Alstom MBCH Service Manual
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Alstom MBCH Service Manual

Alstom MBCH Service Manual

Biased differential relay
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Type MBCH
Biased Differential Relay

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Summary of Contents for Alstom MBCH

  • Page 1 Service Manual Type MBCH Biased Differential Relay...
  • Page 3 The electronic circuits of ALSTOM T&D Protection & Control Ltd products are immune to the relevant levels of electrostatic discharge when housed in their cases. Do not expose them to the risk of damage by withdrawing modules unnecessarily.
  • Page 4 Figure 2 Connections for checking relay operating time Figure 3 Connections for checking the bias curve Figure 4 MBCH 12/13/16 bias curve Figure 5 Connections to the relay to simulate magnetizing inrush current waveform Figure 6 Mesh busbar arrangement requiring three bias inputs to the...
  • Page 5 Figure 12 Three winding transformer showing interposing CTs Figure 13 Block diagram: biased differential protection relay Type MBCH12 with two biased inputs Figure 14 Block diagram: biased differential protection relay Type MBCH13 with three biased inputs Figure 15 Block diagram: biased differential protection relay Type MBCH16 with six biased inputs Figure 16 Connection for six change-over tripping contacts for three phase...
  • Page 7 SAFETY SECTION This Safety Section should be read before commencing any work on the equipment. Health and safety The information in the Safety Section of the product documentation is intended to ensure that products are properly installed and handled in order to maintain them in a safe condition.
  • Page 8 Before energising the equipment it must be earthed using the protective earth terminal, or the appropriate termination of the supply plug in the case of plug connected equipment. Omitting or disconnecting the equipment earth may cause a safety hazard. The recommended minimum earth wire size is 2.5 mm , unless otherwise stated in the technical data section of the product documentation.
  • Page 9 Older Products Electrical adjustments Equipments which require direct physical adjustments to their operating mechanism to change current or voltage settings, should have the electrical power removed before making the change, to avoid any risk of electric shock. Mechanical adjustments The electrical power to the relay contacts should be removed before checking any mechanical settings, to avoid any risk of electric shock.
  • Page 10 Technical Specifications Protective fuse rating The recommended maximum rating of the external protective fuse for this equipment is 16A, Red Spot type or equivalent, unless otherwise stated in the technical data section of the product documentation. Insulation class: IEC 61010-1: 1990/A2: 1995 This equipment requires a Class I protective (safety) earth...
  • Page 11 The MBCH may also be regarded as an alternative to the high impedance relays for the protection of reactors, motors and generators. The relay is extremely stable during through faults and provides high speed operation on internal faults, even when energized via line current transformers of only moderate output.
  • Page 12 Unpacking Care must be taken when unpacking and installing the relays so that none of the parts are damaged or their settings altered, and relays must only be handled by skilled persons. Relays should be examined for any wedges, clamps, or rubber bands necessary to secure moving parts to prevent damage during transit and these should be removed after installation and before commissioning.
  • Page 13 3.1.2 Inspection Remove the polycarbonate front cover by undoing the two knurled plastic nuts with a small screwdriver. The module can now be withdrawn by the handles provided. Carefully examine the module and case to see that no damage has occurred during transit.
  • Page 14 2 multimeters Double pole switch Single pole switch MMLB01 test plug If MMLG Test Block is supplied MMLB02 single finger test plug 8A variable auto-transformer 2 Variable resistors 0 – 100 Ohms, suitably rated Diode rated 7A for magnetising inrush test, if required. Note: The following test instructions are based on injecting current directly into the relay terminals, however if a MMLG test block is incorporated in the scheme,...
  • Page 15 3.2.5.4 Reconnect the 2nd bias coil as shown in Figure 3 and adjust the current shown on ammeter A1 to be 1.7 x In for MBCH 12, 13, 16. (Note that for a 5A relay this current may exceed the continuous rating of the variable auto transformer and should therefore be switched on for short durations only).
  • Page 16 Check that the load current in each bias coil is close to the value which is expected for the particular application. For the MBCH 16 relay particularly, it may be preferable to energize the transformer in different ways to ensure that all connections are satisfactory.
  • Page 17 Section 4 APPLICATION NOTES General The type MBCH relay is a high speed biased differential relay suitable for the protection of two or three winding power transformers, autotransformers, or generator transformer units. Three versions of the relay are available as follows:...
  • Page 18 Ratio and phase matching interposing transformers Matching transformers are available for use in cases where the current transformers on one side of the protected transformer do not match, in current ratio or phase angle, with the current transformers on the other side of the protected transformer. The following versions of matching transformer are available: Description Reference No...
  • Page 19 Application of matching transformer Where the line current transformer ratios on the two sides of the protected transformer are mutually incompatible, the matching transformer may be used as in the following examples: 4.4.1 Single phase transformer 200/5 A 1000/5 A 195 A 780 A 4.875 A...
  • Page 20 The output current, per phase pilot, of the 300/1A current transformers is given by: 262.43 x 1 Is = = 0.875A This should be adjusted by the interposing transformer so that 0.984A flows into the relay. The windings S1–S2, and S3–S4 must be used in series as output windings giving (125 + 90) = 215 turns.
