Power systems are required to remain stable after experiencing any disturbance, which may be caused by a fault, loss of a generator, or loss of a transmission line. Some disturbances may cause out-of-step between the interconnected systems, which may lead to blackouts and equipment damages if no remedial measures are taken to prevent this. In order to avoid these results, the PCS-993 out-of-step controller presents an effective way to prevent system collapse caused by out-of-step.
When the out-of-step condition is detected, the PCS-993 controller will take corresponding actions to maintain a balance between load and generation. These measures include tripping associated circuit breakers to separate the power system into two or more smaller islands at the pre-selected points, shutting down some generators, shedding appropriate loads and triggering other related synchronizers preparing for the system synchronism after the system separation.
The PCS-993 controller adopts the advanced multi-processor platform, supporting IEC 61850-8-1 MMS. In addition, it incorporates the RJ-45 faceplate port for testing and setting in order to make commissioning and maintenance easier.
Based on measurement impedance, R-X plane is divided into six sequential zones. The PCS-993 controller provides two tripping modes for different oscillation cycles; which are the fast tripping mode and the slow tripping mode. The fast tripping mode can operate in the first cycle of out-of-step for oscillation cycles of 200ms and above. The slow tripping mode operates in the second cycle of out-of-step for oscillation cycles of 100ms~200ms. The slow tripping mode operates with the same criteria as fast tripping mode but after 2~15 cycles out-of-step subject to the setting. Therefore, it only serves as a backup operation.
Protection zone restriction
According to dedicated zone measurement elements, the operating zone is individually determined.
Out-of-step Protection (78)
VT circuit supervision (VTS)
CT circuit supervision (CTS)
Event recorder including 1024 change-of-binary-input events, 1024 supervision events and 1024 operating logs
Disturbance recorder including 32disturbance records with waveforms (The format of disturbance recorder is compatible with COMTRADE.)
Up to 4 10Base-T/100Base-TX copper Ethernet ports using IEC 61850 protocol, DNP3.0 protocol or IEC 60870-5-103 protocol over TCP/IP
Up to 2 100Base-FX optical Ethernet ports using IEC 61850 protocol, DNP3.0 protocol or IEC 60870-5-103 protocol over TCP/IP ( Sharing with 2 copper Ethernet ports)
2 RS-485 serial ports using IEC 60870-5-103 protocol
1 RS-485 serial port for clock synchronization
HMI interface with large-size LCD and 9-button keypad on the front panel
1 front RJ-45 port for testing and setting
1 RS-232 or RS-485 rear port for printer
Language selection – English + selected language
Assistant software - PCS-Explorer