PCS-992 / PCS-993 / PCS-994 emergency control systems: stability control, out-of-step protection, UFLS/UVLS
Emergency control systems prevent faults in the power system from developing into cascading outages and large blackouts. The line includes the stability control system PCS-992, the out-of-step protection PCS-993 and the frequency and voltage control devices PCS-994 / PCS-994S. They form the third line of defense of the power system, especially needed where an interruption of supply to consumers is unacceptable.
- PCS-992
- stability control system (PSCS): master, slave and executive stations, optical links, instability prediction
- PCS-993
- out-of-step protection: 6 zones on the R-X plane, fast and slow modes, system splitting
- PCS-994 / 994S
- UFLS with acceleration by df/dt, UVLS with acceleration by dU/dt, generator tripping at frequency rise, splitting by voltage/frequency, self-starting of hydro generators
- Recording
- 32 COMTRADE waveforms, 1024 events
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
The PCS-992 (Power Stability Control System) works at the level of the whole network. Unlike schemes that react to instability that has already occurred, it predicts it, and the control actions are chosen before the system loses stability. The system consists of several master, slave and executive stations linked by optical channels. The master and slave stations calculate tables of control actions for their area and exchange data, and the executive stations trip generators and loads, preventing oscillations and power deficits.
The PCS-993 detects an out-of-step condition between parts of the power system by the impedance trajectory, dividing the R-X plane into six consecutive zones. The fast mode acts already in the first cycle of the out-of-step swing at a swing period from 200 ms. The slow mode acts in the second cycle at a period of 100–200 ms or, by setting, after 2–15 cycles and serves as backup. The measures include splitting the system at pre-selected cutsets into two or more parts, tripping generators, load shedding and starting synchronization. The protected zone is limited by the device's own measuring elements.
The PCS-994 and PCS-994S perform automatic underfrequency load shedding with acceleration by the rate of frequency decline df/dt and automatic undervoltage load shedding with acceleration by dU/dt. They trip generators at frequency rise, split the system at frequency or voltage rise and start hydro generators when frequency drops. Blocking by df/dt, dU/dt and voltage transformer circuit failure prevents false operation during short circuits and feeding from motors. One device covers all four kinds of regime automation, at decrease and at increase of frequency and voltage, so separate cabinets for each function are not needed.
The devices are built on a multiprocessor platform and support IEC 61850-8-1 MMS, DNP3.0 and IEC 60870-5-103 through Ethernet and RS-485 ports. The recorder stores up to 32 COMTRADE waveforms, 1024 binary input changes each, self-supervision events and operating records, and the front RJ45 port is used for testing and setting during commissioning. Exchange between stations runs over digital communication channels through MUX-2M/64 interfaces and G.703 optics.
Technical specifications
| PCS-992 | stability control system (PSCS): master, slave and executive stations, optical links, instability prediction |
|---|---|
| PCS-993 | out-of-step protection: 6 zones on the R-X plane, fast and slow modes, system splitting |
| PCS-994 / 994S | UFLS with acceleration by df/dt, UVLS with acceleration by dU/dt, generator tripping at frequency rise, splitting by voltage/frequency, self-starting of hydro generators |
| Recording | 32 COMTRADE waveforms, 1024 events |
| Protocols | IEC 61850-8-1 MMS, DNP3.0, IEC 60870-5-103 |
| Channels | MUX-2M/64, G.703 optics |
Request a price and lead time
PCS-992 / PCS-993 / PCS-994 emergency control systems: stability control, out-of-step protection, UFLS/UVLS. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 8537 10 98 00 |
|---|---|
| HS, 6 digits | 8537 10 |
| CN (EU) | 8537 10 98 |
| HTSUS (USA) | 8537 10 91 70 |
| China customs tariff | 8537 10 90 90 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
How does the PCS-993 recognize an out-of-step condition?
By the impedance trajectory on the R-X plane, divided into 6 consecutive zones. The fast mode acts in the first cycle at a swing period from 200 ms, and the slow mode serves as backup.
What functions does the PCS-994 perform?
UFLS with acceleration by df/dt, UVLS with acceleration by dU/dt, generator tripping at frequency rise, system splitting and self-starting of hydro generators. Blocking on VT circuit failure excludes false operation during short circuits.
How do the PCS-992 stations exchange data?
The master, slave and executive stations are linked by optical channels. For digital communication channels the MUX-2M/64 interfaces per G.703 are used.
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