Voltage Transformer
Contents
1. function 1 VT Guard description VT Guard Is a preventive device against the ferroresonance phenomenon which may be triggered in power networks with ungrounded or not directly grounded neutral point VT Guard should be used in cooperation with voltage transformers connected in open delta more in User s manual Important Read the User s manual before use 2 Basic operating states Simpl diagram Earth fault a In case of full balance in a three phase network there is zero voltage on an open delta winding VT Guard terminals Uo 0 No current flows through VT Guard The device isn t active b In case of unbalance in a three ohase network there is voltage on VT Guard terminals Uo gt 0 If the Uo is lower than threshold voltage Ut Ut 20 24V then current Uo Rore I Rep RI R2 through the device Total resistance value is higher then 1000hm and voltage Uo is max 24V in this case Current flowing thorough the device has very low value ch a c In case Uo is higher then treshold Switching circuit voltage ferroresonance the switching circuit is switched on and current flows trough Rptc Rer and R1 Because of low values of these resistors there is steep increase of current and fast ferroresonance dumping High current flows trough the device for short time the PTC resistors arn t warm up significantly d In case Uo is higher then treshold voltage earth fault the switching circuit is swi2. terminal box for Voltage transformers One pole insulated voltage transformer 2 measuring windings Measuring and residual winding 2 ratios measuring winding One measuring winding Assembled secondary terminal Phoenix 2 ing and residual gt measuringandresidual Ja In 2a 2n da dn N PE eee winding eco aia laa ual winding Double pole insulated transformer 2 measuring windings 2 ratios measuring winding One measuring winding 1VLM000610 Rev 1 en 2008 12 3 Appendix 2 Wiring diagrams Current transformers Primary current F Pe Prelmary Current P1 F2 gt Sc Secondary Curren Primary curren ical Ese econdary current Secondary Current P1 L Le Pe a1 ce ecaondary current 1VLM000610 Rev 1 en 2008 12 3 Wiring diagrams Voltage transformers Primary woltag Ay N E D Fi econdary voltage Primary voltage A i N 1 Fi Secondary walltog AC ar Secondary woltoug 1VLM000610 Rev 1 en 2008 12 3 Appendix 3 Damping ferroresonance for voltage transformer type TJC TECHNICAL BACKGROUND Ferroresonance is a phenomenon usually characterized by over voltages and very irregular wave shapes and is associated with the excitation of one or more saturable inductors through Capacitance in parallel with nonlinear inductor The saturable inductor usually is present in the form of an instrument trans
3. Instruction for installation use and maintenance for Current and Voltage potential transformers 1VLM000610 Rev 1 en 2008 12 3 Instruction for installation use and maintenance for Current and Voltage potential transformers This installation use and maintenance guide is valid for current and voltage transformers operating in outdoor or indoor conditions These instructions are valid for Current transformer type TPU TPO TP TTR BB BBO KOKS KOFD KOFA IHBF Voltage transformers types TJC TDC TDO TJO TJP TDP KGUG KGUGI KRED 1 Operating conditions Indoor transformers The transformers should be mounted in dry indoor conditions where the ambient air is not significantly polluted by dust smoke corrosive cases vapours or salt The transformers are designed for standard ambient temperature between 5 C and 40 C The altitude for use should be lower than 1000 m above the sea level The transformers may be used also in higher ambient temperatures and higher altitudes when agreed upon with the manufacturer Outdoor transformers The transformers should be mounted in outdoor conditions where the ambient air may be polluted by dust smoke corrosive cases vapours or salt The transformers are designed for standard ambient temperature between 40 C and 40 C The average value of the ambient temperature measured over a period of 24 hours should not exceed 35 C 2 Technical details The technica
