Service Manual Type MFAC High Impedance Differential Relays
Contents
1. 4 Place the module on an antistatic surface or on a conducting surface which is at the same potential as yourself 5 Store or transport the module in a conductive bag More information on safe working procedures for all electronic equipment can be found in BS5783 and IEC 60147 0F If you are making measurements on the internal electronic circuitry of an equipment in service it is preferable that you are earthed to the case with a conductive wrist strap Wrist straps should have a resistance to ground between 500k 10M ohms If a wrist strap is not available you should maintain regular contact with the case to prevent the build up of static Instrumentation which may be used for making measurements should be earthed to the case whenever possible ALSTOM T amp D Protection amp Control Ltd strongly recommends that detailed investigations on the electronic circuitry or modification work should be carried out in a Special Handling Area such as described in BS5783 or IEC 60147 0F ALSTOM TYPES MFAC 14 MFAC 34 CONTENTS SAFETY SECTION INSTALLATION General Unpacking Storage Site COMMISSIONING Description of relay calculation of setting and commissioning preliminaries Instructions to ensure that the relay can be commissioned at the specific settings for the application MAINTENANCE MECHANICAL SETTINGS General Contact settings Mechanical flag settings PROBLEM ANALYSIS Failure to operate Output con2. live side of the test block coloured orange and with terminals allocated with odd numbers 1 3 5 7 etc Earthing Ensure that the case earthing connection above the rear terminal block is used to connect the relay to a local earth bar Insulation The relay and its associated wiring may be insulation tested between a all electrically isolated circuits b all circuits and earth An electronic or brushless insulation tester should be used having a dc voltage not exceeding 1000V Accessible terminals of the same circuit should first be strapped together Deliberate circuit earthing links removed for the tests must subsequently be replaced Terminal allocation Terminals of the relay are normally allocated as below but reference should always be made to the relevant diagram a Single pole relays Normally open contacts 1 3 and 2 4 AC current input 27 28 An alternative version of the relay has additional normally open contacts connected to 5 7 and 6 8 b Triple pole relays Normally open contacts 1 3 and 2 4 The contacts are normally connected in parallel for the three phases but a version of the relay having contacts brought out separately is available AC current inputs 23 24 25 26 27 28 Instructions to ensure that the relay can be commissioned at the specific settings for the application It is only necessary to check the relay at the setting on which it is to be used The rel
3. The action of the de humidifier crystals will be impaired if the bag has been exposed to damp ambient conditions and may be restored by gently heating the bag for about an hour prior to replacing it in the carton Dust which collects on a carton may on subsequent unpacking find its way into the relay in damp conditions the carton and packing may become impregnated with moisture and the de humidifying agent will lose its efficiency The storage temperature range is 25 and 70 C Site The installation should be clean dry and reasonably free from dust and excessive vibration The site should preferably be well illuminated to facilitate inspection An outline diagram is normally supplied showing panel cutouts and hole centres For individually mounted relays these dimensions will also be found in Publication R6008 Publication R7012 is a Parts Catalogue and Assembly Instructions This document will be useful when individual relays are to be assembled as a composite rack or panel mounted assembly Publication R6001 is a leaflet on the modular integrated drawout system of protective relays Publication R6014 is a list of recommended suppliers for the pre insulated connectors Section 2 COMMISSIONING 2 1 2 1 1 2 1 2 2 1 3 Description of relay calculation of setting and commissioning preliminaries Description of MFAC 14 MFAC 34 This is a voltage operated relay having seven equally spaced settings of 15 185 volts 25
