MV12 SINGLE BUSBAR VACUUM SWITCHGEAR 12KV, 800/1250/2000/2500A, 25/31.5kA INSTALLATION, OPERATION AND MAINTENANCE INSTRUCTION MANUAL

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1 INSTALLATION, OPERATION AND MAINTENANCE INSTRUCTION MANUAL MED MV REV 11 MV12 SINGLE BUSBAR VACUUM SWITCHGEAR 12KV, 800/1250/2000/2500A, 25/31.5kA 1

2 SAFETY...3 GENERAL CONSTRUCTION...3 OPERATING CONDITIONS...4 STORAGE CONDITIONS INSTALLATION FOUNDATIONS AND UNIT ERECTION FOUNDATION CHANNELS FOUNDATION BOLTS (EXPANDING TYPE) BUSBAR ASSEMBLY MAIN CABLES UNIT EARTHING MULTICORE CABLES & INTER-UNIT WIRING (BUS-WIRING) INTERLOCKS INSERTING/REMOVING THE CIRCUIT BREAKER INSERTING THE CIRCUIT BREAKER REMOVING THE CIRCUIT BREAKER MECHANICAL AND ELECTRICAL INTERLOCKS PADLOCKING CIRCUIT BREAKER CONTROL MODULE STRUCTURE AND FUNCTION STRUCTURE OF THE OPERATING MECHANISM FUNCTION OF THE ELECTRONIC CONTROL MODULE FUNCTIONS OF THE READY LAMP STORAGE CAPACITOR SENSOR SYSTEM OPERATION PREPARATORY WORK CIRCUIT-BREAKER OPERATION CLOSING OPENING OPENING ON FAILURE OF THE AUXILIARY POWER SUPPLY CLOSING ON FAILURE OF THE AUXILIARY SUPPLY CLOSING IN CIRCUIT EARTH POSITION OPENING IN CIRCUIT EARTH POSITION SERVICE AND GENERAL MAINTENANCE INSPECTION AND FUNCTIONAL TESTING SWITCHING DEVICES IN GENERAL OPERATING MECHANISM MAGNETIC ACTUATOR OPERATING MECHANISM STORAGE CAPACITORS SERVICING REPAIR SPARES COMMISSIONING CHECKS AND TEST PROGRAMME GENERAL CHECKS ELECTRICAL TEST SECONDARY INSULATION ELECTRICAL CIRCUITS CHECKS MEGGER TEST HIGH VOLTAGE TEST ELECTRICAL TESTS PRIMARY INSULATION MEGGER TEST HIGH VOLTAGE TEST HIGH VOLTAGE TESTS INTERGRITY OF VACUUM INTERRUPTER MECHANICAL TESTING AND RECORDING RECORDING COMMISIONING CHECK LIST COMMISIONING CHECK LIST CONTINUED

3 SAFETY Notes on safety at work Before working on the Switchgear it is necessary for the operator to ensure that it has been safely disconnected from electrical supplies and that the necessary safety earths have been fitted and a suitable permit to work issued. In the event of there being doubt in this respect the operator shall seek the advice of his local supply authority to ensure that he has taken the necessary actions to comply with local safety requirements. The circuit breaker actuator supply capacitor is capable of storing a considerable amount of charge and, therefore, care must be taken not to short the supply before discharge of the capacitor. To assist in its safe operation the equipment is fitted with padlocking facilities which shall be applied as appropriate. Before commencing work and after the completion of work any control switches shall be left in the appropriate positions. When any insulation testing is to be performed, make sure that the test voltage does not exceed 2kV r.m.s. All connectors are to be removed for the duration of the test. See fig Varistors, which are required for the EMC strength of the breaker controller, may otherwise be damaged. Should the operator require any guidance or advice regarding the equipment this can be obtained by contacting Medelec Switchgear Ltd. Our policy is one of continuous product development and the right is reserved to supply equipment, which may vary slightly from that described. GENERAL CONSTRUCTION Type MV12 metalclad indoor single busbar air insulated vacuum Switchgear is for use on distribution networks having the highest system voltage up to 12kV, a short circuit current rating up to 31.5kA, a maximum full load current of 2500A and a lightning impulse level up to 75 kvp (BIL). Standard incomer and feeder units comprise two main parts: the fixed housing with run out plate, and the horizontally isolated circuit breaker. The housing is fabricated from sheet steel with separated compartments for the circuit breaker, busbars and current transformers/cable box. Where isolatable and HV fused voltage transformers are fitted, they are housed in a separate compartment and are operated from the rear. An instrument panel at the front of the housing above the circuit breaker compartment accommodates the relay, instruments, terminal blocks, fuses and links for the secondary circuits. The multicore cable glands and terminations are situated at the back. The primary connection spouts in the circuit breaker compartment are equipped with earthed metal safety shutters, which are controlled by arms mounted on the sides of the circuit breaker compartment and operated automatically by movement of the circuit breaker. With the circuit breaker withdrawn from the housing, each shutter can be independently padlocked closed. For testing purposes, each shutter can be propped open with a self cancelling reset device. 3