4. Connection between secondary terminal and base plate ground is shown on the picture Crossection of single line terminal box 4 Always short circuit the secondary of the current transformer which is not currently in use to prevent secondary voltages which may be hazardous to personnel or damaging to the transformer s secondary The secondary like this must be additionally grounded 5 Never short circuit the secondary terminal of a voltage transformer even this is not in use A secondary short circuit will cause the unit to overheat and fail in a very short period of time 6 Protection of single pole insulated voltage transformers against feroresonance phenomena is stated in appendix 3 Damping of the feroresonance in Voltage transformers type TJC 7 Incase of the current transformer with voltage indication coupling electrode included is secondary terminal box equiped with PE terminal which is connected with earthing screw to the base plate which must be generally earthed Connection between secondary terminal and base plate is shown on the picture Crossection of single line terminal box Attention Terminal PE must be always earthed this is hold generally even if the base plate is removed In case of disassembling the base plate producer doesn t warranting the earthing Mounting Following information is general and some details can differentiate according to type and variants of transformers It is necessary to comb
5. a HR Indicator complies with the IEC 61234 5 standard for high resistive voltage indicators b CE Where the values of capacity C1 and C2 are measured C1 is the Capacitance between primary winding and Ck terminal and C2 is the Capacitance between grounded parts and CK terminal These values are mentioned on the rating plate CE capacity according to nominal voltage 10 13 8 19 33 20 90 13 8 17 5 13 23 20 24 10 18 Fuses The fuse can be a part of a supply of voltage transformers with fuse We can supply following fuses 0 3A 12 and 24 kV products fuse type JT6 specially designed for voltage transformers 0 6A 12 kV products fuse type JT6 specially designed for voltage transformers 2A 6 3A all products up to 36 kV IEC fuses manufacturer SIBA 2A products up to 36kV IEC fuses manufacturer BUSSMANN 8 Instruction for use Current transformers are used to convert large currents in the primary circuit to an appropriate level for secondary circuit equipment relays and meters 1VLM000610 Rev 1 en 2008 12 3 to insulate primary and secondary circuit from each otherto protect the secondary equipment from the harmful effects of large current appearing during the operation short circuits The use of current transformer for other purpose then described above is forbidden in not agreed with the producer Routine test report Together with instrument tr
6. da dn terminal marking for residual open delta winding 30VA rated output 0 5 6P accuracy classes 12 28 75 kV highest voltage for equipment power frequency withstand voltage rated lightning impulse voltage IEC 60044 2 referred standard 2002 year of production E temperature class TCM Type approval mark 1VLM000610 Rev 1 en 2008 12 3 3 Instruction for installation General information Instrument transformer is an electrical equipment and the electrical installation shall be done by skilled person only National legislation can set down the minimum age and the criteria for competence of skilled persons working on with or near an electrical installation Where is not the national legislation requirements for competence the criteria shall be used at least according to EN 50110 1 Safety instructions 1 Always consider transformer as a part of the circuit to which it is connected and do not touch the leads and terminals or other parts of the transformer unless they are known to be grounded 2 Always ground the metallic bases of instrument transformer 3 Always ground one secondary terminal of the transformer except if the windings are connected to open delta When the secondary of transformer is interconnected there should be only one grounded point to prevent accidental paralleling with system grounding wire In case of disconnection from the ground the grounding screw has to be removed from the secondary terminal
