Overcurrent Protection
General Information
- Description
In many applications, the integration of protection, control, measurement and automation functions in one device is desirable. The SIPROTEC 4 overcurrent relay family includes many of the secondary ANSI functions, allowing you to use one relay per feeder. This saves investment costs, cuts installation costs, and increases availability. The 7SJ64 multifunction protection relay is highly-flexible and offers the option of up to 20 protection functions.
7SJ64
Multifunction Protection Relay with Synchronization
- Description
- Function overview
The SIPROTEC 4 7SJ64 can be used as a protective control andmonitoring relay for distribution feeders and transmission lines of any voltage in networks that are earthed (grounded), low-resistance earthed, unearthed, or of a compensated neutral point structure. The relay is suited for networks that are radial or looped, and for lines with single or multi-terminal feeds. The SIPROTEC 4 7SJ64 is equipped with a synchronization function which provides the operationmodes ‘synchronization check’ (classical) and ‘synchronous/asynchronous switching’ (which takes the CBmechanical delay into consideration). Motor protection comprises undercurrent monitoring, starting time supervision, restart inhibit, locked rotor, load jamprotection as well asmotor statistics.
The 7SJ64 is featuring the "flexible protection functions".Up to 20 protection functions can be added according to individual requirements. Thus, for example, rate-of-frequency-change protection or reverse power protection can be implemented.
The relay provides easy-to-use local control and automation functions. The number of controllable switchgear depends only on the number of available inputs and outputs. The integrated programmable logic (CFC) allows the user to implement their own functions, e.g. for the automation of switchgear (interlocking). CFC capacity ismuch larger compared to 7SJ63 due to extended CPU power. The user is able to generate user-defined messages aswell.
The flexible communication interfaces are open formodern communication architectures with control systems.
Protection functions
- Time-overcurrent protection
- Directional time-overcurrent protection
- Sensitive dir./non-dir. earth-fault detection
- Displacement voltage
- Intermittent earth-fault protection
- High-impedance restricted earth fault
- Inrush restraint
- Motor protection
- Overload protection
- Temperature monitoring
- Under-/overvoltage protection
- Under-/overfrequency protection
- Rate-of-frequency-change protection
- Power protection (e.g. reverse, factor)
- Breaker failure protection
- Negative-sequence protection
- Phase-sequence monitoring
- Synchronization
- Auto-reclosure
- Fault locator
- Lockout
Control functions/programmable logic
- Flexible number of switching devices
- Position of switching elements is shown on the graphic display
- Local/remote switching via keyoperated switch
- Control via keyboard, binary inputs, DIGSI 4 or SCADA system
- Extended user-defined logic with CFC (e.g. interlocking)
Monitoring functions
- Operational measured values V, I, f,...
- Energy metering values Wp,Wq
- Circuit-breaker wear monitoring
- Slave pointer
- Trip circuit supervision
- Fuse failure monitor
- 8 oscillographic fault records
Communication interfaces
- System interface
– IEC 60870-5-103, IEC 61850
– PROFIBUS-FMS / DP
– DNP 3.0 / MODBUS RTU - Service interface for DIGSI 4 (modem)
- Additional interface for temperature detection (RTD-box)
- Front interface for DIGSI 4
- Time synchronization via IRIG B/DCF77