Alstom MCAG 14 Service Manual
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Alstom MCAG 14 Service Manual

High stability circulating current relays
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Service Manual
Type MCAG 14, 34
High Stability Circulating Current Relays

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Summary of Contents for Alstom MCAG 14

  • Page 1 Service Manual Type MCAG 14, 34 High Stability Circulating Current Relays...
  • Page 3 The electronic circuits of ALSTOM T&D Protection & Control Ltd products are completely safe from electrostatic discharge when housed in the case. Do not expose them to the risk of damage by withdrawing modules unnecessarily.

  • Page 4: Table Of Contents

    TYPES: MCAG 14 MCAG 34 CONTENTS SAFETY SECTION INSTALLATION COMMISSIONING Description of relay Calculation of relay setting External Metrosils Commissioning preliminaries Commissioning tests MAINTENANCE MECHANICAL SETTINGS General Contact settings Mechanical flag settings PROBLEM ANALYSIS Failure to operate Excessive current taken by relay...

  • Page 5: Safety Section

    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 6 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 7 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 8 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 9: Installation

    If damage due to rough handling is evident, a claim should be made to the transport company concerned immediately and the nearest ALSTOM T&D Protection & Control representative should be promptly notified. Relays which are supplied unmounted and not intended for immediate installation should be returned to their protective polythene bags.

  • Page 10: Commissioning

    Section 2. COMMISSIONING Description of relay This is a current operated relay having seven equally spaced settings. The setting ranges are given below. 0.025 – 0.1A 0.05 – 0.2A – 0.4A – 0.8A 0.25 – 1.0A – 2.0A – 4.0A The relays may be used for any type of high impedance circulating current protection.

  • Page 11: Calculation Of Relay Setting

    Calculation of relay setting The minimum setting voltage to ensure stability is: ≥ + 2R The minimum knee point voltage (V ) of the CT must be: ≥ 2V The relay is current calibrated and has settings chosen from the range given in 2.1.1. It has a burden of approximately 1VA at setting.
  • Page 12 Note that shorting switches shown on the relay diagram are fitted internally across the relevant case terminals and close when the module is withdrawn. It is essential that such switches are fitted across all CT circuits. If a test block type MMLG is provided, the connections should be checked to the scheme diagram, particularly that the supply connections are to the ‘live’...

  • Page 13: Commissioning Tests

    Commissioning tests If the relay is wired through an MMLG test block it is recommended that all secondary injection tests should be carried out using this block. Ensure that the main system current transformers are shorted before isolating the relay from the current transformers in preparation for secondary injection tests.

  • Page 14: Maintenance

    For large machines, the machine itself can be used to provide the fault current to check the primary fault setting as shown in Figure 5. The machine should be run up to speed with no excitation. The excitation should then be increased until the relays have all operated.

  • Page 15: Mechanical Settings

    Section 4. MECHANICAL SETTINGS General Armature gap measurements should be made with the top of the feeler gauge level with the centre line of the core. Contact pressures are measured with a gramme gauge at the contact tips. In general, contact gaps and follow through are defined by quoting an armature gap at which the tips should be just closed or just open.

  • Page 16: Excessive Current Taken By Relay

    When ordering spares, quote the full relay model number and any component reference numbers, or briefly describe the parts required. Should the need arise for the equipment to be returned to ALSTOM T&D Protection & Control Ltd for repair, then the form at the back of this manual should be completed...
  • Page 17 Relay Metrosil (if fitted) Stabilising resistor (if fitted) Ammeter (in plug bridge circuit) Figure 1 Secondary injection of relay to check secondary operating current, setting voltage and relay operating current Primary injection test set Relay Stabilising resistor (if fitted) Ammeter (in plug bridge circuit) Figure 2 Sensitivity check of restricted earth fault scheme by primary injection...
  • Page 18 Primary injection test set Temporary connection Metrosil (if fitted) Relay Stabilising resistor (if fitted) Figure 3 Stability check of restricted earth fault protection supply Temporary short circuit Relay Stabilising resistor (if fitted) Figure 4 Stability check on restricted earth fault scheme by back energising with a low voltage supply...
  • Page 19 Temporary short circuit Isolating Generator links 87 Generator differential relay Voltmeter Figure 5 Testing sensitivity of generator differential protection using generator to supply primary current Temporary short circuit Isolating links Generator 87 Generator differential relay A2 Ammeter Figure 6 Checking stability of generator differential protection...

  • Page 21: Commissioning Test Record

    Section 7. COMMISSIONING TEST RECORD High Stability Circulating Current Relay Type MCAG 14, 34 Date _______________ Station ___________________ Circuit ___________________ Relay model no. ___________________ Serial no. ___________________ Setting range ___________________ CT ratio ___________________ Setting voltage ___________________ Relay setting ___________________ Stabilising resistor...
  • Page 22 2.5.5 Stability check by primary injection Restricted earth fault Phase Primary current A1 Spill current A2 A – N B – N C – N Circulating current between two or more sets of current transformers. Phase Primary current A1 Spill current A2 A1 –...

  • Page 23: Repair Form

    REPAIR FORM Please complete this form and return it to ALSTOM T&D Protection & Control Limited 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 24 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 28 Fax: 44 (0) 1785 212232 Email: enquiries@pcs.alstom.co.uk Internet: www.gecalsthomgpc.co.uk ©1998 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 R8008D...

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