Dependability

1.1.1 Programmable Logic controllers (PLC)

Radiation induced trips on SIEMENS PLCs (Presentation AWG, RadWG, JIRA1, JIRA2)

The effect of ionizing radiation has represented the main beam dump cause of the Powering Interlock System (PIC) during the first LHC operational period (2010-2012). A total of 5 preventive dumps have been triggered by the PIC in 2011 while operating with stable beams at 3.5TeV. The cause of such of such dumps was attributed to a memory corruption of the PLC due to single event effects (SEEs), which provoked the passivation of the controller outputs. These issues disappeared after relocating the 9 affected PLCs installed in UJ14, UJ16 and UJ56.

 

1.1.2 Quench Loop and Energy Extraction

Radiation induced fault on mBS board led to unbalanced rupture of the quench loop (TEMPECOMS-505, TEMPECOMS-523, MP3_2015_19th)

Radiation induced faults on mBS boards provoked a glitch on the quench interlock loop. Apparently the glitch was very short and the current in the loop did not decay completely. In this case, the PIC and EE located in the even side of the arc did not received the FPA while the odd-side PIC activated the global protection. It occurred two times in RB.A21 and RB.A67, both of them with the same signature…

Radiation induced fault on BS board led to non-conformed opening of the quench interlock loop (MP3_2015_29th, TEMPECOMS-555)

A radiation induced fault on BS board provoked a non-conform opening of the quench interlock loop. This time the residual current in the loop was enough to trigger the PIC in both sides of the arc but the EE switches took several seconds to open. This undesired behavior is caused by the different detection thresholds set on the EE-FPA boards (~10mA) and the DQQLC (17-20mA).

Incident report for non-opening of energy extraction switches on RB.A34 (EDMS 1159013)

This note summarises the observations and investigations done following a non-opening of the 13kA energy extraction switches on the main dipole circuit of sector 34 during a perturbation on the electrical network on the 24 of April 2011 @ 06.22.30.700 AM. The event sequence leading to the event as well as the history of the circuit during the latest commissioning and operational period is reconstructed. Following these findings and the investigation of the faulty card in the laboratory, a number of recommendations and immediate actions are identified to prevent any further occurrence of such fault. 

Redundant opening of the 13kA Energy Extraction Switches through Software Interlock System (EDMS 1460332)

Functional Specification: Redundant opening of 13kA Energy Extraction Switches through Software Interlock System

 

1.1.3 Optoelectronics

Exchange of CIPAA board in powering interlock controller CIP.UA87.AR8 (EDMS 1578304)

After a short period of access in the morning of the 16th of September 2010, the circuit RB.A81 could not be re-started anymore. The failure was finally traced down to a faulty CIPAA board in the powering interlock controller CIP.UA87.AR8 (HCCIPAA003-CR00012), which was replaced and re-tested, while the faulty card was brought back to the lab for a detailed investigation. The present report summarises the circumstances leading to the incident and the findings of later investigations.

 

1.1.4 Software interlocks

Beam dump triggered by BLM after losing the 60A_PoweringPermit (MPP 75th presentation, JIRA)

On 25.10.2012 the 60A orbit correctors in sector 56 experienced a slow power abort due to a network communication problem and the following removal of the powering permit by the PVSS SCADA of the powering interlock system. This provoked beam losses and the beams were dumped by the BLMs. This event revealed a wrong implementation in the PVSS logic that was immediately corrected.

 

1.1.5 Interface to the Beam Interlock System

Non-conformity identified during the CIBU test campaign (EDMS 1574010)

During the CIBU commissioning campaign carried out during the LS1, a misbehaviour has been detected on the PIC-CIBU interface. It has been observed that the PIC is not able to provide sufficient voltage on the user permit channels when the current drained by the CIBU is higher than 14mA.

 

1.1.6 UPS (Changes in the operational procedure following renovation in LS1)

Actions to be taken upon receiving a Warning Alarm from the LHC UPS System (EDMS 1529773)

The purpose of this document is to outline the actions to be taken by the TI and LHC operators upon receiving a warning alarm from the LHC UPS system, reporting a non-nominal operational state of the LHC UPS distribution system.

 

1.1.7 Power Supplies

1x Replacement of broken redundant power supply SITOP (MAGINT-235)

4x Replacement of AC/DC TRACO modules (MAGINT-233, MAGINT-234)

 

1.1.8 Engineering Change Request (Interlock functionality and databases)

Revised interlock functionality for LHC circuits of interlock type A (EDMS 844815)

This document deals with a modification of protection functionality for LHC circuits of interlock type ‘A’ (RB, RQD, RQF and RQX circuits). For the circuit that created the initial interlock with either a circuit quench or a discharge request, the Powering Interlock Controller (PIC) will not open the Discharge Request output in order to allow for a rearming of the quench protection system (QPS) system after recovering from the initial fault state.

Inclusion of new conditions for powering of 120A correctors into CRYO_START and CRYO_MAINTAIN logic (EDMS 886005)

During first powering tests in sector 45 it was observed that some cryogenic conditions which are essential for powering of the 120A correctors (with local current leads on the SSS) are not yet included in the logic of the CRYO_MAINTAIN and CRYO_START signal of the according powering subsector. The logic should be enhanced, including an alarm to monitor the nominal cryogenic conditions for the thermal screen and include a condition for operational conditions of the beam screen, used as intermediate thermal references for such local current leads.

Improvement of transmission dependability for the Power Permit of 60A DOC (EDMS 944765)

This document describes a modification of the currently implemented logic for the calculation of the Power Permit signal for the 752 60A orbit corrector circuits of the LHC. Currently eight 'Software Power Permit' signals are calculated from the cryogenic and powering conditions of each respective arc cryostat and sent via the timing system to the PO gateways and ultimately to the individual FGCs. In order to avoid unintentional removals of this software power permit signal when beam is present in the machine the software power permit will be forced to TRUE at the level of the PIC and the timing system when beam is present in the LHC. All existing protection mechanisms for the circuits and the related superconducting elements are maintained.

Change of the interlocking of Powering and Access Systems (EDMS 1246780)

This document describes modifications to the interlocking of powering and access system for the LHC after LS1. The link between the LHC Access Safety System and the LHC Software Interlock System, currently based on the TIM infrastructure, will be replaced by a more robust solution, even though the communication will still mostly rely on software.

Change of PIC configuration data for Inner Triplets (EDMS 1203408)

On 10th of June 2011 when operating the LHC machine with stable beams at 3.5 TeV, a powering failure affected the skew quadrupole corrector RQSX3.L1. This trip provoked beam losses in SR7 which caused both LHC beams to be dumped. This ECR proposes to change the configuration data of the Powering Interlock System to directly trigger a beam dump request in case of failures in powering RQSX3 circuits.

Protection of the warm electrical terminal of high-current leads (EDMS 1009868)

The Engineering Change Request concerns the incorporation of a hard-wired interlock to protect the warm terminal of the LHC current leads (13 kA, 6 kA and 0.6 kA) and the corresponding cables against over-heating in case of bad electrical connection between them. An alarm was originally foreseen to serve to this purpose. A software interlock was added after the first LHC commissioning phase. A hard-wired interlock was recommended by the MPP Working Group as need for ultimate protection.

Renaming of MPE systems following the R2E relocation (EDMS 1306496)

In the frame of the R2E project, some of the equipment under the responsibility of MPE will be relocated to new LHC underground areas. Following the relocation, all naming references in the operational databases will have to be modified accordingly. This document describes the updates to be applied to such databases by the end of LS1.

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