4 OPERATING CONDITIONS Ambient temperature. Maximum +40 ºC Minimum - 40 ºC For increased ambient temperature current carrying capacity must be reduced. Provide additional ventilation for heat dissipation. STORAGE CONDITIONS All type MV12 switchgear is intended for clean indoor installation. Thus it is very important that all equipment is stored indoor at all times. Storing switchgear and breakers outside will subject the equipment to dirt and condensation. Humidity Highest mean value measured over 24 hours, Relative humidity 95% Highest mean value measured over 1 Month, Relative humidity 90% Avoid high humidity and/ or major rapid temperature fluctuations since these give rise to corrosion. To prevent condensation MV 12 switchgear is supplied with electric heater to preclude condensation. These must be switch on all the time even if the unit is switched off. Maximum site altitude: 1000m above sea level. 4

5 1.0 INSTALLATION 1.1 FOUNDATIONS AND UNIT ERECTION Correct operation of the Switchgear is dependent on it being level. It is essential, therefore, that care is taken at all stages of erection, in particular the lining up and leveling of the first unit, which will be the datum for all other units. Failure to erect the first unit correctly will result in misalignment throughout the switchboard. Foundation fixings may be of the foundation channel type See fig 1.1 or of the foundation bolt type, expanding type FOUNDATION CHANNELS Prepare the floor and foundations as shown on fig 1.1. Determine the highest point on the channels. This point then becomes the datum for all units. It is useful to use this point for erection of the first unit. With reference to the general arrangement drawing of the switchboard, check the unit serial numbers and remove the circuit breaker from the housing to be erected first. Position the housing on the channels. Locate the foundation bolts and associated washers through the holes in the base of the housing into the spring loaded nuts within the channels. DO NOT TIGHTEN. Using 2 plumb lines level the housing front to back and across the width. Levelling is carried out using the shim plates provided. These shims shall be located adjacent to and on the outside of the foundation bolts such that they will also support the adjacent housing when erected. Shims must also be placed under the base sheet at the front and the rear of the unit and under the circuit breaker runner plates to make up any gap between the floor. Position the next housing to be erected close up to the first, fit the foundation bolts and level up as before. Remove the housing top and rear covers and fit the inter-housing fixing screws. Repeat the above for the remaining housings remembering to check the unit serial numbers. Finally, tighten all foundation bolts and inter-housing fixings. Check the alignment of the instrument panels for squareness and equality of spacing between panels FOUNDATION BOLTS (EXPANDING TYPE) Proceed as section 1.1 and except use the foundation bolts instead. The holes in the base of the housing can be used as a template to drill the floor for accepting M12 x 75mm long expanding bolts. 1.2 BUSBAR ASSEMBLY Access to the busbar compartment for making the busbar joints is via removable covers on top of the housing, busbar chamber. Before assembly, all contact surfaces of the busbars and housing connections must be cleaned to ensure a good contact surface. Unplated contact surfaces shall be cleaned using fine grade emery cloth. Plated contact surfaces shall be cleaned using a branded liquid silver polish. After cleaning, all surfaces shall be wiped with a clean cloth to remove any metal dust, etc. Joints shall be assembled as soon as possible after preparation. The same treatment of contact surfaces shall be carried out on all other joints, such as the tee-off to voltage transformers and main cable connections. Units fitted with 5

6 voltage transformers are supplied with packers for transport only. These should be removed and replaced with the standard busbars (refer to fig 1.6). See fig 1.2 for assembly of busbars up to 1250A and refer to busbar layout drawings supplied with loose gear for 2000A and 2500A busbars. IMPORTANT: BUSBAR JOINTS ARE NOT TO BE INSULATED WITH PLASTIC COMPUND BUT LEFT BARE. cables are terminated on a multicore cable gland. See fig For ease of location, each wire is fitted with an identification ferrule, which corresponds with that on the wiring diagram. Where wires pass through to adjacent panels the holes shall be fitted with a protective grommet. 1.3 MAIN CABLES Access to the main cable terminations is via removable covers at the rear of the housing fig 1.3. The main cable shall be terminated to the cable connection busbar. Care must be taken to ensure that the fixing bolts supplied are used. Make sure that these bolts are not long more than necessary. 1.4 UNIT EARTHING The main earth bars of the units are combined within the unit. The only assembly required on site is, to connect the earth bars of adjacent unit together using the earth stud and earth spacer supplied with the loose gear. The earth bar must be terminated to the station earth system via the 12mm earth stud on the side frame. See fig MULTICORE CABLES & INTER-UNIT WIRING (BUS-WIRING) The only secondary wiring required on site is to run and terminate the multicore cables and connect the inter-unit bus-wires in accordance with the wiring diagrams supplied. The multicore cables are situated at the rear top side of the housing. The multicore 6

