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6F2T0207 (0.01)
Software interlock function (ILK)
Devices must be controlled in accordance with the prevailing operational condition of the
electric power system. If a device does not act or behave in accordance with the operational
circumstances, inappropriate device control can result in outages or fatal incidents for the
network. In order to avoid such circumstances, a software interlock (ILK) function is provided
that is able to examine the current operational situation and determine whether to permit the
control of a particular device.
When using the ILK function, an interlock-check formula is required. The interlock-check
formula examines the operational conditions for all devices, and is stored in the ILK database.
The ILK function provides an output signal "OK/NG decision information"; the "OK/NG
decision information" is transferred to the control functions†, which control the external
devices. Following which, the control functions can commence with the control of the selected
devices in response to the respective "OK/NG decision information".
Prior to controlling a device, the interlock-check function is used to determine whether the
control of a device is correct or not. If the interlock-check finds that the conditions for device
control have not been satisfied in accordance with the appropriate interlock condition, control
of the device is forbidden. Figure 4.4-1 provides an overview of the interlock-check process.
Formulae for interlock-check are stored in an ILK database; these formulae are used in order
to enable the interlock-check function to output a decision. If the proposed operation of a
particular device is deemed correct then an "OK-decision" is determined by the formulae, and
device control is allowed. However, if the proposed operation of the device is deemed incorrect
then an "NG-decision" is determined by the formulae, and device control is not allowed.
GRE200 (5,6)
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