Technical Data TD 61 General Section PDF

Technical Data TD 61 General Section 1800061/04 EN © All rights reserved by Maschinenfabrik Reinhausen Dissemination and reproduction of this document and use and disclosure of its content are strictly prohibited unless expressly permitted. Infringements will result in liability for compensation....

Technical Data TD 61 General Section 1800061/04 EN © All rights reserved by Maschinenfabrik Reinhausen Dissemination and reproduction of this document and use and disclosure of its content are strictly prohibited unless expressly permitted. Infringements will result in liability for compensation. All rights reserved in the event of the granting of patents, utility models or designs. The product may have been altered since this document was published. We reserve the right to change the technical data, design and scope of supply. Generally the information provided and agreements made when processing the individual quotations and orders are binding. The original operating instructions were written in German. Table of contents Table of contents 1 General................................................................................................................................ 6 1.1 Validity................................................................................................................................................ 6 1.2 Subject to change without notice........................................................................................................ 7 1.3 Mode of operation of on-load tap-changers and off-circuit tap-changers........................................... 7 1.3.1 On-load tap-changers and off-circuit tap-changers for oil transformers................................................................ 7 1.3.2 On-load tap-changers for dry-type transformers................................................................................................... 8 1.4 On-load tap-changer function............................................................................................................. 9 1.4.1 On-load tap-changer switching concept................................................................................................................ 9 1.4.2 Basic connection of tapped winding.................................................................................................................... 10 1.4.3 On-load tap-changer designations...................................................................................................................... 11 1.5 Advanced retard switch function....................................................................................................... 16 1.5.1 ARS switching concept....................................................................................................................................... 16 1.5.2 ARS designations................................................................................................................................................ 17 1.6 Off-circuit tap-changer function......................................................................................................... 18 1.6.1 Switching concept and basic connections........................................................................................................... 18 1.6.2 Off-circuit tap-changer designations................................................................................................................... 19 2 Electrical properties......................................................................................................... 20 2.1 Through-current, step voltage, step capacity.................................................................................... 20 2.2 Insulation.......................................................................................................................................... 22 2.3 Leakage reactance with coarse tap selector connection.................................................................. 22 2.4 Tapped winding potential connection............................................................................................... 25 2.4.1 Recovery voltage and breaking current.............................................................................................................. 25 2.4.2 Snap-action contact............................................................................................................................................ 28 2.4.3 Sample potential connection calculation............................................................................................................. 29 2.5 Overload........................................................................................................................................... 33 2.5.1 Through-currents greater than the rated through-current................................................................................... 33 2.5.2 Operation under varying operating conditions.................................................................................................... 33 2.5.3 Details needed for queries relating to overload conditions................................................................................. 34 2.6 On-load tap-changer and off-circuit tap-changer loading from short-circuits.................................... 35 2.7 Enforced current splitting.................................................................................................................. 35 2.8 Permissible overexcitation................................................................................................................ 36 2.9 Multi-column on-load tap-changers.................................................................................................. 36 3 Insulating fluids................................................................................................................ 37 Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 3  Table of contents 4 Mechanical and design properties.................................................................................. 38 4.1 Temperatures................................................................................................................................... 38 4.1.1 Permissible temperature range for operation...................................................................................................... 38 4.1.2 Permissible temperature range for storage and transport................................................................................... 39 4.1.3 Arctic operation................................................................................................................................................... 39 4.2 Permissible pressure loading............................................................................................................ 41 4.2.1 Pressure loading during oil filling and transport.................................................................................................. 41 4.2.2 Pressure loading during operation...................................................................................................................... 42 4.3 Oil conservator for on-load tap-changer oil....................................................................................... 43 4.3.1 Height of the oil conservator............................................................................................................................... 44 4.3.2 Installation height above sea level...................................................................................................................... 