to the 10 A current measurements input sockets Take care to connect the primary with the correct polarity ...

Page 56: ... current m easurement input Once the connection is performed press START the impulse is generated whenever START is pressed Slowly increase the current impulse until the shape of the received wave is clear The display shows OK or KO according to the phase relationship it shows also the primary and secondary current waveforms so that the operator can judge the test conditions Once the result is ach...

Page 57: ...le tests 1 2 1 VT tests ratio and polarity When this test is selected the following menu is displayed Purpose of the test is to measure the actual VT ratio and to verify its polarity This test is performed applying voltage to the primary side and measuring the secondary voltage and phase angle The connection to the loads can be open or closed in order to verify the accuracy error caused by the bur...

Page 58: ...mum test voltage VT is 3000 V and can be much lower that the nominal primary voltage VPN Prior to select the input measurement range compute the nominal measurement voltage VM as follows VM VT VSN VPN Giving some figures if the primary voltage is 30 kV or more LL and the secondary is 100 V or 110 V LL it is advisable to use the 10 V input as it is more accurate than the 600 V input for low voltage...

Page 59: ...Page 59 of 110 A Output connection N 2 High voltage connection cables 4 m long 5 kV with earth screen terminated on both sides with HV connectors N 2 Clamps for the HV connection B Input connection voltage less than 10 V ...

Page 60: ...PUT TO THE PRIMARY AND NOT TO THE SECONDARY SIDE IN CASE OF ERROR YOU WOULD GENERATE A DESTROYING VOLTAGE AT THE VT PRIMARY As the test is to be performed on the 3000 V range press test START button 56 the following message will be displayed The HV is generated only while the START button 56 is kept pressed this is an additional safety feature The operator will have both hands occupied one for the...

Page 61: ... that it does not exceed the limits This test is performed applying voltage to the burden after having disconnected the transformer secondary side and measuring the secondary voltage and phase angle The applied voltage can be measured at the T 2000 output sockets however i f the test current is high and it is desired to increase the test accuracy eliminating the voltage drops along the connection ...

Page 62: ...w voltage connection cables N 2 Clamps IF DESIRED B Input connection voltage less than 10 V N 1 Cable for low voltage measurement connection shielded 4 m long terminated on one side with the measurement connector and on the other side with two 4 mm banana plugs ...

Page 63: ...d Press the ON button and adjust the test current to the desired value by the adjustment knob 6 the screen shows The test current The corresponding voltage drop across the burden The phase angle between current and voltage The corresponding power factor The VA rating of the burden at the nominal voltage This value is computed and it is not just the product of the above measured current and voltage...

Page 64: ...used by the burden The test procedure is the same as the one described in paragraph 1 1 1 The only difference is the value of the secondary voltage typically much lower than with a standard voltage transformer 1 2 4 VT tests voltage withstand When this test is selected the following menu is displayed Purpose of the test is to verify the VT isolation and to measure the corresponding leakage current...

Page 65: ...een primary and ground however as T 2000 reaches only 3000 V the test voltage is normally much less than the nominal voltage rating so the test can be useful to measure the leakage current at lower voltage The test is executed the same way as for CT transformers see paragraph 2 1 6 The connection diagram is the following ...

Page 66: ... test is selected the following menu is displayed Purpose of the test is to verify the setting and the trip timing of the overcurrent protection that protects each phase of the TV secondary The test parameter is the nominal trip current of the protection The connection diagram is the following ...

Page 67: ...ables N 2 Clamps The operator selects accordingly the current range for the test There are two tests Protection threshold start the test and slowly increase the current As the protection intervenes the current drops to zero the current meter holds the last metered value that is the threshold Consider that the intervention is timed so the current should be increased slowly ...

Page 68: ...he three phases 1 3 POWER TRANSFORMERS TESTS When this test is selected the following menu is displayed It is possible to select the tap number this selection is reported in the two available tests i e ratio and resistance of tap changer contacts 1 3 1 PT tests ratio per TAP When this test is selected the following menu is displayed Purpose of the test is to verify that the ratio is correct on all...