4. be VK 2 2VR The operating current of the relay is 38mA irrespective of tap selected excluding the current drawn by the external metrosil When a standard metrosil is included with the relay the relay operating current including the metrosil is given in the table below It must be appreciated that metrosils have large tolerances and these figures are given for guidance only a Low range relay 5V steps Setting voltage VR 15 50 75 100 125 150 175 185 Relay current I g mA 48 38 39 42 46 55 72 B1 including metrosil C 450 b Low range relay Setting voltage VR 29 50 75 100 125 150 175 Relay current I g mA 19 19 20 23 27 36 53 including metrosil C 450 c High range relay Setting voltage Vn 29 75 125 175 225 275 325 Relay current I g mA 19 19 20 22 24 31 44 including metrosil C 900 d 100 400V version Setting voltage VR 100 150 200 250 300 350 400 Setting voltage Ir mA 19 19 20 20 23 27 36 including metrosil C 1100 The primary current for operation is given by Ip N In nlg If the resultant value of Ip is too low it may be increased by the addition of a shunt resistor RsH to give a current of Is Vi RsH The new increased value of primary current Ip N Ig nle Ish External metrosils Each FAC relay is applied with an external metrosil which must be wired across the relay circuit This provides a shunt circuit for high internal fault currents and prevents a high voltage being developed across the CT and re
5. commissioning or servicing the equipment Terminals exposed during installation commissioning and maintenance may present a hazardous voltage unless the equipment is electrically isolated If there is unlocked access to the rear of the equipment care should be taken by all personnel to avoid electric shock or energy hazards Voltage and current connections should be made using insulated crimp terminations to ensure that terminal block insulation requirements are maintained for safety To ensure that wires are correctly terminated the correct crimp terminal and tool for the wire size should be used 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 Before energising the equipment the following should be checked Voltage rating and polarity CT circuit rating and integrity of connections Protective fuse rating Integrity of earth connection where applicable Equipment operating conditions The equipment should be operated within the specified electrical and environmental limits Current transformer circuits Do not open the secondary circuit of a live CT since the high voltage produced may be
6. injection 15 B C Temporary connections Metrosil Relay Stabilising resistor if fitted Figure 3 Stability check of restricted earth fault protection A ly B supply G Stabilising resistor if fitted Figure 4 Stability check on restricted earth fault scheme by back energising with a low voltage supply 16 Temporary short circuit Isolating Generator links CY lt S gt AN 87 Generator differential relay V Voltmeter Figure 5 Testing sensitivity of generator differential protection using generator to supply primary current Isolating Temporary short circuit links Generator O A O B 0 C 87 Generator differential relay A2 Ammeter Figure 6 Checking stability of generator differential protection 17 Section 3 MAINTENANCE 3 1 Periodic maintenance is not necessary However periodic inspection and test is recommended This should be carried out every I2 months or more often if the relay is operated frequently or is mounted in poor environmental conditions Repeat secondary injection tests 2 2 4 to prove operation with emphasis on contact wear and condition Mechanical settings may be checked against those shown in Section 4 Section 4 MECHANICAL SETTINGS 4 1 4 1 1 4 1 2 4 2 4 2 1 4 3 4 3 1 General Armature gap measurements should be made with the top of the feeler gaug
7. lethal to personnel and could damage insulation External resistors Where external resistors are fitted to relays these may present a risk of electric shock or burns if touched Battery replacement Where internal batteries are fitted they should be replaced with the recommended type and be installed with the correct polarity to avoid possible damage to the equipment Insulation and dielectric strength testing Insulation testing may leave capacitors charged up to a hazardous voltage At the N end of each part of the test the voltage should be gradually reduced to zero to discharge capacitors before the test leads are disconnected Insertion of modules and pcb cards N These must not be inserted into or withdrawn from equipment whilst it is energised since this may result in damage Fibre optic communication Where fibre optic communication devices are fitted these should not be viewed directly Optical power meters should be used to determine the operation or signal level of the device gt gt gt gt pp 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