44 4.3.3 Minimum oil conservator volume......................................................................................................................... 46 4.3.4 Drying unit for on-load tap-changer oil................................................................................................................ 48 4.4 Parallel connection of tap selector planes........................................................................................ 50 4.5 Installation information...................................................................................................................... 50 5 Transformer test information.......................................................................................... 51 5.1 Transformer ratio test....................................................................................................................... 51 5.2 Measuring DC resistance................................................................................................................. 51 5.3 Operating the on-load tap-changer during the transformer test........................................................ 52 5.4 Electric high voltage test................................................................................................................... 52 5.5 Dielectric test.................................................................................................................................... 52 6 Applications...................................................................................................................... 53 6.1 Transformers for electric arc furnaces.............................................................................................. 53 6.2 Applications with variable step voltage............................................................................................. 53 6.3 Hermetically sealed transformers..................................................................................................... 54 6.4 Operation in environments at risk of explosion................................................................................. 55 6.5 Special applications.......................................................................................................................... 56 7 Drives for on-load tap-changers and off-circuit tap-changers..................................... 57 7.1 TAPMOTION® ED motor-drive unit.................................................................................................. 57 7.1.1 Function description............................................................................................................................................ 57 7.1.2 Type designation................................................................................................................................................. 57 7.1.3 Technical data for TAPMOTION® ED................................................................................................................. 58 7.2 TAPMOTION® DD manual drive...................................................................................................... 59 7.2.1 Function description............................................................................................................................................ 59 4 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 Table of contents 7.2.2 Technical data for TAPMOTION® DD................................................................................................................ 59 8 Drive shaft......................................................................................................................... 60 8.1 Function description.......................................................................................................................... 60 8.2 Setup/models of drive shaft.............................................................................................................. 60 8.2.1 Drive shaft without cardan shaft, without insulator (= normal model).................................................................. 60 8.2.2 Drive shaft without cardan shaft, with insulator (= special model)...................................................................... 61 8.2.3 Drive shaft with cardan shaft, without insulator (= special model)...................................................................... 61 8.2.4 Drive shaft with cardan shaft, with insulator (= special model)........................................................................... 62 8.2.5 Delivery lengths................................................................................................................................................... 62 9 RS protective relay........................................................................................................... 63 9.1 Function description.......................................................................................................................... 63 9.2 Technical data.................................................................................................................................. 63 10 OF 100 oil filter unit.......................................................................................................... 65 10.1 Function description.......................................................................................................................... 65 10.2 Criteria for operation......................................................................................................................... 66 10.3 Technical data.................................................................................................................................. 67 11 On-load tap-changer selection........................................................................................ 68 11.1 Selection principle............................................................................................................................. 68 11.2 Example 1......................................................................................................................................... 70 11.3 Example 2......................................................................................................................................... 72 12 Appendix........................................................................................................................... 74 12.1 TAPMOTION® ED-S, protective housing (898801)......................................................................... 74 12.2 TAPMOTION® ED-L, protective housing (898802).......................................................................... 75 12.3 Bevel gear - dimensional drawing (892916)..................................................................................... 76 List of key words.............................................................................................................. 77 Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 5  1 General 1 General 1.1 Validity This general section applies to the technical data for the following on-load tap-changers (resistance-type fast tap-changer principle), ARS, off-circuit tap-changers, drives and their accessories: Product Technical data VACUTAP® VT® TD 124 VACUTAP® VV® TD 203 VACUTAP® VM® TD 2332907 VACUTAP® VR® TD 2188029 OILTAP® V TD 82 OILTAP® MS TD 60 OILTAP® M TD 50 OILTAP® RM TD 130 OILTAP® R TD 115 OILTAP® G TD 48 COMTAP® ARS TD 1889046 DEETAP® DU TD 266 TAPMOTION® ED TD 292 Table 1: Overview The right-hand column contains the document number of the specific techni- cal data for the corresponding product. These documents contain further de- tailed information about the various product variants and their properties. The associated assembly instructions, commissioning instructions and/or op- erating instructions are supplied with the product. These contain descriptions on the safe and proper installation, connection, commissioning and monitor- ing of the product. Standards quoted If standards or guidelines are provided as references without the edition (year of publication) being stated, the version applicable when this document went to print shall apply. 