Comprehensive monitoring routines in the P63x ensure that internal faults are detected and do not lead to malfunctions.
Tests during start-up
After the supply voltage has been turned on, various tests are carried out to verify full operability of the P63x. If the P63x detects a fault in one of the tests, then start-up is terminated. The display shows which test was running when termination occurred.
No control actions may be carried out. A new attempt to start up the P63x can only be initiated by turning the supply voltage off and then on again.
Cyclic tests
After start-up has been successfully completed, cyclic self-monitoring tests will be run during operation. In the event of a positive test result, a specified monitoring signal will be issued and stored in a non-volatile memory – the monitoring signal memory – along with the assigned date and time (see also Monitoring Signal Recording).
The self-monitoring function monitors the built-in battery for any drop below the minimum acceptable voltage level. If the associated monitoring signal is displayed, then the battery should be replaced within a month, since otherwise there is the danger of data loss if the supply voltage should fail. Chapter 11 gives further instructions on battery replacement.
Signals
The monitoring signals are also signaled via the output relay configured to S F M O N : W a r n i n g . The output relay operates as long as an internal fault is detected.
3-64 Monitoring signals
Device response
The response of the P63x depends on the type of monitoring signal. The following responses are possible:
Signaling Only
If there is no malfunction associated with the monitoring signal, then only a signal is issued, and there are no further consequences. This situation exists, for example, when internal data acquisition memories overflow.
Selective Blocking
If a fault is diagnosed solely in an area that does not affect the protective functions, then only the affected area is blocked. This would apply, for example, to the detection of a fault on the communication module or in the area of the PC interface.
Warm Restart
If the self-monitoring function detects a fault that might be eliminated by a system restart – such as a fault in the hardware –, then a procedure called a warm restart is automatically initiated. During this procedure, as with any start-up, the computer system is reset to a defined state. A warm restart is characterized by the fact that no stored data and, in particular, no setting parameters are affected by the procedure.
A warm restart can also be triggered manually by control action. During a warm restart sequence the protective functions and the communication through serial interfaces will be blocked. If the same fault is detected after a warm restart has been triggered by the self-monitoring system, then the protective functions remain blocked but communication through the serial interfaces will usually be possible again.
Cold Restart
If a corrupted parameter subset is diagnosed during the checksum test, which is part of the self-monitoring procedure, then a cold restart is carried out. This is necessary because the protection device cannot identify which parameter in the subset is corrupted. A cold restart causes all internal memories to be reset to a defined state.
This means that all the protection device settings are also erased after a cold restart.
In order to establish a safe initial state, the default values have been selected so that the protective functions are blocked. Both the monitoring signal that triggered the cold restart and the value indicating parameter loss are entered in the monitoring signal memory.
P63X/EN M/Ba4 // AFSV.12.09701 D /// P631-305-403/404-610 // P632-305-403/404-610 // P633-305-404/405/406-610 // P634-305-403/404-610 3-99 Monitoring signal memory
(as of version P63x -605)
Depending on the type of internal fault detected the device will respond by trying to eliminate the problem with a warm restart. (See above; for further details read also about device behavior with problems in Chapter 10 ,Troubleshooting’.) Whether or not this measure will suffice can only be determined if the monitoring signal has not already been stored in the monitoring signal memory because of a previous fault. If it was already stored and a second fault is detected then, depending on the type of fault detected, the device will be blocked after the second warm restart. Previously this occurred
independently of the time duration that had passed since the first monitoring signal was issued.
The behavior caused by sporadic faults could lead to an unwanted blocking of the device if the monitoring signal memory has not been reset in the interim, for example, because the substation is difficult to reach in wintertime or reading-out and clearing of the monitoring signal memory via the communication interfaces was not enabled. A
"memory retention time" timer stage has been introduced to defuse this problem.
SFMON: Mon.sig. retention
Now device blocking only occurs, when the same internal device fault is detected twice during this time duration. Otherwise, the device will continue to operate normally after a warm restart. In the default setting this timer stage is blocked so that, when an internal fault is detected, the device will operate in the same way as the previous versions.
Monitoring signal memory time tag
(as of version P63x -605)
Because of these changes the significance of the time tag for entries to the monitoring signal memory has been re-defined. The time when the device fault occurred first was previously recorded. As of version P63x –605 the time when the device fault occurred last is now recorded.