GUID-8C333BC0-AA7A-4ED1-A772-18C22E8EEE62 v6When CHNGLCK has a logical one on its input, then all attemptsto modify the IED configuration and setting will be denied and themessage "Error: Changes blocked" will be displayed on the localHMI; in PCM600 the message will be "Operation denied by activeChangeLock". The CHNGLCK function should be configured sothat it is controlled by a signal from a binary input card. Thisguarantees that by setting that signal to a logical zero, CHNGLCKis deactivated. If any logic is included in the signal path to theCHNGLCK input, that logic must be designed so that it cannotpermanently issue a logical one to the CHNGLCK input. If such asituation would occur in spite of these precautions, then pleasecontact the local ABB representative for remedial action.20.4 Denial of service SCHLCCH/RCHLCCH20.4.1 Application GUID-64F4D905-9F73-4073-B8F6-8D373155316A v5The denial of service functionality is designed to limit the CPU load that can beproduced by Ethernet network traffic on the IED. The communication facilitiesmust not be allowed to compromise the primary functionality of the device. Allinbound network traffic will be quota controlled so that too heavy network loadscan be controlled. Heavy network load might for instance be the result ofmalfunctioning equipment connected to the network.The functions Access point diagnostics function block measure the IED load fromcommunication and, if necessary, limit it for not jeopardizing the IEDs control andprotection functionality due to high CPU load. The function has the followingdenial of service related outputs:• LINKSTS indicates the Ethernet link status for the rear ports (singlecommunication)• CHALISTS and CHBLISTS indicates the Ethernet link status for the rear portschannel A and B (redundant communication)• LinkStatus indicates the Ethernet link status for the front port20.4.2 Setting guidelines GUID-CE3344E8-539B-47E0-9C19-8239988BDBCF v3The function does not have any parameters available in the local HMI or PCM600.1MRK 505 393-UEN B Section 20SecurityLine differential protection RED650 2.2 IEC 401Application manual