6 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General 1.2 Subject to change without notice The information contained in this technical file comprises the technical speci- fications approved at the time of printing. Significant modifications will be in- cluded in a new edition of the technical file. The document number and version number of this technical file are shown in the footer. 1.3 Mode of operation of on-load tap-changers and off-circuit tap-changers On-load tap-changers and off-circuit tap-changers are used to set the volt- age on transformers. The voltage is set in stages by changing the transmis- sion ratio. To do this, the transformer is fitted with a tapped winding, the taps of which are connected to the on-load tap-changer's tap selector, the ARS or the off-circuit tap-changer. On-load tap-changers are used for interrupt-free transformer voltage setting under load. Voltage setting with off-circuit tap-changers on the other hand requires the transformer to be fully switched off. This document refers only to on-load tap-changers following the resistance- type fast tap-changer principle. It mainly looks at issues affecting on-load tap-changers, ARS and off-circuit tap-changers for oil transformers. 1.3.1 On-load tap-changers and off-circuit tap-changers for oil transformers Most on-load tap-changers and off-circuit tap-changers are designed for countersunk installation in the transformer tank such that the tapped winding take-off leads require little routing to the tap selector or off-circuit tap- changer. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 7  1 General On-load tap-changers are operated by a motor-drive unit. The motor-drive unit is connected mechanically to the on-load tap-changer head via drive shafts and bevel gears. Off-circuit tap-changers can be operated with either a motor-drive unit or manual drive. Figure 1: Transformer with on-load tap-changer, schematic presentation 1 On-load tap-changer 3 Protective relay 2 Motor-drive unit 4 Oil conservator for on-load tap- changer oil H Height of oil column in oil conservator above the on-load tap-changer head cover 1.3.2 On-load tap-changers for dry-type transformers The VACUTAP® VT® on-load tap-changer can be used for interrupt-free voltage setting on dry-type transformers. The VACUTAP® VT® on-load tap-changer is secured to the active part of the dry-type transformer and has been designed as a single-phase module with direct assignment to one of the transformer legs. A motor-drive unit pro- vides mechanical operation. The single-phase modules can be easily cou- pled to produce a three-phase system. 8 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General 1.4 On-load tap-changer function 1.4.1 On-load tap-changer switching concept Figure 2: On-load tap-changer switching concept A Diverter-switch tap-selector concept B Selector switch concept 1 Tap selector 2 Diverter switch 1.4.1.1 Diverter-switch tap-selector principle On-load tap-changers which use this switching principle consists of a di- verter switch and tap selector. The tap selector provides preparatory selection of the desired tap which is then connected to the dead side of the diverter switch. The subsequent di- verter switch operation results in this tap then taking on the operating cur- rent. During the tap-change operation, the functions of the diverter switch and tap selector are therefore coordinated. 1.4.1.2 Selector switch concept On-load tap-changers using the selector switch concept combine the proper- ties of a diverter switch and tap selector. The switch from one tap to the next is undertaken in just one step. Difference between standard selector switches and those with vacuum tech- nology: In standard selector switches, the contacts through which the choice of de- sired tap is made also undertake the diverter switch operation. In selector switches with vacuum switching technology, the diverter switch operation is handled by separate contacts (vacuum switching cells). Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 9  1 General 1.4.2 Basic connection of tapped winding The following diagram shows the common basic connections for the tapped winding. Please refer to the relevant technical data for the possible basic connections for the various on-load tap-changer types. Figure 3: Basic connections a Without change-over selector b With reversing change-over selector c With coarse change-over selector 10 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General 1.4.3 On-load tap-changer designations Each type of on-load tap-changer is available in a number of models, offer- ing a different number of phases, maximum rated through-current, highest voltage for equipment Um, tap selector size and basic connection diagram. The designation of a particular on-load tap-changer model therefore de- pends on these features, hence ensuring an unmistakable and non-inter- changeable on-load tap-changer designation. 1.4.3.1 Example of on-load tap-changer type designation VACUTAP® VM® on-load tap-changer, single-phase, maximum rated through-current Ium = 650 A, highest voltage for equipment Um = 123 kV, tap selector size B, tap selector in accordance with basic connection diagram 10191W. Type designation VACUTAP® VM® I 651-123/B-10191W VACUTAP® VM® On-load tap-changer type I Number of phases 651 Maximum rated through-current Ium in A and number of parallel main switching contacts (last digit) for sin- gle-phase on-load tap-changers 123 Highest voltage for equipment Um (in kV) B Tap selector size 10191W Basic connection diagram Table 2: Example of designation of on-load tap-changer 1.4.3.2 Number of positions and basic connection diagram The tap selector can be adapted to a large extent to the required number of positions and tapped winding circuit. The corresponding basic connection di- agrams differ in terms of tap selector division, number of operating positions, number of mid-positions and change-over selector model. Example: Tap selector division 10, maximum of 19 operating positions, 1 mid-position, change-over selector designed as reversing change-over se- lector Designation of basic con- 10191W nection diagram 10 Contact circle pitch of tap selector 19 Maximum number of operating positions 1 Number of mid-positions W Change-over selector model (W=reversing change- over selector, G=coarse tap connection) Table 3: Example of designation of basic connection diagram Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 11  1 General 1.4.3.3 Overview of on-load tap-changer types The following table provides an overview for the various on-load tap-changer types in terms of number of phases, maximum rated through-currents Ium, highest voltages for equipment Um and maximum number of operating posi- tions. On-load tap-changer type Number of maxi. max. Number of max. operating posi- phases Ium Um tions [A] [kV] without with change-over se- change-over se- lector lector VACUTAP® VT® I 500 40.5 9 - VACUTAP® VV® I, III 600 145 12 23 VACUTAP® VM® II, III 650 300 22 35 I 1,500 300 22 35 VACUTAP® VRC III 700 245 18 35 II 700 300 18 35 I, I HD 1,300 300 18 35 VACUTAP® VRD III 1,300 245 18 35 I, I HD 1,300 300 18 35 VACUTAP® VRE III 700 245 18 35 I, I HD 1,300 300 18 35 VACUTAP® VRF III 1,300 245 18 35 I HD, II 1,300 362 18 35 1) I 1,600 362 18 35 I 2,600 362 18 35 VACUTAP® VRG III 1,300 245 18 35 I HD, II 1,300 362 18 35 1) I 1,600 362 18 35 I 2,600 362 18 35 OILTAP® V III 350 123 14 27 I 350 76 14 27 OILTAP® MS I, II, III 300 245 14 27 OILTAP® M II, III 600 245 22 35 I 1,500 300 22 35 OILTAP® RM III 600 300 18 35 I 1,500 300 18 35 OILTAP® R III 1,200 300 18 35 I 3,000 300 18 35 12 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General On-load tap-changer type Number of maxi. max. Number of max. operating posi- phases Ium Um tions [A] [kV] without with change-over se- change-over se- lector lector OILTAP® G III 1,600 300 16 31 I 3,000 300 16 31 Table 4: On-load tap-changer types 1) VACUTAP® VRF I 1601 and VACUTAP® VRG I 1601 can be used with applications up to Ium = 1,600 A without enforced current splitting (parallel winding branch). Refer to the technical data for the corresponding on-load tap-changer for fur- ther details and information about special models. 