8. 175 volts 25 375 volts or 100 400 volts which may be selected by means of a plug bridge The relays may be used for any type of high impedance circulating current protection List of abbreviations lE Current transformer exciting current at relay setting voltage referred to the CT secondary current IF Maximum value of primary through fault current for which protection must remain stable IFM Maximum value of primary fault current for internal fault Ip Primary current for operation of protection IR Relay operating current IsH Current in shunt resistor at relay setting Vr N Turns ratio of current transformer n o of current transformers in parallel with relay Rct Secondary resistance of current transformer RL Lead resistance between furthest current transformer and relay connection point RR Relay impedance RsH Value of shunt resistor Vr The theoretical voltage which would be produced across the relay circuit under internal fault condition Vr FM RcT 2RI RR N Vk Knee point voltage of current transformer VP Peak voltage across relay circuit under maximum internal fault conditions Vs Minimum setting voltage calculated VR Relay setting voltage Calculation of relay setting The minimum setting voltage to ensure stability is Vs 2 IF Ret 2R N The relay plug setting voltage Vr must be set to the nearest tap above Vs 10 The minimum knee point voltage must
9. Service Manual Type MFAC High Impedance Differential Relays ALSTOM Service Manual Type MFAC High Impedance Differential Relays HANDLING OF ELECTRONIC EQUIPMENT A person s normal movements can easily generate electrostatic potentials of several thousand volts Discharge of these voltages into semiconductor devices when handling electronic circuits can cause serious damage which often may not be immediately apparent but the reliability of the circuit will have been reduced The electronic circuits of ALSTOM T amp D Protection amp 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 Each module incorporates the highest practicable protection for its semiconductor devices However if it becomes necessary to withdraw a module the following precautions should be taken to preserve the high reliability and long life for which the equipment has been designed and manvfactured 1 Before removing a module ensure that you are at the same electrostatic potential as the equipment by touching the case 2 Handle the module by its front plate frame or edges of the printed circuit board Avoid touching the electronic components printed circuit track or connectors 3 Do not pass the module to any person without first ensuring that you are both at the same electrostatic potential Shaking hands achieves equipotential
10. ay CT shorting switches With the relay removed from its case check electrically that the CT shorting switch is closed Secondary injection testing Connect the circuit as shown in Figure 1 and ensure that the current transformer primary is open circuit and that if any earthing connections are fitted they do not short out the primaries of any current transformers Increase the voltage until the relay just operates Note the current in the relay this can be done using the miniature split plug inserted into the appropriate position of the plug bridge connected to an ammeter It should be approximately 38mA at setting Note also the voltage at which the relay operates which should correspond to the setting VR of the relay with a tolerance of 10 The total secondary current for operation will be given on ammeter Al This test should be repeated for each pole of the relay Drop off Pick up ratio Check that this ratio is greater than 50 13 2 2 5 2 2 6 2 2 7 Primary injection testing It is essential that primary injection testing is carried out to prove the correct polarity of current transformers Before commencing any primary injection testing it is essential to ensure that the circuit is dead isolated from the remainder of the system and that only those earth connections associated with the primary test equipment are in position Primary fault setting The primary fault setting of any balanced scheme can be checke
11. ay must not be used at any setting other than that for which the setting has been calculated 12 2 2 1 2 2 2 2 2 3 2 2 4 Test equipment required 1 Secondary injection test equipment capable of providing an ac voltage supply of up to at least 120 of the relay setting 1 Multifinger test plug type MMLB O1 for use with test block type MMLG if fitted 1 Miniature split plug type MMLB 03 to fit relay plug bridge 3 Calibrated multimeters 0 10 amp ac 0 400 volt ac 1 Set primary injection testing equipment General 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 DANGER DO NOT OPEN CIRCUIT THE SECONDARY CIRCUIT OF A CURRENT TRANSFORMER SINCE THE HIGH VOLTAGE PRODUCED MAY BE LETHAL AND COULD DAMAGE INSULATION When type MMLG test block facilities are installed it is important that the sockets in the type MMLB O1 test plug which correspond to the current transformer secondary windings are LINKED BEFORE THE TEST PLUG IS INSERTED INTO THE TEST BLOCK Similarly a MMLB 02 single finger test plug must be terminated with an ammeter BEFORE IT IS INSERTED to monitor CT secondary currents It is assumed that the initial preliminary checks have been carried out Rel
