Alstom MiCOM P846, Техническое руководство

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Application Notes P846/EN AP/D
MiCOM P846
(AP) 6-3
AP
1. INTRODUCTION
1.1 Protection of power systems
Modern power systems are operating nearer to their stability limits, in order to meet the
increased demands from a deregulated market. In order to operate closer to these limits, fast
discriminatory protection is required to detect and react quickly to changes in the power
system. Detection of changes in system topology is a strategic function for utilities, which
allows them to plan their system defense for severe contingencies such as a loss of corridor
situation.
Three-phase faults, loss of generation and cascaded events are severe conditions that can
affect stability on the power system especially when it occurs on transmission level. This can
result in angular, frequency or voltage instability, overload conditions on the system and
remedial actions such as load shedding, generation rejection, islanding are common
corrective actions taken to stabilize the system. Typically out-of-step, frequency,
undervoltage and overvoltage protection schemes are implemented to operate under these
unstable power system conditions but these are usually operational when certain critical
system conditions have been reached and further system collapse must be prevented in
order to stabilize the system.
The need to prevent a system from going into unstable conditions by means of other
techniques has been critical as power systems are now operated closer to their stability
limits and any major disturbance could result in the loss of a large portion if not the complete
power system. A fast, reliable and secure detection of the loss of bulk power on a major
transmission line or corridor can allow for quick remedial action to be taken and prevent a
possible system stability condition. In terms of defense strategy, this technique is called
"event detection". The open line detector has been specifically designed for this purpose. It
can be used in a wide-area defense system or simply dedicated to exercise a local
protection action on a subsystem.
Fast topology or open line detection is therefore an essential function allowing for quick
protection action to be taken independent of existing plant indication and standard protection
devices.