The busbar protection is a selective, safe, and fast protection against busbar short circuits in medium voltage, high-voltage and very high voltage systems with the most various busbar configurations. Selection of the device is based functionalities and the modular hardware structure allow optimum adaptation of the busbar protection to a large variety of system configurations and functional requirements up to a complete station protection. 

The 7SS85 CU is the central unit of a distributed busbar protection system. The merging unit 6MU85 or each other modular SIPROTEC5 device can be used as a bay unit for the distributed busbar protection. 

Busbar protection devices are part of a modular protection series and their main function bases on the principle of differential protection. 
Applications 

The device is designed for the following substation layouts

• Single to five-way busbars with/without transfer busbar and
• Breaker and a half scheme
• Dual circuit breaker systems and one or two current transformer( per feeder)
• Truck-type switchgear
• Combined busbar systems (alternatively main/transfer busbar) 
• H connection arrangement with busbar coupler or disconnection 
• Ring busbars 

The busbar protection encompasses the following maximum quantity 

• Up to 48 3-phase measuring points (current transformer) 
• Up to 20 busbars and coupler  
• Up to 10 auxiliary busbars (busbar sections without measuring function 

Features

• Phase-selective measurement and Display 
• Selective tripping of faulty busbar sections 
• Connector-independent check zone as additional tripping criterion 
• Shortest tripping times to ensure network stability and minimize damage to the system - 10 ms (Relais Typ F) 