7 Figure 1. 1 Foundation Layout 7

8 Figure 1. 2 Busbar Assembly 8

9 Figure 1. 4 Main Earth Stud Figure 1. 3 Main Cable Box Figure 1. 5 Multicore Terminations 9

10 Figure 1. 6 Wood Packers between busbar monoblock and VT Connection for transport only. 10

11 2.0 INTERLOCKS 2.1 INSERTING/REMOVING THE CIRCUIT BREAKER INSERTING THE CIRCUIT BREAKER Bring the circuit breaker in front of the housing and attach the secondary plug on the switchboard to the secondary socket on the circuit breaker. Push the circuit breaker inside until no further movement is possible. Couple the racking handle into the Engage/Isolate seat. Start turning the handle clockwise to engage the circuit breaker to the plug contacts of the primary connection spouts. Stop turning the handle until Circuit Breaker Engaged on the base plate label can be read. Remove the racking handle and turn the isolating mechanism handle to the LOCKED Position REMOVING THE CIRCUIT BREAKER Turn the isolating mechanism to the FREE position. Insert the racking handle into the Engage/Isolate seat. Start turning the handle anti-clockwise to disengage the circuit breaker from the plug contacts of the primary connection spouts. Note that the circuit breaker stops moving at the end of the label until Circuit Breaker Disengaged is not visible. Remove the racking handle. Pull the circuit breaker from the handles outside the unit. N.B. It is essential that multi-fingered contacts are slightly greased with contact grease supplied with loose gear. 2.2 MECHANICAL AND ELECTRICAL INTERLOCKS Interlocks are provided to ensure that:- i. The circuit breaker can only be inserted into or withdrawn from a unit with the operating mechanism OFF and the isolating mechanism FREE. ii. iii. iv. The circuit breaker cannot be raised or lowered unless withdrawn from the unit with the operating mechanism OFF and the isolating mechanism FREE. The raise and lower drive shaft is blocked when the circuit breaker is racked in. Thus the raise and lower handle cannot be engaged. The circuit breaker can only be CLOSED with the isolating mechanism in the LOCKED position. The isolating mechanism can only be operated to the LOCKED position with the circuit breaker withdrawn or plugged in position and with the racking handle disconnected. v. The circuit breaker cannot be inserted into any other unit location other than that which has the same current rating. vi. The circuit breaker cannot be electrically TRIPPED when inserted in circuit earth position. vii. The circuit breaker can only be TRIPPED manually in the service position when no control voltage is 11

12 applied, and cannot be CLOSED manually. (Note: to close breaker when no D.C supply is available refer to section ) 2.3 PADLOCKING In addition to the interlocks described in section 2.2 padlocking facilities are provided for: i. For locking the unit safety shutters CLOSED. Fig. 2.1 & 2.2. ii. iii. iv. For locking the unit location selector in any one of the three locations, viz Busbar Earth fig 2.3, Circuit Service" fig 2.4 or Circuit Earth, fig 2.5 preventing selection of the other two. For locking the voltage transformer operating cover in both the SERVICE and OPEN position. fig 2.6 & 2.7 For locking the circuit breaker open switch in the OFF position see fig 2.8 or the OPEN/CLOSE switches (if fitted) inoperative see fig 2.9. v. For locking the circuit breaker control selector switch (if fitted) in either the LOCAL or REMOTE position. See fig CIRCUIT BREAKER CONTROL MODULE (refer to fig 2.10 & 2.12) The circuit breaker control module is used for control of the opening and closing commands to the magnetic actuator mechanism. Functions are defined in a permanently programmed logic module: i. The opening and closing of the circuit breaker can be controlled by applying a voltage to inputs (terminals 15,16) for ON operation and a voltage to inputs (terminals 17,18) for OFF operation. ii. iii. The moving contacts in the circuitbreaker poles must be in a defined ON or OFF limit position. The closing coil can only be activated with the breaker in the OFF position. iv. The opening coil can only be activated with the breaker in the ON position. v. Closing signal is blocked when an opening command is simultaneously active vi. Activation of the closing coil can be disabled by an external blocking signal. (terminals 25,26) vii. The antipumping system ensures that, when a closing command is applied and followed by an opening command, only one ON-OFF switching operation is performed. For the next closing operation, the active closing command has to be cleared and must be issued again. viii. Deactivation of the opening or closing coil takes place when the relevant limit position has been reached. ix. The closing coil can only be activated with the isolating mechanism in the locked position. These features are included with the auxiliary voltage (terminals 48,49) applied to the control module. 12

13 Figure 2.1 Locking of Busbar Safety Shutters Figure 2.2 Locking of Circuit Safety Shutters Figure 2.3 Locking in Busbar Earth Position Figure 2.4 Locking in Circuit Service Position Figure 2.5 Locking in Circuit Earth Position Figure 2.6 Voltage Transformer Padlocked in Service 13

14 Figure 2.7 Voltage Transformer Padlocked in Isolation Figure 2.8 Open Switch Padlocked in the Off Position Figure 2.9 Close Switch Padlocked Inoperative Figure 2.10 Local Remote Switch 14