Page 69: ...This is the case foreseen by the test set Test parameters are The primary voltage in kV either Line to Line or Line to neutral The secondary voltage in V either Line to Line or Line to neutral The selected input measurement range To this purpose consider that the maximum test voltage VT is 3000 V and can be much lower that the nominal primary voltage VPN Prior to select the input measurement range...

Page 70: ...732 t 1 732 hence t T 1 732 The software multiplies the ratio by 1 732 and displays the actual ratio Case 3 Type Dy Voltage is applied between A and C on the HV side and it is measured between a and n on the secondary side The measured ratio is therefore T VAC Van VAC Vac 1 732 VAC Vac 1 732 t 1 732 hence t T 1 732 The software divides the ratio by 1 732 and displays the actual ratio The connectio...

Page 71: ...71 of 110 A Output connection N 2 High voltage connection cables 4 m long 5 kV with earth screen Terminated on both sides with HV connectors N 2 Clamps for the HV connection B Input connection N 2 measurement cables N 2 Clamps ...

Page 72: ... The operator will have both hands occupied one for the knob 6 the other for the button 56 however this is much safer than starting the HV generation and then forgetting it in the ON state You have to turn ON the HV key 28 and adjust the VSEC voltage to the nominal voltage if it is less then 3000 V or aT 2000 V by the adjustment knob 6 the screen shows The applied primary voltage The primary curre...

Page 73: ...e selection is performed the resistance can be measured The resistance will slightly change from the lowest voltage output tap to the highest one This test is performed applying DC current to the PT primary and measuring the corresponding DC voltage drop This voltage can be measured at the T 2000 output sockets however if it is desired to increase the test accuracy eliminating the voltage drops al...

Page 74: ...cted to the winding PT secondary are short circuited to ground this nulls the effect of the primary inductance For the connection use the following cables A Output connection N 2 Low current connection cables 10 sq mm 4 m long Terminated on one side with the current clamp IF DESIRED B Input connection ...

Page 75: ...oltage drop The ohm burden at the ambient temperature The ohm burden at reference temperature These measurements will not change very much with the test current however it is advisable to use the same test current for each phase Given the delay of the current growth caused by the inductance you should not save the result until the value is stable enough The following message tells you how much the...

Page 76: ...e current If you press STOP when the adjustment knob is not at zero the following message is displayed AND THE CURRENT IS NOT REMOVED You have to move the knob to zero then press STOP for some time until the magnetization energy is not discharged and some current flows into the discharger the following message is displayed DO NOT PERFORM THE TEST WITHOUT THE PRIMARY SHORT CIRCUIT AT THE END OF THE...

Page 77: ...7 of 110 This test applies to the resistive LTC s it is performed applying DC current to the PT primary and measuring the dynamic resistance change as the operator issues a change command The connection diagram is the following ...

Page 78: ...nding PT secondaries are short circuited to ground this nulls the effect of the primary inductance Also the other two primaries should be short circuited For the connection use the following cables A Output connection N 2 Low current connection cables 10 sq mm 4 m long Terminated on one side with the current clamp ...

Page 79: ...resistance diagram on the display Note that the vertical axis is autoranging so for the measurement of the limiting resistor take into account the measurement of the winding resistance Save the result then before performing the next test change the test number high left on the screen Continue the same way until the stop position of the tap changer has been reached The Load Tap Changer fault is eas...

Page 80: ...ble gives the limits for the X R parameter X R L R WAVEFORM 2 0 5 GOOD 5 2 LIMIT 20 5 MASKED However this does not mean that the LTC cannot be tested it means that the resistors values cannot be measured If during the test the LTC has a fault open circuit then the R of L R becomes infinite and the resistance waveform clearly shows the problem The following pictures show some recorded test results ...

Page 81: ...DOC MIE11110 Rev 5 Page 81 of 110 2 Selection time about 30 ms LTC fails ...

Page 82: ...DOC MIE11110 Rev 5 Page 82 of 110 3 Selection time about 30 ms L R time constant very high the resistance cannot be measured LTC is OK ...