• Highest stability is case of external faults, also in case of transformer saturation through stabilization with flowing currents 
• Operate curve with freely adjustable characteristic-curve sections  
• Highest stability in case of external faults – even in case of transformer saturation – through stabilization with flowing currents
• Operate curve with freely adjustable characteristic curve sections 
• Additional operate curve with increased sensitivity for low-current errors, for example in resistance-grounded power systems 
• Fast recognition of internal and external errors requires only 2 ms of saturation-free time of the current transformer 
• Using closed iron core or linearized current transformers in a plant is possible 
• Adaptation of different current transformer ratios per parameterization 
• Straight-forward dimensioning of current transformers and stabilization factor 
• Three interacting methods of measurement allow minimum tripping times after busbar faults and ensure maximum stability in case of large short-circuit currents 
• The integrated circuit-breaker failure protection recognizes circuit breaker faults in the event of a busbar short  
• Circuit and provides a trip signal for the circuit breaker at the line end. The adjacent busbar trips if a coupling circuit breaker fails
• There is extensive monitoring of current transformer circuits, measured value acquisition and processing, and trip circuits. This prevents the protection from subfunction, which reduces the effort for routine checks. 
• Various control possibilities, such as bay out of order, acquisition blocking from disconnectors and circuit breakers, blocking of protection zones or circuit-breaker failure protection, make the adaptation to operationally-caused special states of your plant easier 
• 1/3-pole or 3-pole circuit-breaker failure protection using the integrated disconnector image for tripping  
• All circuit breakers of the busbar section affected 
• End-fault protection for the protection of the section between circuit breaker and current transformer for feeders and bus couplers 
• Direct tripping of protection zones through external signals 
• Release of the tripping of a protection zone through additional external signals 
• Release of tripping through additional, external phase-selective signals 
• Cross stabilization against overfunctions in case of transformer influence on the secondary side 
• Bus coupler differential protection for fault clearing in couplers with two current transformer 
• Additional operate curve with increased sensitivity for low current faults, for example in resistance-grounded networks  
• Only 2 ms saturation-free time of the current transformer required through fast recognition of internal and external faults 
• Use of closed iron core or linearized current transformer within one substation possible  
• Adaptation of different current transformer ratio per parameterization  
• Uncomplicated dimensioning of the current transformers and the stabilization factor 
• 3 interdependent methods of measurement make possible the shortest tripping times in case of busbar faults and ensure maximum stability in case of large flowing short circuit currents 
• The integrated circuit-breaker failure protection recognizes circuit-breaker faults in case of busbar short-circuits and generates a tripping signal for the circuit breaker at the remote line end. In case of a failure of a coupler circuit breaker, the adjacent busbar is tripped. 
  (Available in the bay unit!) 
• Comprehensive monitoring of the current circuits, the measured-value processing and trip circuits prevent over-functions and under-functions of the protection and reduce the effort for routine checks 
• Various control possibilities, such as bay out of service, acquisition blocking for disconnectors and circuit breakers, blocking of protection zones or of the entire circuit-breaker failure protection, make the adaptation to operationally-caused special states of your system easier  
• Optional 1/3- or 3-pole circuit-breaker failure protection with use of the integrated disconnector image to trip all circuit breakers of the concerned busbar section. 
  (Available in the bay unit!) 
• Optional end-fault protection for the protection of the area between circuit breaker and current transformer for feeders and couplers. 
  (Available in the bay unit!) 
• Direct tripping of protection zones through external signals 
• Release of tripping of a protection zone through additional external signals 
• Release of tripping through additional, external phase selective signals. 
• Algorithm certified by KEMA 
• Protection view in the single-line monitoring for a graphical presentation of the measurement system limits 
• Ruggedized design and conformal coated electronical boards for high electric strength and installations in harsh environments - as standard 
• Redundant power supply optional 
• Large process data range (up to 40 current and voltage transformers for protection applications and up to 80 for central busbar protection; more than 200 inputs and outputs for recording applications possible) 
• Easy and straight forward selection of the device type using typicals (Significant festures)
• Easy integration and retrofit of arc protection, transient ground-fault detection, transformer control, PMU and process bus for efficient network operation 
• Optional arc protection with a tripping time of 3-4 ms for protection of assets and personal – Safety first 
• Operation panel that is freely selectable for all device types (for example, large or small display, with or without key switches, detached operation panel) 
• Graphical engineering in a single line editor of the engineering tool 
• Graphical logic editor to create powerful automation functions and switching sequences in the device according to IEC 61131-3 standard 
• Detection of current and voltage signals up to the 50th harmonic with high accuracy for selected protection functions and operational measured values 
• Integrated electrical Ethernet RJ45 for Engineering PC and IEC 61850 (reporting and GOOSE) 
• Two slots for optional plug-in modules for serial and/or Ethernet-based protocols 
• Optional communication module with further 3 slots plug-in modules for serial and/or Ethernet-based protocols and full availability of the communication ring when the switchgear is enabled for servicing operations by means of separate auxiliary power supply of the communication module 
• Large number of serial and Ethernet-based protocols: IEC 60870-5-103, DNP3 serial and TCP, Modbus TCP, IEC 60870-5-104, PROFINET, and IEC 61850 Ed1
  and Ed2.1  
• Reliable data transmission via Ethernet redundancy protocols PRP for process bus and PRP and HSR for high-availability station communication
• IoT interface for integration in cloud based systems 
• Serial protection data communication via optical fibers, two- wire connections and communication networks (SDH networks, MPLS electrical power systems, for example using IEEE C37.94, and others), including automatic switchover between ring and chain topology. 
• Powerful fault recording (buffer for a max. record time of 5 sec. at 2 kHz) 
• Easy, fast and secure access to device via Web-Browser from the device: Download of logs as files according IEEE C37.239 COMFEDE with https connection 
• Fault recording: Download, delete and triggering of fault records 

Displaying of Single line diagrams and device display pages, indications, 

vector diagrams of energizing quantities 

• Parameterization: Change of settings within an active setting-grou
• Optional Phasor Measurement Unit (PMU) for detection of Synchrophasor measured values and transmission with standard IEEE C37.118 protocol
• Time Synchronization with IEEE 1558v2/PTP, PPS, IRIG-B 
• Role-based Access Control (RBAC) protocolling security-related events, signed firmware or authenticated network access IEEE 802.1X with central user management in RADIUS/Active Directory 
• Protection against unauthorized access to device through inbuilt RADIUS authentication and authorization option 
• Standard roles and rights in adherence to standards and guidelines such as IEC 62351-8, IEEE 1686 and BDEW White paper 
• Syslog support for central recording and logging of security-relevant events and alarms in accordance with the requirements and regulations such as IEEE 1686, IEC 62443 and BDEW Whitepaper 
• Individual Assignment of write and read permission for each device port 
• Auxiliary functions for simple tests and commissioning 

Standard variants 

The number of inputs and outputs, LEDs and communication modules are flexible and expandable with 1/6 expansion modules plugged on the 1/3 base unit of a modular system. 