15 Figure Control Module - Diagram of Connection 15

16 Figure 2.12 Control Module Inside the MV12 Breaker 16

17 3.0 STRUCTURE AND FUNCTION 3.1 STRUCTURE OF THE OPERATING MECHANISM The operating mechanism is of the magnetic actuator type. Referring to fig 3.1 it fundamentally consists of the magnetic actuator (7), the drive shaft (4), which transmits the force to the breaker poles (2) via the push rods (3). The actuator is the heart of the circuit breaker operating mechanism. It combines the following integrated functions: i. Latching in the limit positions ii. iii. Release to switch OFF Switching to switch ON The actuator is a bistable permanent magnet system in which the armature motion is effected by activating the ON or OFF coil The opening and closing processes are initiated via operation of push-button on the instrument panel. In the closing process, the actuator (7) acts on the three breaker poles via drive shaft (4) and the push rod (3) until the contacts meet. In the remaining movement, the pretension spring arrangement in the push rod is compressed to the required tension and the necessary contact force thus applied. The available over travel is greater than the maximum contact burn-off throughout the life of the vacuum interrupter. In the limit positions, the armature is held in place magnetically by the field of two permanent magnets. Release of a switching operation is effected by exciting one of the two coils until the latching force of the permanent magnets is exceeded. 3.2 FUNCTION OF THE ELECTRONIC CONTROL MODULE (refer to figs 2.11 & 3.2 and tables 1 & 2) 17 The Control module produces a voltage of 80V from any supply voltage within the input voltage range, with which the storage capacitor is charged. This is also used to generate a voltage of 12V to supply the breaker controller. The circuit breaker control module consists of: a microprocessor electronic optocouplers for input relays for output power electronics to control the actuator coils Along the functions described in section 2.4, this module has further functions: (refer to fig 3.2) Undervoltage release function. This input, (terminals 27,28) switches the MV12 breaker off if the voltage applied falls below the tolerance range stipulated in IEC The nominal value of the voltage supply to be monitored is selected by dip switch I In order to prevent switch-off when the voltage briefly falls below the specified level (e.g. on motor startup), a time delay can additionally be set. See dip switch I 1004 to set time delay. Dip switch I1002 has closing support for the undervoltage input (27,28). If this feature is activated a closing operation is allowed even if no voltage is applied to (terminals 27,28). After the performing of closing, the normal undervoltage function is active i.e. the controller will trip even if no voltage is applied after closing. AUTO-OFF at declining capacitor voltage. This function is usually deactivated. This means that the MV12 breaker can be opened and closed without any voltage being applied. However if it is activated when no voltage is applied the MV12 cannot be closed.

18 Monitoring of the closing and opening coil of the actuator. This function monitors the closing and opening coil of the actuator for cable breakage. If such a breakage is detected, the Ready lamp on the front panel of the switchboard goes out (fig3.5). The ready signal is connected via terminals 9,10. Maximum Unsuccessful Attempts After 10 incomplete shots the unit will go in the NOT READY condition. The MV12 breaker can no longer be operated. In this case it is necessary to reset the breaker controller by removing the auxiliary supply and wait for the capacitor to discharge (see section 5.1). This function saves the components on the breaker controller and forces the operator to check the circuit breaker. Contacts for position signalling Terminals 1,2 and 3,4 are a pair of NO contacts used to signal the ON and OFF positions respectively. 3.3 FUNCTIONS OF THE READY LAMP This lamp monitors the following conditions. supply of auxiliary power to the MV12 circuit breaker. detection of a defined on or off position by the position sensors. monitoring of the controlled function of the microprocessor. sufficient voltage at the capacitor of the next switching operation. continuity of the actuator coils. 3.4 STORAGE CAPACITOR (fig 3.4) operating sequence is available without recharging. The energy stored by the capacitor is permanently monitored. This is achieved by measuring the capacitor voltage. The Ready lamp indicates that auxiliary voltage is applied and the circuit breaker is ready for the impending switching operation. The criterion for the Ready lamp to light up is the energy in the storage capacitor at the particular time; otherwise an error signal is issued. Case 1: Breaker in the OFF position. The energy available in the capacitor is sufficient for an ON and an OFF switching operation. Case 2: Breaker in the ON position. The energy available in the capacitor is sufficient for an OFF-ON-OFF switching sequence. The energy available is sufficient for an OFF switching operation in the first 200 s after failure of the auxiliary power supply. (see also section 4.2.3). 3.5 SENSOR SYSTEM The systematic use of sensors permits control of the circuit breaker without using the auxiliary switches. Two inductive proximity switches (fig 3.3) are used to detect the mechanical limit positions, which also provide for selfmonitoring of the system. The energy for operation of the circuit breaker is stored electrically in a capacitor. This capacitor is designed in such a way that the energy for an OFF-ON-OFF 18

19 Table 1 Terminal Assignment (refer to fig 2.11) Terminal Use General Purpose Binary Outputs 1-2 OFF signal 1 (NOC) ON signal 1 (NOC) 9-10 READY (NOC) NOT READY (NCC) General Purpose Binary Inputs ON-Command OFF-Command Closing lock-out (closed circuit) Switching Command OFF (closed circuit) Magnetic Actuator Position 29 OFF Position 30 ON Position Vdc Vdc 33 0Vdc 34 0Vdc Power Output and Capacitor Link Vdc Vdc 37 0Vdc 38 0Vdc 39 + On Coil (+80Vdc) 40 + On Coil (+80Vdc) 41 + Off Coil (+80Vdc) 42 + Off Coil (+80Vdc) 43 - On Coil 44 - On Coil 45 - Off Coil 46 - Off Coil Auxiliary Supply and Auxiliary Capacitor Connection 47 Not used 48 Voltage Supply 49 Voltage Supply 50 -V Cap 51 +V Cap 10Kohm resistor 52 +V Cap 19