1.4.3.4 Adjustment position and mid-position The adjustment position is the position in which the on-load tap-changer is supplied. During maintenance work (removal or installation of on-load tap- changer insert) the on-load tap-changer must be in the adjustment position. For further details, please refer to the corresponding operating and mainte- nance instructions. The adjustment position is explicitly indicated in each de- tailed connection diagram of the on-load tap-changer. A distinction is made between circuits with 1 mid-position and 3 mid-posi- tions. The mid-position (if there are 3, the central mid-position) is usually also the adjustment position (see detailed connection diagram of on-load tap- changer). In the mid-position (if there are 3, the central mid-position), the "K" contact is live with the reversing change-over selector model or coarse tap design. Power does not flow through the tapped winding in this position. The change-over selector (reversing change-over selector or coarse change-over selector) can only be switched when in this position. With 1 mid-position, tap-changes to positions immediately before and after the mid-position result in a change in voltage. With 3 mid-positions, there is no change in voltage between the mid-positions. Bridged contacts (see e.g. Parallel connection of tap selector planes chapter [►Section 4.4, Page 50]) are not considered to be mid-positions. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 13  1 General 1.4.3.5 Designation of tap selector connection contacts and operating positions When an order is placed, a detailed connection diagram is produced for each on-load tap-changer. This is the only binding source of reference for the on-load tap-changer connection to the transformer. Other than electrical connections, this detailed connection diagram contains a schematic illustration of the geometric arrangement of connection contacts viewed from above. In this detailed connection diagram, the tap selector connection contacts and operating positions for the affected on-load tap-changers are designated as specified by the customer. The contact designations used in dimensional drawings for on-load tap- changers always correspond to the normal version in accordance with MR standard. The position designation of the on-load tap-changer is identical to that of the motor-drive unit. 1.4.3.5.1 Normal version in accordance with MR standard When designating the connection contacts and operating positions in accor- dance with the MR standard, tap selector connection contact 1 is live in op- erating position 1. Operating position 1 is also the end position and is reached by moving counter-clockwise through the set range for tap selector contact bridge movement. Example of basic connection diagram 10193W: Position 19 18 17... 11 10 9... 3 2 1 Live 9 8 7... 1 K 9... 3 2 1 tap selector connection contact Change-over selector connecting 0- → 0- 0- 0+ → 0+ ← 0- 0+ 0+ ← Actuation following → "Raise" → ← "Lower" ← Hand crank direction of rotation → Clockwise → ← Counterclockwise ← Tap selector contact bridge → Counterclockwise → ← Clockwise ← Motor-drive unit control → By "K2" motor contactor → ← By "K1" motor contactor ← Table 5: Assignment of designations for normal version in accordance with MR standard taking the example of basic connection dia- gram 10193W 14 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General The following diagram shows the contact designation of the two tap selector planes from above with 1...9, K (clockwise). The on-load tap-changer is in position 2, the change-over selector is con- necting contacts 0 and +. Position 1 is reached by operating the other tap selector contact bridge counter-clockwise (viewed from above), i.e. manually by turning the hand crank to the right (clockwise) or with a motor-drive unit by activating motor contactor K2. The direction of rotation on the on-load tap-changer is retained regardless of the drive shaft arrangement selected. Figure 4: Directions of rotation for normal version in accordance with MR standard Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 15  1 General 1.5 Advanced retard switch function 1.5.1 ARS switching concept An Advanced Retard Switch (ARS) is used to switch over a winding during transformer operation and basically has two operating positions. During an ARS operation the through-current is commutated from one current path to another current path with the same potential. Figure 5: Advanced Retard Switch (ARS) for reversing the polarity of a winding a) ARS in operating position 1 b) ARS during tap-change operation c) ARS in operating position 2 The ARS can be used for different applications in combination with an on- load tap-changer. The ARS is mainly used in applications with a large regu- lating range (e.g. phase shifter transformers) to switch the polarity of the tapped winding (double reversing change-over selector switching concept). You can find more information in the technical data for the COMTAP® ARS. 16 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General 1.5.2 ARS designations Example ARS I 1822 - 145 - 18 02 0 DW ARS Product designation ARS COMTAP® ARS I Number of phases I Single-phase III Three-phase 1822 Maximum rated through-current Ium and identifi- 1000 1000 A cation of necessary current splitting (3rddigit) and indication of parallel switching planes per No current splitting phase (4th digit) No parallel switching planes 1822 1800 A Double current splitting 2 parallel switching planes 2433 2400 A Triple current splitting 3 parallel switching planes Just single-phase 145 Highest voltage for equipment Um 123 123 kV 145 145 kV 170 170 kV 18 Contact circle pitch 18 18 pitches, contact circle diameter 850 mm 02 Number of operating positions 02 2 operating positions 0 Number of mid-positions 0 No mid-position DW Type of tap-change operation DW Double reversing change-over selector Table 6: Explanation of designations for advanced retard switch Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 17  1 General 1.6 Off-circuit tap-changer function 1.6.1 Switching concept and basic connections The off-circuit tap-changer is changed over from one operating position to the next by rotating an insulating drive shaft. Off-circuit tap-changers can be operated with either a motor-drive unit or manual drive. Special connections are possible in addition to the basic connections shown in the following diagram. Figure 6: Basic connections for DEETAP® DU off-circuit tap-changer Refer to the technical data for DEETAP® DU for further information. 