12. current transformer ratio indicates that one of the current transformers is reversed Injection should be carried out through each phase to netural Where primary injection is not practicable in the case of restricted earth fault protection on a transformer it may be possible to check stability by means of back energising the transformer from a low voltage 415V supply as shown in Figure 4 In the case of machine protection similar stability tests must be carried out by injecting into one and out of another current transformer connected on the same phase For large machines the machine itself can be used to provide the fault current but the short circuit must now be fitted as shown in Figure 6 The machine should be run up to normal speed and the excitation increased until the primary current is approximately full load when the spill current should be checked All other types of balanced protection should be tested in a similar manner At the conclusion of the tests ensure that all connections are correctly restored and any shorting connections removed l4 Metrosil 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 Stabilising resistor if fitted Ammeter in plug bridge circuit Figure 2 Sensitivity check of restricted earth fault scheme by primary
13. d using the circuit shown in Figure 2 The primary current is injected into each current transformer in turn and increased until the relay operates The voltage at which the relay operates should be within 10 of the relay setting voltage Vr The primary current for operation and relay current should be noted In the case of machine protection similar tests must be carried out by injecting first into each current transformer in turn to determine the primary fault setting 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 The primary current relay current and relay voltage should be noted as each relay operates Through fault stability With any form of unbalanced protection it is necessary to check that the current transformers are correctly connected For this purpose with a restricted earth fault scheme the circuit shown in Figure 3 may be used During this test it is necessary to measure the spill current in the relay circuit and short out the relay and stabilising resistor if fitted The current is increased up to as near full load as possible and the spill current noted The spill current should be very low only a few milliamps if the connections are correct A high reading twice the injected current referred through the
14. e 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 The relay contact state is always defined with the relay in the unenergised position unless otherwise specified on the appropriate circuit diagram With the armature closed the clearance between the back of the armature and the back stop should be 0 003 0 008 Nominal armature gap open 0 060 for all types Set screw in armature so that armature gap when closed is approximately 0 005 0 010 Contact settings Normal duty make contacts With the armature closed onto a 0 011 feeler gauge the make contacts should be closed but should be open using a 0 013 feeler gauge Contact settings 2 contacts 4 contacts MFAC 34 MFAC 14 Force to just close the make 20 25 grams 15 20 grams contacts Force to just lift the fixed contact 15 20 grams 20 25 grams off its support Nominal contact gap 0 060 0 080 Mechanical flag settings Settings for self reset units MFAC 14 34 With the armature closed on to a 0 013 feeler gauge the flag should be free to fall but should not fall using an 0 018 feeler gauge Adjustment is made to the catch spring on the flag 18 Section 5 PROBLEM ANALYSIS 5 1 5 2 Failure to operate Check diagram for correct inp
15. issioning Engineer Customer Witness Date Date 22 REPAIR FORM Please complete this form and return it to ALSTOM T amp D Protection amp Control Ltd with the equipment to be repaired This form may also be used in the case of application queries ALSTOM T amp D Protection amp Control Ltd St Leonards Works Stafford ST17 ALX England For After Sales Service Department Customer Ref Model No Contract Ref Serial No Date 1 What parameters were in use at the time the fault occurred AC volts Main VT Test set DC volts Battery Power supply AC current Main CT Test set Frequency 2 Which type of test was being used 3 Were all the external components fitted where required Yes No Delete as appropriate 4 List the relay settings being used 5 What did you expect to happen continued overleaf 23 6 What did happen 7 When did the fault occur Instant Yes No Intermittent Yes No Time delayed Yes No Delete as appropriate By how long 8 What indications if any did the relay show 9 Was there any visual damage 10 Any other remarks which may be useful Signature Title Name in capitals Company name 24 25 26 27 ALSTOM ALSTOM T amp D Protection amp Control Ltd St Leonards Works Stafford ST17 ALX England Tel 44 0 1785 223251 Fax 44 0 1785 212232 Email enquiries pcs alstom co uk Internet www alstomgpc co uk 1998 ALSTOM T amp D Protection amp Contr