Page 83: ...DOC MIE11110 Rev 5 Page 83 of 110 4 Same LTC as above fault on this selection ...

Page 84: ...4 PT tests PT ratio test Connect low V to the transformer HV side phase 1 and 2 Adjust the voltage of V1 to 100 V Connect the measuring input Ext V the 600 V or the 10 V input as a function of the transformer ratio between one phase and ground You will find that two outputs have half ...

Page 85: ...C MIE11110 Rev 5 Page 85 of 110 value with respect to another say Ea This is normal because of the single phase feeding The transformer ratio is Type Dy shown 100 Ea 1 73 Type Yd 173 Ea Types Dd Yy 100 Ea ...

Page 86: ...rcuit breaker contacts or any resistance of interest It is intended that the burden is not inductive for the measurement of transformers windings please refer to CT VT or PT tests The test is performed applying an high DC current to the test item The test can be performed only taking advantage of the optional module called High IDC module The module includes a circuit that measures the current gen...

Page 87: ...ut The voltage drop across the test item is measured in the meanwhile the resistance is computed as the ratio of voltage versus current The test is performed with high DC current in order to increase the voltage drop to be measured besides the AC noise is filtered out The connection diagram is the following ...

Page 88: ...erformed at lower current it is possible to increase the cable length by using the cables 4 m long included in T 2000 or even putting these cables in series in order to obtain a total cable length of 6 m C Input connection N 2 measurement cables for the output current N 1 cable for low voltage measurement connection shielded 4 m long for the 10 V measurement The clamp or the vice shall be well tig...

Page 89: ...utomatically the test and you have to wait until the recover time is elapsed Also consider that you are sinking power from the mains supply the supply cable wires should have a cross section suitable for a current supply of 10 to 20 A The table lists the current supply When you are satisfied with the result press SAVE test result is saved Return to zero the adjustment knob 6 WHEN YOU DISCONNECT TH...

Page 90: ... the plant arrives with respect to a far ground is the fault current by the soil resistance the lower the resistance the lower the voltage at which operators can be subject The test is performed by applying the test current to the grounding net of the system u nder test and closing the loop by an auxiliary earth connection As we are dealing with a system with a big dimension the first problem is t...

Page 91: ...DOC MIE11110 Rev 5 Page 91 of 110 The connection diagram is the following ...

Page 92: ...owing shape The test is performed moving the voltage probe along the line until the voltage drop Vd does not change significantly as a rule of thumb the good point is located from 30 to 50 of the distance d The third problem is that for small systems D is small and the cable provided 100 m long is far enough to reach the auxiliary earth connection With larger systems such as substations the dimens...

Page 93: ...RP Impedance of the conductors ZC Earth resistance of the auxiliary system RA ZT RP ZC RA For this test the T 2000 output can reach a maximum voltage of 80 V A typical value of the earth resistance to be tested is 10 Ohm or less If we want to perform the test with a current of 1 A so that the voltage drop is 10 V the value of ZT must be less than 80 Ohm As ZC can be neglected this leaves 70 Ohm fo...

Page 94: ...e for the connection to the local grounding net 10 m long section 2 5 sq mm plus clamp A single pole cable for the connection from the test set to the connection reel 4 m long section 2 5 sq mm A single pole cable for the connection to the auxiliary dispersion spike 100 m long section 2 5 sq mm Wound on a wheel One or two auxiliary dispersion spikes with screw for insertion into the ground Complet...

Page 95: ...a value close to the maximum allowed by the output The display shows The applied test voltage The injected current The voltage drop between the system earth connection and the voltage spike The corresponding earth resistance Now it is necessary to move the voltage spike as said before until the resistance measurement does not change very much this is the earth resistance of the system Once the res...

Page 96: ... across the soil in other two spikes arranged as shown in the following connection diagram The depth of insertion into the soil is relevant only for the amount of current that can be injected into the ground the distance d instead influences the result as the measured resistivity is the one of the volume of soil having a depth equal to d In practice if ...