18 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 1 General 1.6.2 Off-circuit tap-changer designations Example: DU III 1000 - 145 - 06 05 0 Y DU Product designation DU DEETAP® DU III Number of phases I Single-phase III Three-phase 1000 Maximum rated through-current 200 200 A Ium 4XX 400 A 600 600 A 8XX 800 A 1000 1000 A 12X2 1200 A 16X2 1600 A 2022 2000 A Ium > 2000 A on request Current splitting required XX0X No current splitting XX2X Double current splitting Parallel switching planes XXX0 None XXX2 2 per phase 145 Highest voltage for equipment 36; 72.5; 123; 145; 170; 245 Um [kV] Um > 245 kV on request 06 Contact circle pitch 60 6 pitches (400 mm) 12 12 pitches, (600 mm) 18 18 pitches, (850 mm) 05 Number of operating positions Depending on model, 2 to 17 operating positions are possible 0 Number of mid-positions 0 No mid-position 1 One mid-position Y Type of tap-change operation Y Linear off-circuit tap-changer for neutral application D Linear off-circuit tap-changer for delta application ME Single-bridging off-circuit tap-changer MD Double-bridging off-circuit tap-changer SP Series-parallel off-circuit tap-changer YD Star-delta off-circuit tap-changer BB Buck-and-boost off-circuit tap-changer S Special connection Table 7: Explanation of designations for off-circuit tap-changer Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 19  2 Electrical properties 2 Electrical properties This chapter contains general information about the electrical properties of on-load tap-changers, off-circuit tap-changers and Advanced Retard Switches (ARS). More information about special applications can be found in the Applications [►Section 6, Page 53] chapter. 2.1 Through-current, step voltage, step capacity The through-current is the current which flows through the on-load tap- changer and off-circuit tap-changer under normal operating conditions. The level of an on-load tap-changer's through-current generally differs over the set voltage range (e.g. while the transformer's rated power remains con- stant). Rated through-current Iu The maximum through-current which a transformer can continuously carry must be used to rate the on-load tap-changer and off-circuit tap-changer. This maximum permitted continuous through-current of the transformer is the rated through-current Iu of the on-load tap-changer or off-circuit tap-changer. Step voltage Ust The step voltage is the operating voltage found between adjacent taps. The step voltage may remain constant or change over the entire set range. If the step voltage is variable, the transformer's maximum step voltage Ust is used to rate the on-load tap-changer and off-circuit tap-changer. Maximum rated through-current Ium The maximum rated through-current Ium is the maximum design-dependent through-current of an on-load tap-changer and off-circuit tap-changer to which the current-related type tests relate. Rated step voltage Ui The rated step voltage Ui of an on-load tap-changer is the highest step volt- age permissible for one particular value of the rated through-current Iu. To- gether with a rated through-current, this is known as the associated rated step voltage. Maximum rated step voltage Uim The maximum rated step voltage Uim is the maximum permissible design-de- pendent step voltage of an on-load tap-changer or off-circuit tap-changer. 20 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties Transition resistors The diverter switch's transition resistors are configured depending on the levels of maximum step voltage Ust and the rated through-current Iu of the transformer for which the on-load tap-changer is intended. Since the permissible rated through-current Iu and permissible step voltage Ust depend on value of the transition resistors, the rated levels relate to the relevant application. If an on-load tap-changer is operated with step voltage and through-current values other than those stated in the order, Maschinenfabrik Reinhausen GmbH (MR) must check whether this is possible. For example, if the trans- former power is increased by means of improved cooling or the on-load tap- changer is used in a different transformer, the transition resistors may have to be adapted. This also applies if the desired new rated values Iu and Ust are below the orig- inal values. The transition resistor configuration affects both the switching capacity loading of the contacts and the consistent contact wear. Rated step capacity PStN The rated step capacity PStN is the product of the rated through-current Iu and associated rated step voltage Ui: PStN = Iu x Ui The following diagram shows the typical load limits of a diverter switch. This shows that the permissible operating range is limited by the maximum rated step voltage Uim and maximum rated through-current Ium. Figure 7: Rated step capacity diagram for diverter switch 1 Upper corner 2 Lower corner The curve points between corners 1 and 2 are only provided by the permissi- ble rated switching capacity. The permissible rated switching capacity be- tween corners 1 and 2 corresponds to linked pairs of values for Iu and Ui and may be constant or variable. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 21  2 Electrical properties The rated step capacity diagram and individual values for Iu and Ui in corners 1 and 2 are stated separately for each on-load tap-changer type (see techni- cal data for relevant on-load tap-changer). Limit step capacity and limit switching capacity The limit step capacity is the largest step capacity which can be switched with certainty. In its standard model, each MR on-load tap-changer can switch at least twice the rated through-current Iu at the step voltage Ust for which the on-load tap-changer was configured. This limit switching capacity is proven by type testing in accordance with IEC 60214. Appropriate mea- sures must be taken to prevent tap changes with currents of more than twice the rated through-current Iu. 2.2 Insulation The insulation capacity of the various insulation distances and assignment of this to the voltages of the transformer windings are detailed in the technical data for the relevant on-load tap-changer, ARS or off-circuit tap-changer. The stated rated withstand voltages for the insulation arrangement apply to new, perfectly dried insulation in prepared transformer oil (at an ambient temperature of at least 10 °C). The following details are needed to select an on-load tap-changer, ARS or off-circuit tap-changer: ▪ Maximum mains-frequency operating voltages ▪ Test AC voltages during transformer test ▪ Impulse voltages during transformer test (lightning surge, switching surge, wave isolated in back and wave isolated in front) The transformer manufacturer is responsible for the correct choice of rated withstand voltages depending on insulation coordination at the operating site. The necessary rated withstand voltages should be observed for the var- ious insulation distances: ▪ Insulation to ground ▪ With multi-phase types: Insulation between phases ▪ Insulation between a phase's contacts The details required depend on the type of regulation (e.g. basic connection of tapped winding with on-load tap-changers) and the tap-changer type. 2.3 Leakage reactance with coarse tap selector connection Only the leakage reactance of one tap is active for most of the on-load tap- changer's switching operations. This has very little impact on how the on- load tap-changer works. 