O 19 BI, 10 BO, 1 Life, 16 LEDs, 1x communication module with 2x FO 

  interfaces, 1/3 x 19 inches 

  Attention: Current- and Voltage Transformers can’t be used. 
Housing 

Robust hardware in the form of a closed housing for maximum strength in terms of voltage, EMC, climate and mechanical stress in accordance with the IEC 60255 product standard and an extended temperature range of -25°C to + 70°C.  

Additional conformal coating of the electronic components for maximum availability even under extreme environmental conditions 

Housing width 1/3 x 19 inches to 2/1 x 19 inches with large, small or without display. Flexible adjustable and expandable I/O quantity structure within the scope of the system with 1/6 expansion modules. 

Type of housing: 

X Flush mounting 

O Surface mounting 

Power Supply: 

X Standard 

O Redundant 

Operation panel: 

X Integrated 

O Detached HMI, only for surface mounting housing 

Type of display: 

O No display 

X Small Display 

O Large Display 

Key switch: 

X without 

O with, only for flush mounting housing 

LEDs/Push buttons: 

X 16 LEDs 

O 32 LED 

O 48 LED 

O 64 LED 

O 80 LED 

O 8 Push buttons + LEDs 

Rated auxiliary voltage 

O DC 60 to 125 V DC 

X DC 110 V-250 V, AC 100V - 230 V 

Communication 

The base unit has two free slots on the rear for plug-in modules for communication or special applications. The base unit is expandable with a communication module with up to three further slots for plug-in modules. 

• USB operator interface on the front for notebook or PC 
• D-Sub 9-interface, rear for time synchronization 
• Integrated Ethernet interface 
  X for Engineering Tool 
  O for Engineering Tool and IEC 61850 Reporting and GOOSE 
  O for Engineering Tool and IEC 61850 Reporting 

Communication module, max 1 for each device with additional 3 slots plug-in modules for serial and/or Ethernet-based protocols and full availability of the communication ring when the switchgear is enabled for servicing operations by means of separate auxiliary power supply of the communication module 
X without 
O with one communication module for up to three additional plug-in modules 

Serial Plug-In modules for asynchronous serial protocols like IEC 60870-5-103, DNP for system port 
X Without 
O electrical, 1 interface 
O electrical, 2 interface 
O optical 820 nm, 1.5 to 2km ,1 interface 
O optical 820 nm, 1.5 km to 2km, 2 interfaces

Serial Plug-in modules for protection interface for unidirectional data exchange 

X without 
O optical 1300 nm, max. 24 km via 2 single mode optical fibers or  
  max. 4 km via 2 multimode optical fibers, 1 interface 
O optical 1300 nm, max. 24 km via 2 single mode optical fibers or max. 4 km 
  via 2 multimode optical fibers, 2 interface 
O optical 1300 nm, max. 60 km via single mode optical fiber, 1 interface 
O optical 1300 nm, 60 km via single mode optical fiber, 2 interface 
O optical 1550nm, 100 km via single mode optical fiber, 1 interface 
O optical 1550nm, 100 km via single mode optical fiber , 2 interface 

  Serial Plug-in modules for protection interface for bidirectional data
     exchange 
O without 

O optical 1300 nm, max. 40 km via one single- mode optical fiber  

  (with integrated fiber-optic multiplexer, 1 interface) 
O optical 1300 nm, max. 40 km via one single- mode optical fiber  

  (with integrated fiber-optic multiplexer, 2 interface) 