16. ither despatched individually or as part of a panel rack mounted assembly in cartons specifically designed to protect them from damage Relays should be examined immediately they are received to ensure that no damage has been sustained in transit If damage due to rough handling is evident a claim should be made immediately to the transport company concerned and the nearest ALSTOM T amp D Protection amp Control Ltd representative should be promptly notified Relays which are supplied unmounted and not intended for immediate installation should be returned to their protective polythene bags Unpacking Care must be taken when unpacking and installing the relays so that none of the parts are damaged or their settings altered and must at all times be handled by skilled persons only 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 Relays which have been removed from their cases should not be left in situations where they are exposed to dust or damp This particularly applies to installations which are being carried out at the same time as constructional work Storage IF relays are not installed immediately upon receipt they should be stored in a place free from dust and moisture in their original cartons and where de humidifier bags have been included in the packing they should be retained
17. lay circuits Commissioning preliminaries Inspection Carefully examine the module and case to see that no damage has occurred during transit Check that the relay serial number on the module case and cover are identical and that the model number and rating information are correct Carefully remove any elastic bands packing fitted for transportation purposes Carefully actuate the armature of each unit in turn with a small screwdriver probe Note that immediately after the point where any normally open contacts just make 11 2 2 there is a small further movement of the armature This ensures that contact follow through and wiping action is present On units fitted with hand reset flag indicators check the flag is free to fall before or just as any normally open contacts touch Check that the external wiring is correct to the relevant relay diagram or scheme diagram The relay diagram number appears inside the case Particular attention should be paid to the correct wiring and value of any external resistors indicated on the wiring diagram relay rating information 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
18. ng 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 Installation Category Overvoltage Environment Product safety ce IEC 61010 1 1990 A2 1995 Class EN 61010 1 1993 A2 Class 1995 IEC 61010 1 1990 42 1995 Category Ill EN 61010 1 1993 A2 1995 Category Ill IEC 61010 1 1990 42 Pollution degree 2 EN 61010 1 1993 A2 Pollution degree 2 1995 1995 73 23 EEC EN 61010 1 1993 A2 1995 EN 60950 1992 A11 1997 This equipment requires a protective safety earth connection to ensure user safety Distribution level fixed installation Equipment in this category is qualification tested at 5kV peak 1 2 50ys 5000 0 5J between all supply circuits and earth and also between independent circuits Compliance is demonstrated by reference to generic safety standards Compliance with the European Commission Low Voltage Directive Compliance is demonstrated by reference to generic safety standards Section 1 INSTALLATION 1 1 1 2 1 3 1 4 General Protective relays although generally of robust construction require careful treatment prior to installation and a wise selection of site By observing a few simple rules the possiblity of premature failure is eliminated and a high degree of performance can be expected The relays are e