22 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties However if a switch is made from the end of the coarse winding to the end of the tapped winding (or vice versa), all windings of the coarse and tapped windings lie between the selected and preselected taps. Although from an electrical standpoint the on-load tap-changer only switches a maximum of one tap, this produces considerably more leakage reactance for the switch- ing circuit which acts as internal resistance of the step voltage. This in- creased leakage reactance causes a phase shift on the transition contacts of the on-load tap-changer between the breaking current and recovery voltage which may result in longer arc times. In applications with a coarse winding positioned right next to the tapped winding, the active leakage reactance can be established using the short-cir- cuit impedance of these two windings. Figure 8: Determining leakage reactance F Tapped winding G Coarse winding V Voltmeter W Wattmeter A Ammeter U Supply voltage One method of measurement in which the connection terminals can be reached via the diverter switch is shown in the following diagram. Figure 9: Leakage reactance with coarse tap selector connection Analytical formulas for calculating the leakage reactance between two wind- ings can also be used to calculate the leakage reactance between the coarse winding and tapped winding. For concentric winding arrangements, the accuracy of the calculated values is sufficient. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 23  2 Electrical properties For applications with coarse taps which are not directly adjacent to the tapped winding (e.g. multiple coarse taps), all windings and their couplings must be used for the switching circuit analysis. All the calculations required can be undertaken by Maschinenfabrik Reinhausen GmbH (MR). The wind- ing design and connection of all winding parts should be stated for this pur- pose. MR will provide the necessary form. 24 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties 2.4 Tapped winding potential connection 2.4.1 Recovery voltage and breaking current During its switching operation the tapped winding is briefly electrically iso- lated from the main winding by the reversing change-over selector or coarse change-over selector. It then adopts a potential resulting from the voltages of the adjacent windings and coupling capacities for these windings or earthed parts. This potential shift of the tapped winding produces corresponding voltages between the deactivating change-over selector contacts because one con- tact is always connected to the tapped winding and the other contact is al- ways connected to the main winding. This voltage is known as the recovery voltage UW. When separating the change-over selector contacts, a capacitive current has to be interrupted. This current depends on the aforementioned coupling ca- pacities of the tapped winding. This current is known as the breaking current IS. The recovery voltage UW and breaking current IS may result in impermissible signs of discharge on the change-over selector. The permissible range of re- covery voltage UW and breaking current IS for the different on-load tap- changer types can be seen in the following diagrams. Without tie-in resistor (R, VRD and VRF with tap selector size C/D): Figure 10: Approximate values for Uw and Is without tie-in resistor RP UW Recovery voltage IS Breaking current Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 25  2 Electrical properties Without tie-in resistor (R and VRG with tap selector size E): Figure 11: Approximate values for Uw and Is without tie-in resistor RP If the calculations produce pairs of values for UW and IS which are outside the permissible range, the tapped winding must be connected during the switch- ing process with a tie-in resistor. Possible tie-in measures are shown in the following diagram. In connection a, the tapped winding is connected with an ohmic resistor RP (tie-in resistor). In connection b, this tie-in resistor is only activated during the change-over selector's switching phase through the use of an additional po- tential switch SP. The design solutions for these tie-in measures differ depending on on-load tap-changer type. For more details, please refer to the technical data for the relevant on-load tap-changer. Figure 12: Potential connections (reversing change-over selector in mid-position) a With tie-in resistor RP b With potential switch SP and tie-in resistor RP The potential connection of the tapped winding with a tie-in resistor reduces the recovery voltage UW at the change-over selector contacts, but the break- ing current IS is increased by the additional current through the tie-in resistor. 26 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties With tie-in resistor (R, VRD and VRF with tap selector size C/D): Figure 13: Approximate values for Uw and Is with tie-in resistor RP UW Recovery voltage IS Breaking current With tie-in resistor (R and VRG with tap selector size E): Figure 14: Approximate values for Uw and Is with tie-in resistor RP The diagrams show the ranges of recovery voltage UW and breaking current IS for the different on-load tap-changer types which can be used with tie-in resistors without having to contact Maschinenfabrik Reinhausen GmbH (MR). This applies to cases where the breaking current IS is determined mainly by the tie-in resistor. If the stated ranges are exceeded, the opinion of MR is needed. Reducing the recovery voltage UW by means of a tie-in resistor increases the breaking current IS. For this reason, for winding arrangements with an unfa- vorable capacitive coupling there is not always a solution with a permissible change-over selector capacity. In these cases, either a change-over selector with a higher permissible breaking current IS has to be used or the winding arrangement has to be changed. The change-over selector capacity must therefore be checked in Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 27  2 Electrical properties good time, especially for transformers with high ratings (i.e. large coupling capacities) and high operating voltages (i.e. large potential shift of tapped winding during change-over selector connection). MR can calculate the recovery voltage UW and breaking current Is and con- figure any tie-in resistors needed. The following details are required: ▪ Winding arrangement, i.e. local position of tapped winding in relation to adjacent windings ▪ Capacity of tapped winding in relation to adjacent windings or capacity of tapped winding to earth or adjacent earthed windings ▪ AC voltage under operating conditions across windings or positions of windings adjacent to the tapped winding The following details are also needed to size the tie-in equipment: ▪ Loads expected from lightning impulse voltage across the half tapped winding ▪ Operating and test AC voltage across the half tapped winding (generally apparent from the standard order details for the on-load tap-changer). 2.4.2 Snap-action contact The snap-action contact is a concept for reducing the amount of gas pro- duced during a change-over selector connection. The snap-action contact is used with tap selector size E when particular limit values are exceeded. High loads on the change-over selector, caused by large breaking currents and large recovery voltages (typically e.g. in HVDC applications), result in the formation of more gas. Maschinenfabrik Reinhausen GmbH (MR) will calculate the volume of gas in such cases. The snap-action contact can always be selected as an option. Use of the snap-action contact is recommended when average gas volumes of 7 ml and more are being created per change-over selector connection. The vol- ume of gas can thereby be reduced by around 90%. 