O optical 1550 nm, max. 40 km via one single- mode optical fiber  

  (with integrated fiber-optic multiplexer, 1 interface) 
O optical 1550 nm, max. 40 km via one single- mode optical fiber  

  (with integrated fiber-optic multiplexer, 2 interface) 

   Plug-in Modules for Ethernet  

O Without 

O 2x RJ45 electrical, configurable with or without integrated switch  

  with max. distance of 20 meters 
O 2x optical duplex LC 1300 nm interface, configurable with or without 

  integrated switch. The maximum optically permitted distance via 50/125 µm 

  or 62.5/125 µm multimode optical fibers is 2 km.  

O 2x optical for process bus, duplex LC 1300 nm interface, configurable with 

  or without integrated switch. The maximum optically permitted distance  

  via 50/125 µm or 62.5/125 µm multimode optical fibers for up to 2 km.  

O 2x optical for process bus, duplex LC 1300 nm interface, configurable with 

  or without integrated switch. The maximum optically permitted distance  

  via 50/125 µm or 62.5/125 µm multimode optical fibers for up to 24 km.  

The optical transmission and receiving level are measured in the module and can be displayed. 

In accordance with the selected communication interface the required communication protocol should be easily activated via the engineering tool depending on the selected type of serial or Ethernet plug-in module 

Serial protocols 
IEC 60870-5-103 
DNP3 serial 
Modbus RTU 

Ethernet protocols 

IEC 61850 Edition 2.1 

IEC 61850-8-1 Client-Sever Communication 

IEC 61850-8-1 GOOSE 

IEC 60870-5-104 
DNP3 TCP 
Modbus TCP 
PROFINET IO 

Additional Ethernet protocols and services 
DHCP, DCP (with automatic IP configuration) 

Line mode 
RSTP, PRP, HSR Ethernet ring redundancy 

SNTP time synchronization via Ethernet 

SNMP V3 network management protocol 

IEEE 1588v2 PTP protocol via Ethernet 

The merging unit 6MU85 or each modular SIPROTEC 5 device can be used as a bay unit for the 7SS85 CU 

O Up to 16 current measuring points (1x Ethernet plug-in module with 2x FO) 

O Up to 32 current measuring points (2x Ethernet plug-in module with 2x FO) 
O Up to 48 current measuring points (3x Ethernet plug-in module with 2x FO) 

Plug-in modules for various applications 
O Measuring-transducer module with four 20-mA analog inputs 

O Measuring-transducer module with 1 direct voltage input  

O Arc protection module with up to 3 optical point or line sensors per  

  arc protection plug-in module, up to max. 15 sensors for modular devices 

  X Point sensors with line lengths from 3 m to 35 m.  

  O Line sensors detect arcs along the entire sensor length.  

    Lengths from 5 m to 40 m are available.  

    Line sensors are connected via a line to the arc protection module. 

Functionality 

The protection device is equipped with the following protection functions: 

X Basic functions: 

• Protection functions for 3-pole tripping 
• Hardware quantity structure expandable 
• Process Bus Client protocol for 7SS85 CU 
• IEEE 1588v2/PTP Grandmaster Clock (Note: This function requires a

    dedicated Ethernet module with 2x fiber optic interfaces)

• Differential protection, busbar (87B) 
• Stub-fault differential protection for breaker-and-a-half-protection

    (87STUB) 

• Arc protection (only with the plug in module for arc)
• Measured values, standard 
• CFC (standard, control) 
• External trip initiation 
• Monitoring and supervisions 
• Fault recording of analog an binary signal 

Optional functions 

O Busbar coupler differential protection (87B) 

O Cross stabilization 

O CFC arithmetic 

O CFC switching sequences 

O Slow-scan recorder 

O Continuous recorder 

O PQ-1012/ cycle value for continuous recorders 

O Trend recorder 

O PQ-Trend value for Trend Recorder 

O PQ-Flicker values for Trend recorder 

O Cyber Security: Role based Access Control RBAC 

O Cyber Security: IEEE 802.1x based network authentication