overwritten. The list contents cannot be modified, but the whole list can be cleared using theReset menu in the LHMI.The list of internal events provides valuable information, which can be used during commissioningand fault tracing.The information can, in addition to be viewed on the built in HMI, also be retrieved with the aid of aPC with PCM600 installed and by using the Event Monitoring Tool. The PC can either be connectedto the front port, or to the port at the back of the IED.20.3 Change lock CHNGLCK GUID-B48775D0-ACF0-49C6-A7F6-69AF37F1C68F v120.3.1 Application GUID-51EEC9C7-8ECF-4546-BC26-326861654340 v4Change lock function CHNGLCK is used to block further changes to the IED configuration once thecommissioning is complete. The purpose is to make it impossible to perform inadvertent IEDconfiguration and setting changes.However, when activated, CHNGLCK will still allow the following actions that does not involvereconfiguring of the IED:• Monitoring• Reading events• Resetting events• Reading disturbance data• Clear disturbances• Reset LEDs• Reset counters and other runtime component states• Control operations• Set system time• Enter and exit from test mode• Change of active setting groupThe binary input controlling the function is defined in ACT or SMT. The CHNGLCK function isconfigured using ACT.LOCK Binary input signal that will activate/deactivate the function, defined in ACT or SMT.GUID-8C333BC0-AA7A-4ED1-A772-18C22E8EEE62 v4When CHNGLCK has a logical one on its input, then all attempts to modify the IED configurationand setting will be denied and the message "Error: Changes blocked" will be displayed on the localHMI; in PCM600 the message will be "Operation denied by active ChangeLock". The CHNGLCKfunction should be configured so that it is controlled by a signal from a binary input card. Thisguarantees that by setting that signal to a logical zero, CHNGLCK is deactivated. If any logic isincluded in the signal path to the CHNGLCK input, that logic must be designed so that it cannotpermanently issue a logical one to the CHNGLCK input. If such a situation would occur in spite ofthese precautions, then please contact the local ABB representative for remedial action.Section 20 1MRK 511 364-UUS ASecurity278Application manual