7. 20 Nm Maximum allowed cantilever strength is Voltage transformers 2000 N Current transformers 5000 N Primary reconnectable transformers PRIMARY CONNECTION LOW RATIO HIGH RATIO 1VLM000610 Rev 1 en 2008 12 3 Secondary connections The terminals screws nuts and washers are made of stainless steel Secondary grounding screws and secondary terminal fastening screws are made of nickel plated brass The secondary terminal cover box for indoor use is made from the plastic and provided with three detachable threaded inserts Pg16 The terminals are provided with M5 screws for secondary wiring connection and with through going holes for direct earthing of the secondary circuit by M5 screws The terminal cover is seal able The secondary cover for outdoor CT is made of epoxy resin and provided with one insert Pg21 The secondary cover for outdoor VT is made of plastic and provided with two insert Pg21 Degrees of IP protection Indoor transformers IP40 or IP30 for transformers TTR BB KOKS Outdoor transformers IP54 For terminal marking see appendix 1 a ed sd La jhe a o Sa a P TJP TJC TDC TJO7 TJO6 TDO6 Details of voltage transformers casted terminal boxes 1VLM000610 Rev 1 en 2008 12 3 Cross section of single line secondary terminal box Capacitive voltage indicator divider The transformer can be supplied with the capacitive voltage indicator on the request There are two possible solutions
8. ansformer are delivered routine test report two rating plates one plastered on the transformer and one free The following information can be included on the request These are free of charge theoretical current voltage errors and phase displacement values theoretical excitation curves There are additional extra paid reports which can be supplied on request accuracy test report magnetizing curve for current transformers additional labels if more then 2 verification tests 9 Instruction for maintenance Excessive dust or other kind of pollution must be brushed off the transformer Polluted transformers can be cleaned with spirit petrol or toluene Traces of arcs and minor surface damages can be easily removed with sandpaper after which the surface is to be treated by applying a thin layer of silicone paste on it Instruction for repairing greater surface damages must be requested from the manufacturer 70 Transport and storage The permissible transport and storage temperature is from 40 C to 70 C During transport and storage the transformers must be protected against direct sunshine The transformers are delivered fastened to a transport pallet 11 Disposal Materials used in instrument transformers are considered as materials without dangerous environmental impact and materials are not toxic Disposal of instrument transformers is controlled by national legislation of communal waste 12 Normative r
9. eferences IEC60044 1 Instrument transformers Current transformers IEC60044 2 Instrument transformers Voltage transformers IEC61243 5 Voltage detectors Voltage detecting systems VDS IEC60529 Degrees of protection provided by enclosures IP Code IS012100 Safety of machinery Basic concepts general principles for design EN 50110 1 Operation of electrical installations 1VLM000610 Rev 1 en 2008 12 3 Appendix 1 Examples of secondary terminal marking for casted terminal box for current transformers One core One core with CD No tap a S S T 1 tap Msi lise iss T 2 taps E T 3 taps List is2 is3 is4 iss 4 taps SI 8 BSE IS a Two cores Two cores with CD No tap SSS EIS I Me ea a 1 tap fis3 2s3 2 taps fis3 1s4 2s3 2s4 1s3 1s4 2s3 2s4 o 3 taps 1s4 1is5 _ 2s4 2s5 _ 3 cores 3 cores with CD No tap Lisi 1s2 2s1 2s2 351 352 fis2 2s2 3s2 L L L O 1 tap s3 2s3 3s3 _1s2 1s3 2s3 3s2 353 2 taps ee 4 cores 4 cores with CD No tap 1s2 2s2 3s2 4s2 _1s2 2s2 3s2 4s2 o 1 tap peee 5 cores 5 cores with CD No tap _1s2 2s2 3s2 4s2 5s2 O 6 cores 6 cores with CD No tap terminal not earthed terminal earthed 1VLM000610 Rev 1 en 2008 12 3 2nd line of terminal 1st line of terminal Examples of secondary terminal marking for casted and assembled phoenix
10. former power transformer or reactor witch utilizes an iron core Ferroresonance of single pole insulated transformers in unearthed network is one of the most common ferroresonance case Depending on the supply voltage capacitance and inductance the oscillation can be either periodic over or sub harmonic or with fundamental frequency or aperiodic Using damping resistor or VT guard in the residual voltage secondary shown in Fig 1 can considerably reduce the risk for ferroresonance There is additionally factor that can in some cases reduce or totally eliminate the risk for ferroresonance and it is over voltage factor According to IEC standard is the rated over voltage factor 1 9xUn 8h Higher rated over voltage factor shift the operating point towards lower flux values of voltage transformer It results in smaller sensitivity of transformer to some kind of transients usually initiate ferroresonance RECOMMENDATION Rated voltage factor We recommended using the voltage transformers with the over voltage factor in the range 2 5 3 xUn 8h We cannot guarantee the value of the over voltage factor if the requirements for the secondary winding are too high Damping resistor See the recommended value of damping resistor below Voltage of residual Value of Rdamp Dampina power winding ili osy za 30W secondary Residual voltage secondary R damping resistor or VI guard Fig 1 1VLM000610 Rev 1 en 2008 12 3 VT Guard