Page 97: ...the generator The upper part that will protrude from the ground is isolated with rubber Handle to screw the spike into the ground B Measurement connection Two single pole cables for the connection to the voltage probes 10 m long section 2 5 sq mm Two test probes to measure the voltage drop material zinc plated iron length 0 5 m Complete with connector for the measurement cable Once the connection ...

Page 98: ...DOC MIE11110 Rev 5 Page 98 of 110 Once the result is achieved press SAVE slowly reduce to zero the current and repeat the test in the formerly defined points of the site to be verified ...

Page 99: ...o measure the impedance of the line under test in module and argument The connection to be performed is shown on the screen the 10 A output used as a voltage source is connected to two phases that are short circuited on their end Considering an average value of 0 2 Ohm km that becomes 0 4 Ohm km as there are two lines in series the following table lists the average line impedance and test current ...

Page 100: ...hort circuited between them at the other end of the line Open SU3000 Connect one side to ground and the other side to two cables one will go to T 2000 the other to the line to be tested Note that until the SU3000 is OPEN the switch is open and there is no ground connection Close SU3000 close the switch the two cables are connected to ground Now you can connect to T 2000 output and to the line no 1...

Page 101: ...ceed with the test current otherwise you will be halted by an overload message When you are satisfied with the measurement press SAVE You can repeat the test with lines 1 and 3 to verify that the measured ZL is the same As you have finished you can proceed with the measurement of the earth factor 3 2 EARTH IMPEDANCE MEASUREMENT When this test is selected the following menu is displayed This test c...

Page 102: ...DOC MIE11110 Rev 5 Page 102 of 110 The connection for this test is modified as shown in the following figure ...

Page 103: ...d the other output of T 2000 SU3000 should now be opened and the test can be started Slowly increase the output voltage and verify the corresponding earth impedance ZE and argument and also the earth factor KE and the corresponding argument As the impedance is the ratio voltage versus current its value should not change very much as the current is increased Note that the average value for KE is 1 ...

Page 104: ...h the fault and line 2 the parallel line the computation formula is the following Where VF is the voltage on line 2 Beta is the matching parameter In our test we open line 1 so that I1 0 inject a current into line 2 and measure VF that is From which we compute 1 I Z V L F β Note that ZL has already been measured The connection schematic is the following p E L F I I K I Z V 2 1 1 β p L F I Z V 2 β ...

Page 105: ...DOC MIE11110 Rev 5 Page 105 of 110 ...

Page 106: ...se SU3000 close the switch the cable is connected to ground Now you can connect to T 2000 and to line 2 that will be closed to ground Connect to ground the other output of T 2000 Connect the 10 V voltage measurement input to line 1 red connector and to ground black connector SU3000 should now be opened and the test can be started Slowly increase the output current and verify the beta factor in mod...

Page 107: ... TAP CHANGER TESTING The test performed by T 3000 has the purpose of allowing the verification of the tap changer device the following design shows a possible configuration of the power transformer and TAP changer PRIMARY FIXED END PRIMARY ADJUSTED END ...

Page 108: ...s during a single TAP change We start from TAP N we have to move to TAP N 1 Before the movement position 1 there is a direct connection between TAP N and the input the primary winding resistance is RN As the movement starts up to position 2 nothing happens from 2 on the resistor R is put in series to TAP N and the resistance of the primary windings grows to R RN As the movement continues the secon...

Page 109: ...any of the changes there is an open circuit or a short circuit It is also possible to see that as R is bigger than the biggest primary resistance RN it is possible to set a resistance threshold for all TAPs for the resistance change recording The actual possibility of performing the test is limited by the parasitic inductance of the transformer winding In fact even if the secondary winding is shor...

Page 110: ...e value of R can be measured if it is big as compared to the switching time then R cannot be measured however the effect of a mis operation can be seen as R in this case is infinity The drawing above shows the resistance waveform with three different time constants 1 Small L R as compared to the selection time R can be measured 2 Limit value for L R 3 Big L R constant R cannot be measured ...

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