20 Table 2 Technical Characteristics of Control Module Input Voltage Power Consumption on the input side during a charging process Power consumption in normal position Charging times of the capacitor Initial charging on commissioning Recharging after a switching operation Binary Inputs Electrical Isolation from the electronics Electrical Isolation between the inputs Current consumption Inputs protected from voltage surges Binary Outputs Electrical Isolation from the electronics Electrical Isolation between the outputs Switching current ON Resistance Low Voltage Range 24 to 60Vdc 24 to 48Vac High Voltage Range 110 to 250Vdc 100 to 240Vac 100W <10W Max 10s Max 3s 2.0 kv AC kv AC 1 2mA at 250V AC/DC YES 2.0 kv AC kv AC 1 Max 6A / 250 V AC (resistive) 100mΩ 1) Note: When any insulation testing is to be performed, all the connectors on the card have to be disconnected for the duration of the test (see fig 3.6). 20

21 Figure 3.1 MV12 Circuit Breaker 21

22 Figure 3. 2 Jumper settings of the Control Module 22

23 Figure 3.3 Proximity Sensors Figure 3.4 Storage Capacitors Figure 3.5 Circuit Breaker Ready Light Figure 3.6 Connectors Removed 23

24 4.0 OPERATION 4.1 PREPARATORY WORK Preparatory Work Before Connecting The Primary Voltage. i. Check the circuit-breaker for damage and have it repaired if necessary. ii. iii. iv. Remove any dirt which might have accumulated during transport, storage or installation (particularly on insulating materials). Check the primary and secondary connections and the earth conductor connection. In the case of a (voltage-free) storage period of more than 2 years, an increased current consumption, which is nevertheless below 2 A, occurs at the breaker control module during commissioning as a result of reforming the storage capacitor v. Display the instruction manual at a location accessible to the operators at all times. 4.2 CIRCUIT-BREAKER OPERATION Adjust the position selector switch to the position required. (fig 4.1) Make sure that the isolating mechanism handle is in the free position before raising or lowering breaker. (figs 4.2 & 4.3) For service position the breaker should be raised until the handle aligns with the arrow on the label. (fig 4.2) Check that the isolating mechanism can be operated FREE to LOCKED. For circuit earth position the breaker should be lowered until the handle aligns to the arrow on the label. (fig 4.3) Raise and Lower can only be done when the breaker is outside the housing. Once the breaker is racked inside the housing the racking handle cannot be inserted in the raise and lower seat. For the insertion and removal instructions of the breaker refer to section 2.1 With the circuit breaker outside the unit and the secondary socket lead plugged in, the supply is connected to the breaker. After 15 seconds that the auxiliary power supply has been established the Ready Lamp lights up and the breaker can be operated CLOSING Closing can only be achieved if all the interlocks are correct see section 2.2 & 2.4. The interlock handle must be moved from FREE to LOCKED. Closing can be done either by remote control via closing contacts on multicore terminal or locally by pressing the ON push-button on the instrument panel. (fig 4.4) OPENING Opening can be made by remote control via closing contacts on the multicore terminals or locally by pressing the OFF push-button on the instrument panel. After each operating cycle ON-OFF, the mechanical counter is incremented by one full digit. (figs 4.4 & 4.5) Perform test closing and opening of the circuit-breaker by pressing ON-OFF pushbuttons OPENING ON FAILURE OF THE AUXILIARY POWER SUPPLY Electrical opening is possible only within the first 200 s. of the auxiliary power 24

25 supply failure. After a period of 200 s, emergency manual opening is necessary:! Manual opening must be performed on a dead line only. To perform a manual opening when breaker is in service position, remove the front screws holding the cover of the circuit breaker and remove the circuit breaker front cover. Insert the Emergency Trip Handle into actuator shaft and turn it anticlockwise to open the circuit breaker. (figs 4.6 & 4.7) instructions on this device refer to the maintenance closing device instruction handbook. Having restored the supply to the battery and the auxiliary supply the other feeders can now be closed CLOSING IN CIRCUIT EARTH POSITION Closing can only be achieved electrically if all the interlocks are correct and the isolating mechanism handle moved, from FREE to LOCKED CLOSING ON FAILURE OF THE AUXILIARY SUPPLY! WHEN CLOSING A BREAKER WITH THE PROTECTION INACTIVE, IT IS COMMON PRACTICE TO SWITCH THE SUPPLY FROM THE REMOTE FEEDERS. Closing with auxiliary supply fail is not recommended with primary voltage energised OPENING IN CIRCUIT EARTH POSITION The electrical tripping of the circuit breaker in the Circuit Earth position is inoperative both during closing and when closed. This can only be achieved manually by using the Emergency Trip Handle (fig 4.8). In this case the cover does not need to be removed. In case of loss of the DC system, the circuit breaker can be closed, by using the Maintenance Closing Device. For 25

26 Figure 4.1 Position Selector Figure 4.2 Isolating Mechanism in the Free Position - Serviee Figure 4.3 Isolating Mechanism in Free Position Circuit Earth Figure 4.4 Close/Open Switches and Ready Lamp 26

27 Figure 4.5 Operations Counter Figure 4.6 Emergency Trip Handle used for Manuel Tripping Figure 4.7 Manual Trip in the Service Position Figure 4.8 Manual Trip in the Circuit Earth Position 27