11. ine it with other technical and marketing specifications like catalogues dimensional drawings and rating plate for specific transformer type Indoor current and voltage transformers The mounting position of the indoor transformer can be freely chosen The transformer is fixed using the mounting base with four screws M10 and washers Fastening must be done on a smooth surface There is a M8 screw for earthing the transformer on the base plate 1VLM000610 Rev 1 en 2008 12 3 Outdoor current and voltage transformers The mounting position of the outdoor transformer is only horizontal The other position can be agreed with the supplier The transformer is fixed using the mounting base VT with four screws M10 and washers or two U profiles CT with M12 screws Fastening must be done on a smooth surface There is a M12 screw for grounding of current transformer and M8 screw for grounding of voltage transformer Primary connection Primary terminals of the current transformer are made of cooper and they are silver or tin plated There are M12 screws used for fastening of primary conductor to the terminal For primary reconnectible transformers the ratio can be reconnected by changing position of the links fixed by M8 screws without removing already fitted primary conductors Maximum allowed torques for screw connections of current transformers O MS 8B 28 Maximum allowed torque for screw connection of voltage transformer is
12. l details for each individual transformer are mentioned on the rating plate fastened on the transformer Values mentioned on the rating plate must not be exceeded Markings used on the rating plate are as follows Current transformers ABB 1234567890 TPU 40 13 200 400 1 1 A 50 Hz 1S1 1S2 200 1A 5VAcl 0 5FS5 1S1 183 400 1A 10VA cl 0 5 FS 5 291 252 200 1A 5VA cl 5P15 291 253 400 1A 10VA cl 5P15 12 28 75 kV 50 18 125 kA 2002 IEC 60044 1 E TCM 212 95 2150 1VLM000610 Rev 1 en 2008 12 3 Where 1234567890 serial number TPU 40 13 transformer type code 50Hz rated frequency 200 400 1 1 A rated transformer ratio 1S1 1S2 terminal marking for core number 1 first tap 181 183 terminal marking for core number 1 second tap 5VA rated output 0 5 5P accuracy classes FS5 instrument security factor 12 28 75 kV highest voltage for equipment power frequency withstand voltage rated lightning impulse voltage IEC 60044 1 referred standard s 50 18 125kA rated short time thermal current thermal time rated dynamic current 2002 year of production E temperature class TCM Type approval mark Voltage transformers ABB 6600 V3 100 V3 100 3 V a n 30VA cl 0 5 da dn 30VA cl 6P 7 2 20 60 kV 2002 IEC 60044 2 E TCM 212 95 2151 Where 1234567890 serial number TJC 4 Transformer type code 50Hz rated frequency 6600 V3 100 V3 100 3 V rated voltage ratio a n terminal marking for first secondary winding
13. tched on and current flows trough Rptc Rer and R1 Because of low values of these resistors there is steep increase of current High current flows trough the device and cause to warm up PTC resistors PTC resistor increase their resistance The resistance is proportional to flowing current Current is limited Time needed for worming up PTC resistors for Uo 100V Is approximately 1 4s After earth fault is removed the PTC resistors cool down approximately 3 min It is necessary to mount VT Guard in vertical position far from other thermal sources indication flows 1VLM000610 Rev 1 en 2008 12 3 ABB sno Org Unit EJF Ley sieve rame menl laniskonmnes joi lt 420 5 715 2502 YWde es 117 reo 4 4715 250 G19 02 Ermo Czesci Repuoiic Pex 420 5 4715 2526 L mall nile Pec abb cor bhp aa abo ze 1VLM000610 Rev 1 en 2008 12 3 The data and ilustrations in this catalogue are not binding We reserve the right to make changes of the content in the course of technical development of the product 1VLM000610 Rev 1 en 2008 12 3
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