28 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties 2.4.3 Sample potential connection calculation Below is an example for the approximate calculation of recovery voltage on the change-over selector. ▪ On-load tap-changer combination: – VM I 301 / VM II 302 - 170 / B - 10 19 3W ▪ Transformer data: – Rated power 13 MVA – High voltage winding 132 kV ± 10 % – Delta connection, 50 Hz – Tapped winding in reversing change-over selector connection – Double concentric structure of high voltage winding with internal main winding (disk-type coils) and external tapped winding – Winding capacities C1 = 1810 pF (between main winding and tapped winding) C2 = 950 pF (between tapped winding and earth) Figure 15: High voltage winding connection U1 High voltage winding voltage UF Tapped winding voltage C1 Winding capacity between main winding and tapped winding C2 Winding capacity between tapped winding and earth Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 29  2 Electrical properties Assuming that the winding capacities C1 and C2 are both active in the wind- ing center, the following is true for the recovery voltages UW+ and UW–: and the voltage across C1 and therefore as a vector variable and amount 30 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties Figure 16: Winding arrangement with associated winding capacities 1 Transformer core 2 Transformer tank C1 Winding capacity between main winding and tapped winding C2 Winding capacity between tapped winding and earth Figure 17: Diagram for calculating the recovery voltages at change-over selector contacts (+) and (-) U1 High voltage winding voltage UF Tapped winding voltage UW+ Recovery voltage on change-over selector contact (+) UW- Recovery voltage on change-over selector contact (-) UC1 Voltage drop at winding capacity C1 UC2 Voltage drop at winding capacity C2 Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 31  2 Electrical properties When C1 = 1810 pF, C2 = 950 pF, U1 = 132 kV, UF = 13.2 kV, the following values are calculated for the recovery voltages UW+ and UW–: The breaking currents IS+ and IS- are: The figures stated above result in: IS+ = 63.97 mA IS– = 52.75 mA A tie-in resistor is needed because of the high values for UW. Fitting a tie-in resistor RP = 235 kΩ results in: UW+ = 17.11 kV UW– = 12.47 kV IS+ = 74.29 mA IS– = 54.15 mA 32 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties 2.5 Overload 2.5.1 Through-currents greater than the rated through-current MR on-load tap-changers and off-circuit tap-changers are suitable for all loadings of the transformer in accordance with IEC 60076-7:2005 "Loading guide for oil-immersed power transformers". IEC 60076-7 distinguishes between three types of operation: ▪ Normal cyclic loading ▪ Long-time emergency loading ▪ Short-time emergency loading The suitability of on-load tap-changers and off-circuit tap-changers for the above types of power transformer operation is proven by type testing in ac- cordance with IEC 60214-1:2003. MR on-load tap-changers and off-circuit tap-changers are also suited to all transformer loads in accordance with IEEE Std C57.91™-2011 "IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage-Regula- tors" with the following exception: Overload requirement greater than 200%. Overload requirementsgreater than 200% may arise, e.g. for the "Short time emergency loading" type of operation with distributor transformers and must be stated in the query. IEEE C57.91 distinguishes between four types of operation: ▪ Normal life expectancy loading ▪ Planned loading beyond nameplate rating ▪ Long-time emergency loading ▪ Short-time emergency loading When operating with "normal cyclic loading" or "normal life expectancy load- ing", through-currents greater than the rated through-current may arise dur- ing a daily load cycle. If the operating conditions stated in IEC 60076-7 and IEEE C57.91 (duration and level of power during one daily cycle, transformer oil temperature etc.) are observed, this is not considered extraordinary load- ing but normal operation. Therefore, for the types of operation stated, partic- ular consideration does not have to be given to the possible brief instances of through-currents greater than the rated through-current when selecting the on-load tap-changer. 2.5.2 Operation under varying operating conditions If a transformer is operated under varying operating conditions with varying power levels (e.g. increased transformer power due to type of cooling or am- bient temperature), note the following: The rated through-current required for an on-load tap-changer must be based on the maximum transformer power as the rated power; see also IEC 60076-1:2011. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 33  2 Electrical properties This is necessary because, due to increased power, the transformer's oil temperature is not reduced despite increased transformer cooling and there- fore, contrary to the transformer, the external operating conditions of the on- load tap-changer are not improved. It is also necessary because the transition resistors of the on-load tap- changers are designed on the basis of the maximum through-current in or- der to limit the switching capacity loading on the on-load tap-changer con- tacts to permissible values. 2.5.3 Details needed for queries relating to overload conditions When making queries relating to overload conditions, a definition with refer- ence to the above types of operation is needed to avoid misunderstanding. The operating conditions must be described clearly. In the event of types of operation which cannot be defined by reference to IEC 60076-7:2005 or IEEE Std C57.91™-2011, the following details are needed: ▪ Through-currents and associated loading duration during one daily cycle ▪ Oil temperature of the transformer during one daily cycle ▪ Expected number of tap-change operations during loading phases of one daily cycle (for on-load tap-changer only) ▪ Duration of overload operation in days/weeks/months ▪ Frequency of overload operation, e.g. "once a year" or "rarely, only if other transformers fail". 34 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 2 Electrical properties 2.6 On-load tap-changer and off-circuit tap-changer loading from short-circuits The permissible loading from short-circuits is given by: ▪ Rated short-time current as effective value of permissible short-circuit cur- rent ▪ Rated peak withstand current as highest permissible peak value of short- circuit current ▪ Rated duration of short-circuits as permissible short-circuit duration when loaded with rated short-time current All MR on-load tap-changers and off-circuit tap-changers at least satisfy the requirements of IEC 60214-1:2003 in terms of short-circuit strength. The per- missible short-circuit duration when loaded with short-time currents lower than the rated short-time current or the permissible short-time current for du- rations longer than the rated duration of short-circuits can be calculated us- ing the following equation: Ix2 · tx = IK2 · tK IK Rated short-time current tK Rated duration of short-circuits Ix Permissible short-time current during short-circuit duration tx (where tx is al- ways greater than tk) tx Permissible short-circuit duration during loading with Ix (where Ix is always less than Ik) Given that the dynamic loading is determined solely by the peak current, a peak current greater than the rated peak withstand current is not permitted. The rated values cannot therefore be converted to higher peak currents and short-time currents over a shorter short-circuit duration! Short-circuit loads normally only occur very rarely when operating a trans- former. This must be taken into account for applications with very frequent short-circuit loads - e.g. special test transformers - by selecting an on-load tap-changer with increased resistance to short-circuits. Details about the level and frequency of short-circuit loads expected are needed for this pur- pose. 2.7 Enforced current splitting With single-phase on-load tap-changers and off-circuit tap-changers for large rated through-currents, current paths are switched in parallel. A distinc- tion is made here between applications with and without "enforced current splitting". Applications with and without "enforced current splitting" with the same rated through-current require different on-load tap-changer and off-cir- cuit tap-changer models. Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 35  2 Electrical properties Parallel contacts must not be bridged in arrangements with enforced current splitting. The voltage between parallel tapped windings must be noted when loaded with impulse voltage. The transformer manufacturer must state the resistance to impulse voltage required between the parallel tapped windings. The significance of "enforced current splitting" is different for on-load tap- changers and off-circuit tap-changers: On-load tap-changers: During diverter switch operation, equal current splitting on the parallel con- tacts must be ensured. This requires a split tapped winding and a split main winding in every case. The leakage impedance between the parallel main windings must be at least three times the transition resistance of the on-load tap-changer. Maschinenfabrik Reinhausen GmbH (MR) must be contacted to discuss such applications. A sketch of the complete winding arrangement with all parallel winding parts is required for this purpose. Off-circuit tap-changers: The tapped winding must be fully split. Several windings of the main winding connecting to the tapped winding must also be split. 2.8 Permissible overexcitation MR on-load tap-changers satisfy the requirements of IEC 60076-1:2011 (5 % overexcitation) and IEEE Std C57.12.00™-2010 (10 % overexcitation). 2.9 Multi-column on-load tap-changers Multi-column on-load tap-changers (e.g. 3 x VRC I) do not switch in synch, regardless of whether they are operated by one or more motor-drive units. A tap offset may result in impermissibly high circulating currents which are only limited by the impedance of this current circuit. Superimposing these cir- culating currents with the load current impacts on the load of the on-load tap- changer which performs the last tap change. In all applications in which circulating currents may arise due to asynchro- nous operation of multi-column on-load tap-changers, the transformer manu- facturer must state the maximum circulating current. Maschinenfabrik Rein- hausen GmbH (MR) can therefore take into account the increased switching capacity when selecting the on-load tap-changer and configuring the transi- tion resistors (see also IEC 60214-2, Section 6.2.8). 36 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 3 Insulating fluids 3 Insulating fluids ▪ Unused insulating oils derived from petroleum products1) in accordance with IEC60296 and ASTM D3487 (equivalent standards on request) ▪ Unused insulating oils derived from other virgin hydrocarbons in accor- dance with IEC60296, or blends of these oils with petroleum products1) in accordance with IEC60296, ASTM D3487 or equivalent standards on re- quest ▪ Alternative insulating fluids, such as natural and synthetic esters or sili- cone oils, on request. 1) Gas-to-liquid oils (GTL oils) are understood in this context as petroleum products Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 37  4 Mechanical and design properties 4 Mechanical and design properties This chapter contains general information about the mechanical and design properties of on-load tap-changers, off-circuit tap-changers and Advanced Retard Switches (ARS). More information about special applications can be found in the Applications [►Section 6, Page 53] chapter. 4.1 Temperatures Please contact Maschinenfabrik Reinhausen GmbH (MR) for temperatures outside the stated ranges or in the event of deviations from the stated oper- ating conditions. You will find the permitted temperatures for drying in the product-specific as- sembly instructions or operating instructions. 4.1.1 Permissible temperature range for operation With oil-insulated products, the temperature details relate to use of mineral oil in accordance with IEC 60296. Customers are asked to specify the ambient temperature of the transformer, i.e. the air temperature, in the order details. All MR products are available for use at an ambient air temperature of - 25 °C to + 50 °C. - 25 °C is also the lower oil temperature limit for applications with oil trans- formers. The upper limit value for the oil temperature is determined by the defined operating conditions in IEC 60214-1. The following MR products can be used up to a maximum transformer oil temperature of 115 °C even if the transformer is temporarily overloaded: Product Tmin(oil) Tmax(oil) VACUTAP® VV®, VM®, VR® - 25 °C 115 °C OILTAP® G, M, MS, R, RM, V - 25 °C 115 °C DEETAP® DU, COMTAP® ARS - 25 °C 115 °C Table 8: Permissible operating temperature range The VACUTAP® VT® on-load tap-changer, which is used for dry-type trans- formers, can be operated up to a maximum ambient air temperature of 65 °C. The ambient air temperature is crucial for products not installed in the trans- former: Product Tmin(air) Tmax(air) TAPMOTION® ED motor-drive unit - 25 °C 50 °C Manual drive TAPMOTION® DD - 45 °C 70 °C Drive shaft - 25 °C 80 °C 38 General Section 1800061/04 EN Maschinenfabrik Reinhausen GmbH 2021 4 Mechanical and design properties Product Tmin(air) Tmax(air) Protective relay RS2001 - 25 °C 50 °C OF100 oil filter unit, standard model 0 °C 80 °C OF 100 oil filter unit - 25 °C 80 °C Table 9: Permissible operating temperature range For special models (e.g. EX protection variants), please contact Maschinen- fabrik Reinhausen GmbH (MR). 4.1.2 Permissible temperature range for storage and transport A lower ambient temperature limit of - 40 °C applies to the transport and storage of all products with the following exceptions: Product Lower limit value VACUTAP® VT® Minimum - 25 °C TAPMOTION® ED motor-drive unit Minimum - 25 °C with electronic components DEETAP® DU Minimum - 45 °C Manual drive TAPMOTION® DD Minimum - 45 °C Table 10: Exceptions for storage temperature limit The maximum air ambient temperatures stated for operation apply for the upper limit value. Exception: The upper storage and transport limit value for the TAPMOTION® ED motor-drive unit is 70 °C. 4.1.3 Arctic operation Use at temperatures below - 25 °C is known as Arctic operation. A corre- sponding special model is available for the following on-load tap-changers: Product Tmin(oil) Restrictions VACUTAP® VV® - 40 °C ▪ Only permitted with normal mo- VACUTAP® VM® tor runtime VACUTAP® VR® ▪ Only permitted when using LU- MINOLTM TR/TRi mineral oil for transformers and on-load tap- changers OILTAP® M, MS - 40 °C ▪ Only permitted with normal mo- OILTAP® R, RM tor runtime OILTAP® V - 40 °C ▪ At less than - 25 °C only rigid operation is permitted (no switching operations) Table 11: Arctic model on-load tap-changer Maschinenfabrik Reinhausen GmbH 2021 1800061/04 EN General Section 39  4 Mechanical and design properties At ambient temperatures of less than - 25 °C, a thermostat is provided to in- crease operating reliability. The thermostat comprises a thermo-sensor and measuring amplifier. The thermo-sensor is fitted in the on-load tap-changer head cover and records the temperature of the on-load tap-changer oil. In the control circuit, the measuring amplifier ensures that the motor-drive unit is blocked for electrical operation when the thermostat is activated. In addition to on-load tap-changers, you can also receive the following prod- ucts which are suited to Arctic operation (sometimes under particular condi-