  • Page 21 interposing CT. Output windings S1–S2 and S3–S4 must be connected in series to give 43 turns, thus: Is/√ 3 Tp = x Ts 5 x 43 Primary turns (Tp) = = 26.86 say 27 turns. √3 x 4.62 Table 1 indicates that primary taps nos. 3–6 will give 27 turns. To 500kV line Relay...
  • Page 22 To 138kV line current transformer 13.45kV winding: Based on 400 MVA the corresponding current would be: 17170.2 x 5 400 x 10 In = = 17170.2A Is = = 17.17A √3 x 13.45 x 10 5000 In this case the transformer winding (13.45kV) is delta connected, and the associated line current transformers are star connected.
  • Page 23 Section 5 SETTINGS When protecting a power transformer, the differential setting should not be less than 20% of the relay rated current, to give stability for moderate transient overfluxing. The maximum spill current with through load current should generally be kept below 20% of relay rated current, allowing for CT mismatch and possible tap changer operation.
  • Page 24 Suspected faulty module Check that auxiliary dc supply voltage and polarity are correct Apply correct Correct dc voltage Check auxiliary dc current drain Conclusion: Correct Internal wiring faulty and/or pcb 1, 2 or 3 faulty. Isolate auxiliary dc voltage. Apply correct auxiliary Remove module from case.
  • Page 25 27 and 28. Conclusion: Monitor tripping contacts voltage faulty pcb 1, pcb 2 or correct transformers T1 or T2 tripping Conclusion: Conclusion: contacts faulty pcb1 close faulty pcb1 the relay Follow an MBCH 12 Flowchart 4 version Follow Flowchart 3 Flowchart 2...
  • Page 26 Link terminals 26 and 27. Inject In into terminals 25 and 28. Monitor TP4. Link terminals 24 and 27. voltage Inject In into terminals 23 correct and 28. Monitor R1. Conclusion: voltage Inject In into terminals 25 Faulty transformer T3. correct and 28.
  • Page 27 Inject In into terminals Faulty pcb1 correct ? 21 and 28. (note 3) Conclusion: voltage Faulty pcb1, pcb2 or the relay Conclusion: correct transformer T5 an MBCH Relay appears to be functioning correctly version Conclusion: Faulty pcb1 Follow Flowchart 5 Flowchart 4...
  • Page 28 Link terminals 2 and 27. Inject In into terminals 19 and 28. Monitor R1 voltage Inject In into correct ? terminals 19 and (note 3) Conclusion: voltage Link terminals Faulty pcb1, correct ? 18 and 27. pcb2 or (note 3) Inject In into terminals transformer T6 17 and 28...
  • Page 29 Relay trips when magnetizing inrush current flows into the power transformer Monitor R2 (note 4). Inject In into terminals 27 and 28 Conclusion: Voltage Faulty pcb1, pcb2, or correct transformers T1 or T2 Monitor TP2 (note 7). Inject 0.5In into terminals 27 and 28 Conclusion: Voltage...
  • Page 30 MBCH RELAY bias Overcurrent differential test set Figure 1 Connections for checking relay settings MBCH RELAY bias start Overcurrent differential timer test set stop timer Figure 2 Connections for checking relay operating time...
  • Page 31 6th bias 5th bias MBCH 16 ONLY 4th bias 3rd bias MBCH 13, 16 1st bias ONLY 2nd bias 0–100Ω Differential coil Variable supply Auto transformer 0–100Ω Figure 3 Connections for checking the bias curve...
  • Page 32 Is = 0.5 In 0.4 In 0.3 In 0.2 In 0.1 In Mean bias current (Amps x In) Figure 4 MBCH 12/13/16 bias curve...
  • Page 33 MBCH RELAY bias variable differential auto transformer 0–100Ω supply Figure 5 Connections to the relay to simulate magnetizing inrush current waveform...
  • Page 34 Bias inputs Operating Circuit Relay Type MBCH13 Figure 6 Mesh busbar arrangement requiring three bias inputs to the differential relay...
  • Page 35 Sole infeed Relay type MBCH Bias winding Operating Circuit Loads Figure 7 Three winding transformer – one power source...
  • Page 36 Relay Type Bias Windings MBCH 16 Operating circuit Figure 8 Switchgear arrangement where six bias inputs may be required...
  • Page 44 Phase ‘A’ All output contacts shown are instantaneously initiated for any internal fault condition when Phase ‘B’ terminals No. 10 on each phase unit are connected together as shown. Correct phase indication is maintained. Phase ‘C’ Figure 16 Connection for six change-over tripping contacts for three phase tripping of up to six circuit breakers...
  • Page 45 Section 6 COMMISSIONING TEST RECORD PROTECTION RELAY TYPE MBCH Date _________________________________ Station _______________________________ Transformer ___________________________ Biased Differential Transformer Serial No. _____________________________________________ Relay Model No _______________________ Relay Serial Nos. Phase A__________________ Phase B ___________ Phase C ___________ DC Auxiliary Voltage Vx ___________________ Relay Rated Current In 3.2.2...
  • Page 46 3.2.6 Check bias interconnection _____________________________________________ 3.2.7 If required check 3 phase tripping _______________________________________ 3.2.8 On load tests Load conditions Measured differential current __________ __________ __________ A 3.2.9 Magnetizing current inrush test _________________________________________ _________________________________ __________________________________ Commissioning Engineer Customer Witness _________________________________ __________________________________ Date Date...
  • Page 47 REPAIR FORM Please complete this form and return it to ALSTOM T&D Protection & Control Ltd with the equipment to be repaired. This form may also be used in the case of application queries. ALSTOM T&D Protection & Control Ltd St.
  • Page 48 What did happen? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ When did the fault occur? Instant Yes/No Intermittent Yes/No Time delayed Yes/No (Delete as appropriate). By how long? ___________ What indications if any did the relay show? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Was there any visual damage? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________...
  • Page 52 Fax: 44 (0) 1785 212232 Email: pcs.enquiries@tde.alstom.com Internet: www.alstom.com ©1999 ALSTOM T&D Protection & Control Ltd Our policy is one of continuous product development and the right is reserved to supply equipment which may vary from that described. Publication R8017G...

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Mbch12Mbch13Mbch16

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