28 5.0 SERVICE AND GENERAL MAINTENANCE The life expectancy of the MV12 vacuum circuit breaker is determined by: i. The maintenance-free vacuum interrupters with up to 20,000 operating cycles. ii. iii. The magnetic actuator mechanism, maintenance-free under normal operating conditions up to 100,000 operating cycles. The maintenance-free control module with sensor systems. The servicing intervals and scope are determined by the environmental influences, the switching frequency and the number of short-circuit breaking operations. In those applications where the load is switched many times a day, experience shows that the mechanical life is likely to be reached before the limit of contact wear. relevant safety regulations. It is recommended that Medelec Switchgear personnel should be called in, at least during the performance of servicing and repair work. Note: In order to prevent accidents (particularly injury to hands!) extreme care should be taken during all repair work on the operating mechanism, especially with circuit breaker front plate removed. The energy of the storage capacitor can be discharged uncontrollably during incorrect handling! Where the limit of contact wear has been reached on any phase, the complete set of 3 interrupters must be replaced. Replacements and the necessary instructions can be made available on application to Medelec Switchgear Ltd. Should the user identify any area of concern and require advice, the Contracts Department of Medelec Switchgear Ltd should be informed. On completion of an Overhaul, Commissioning Checks and Inspection should be carried out in accordance with Section 6 of this manual. Note: Maintenance work may only be performed by fully trained personnel, observing all the 28

29 5.1 PROCEDURE FOR CAPACITOR DISCHARGE i. Switch off the auxiliary power supply F2 (control & close fuse) ii. Switch the vacuum circuit-breaker on and off until it no longer responds. iii. After a waiting period of approx. 5 minutes, the storage capacitor will have discharged to <15V. 5.2 INSPECTION AND FUNCTIONAL TESTING SWITCHING DEVICES IN GENERAL Under normal operating conditions, inspection within the stated number of operating cycles is not necessary. Inspection may be necessary under exceptional operating conditions (including adverse climatic conditions) and/or particular environmental stresses (e.g. serious contamination and aggressive air). The inspection primarily comprises visual examination for contamination, corrosion, moisture and discharge phenomena on the high voltage side. If an irregular condition is found, appropriate maintenance work is to be initiated OPERATING MECHANISM A first functional test of the operating mechanism is to be performed during maintenance work. Before the functional test, switch off the circuit-breaker and withdraw the circuitbreakers. Observe the procedure for capacitor discharge as set down in section 5.1. Perform visual examination of the condition of the circuit breaker with the front plate removed, e.g.: i. the operating cycle counter, ii. the sensor mounting, iii. the position indicator. Functional testing: Connect the auxiliary power supply. Perform several switching operations under no load. This is predominantly applicable to circuit-breakers which are rarely operated under normal circumstances. To check the storage capacitor, switch the circuit-breaker rapidly OFF-ON-OFF once, by pressing ON and OFF push-buttons rapidly in succession. The LEDs on the inductive proximity switches fig 3.5 are activated when the circuit-breaker has reached its OFF and ON limit positions MAGNETIC ACTUATOR OPERATING MECHANISM The magnetic actuator operating mechanism is maintenance-free up to 100,000 operating cycles. Under normal operating conditions, inspection within the stated number of operating cycles is not necessary. Inspection may be necessary under exceptional operating conditions (including adverse climatic conditions) and/or particular environmental stresses (e.g. serious contamination and aggressive air). Inspection should be centred on the two Magnet Covers one on each side. If the brass magnetic cover is found crippled the circuit breaker should be kept out of service and the matter reported to Medelec Switchgear Ltd. 29

30 Circuit Breaker and Busbar chambers Before accessing any of these components make sure that the HV supply is de-energised and securely earthed STORAGE CAPACITORS Inspection may be necessary under exception operating conditions such as high temperature. Adverse climatic conditions and serious contamination of the air may also influence the lifetime of these capacitors. The vent of the capacitor must be examined to determine the state. If the vent is found ruptured, the capacitor must be immediately replaced. To perform this operation make sure that the capacitor discharge procedure (5.1) has been completed. 5.3 SERVICING If the necessity of cleaning is established during inspections the following procedure has to be done. Prior to cleaning, isolate and secure the working area safe. Observe procedure of capacitor discharge (5.1) Cleaning of insulating surfaces (cast-resin components) Circuit-Breaker Each vacuum interrupter housing has to be cleaned both from the outside and inside. To access all locations, polycarbonate covers and contact fingers have to be removed. Removing polycarbonate cover and contact fingers Unscrew the 4 nylon screw using a flat screwdriver. Use an allen-key size 5 to unscrew the upper and lower contact fingers. Clean thoroughly behind the polycarbonate covers using a lint free cloth. Busbar Monoblock This has to be accessed by removing the top cover. All insulating parts have to be cleaned using a lint free cloth. The other part has to be accessed from the circuitbreaker chamber. The shutter mechanism has to be opened to access all areas. CT Bushings Make sure that the cable connected to the bushings is de-energised and earthed. From the circuit-breaker chamber open the shutter in front of the bushings and put it in the open position. Clean all insulating surfaces using a lint free cloth. 5.4 REPAIR Replacement of circuit-breaker parts and accessories: Only remove and reassemble circuitbreaker parts and accessories when the breaker has been switched off and the working area is isolated and secured against reclosing: The storage capacitor is to be discharged in accordance with the instructions in section 5.1. All auxiliary voltage sources must be disconnected and secured to prevent reconnection during the removal and installation work. Replacement of the circuit-breaker control module may only be performed by Medelec Switchgear after-sales service staff or by trained skilled personnel. Remove all rust from damaged paintwork areas on sheet steel and other steel parts mechanically, e.g. with a wire brush. Lightly grind the surrounding paint coat 30