19. of electric shock Draw out case relays Removal of the cover on equipment incorporating electromechanical operating elements may expose hazardous live parts such as relay contacts Insertion and withdrawal of extender cards When using an extender card this should not be inserted or withdrawn from the equipment whilst it is energised This is to avoid possible shock or damage hazards Hazardous live voltages may be accessible on the extender card Insertion and withdrawal of heavy current test plugs When using a heavy current test plug CT shorting links must be in place before insertion or removal to avoid potentially lethal voltages Decommissioning and Disposal Decommissioning The auxiliary supply circuit in the relay may include capacitors across the supply or to earth To avoid electric shock or energy hazards after completely isolating the supplies to the relay both poles of any dc supply the capacitors should be safely discharged via the external terminals prior to decommissioning Disposal It is recommended that incineration and disposal to water courses is avoided The product should be disposed of in a safe manner Any products containing batteries should have them removed before disposal taking precautions to avoid short circuits Particular regulations within the country of operation may apply to the disposal of lithium batteries Technical Specifications Protective fuse rating The recommended maximum rati
20. ol Ltd Our policy is one of continuous product development and the right is reserved to supply equipment which may vary from that described Publication R8007E Printed in England
21. omponent reference numbers or briefly describe the parts required Should the need arise for the equipment to be returned to ALSTOM T amp D Protection amp Control Ltd for repair then the form at the back of this manual should be completed and sent with the equipment together with a copy of any commissioning test results 20 Section 7 COMMISSIONING TEST RECORD High Impedance Differential Relay Type MFAC Date Station Circuit Relay Model No Serial No Setting range CT ratio Setting voltage Relay setting Type of ext metrosil Shunt resistor ohms if fitted Calculated primary operating current Test results 2 2 3 Relay CT shorting switch 2 2 4 Secondary voltage to operate relay Phase Total current Al Relay current A2 PU volts DO volts A B C Drop off pick up rotio check 2 2 6 Primory current to operate relay Phase Primary current A1 Relay current A2 Relay voltage A B 2 2 2 7 Stability check by primary injection Restricted earth fault Phases Primary current A1 Spill current A2 A N B N C N Circulating current between two or more sets of current transformers Phases Primary current A1 Spill current A2 A1 A2 B1 B2 C1 C2 Where more than two sets of current transformers are involved injection should be carried out between set and each other set in turn Comm
22. tacts not changing state SPARES COMMISSIONING TEST RECORD REPAIR FORM O O 00000 0 a la lll 22 i 090 000000 00 N NO N N W O 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 It is assumed that everyone who will be associated with the equipment will be familiar with the contents of the Safety Section Explanation of symbols and labels The meaning of symbols and labels which may be used on the equipment or in the product documentation is given below A Caution refer to product documentation Caution risk of electric shock e Protective safety earth terminal ei Functional earth terminal Note this symbol may also be used for a protective safety earth terminal if that terminal is part of a terminal block or sub assembly eg power supply Note The term earth used throughout the product documentation is the direct equivalent of the North American term ground Installing Commissioning and Servicing AN Equipment connections Personnel undertaking installation commissioning or servicing work on this equipment should be aware of the correct working procedures to ensure safety The product documentation should be consulted before installing
23. ut connections Check tap voltage this is marked above or below the plug bridge on the front of the module Note with the plug removed the relay setting goes to the highest tap value Measure the input current at Vs this should be 38mA excluding the metrosil Flag spring may be jammed between armature and core face preventing armature closure Check internal wiring for damage Check choke continuity resistance 240 ohms 1576 Check resistor values remove pcb from module and fold down to gain access to board Setting range 15 185 Adjustable resistor Capacitor Relay coil Setting range 25 175 25 327 Adjustable resistor RV 1 Capacitor Relay coil Setting range 100 400 Resistors on PCB ZJ0038 RI R3 R5 R6 R7 R8 R9 6800 6800 1500 1200 0 100090 3 3uF 1900 Resistors on PCB ZJ0038 R1 R 1 3KQ 2 4KQ 51090 C1 1 7uF 5 50Hz 1 18uF 5 60Hz 5600 15 Resistors on PCB ZJ0038 R1 R6 2 7KQ R9 3 9KQ Output contacts not changing state Check output terminals with reference to appropriate diagram Operating pushrods not in position Internal wiring damaged Contamination of contacts Contacts should be cleaned with the burnishing tool supplied in the relay tool kits On no account should knives files or abrasive materials be used Check mechanical settings as per Section 4 19 Section SPARES When ordering spares quote the full relay model number and any c
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