Upgrades and Activities of 13kA EE systems during LS1 Bozhidar Panev TE-MPE-EE

Installation of Snubber capacitors in RQD/F EE systems The benefit: To suppress the voltage transient perturbations in the circuits during switch commutation and to make the opening process lighter by reducing the electrical arc existence All 16 EE systems of RQD/F circuits will be equipped. Four snubber capacitors per system + associated auxiliary boards  in total 64 snubbers and 64 boards All parts and components have been manufactured, commissioned, packed and prepared to be transported to each UA area. Transport will be required 2

Difficulties during the installation: Installation of Snubber capacitors in RQD/F EE systems The last issue has been discussed with S. Pelletier from transport service in the presence of a safety person. The accepted solution is to use a lifting mechanism, fixed at the ceiling inside of the switch housing.  Limited space inside the switch acoustic shield housing  The installation of snubbers on the upper stage requires to lift and handle heavy stuff at 2m height over the ground. The IHEP team (4 experienced persons) is scheduled to perform the work. All of them have previously participated in the EE systems maintenance and the RB snubbers installation The work is planed to start in May The time estimation is 3 days per one UA area  24 days in total 3

New arc chambers for RQD/F EE switches  Identical design as in the dipole EE systems  Good performance up to 1050V (arc feeding voltage) is guaranteed  All chambers have been delivered to CERN earlier this year It will be combined with snubber capacitors installation. Two sectors (S12 and S23) are already equipped. Still 12 EE systems  96 arc chambers have to be replaced. The currently installed arc chambers  up to 200V arc feeding voltage (design specification and hard limit) The new arc chambers: The activity does not require the transport service 4

To prevent the potential damage of the DQRBs in case of double amount of energy deposited in the dump resistors Difficulties  mainly due to lack of space at the end of some DQRBs Mechanical modification in all RB dump resistors (DQRB) 53 dump resistors (16 RB EE systems + spares) will be modified. The estimated time  3 DQRBs per day  ~ 20 days totally The activity is scheduled to start in July The IHEP team + AGH team (3 persons) will perform the work.  e.g. in P1, P3 and P5 the “Roman pots” or beam pipe supports are placed between dump resistors The transport service will be involved to move temporarily some dump resistors in order to gain enough space 5

RB Dump resistors – thermostat replacement The installation of new thermostat is not fully completed  Two dump resistors: one in RR73 and one in RR77 still need to be equipped Difficulty:  Resistors are blocked by concrete shield and there is little access for manipulation During next TS both two places will be visited and carefully observed The activity is planed to start in Aug Expected duration: One week IHEP team + AGH team will be involved 6

A recent inspection has found the significant erosion of contacts due to electrical arc. The risk to burn the holding coil increases. In the beginning of closing process I = 22A(230V) then switched to 0.5A(8V) As a part of preventive maintenance it has been decided to replace these relays in all EE systems (RB and RQD/F) Power switching relay (230V/8V) of holding coil (RL4,6,8,10 in BCMs) 8 relays per EE system  32 systems  256 relays in total The new selected relay (still under consideration):  Better contact material - AgSnO2 instead of AgCdO  Maximum peak current - (4 times higher) TE-MPE-EE staff will perform the activity. 7

Dump resistors re-configuration The activity is planed to start in Sep. and will take 2 weeks The work will be executed by IHEP team + AGH team + TE-MPE-EE The expected new conditions in LHC after LS1 require a new configuration of the dump resistors in RB and RQD/F EE systems RB_EE system  requires only cable reconnection to get all three resistors in parallel RQD/F_EE system  dump resistor internal modification - Curren situation: R = * = 28.9 mΩ (51 MQ / circuit) R = * = 27.8 mΩ (47 MQ / circuit) - After LS1: R = * = 18.9 mΩ (51 MQ / circuit) R = * = 17.8 mΩ (47 MQ / circuit) 8

RB Dump resistor – 4 water cooling stations relocation in P1 and P5 The reason: Installation of new collimators in the place which, currently occupied by water cooling station Cooling stations together with adjacent electrical cupboards will be moved on top of one of the RB-dump resistors. Such a installation has already been done in P3 EN-CV and EN-EL will be involved The activity is scheduled to start  in Aug. and it will take 2 weeks. The participants  AGH team (3 persons) + TE-MPE-EE 9

Water cooled cable exchange of some 13kA EE systems Cracks in the rubber of the water cooled cables have been observed close to the connection point with “busway” All cables susceptible of containing such a cracks will be replaced:  P4 right  RB, RQD/F  P6 left & right  RB, RQD/F  P8 left and right  RB, RQD/F The work will be performed by EN-EL. The presence of a EE specialist is needed during establishing the connection with the switch “busway” The voltage drop measured across the connection point must determine the resistance of  ≈ 0.6 μΩ Modification in SUM_Fault electronic board A few suspected diodes will be replaced The signal “ST_OPENFAIL” will be removed by hardware modification 32 PCBs will be modified  1 per EE system TE-MPE-EE staff will perform the work. 10

General maintenance of all 13kA EE systems Micro-switches(S1/2/3/4) functional check Air gaps of the breakers (∆1 and ∆2)  measurement and adjustment Mechanical pressure verification of the main contacts  adjustment if required Cleaning of the main and arcing contacts Time delay check (600ms and 340ms) only RB EE system Verification of all bolted electrical connection All 32 EE systems (RB and RQD/F) The activity is scheduled for Sep.-Oct and it will take ~1.5 months The work will be performed by IHEP team + AGH team supervised by TE-MPE-EE 11

Recourses and Conclusions The main contract with IHEP is ready for approval but not yet signed As a back up solution  The AGH team can handle the work but some training is needed in order to get more familiar with the EE systems. In that scenario at least 30% more time must be added All technical details are determined and most of the equipment is already available All issues are included in Katy’s general planning CERN supervision team is: Mathieu, Knud, Bozhidar 12

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