31 and carefully degrease the entire area. Then immediately apply an antirust primer and, after an appropriate hardening period, apply the top coat. Use top coat paint in the standard colour RAL 7032, or the relevant special colour. Only use suitable and compatible paint products. CRITERIA FOR OVERHAUL Interrupter Type Rating Current Rating Interrupter Mechanism ABB VG4 (VC on older version) 25kA or 31.5kA 800/1250/ A 1,000 operations 1,000 operations MINIMUM ELECTRICAL INTERRUPTER LIFE At Rated Normal Current At rated-short circuit current 5.5 SPARES 10,000 operations 30 operations The following spares should be kept in stock, actual quantities will depend on the number of circuit breakers in service and operating conditions. LT Fuses Voltage transformer High Voltage fuses. All spares should be stored in such a manner as to protect against corrosion, humidity, adverse atmospheric conditions, mechanical damage and vermin. When ordering spares or replacements a complete description should be given, together with relevant nameplate data and serial numbers. After the switchgear has been installed and all connections have been completed, commissioning tests are recommended to be performed. The purpose of these tests is to confirm that transportation and storage have not damaged the circuit breaker or any part of the fixed portion. In addition when the assembly adjustment is performed on site, tests are required to confirm compatibility of the sub-components and the satisfactory nature of both the site work and the functional characteristics. The purpose of the commission tests is for confirmation of: i. Absence of damage; ii. Compatibility of separate units; iii. Correct assembly; iv. Correct performance of the assembled unit 6.0 COMMISSIONING CHECKS AND TEST PROGRAMME The test outlined in this section is to be made after the equipment has been erected, but before energising. 31

32 6.1 GENERAL CHECKS Assembly to manufacturer's drawings and instructions; Tightness of circuit-breaker, and control devices; External insulation and internal insulation is undamaged and clean; Paint and other corrosion protection is sound; Operating devices, especially operating mechanisms, are free from contamination: Adequacy and integrity of the earth connection up to and including the interface with the substation earthing system. 6.2 ELECTRICAL TEST SECONDARY INSULATION ELECTRICAL CIRCUITS CHECKS Electrical Circuits conformity to the wiring diagram Correct operation of signalling lamps Correct operation of heating INSULATION TAKE THE FOLLOWING PRECAUTIONS: DISCONNECT THE WIRING TO THE BREAKER BY REMOVING THE SECONDARY PLUG DISCONNECT THE WIRING TO/WITHDRAW ANY RELAY DEVICES. SHORT CIRCUIT CURRENT TRANSFORMER SECONDARY WINDINGS. ISOLATE THE ISOLATABLE VOLTAGE TRANSFORMERS. AFTER COMPLETION OF TESTING, ALL CONDUCTORS SHALL BE DISCHARGED TO EARTH, TEMPORARY CONNECTIONS REMOVED AND COMPONENTS RECONNECTED. The secondary insulation includes the insulation associated with the secondary wiring. For this test the ends of the secondary wiring should be looped together at some convenient point such as the terminal board, and using a 500 volt megger measure the resistance, which should not be less than 2 megohms between the loops and earth HIGH VOLTAGE TEST MEGGER TEST WARNING: BEFORE COMMENCING THE TESTS DESCRIBED IN SECITONS AND ON THE SECONDARY 32 For this test the ends of the secondary wiring should be looped together at some convenient point such as the terminal board and a voltage of 2kV r.m.s. applied for 1 minute between the loops and earth. Remove connectors from the control module. Varistors which are required for the EMC strength of the breaker controller may otherwise be damaged. 6.3 ELECTRICAL TESTS PRIMARY INSULATION WARNING: BEFORE COMMENCING TESTS AND ON THE

33 PRIMARY INSULATION TAKE THE FOLLOWING PRECAUTIONS: SHORT CIRCUIT AND EARTH CURRENT TRANSFORMER SECONDARY WINDINGS. UNDER NO CIRUMSTANCES SHALL CURRENT TRANSFORMER SECONDARIES BE OPEN CIRCUITED WITH THE PRIMARY ON LOAD. ON FIXED VOLTAGE TRANSFORMERS REMOVE THE CONNECTION BETWEEN THE PRIMARY TERMINAL AND THE FIXED CONTACT ON ANY EARTHING SWITCHES. ISOLATE ANY ISOLATABLE VOLTAGE TRANSFORMERS. AFTER TESTING, ALL CONDUCTORS SHALL BE DISCHARGED TO EARTH, TEMPORARY CONNECTIONS REMOVED AND ANY COMPONENTS RECONNETED MEGGER TEST The primary insulation includes the insulation associated with the high voltage circuit. While carrying out this test it should be noted that, insulation varies considerably with atmospheric conditions, dryness and cleanliness of the equipment; low readings may occur as a result of surface leakage over the insulation. Using a 500V megger measure the resistance to earth of each phase in turn. If the resistance falls below an absolute minimum of 1000 megohms after careful cleaning and drying of all exposed surfaces, a check of the equipment should be made for insulation damage HIGH VOLTAGE TEST IEC60694: 2002 gives full information regarding high voltage testing after erection on site. With the circuit breaker CLOSED, a power frequency voltage should be applied to each phase in turn with the other two phases and the VCB frame earthed for 1 minute. 12kV highest system voltage 22.4kV AC rms power frequency. After high voltage tests have been completed, a further megger test should be made to check that the initial resistance has not altered significantly. 6.4 HIGH VOLTAGE TESTS INTERGRITY OF VACUUM INTERRUPTER The integrity of the vacuum interrupters can be checked on site by applying a test voltage of 20kV AC r m s or 30kV DC for 2 or 3 seconds across the open contacts of each phase in turn with the other side earthed. Provided that there is no evidence of breakdown the interrupter is in a satisfactory condition. Should a breakdown occur, the circuit breaker should be kept out of service and the matter reported without delay to Medelec Switchgear Ltd. 6.5 MECHANICAL TESTING AND RECORDING Manual operational checks should be carried out on the circuit breaker to ensure correct operation of interlocks, primary connection safety shutters, operating mechanism, trips, auxiliary switches and the circuit breaker racking mechanism. The equipment should be given a final inspection before it is put into service. Check that all covers are in place and fully secured. 33

34 Check earth bars for continuity. Check that all fuses and links are inserted. Check that padlocks are fitted. Check all moving parts of the safety shutters, the circuit breaker racking mechanism, circuit, isolatable voltage transformer operating mechanisms and all interlocks. Operate the circuit breaker electrically to ensure it is functional. Ensure all insulation surfaces are clean and dry. Touch up paint work where necessary RECORDING In order that a complete history is available, records should be started immediately after erection and should include: Date of Completion. Interrupter contact wear check. VC3 INTERRUPTERS See fig 6.1 for method of checking contact wear of VC3 interrupters. If contact wear gauge cannot be inserted in the snatch gap circuit breaker must not be used. VG4 INTERRUPTERS The polycarbonate brackets must be removed to check for contact wear. (see figs 6.2). If contact wear gauge CANNOT be inserted in the snatch gap (fig 6.2b) the MV12 breaker IS Operational. If contact wear gauge CAN be inserted in the snatch gap, the MV12 breaker IS NOT Operational and cannot be used. For this check MV12 breaker must be in the ON position. This gauge must be used as a Go No-Go check only. Number of short circuit operations. Details of any work carried out. Circuit breaker operations counter reading. Record the number on the operations counter at delivery; Record the number on the operations counter at completion of all site testing; Record the number on the operations counter at first energisation. Records are of value in establishing the frequency of maintenance, therefore careful notes should be taken of relevant items each time maintenance is carried out. These readings can be recorded in table attached. Under Section In order that a complete history is available, records should also be taken immediately after commissioning and should include: 34

35 Figure 6. 1 Contact Wear Gauge for circuit breakers with VC3 Interrupters 35

36 Figure 6. 2a Inserting the Contact Wear Gauge Figure 6. 2b No Contact Wear NO GO Figure 6.2c Contact Wear -GO Figure 6.2 Contact Wear Gauge for VG4 Interrupter COMMISIONING CHECK LIST A 1 Equipment bolted down correctly A 2 Instrument panels straight and aligned A 3 All gaskets and covers in place A 4 Prove tightness of all fastenings A 5 All insulators undamaged and clean A 6 Earth strap connections A 7 Labeling A 8 Switchgear Heaters A 9 Isolating and Earthing Arrangements A 10 Circuit-Breaker and Mechanism Alignment A 11 A 12 Auxiliary Switches Voltage transformer can be switched and isolated correctly B: ELECTRICAL CHECKS B 1 Battery charged B 2 DC available throughout switchboard B 3 All fuses checked B 4 Battery disconnection links left in open/close position after C: ELECTRICAL TESTS C 1 High voltage tests carried out is performed C 2 Primary and secondary injection tests carried out as per form 36

37 C 3 HV Switchboard volt meters checked at 110V and zeroed C 4 Power factor meters checked by secondary current injection and supply voltage C 5 KWH checked by secondary injection and supply voltage Remarks: TESTS CARRIED OUT BY: DATE:.. TESTS WITNESSED BY: EQUIPMENT ENERGISED: DATE: COMMISIONING CHECK LIST CONTINUED. DESCRIPTION VACUUM INTERRUPTERS 20 kv AC CHECK BREAKER ON/OFF COUNTER AT DELIVERY COUNTER AT COMPLETION COUNTR AT FULL ENERGISATION CONTACT WEAR CHECKED SHORT CIRCUIT OPERATION UNIT 1 UNIT 2 UNIT 3 UNIT 4 UNIT 5 UNIT 6 UNIT 7 Other Details 37

38 The right is reserved to alter design, dimensions and technical data without prior notice Manual MED MV REV 11 38

39 39