The relay can be connected to Ethernet-based communication

systems in a station bus using the RJ-45 connector (100Base

TX) or the multimode fiber optic LC connector (100Base-FX). A

dedicated protection communication port uses a pluggable

multimode or single-mode fiber optic LC connector (100Base

FX). If connection to a serial bus is required, the RS-485 or

fiber-optic serial communication ports can be used.

Modbus implementation supports RTU, ASCII and TCP modes.

Besides standard Modbus functionality, the relay supports

retrieval of time-stamped events, changing the active setting

group and uploading of the latest fault records. If a Modbus

TCP connection is used, five clients can be connected to the

relay simultaneously. Further, Modbus serial and Modbus TCP

can be used in parallel, and, if required, both IEC 61850 and

Modbus can be run simultaneously.

HSR applies the PRP principle of parallel operation to a single

ring. For each message sent, the node sends two frames, one

through each port. Both frames circulate in opposite directions

over the ring. Every node forwards the frames it receives from

one port to another to reach the next node. When the

originating sender node receives the frame it sent, the sender

node discards the frame to avoid loops. The HSR ring supports

the connection of up to 30 relays. If more than 30 relays are to

be connected, it is recommended to split the network into

several rings to guarantee the performance for real-time

applications.

When the relay uses the RS-485 bus for the serial

communication, both two- and four-wire connections are

supported. Termination and pull-up/down resistors can be

configured with DIP switch on the communication card so that

external resistors are not needed.

The IEC 61850 standard specifies network redundancy which

improves the system availability for the substation

communication. The network redundancy is based on two

complementary protocols defined in the IEC 62439-3 standard:

PRP and HSR protocols. Both protocols are able to overcome a

failure of a link or switch with a zero switchover time. In both

protocols, each network node has two identical Ethernet ports

dedicated for one network connection.

The protocols rely on the duplication of all transmitted

information and provide a zero switchover time if the links or

switches fail, thus fulfilling all the stringent real-time

requirements of substation automation.

In PRP, each network node is attached to two independent

networks operated in parallel. The networks are completely

separated to ensure failure independence and can have

different topologies. As the networks operate in parallel, they

provide zero-time recovery and continuous checking of

redundancy to avoid failures.

Relays with process bus based applications use IEEE 1588

edition 2 for high-accuracy time synchronization.

For redundant Ethernet communication in station bus, the relay

offers either two optical or two galvanic Ethernet network

interfaces. An optional third port with optical or galvanic

Ethernet network interface is also available. The relay also

provides an optional fiber-optic port for dedicated protection

communication which can be used for up to 50 km distances

depending on the selected fiber transceiver. The intended

teleprotection applications for this port are line differential and

line distance protection communication or binary signal

transfer. The optional third Ethernet interface provides

connectivity for any other Ethernet device to an IEC 61850

station bus inside a switchgear bay, for example connection of

a remote I/O. Ethernet network redundancy can be achieved

using the high-availability seamless redundancy (HSR) protocol

or the parallel redundancy protocol (PRP), or with a self-healing

ring using RSTP in the managed switches. Ethernet

redundancy can be applied to the Ethernet-based IEC 61850.

Modbus and DNP3 protocols.

The relay also supports IEC 61850 process bus concept by

sending and receiving sampled values of currents and voltages.

With this functionality the galvanic interpanel wiring can be

replaced with Ethernet communication. The analog values are

transferred as sampled values using the IEC 61850-9-2 LE

protocol. REX640 supports publishing of one and subscribing

of four sampled value streams. The intended application for

sampled values are current-based differential protection

functions or sharing the voltage values with the relays that have

voltage-based protection or supervision functions. The relay

can receive up to four sampled value streams and totally 16

measurements can be connected into the protection relay

application.

In PRP, each network node is attached to two independent

networks operated in parallel. The networks are completely

separated to ensure failure independence and can have

different topologies. As the networks operate in parallel, they

provide zero-time recovery and continuous checking of

redundancy to avoid failures.

The IEC 61850 communication implementation supports

monitoring and control functions. Additionally, parameter

settings, disturbance recordings and fault records can be

accessed using the IEC 61850 protocol. Disturbance

recordings are available to any Ethernet-based application in

the standard COMTRADE file format. The relay supports

simultaneous event reporting to five different clients on the

station bus.

The relay can send binary and analog signals to other devices

using the IEC 61850-8-1 GOOSE (Generic Object Oriented

Substation Event) profile. Binary GOOSE messaging can, for

example, be used for protection and interlocking-based

protection schemes. The relay meets the GOOSE performance

requirements for tripping applications in distribution

substations, as defined by the IEC 61850 standard (class P1.

<3 ms data exchange between the devices). The relay also

supports the sending and receiving of analog values using

GOOSE messaging. Analog GOOSE messaging enables easy

transfer of analog measurement values over the station bus,

thus facilitating, for example, the sending of measurement

values between the relays when controlling transformers

running in parallel.

Station communication

Operational information and controls are available through a

wide range of communication protocols including IEC 61850

Edition 2. IEC 61850-9-2 LE, IEC 60870-5-103. IEC

60870-5-104. Modbus® and DNP3. The Profibus DPV1

communication protocol is supported via the protocol

converter SPA-ZC 302. Full communication capabilities, for

example, horizontal communication between the relays, are

only enabled by IEC 61850.

The IEC 61850 protocol is a core part of the relay as the

protection and control application is fully based on standard

modelling. The relay supports Edition 2 and Edition 1 versions

of the standard. With Edition 2 support, the relay has the latest

functionality modelling for substation applications and the best

interoperability for modern substations. The relay supports

flexible product naming (FPN) facilitating the mapping of relay’s

IEC 61850 data model to a customer defined IEC 61850 data model.

The relay supports full Public Key Infrastructure as defined by

IEC 62351-9. With this, the user can ensure that the certificates

used in secured communication are from a user-approved

provider instead of device self-signed certificates.

User accounts can be managed by PCM600 or centrally. A

central account management is an authentication infrastructure

that offers a secure solution for enforcing access control to

relays and other systems within a substation. This incorporates

management of user accounts, roles and certificates and the

distribution of such, a procedure completely transparent to the

user. The central server handling user accounts can be, for

example, SDM600 or an Active Directory (AD) server such as

Windows AD.

The nonvolatile memory does not need battery

backup or regular component exchange to maintain the

memory storage. File transfer and Web HMI use communication

encryption protecting the data in transit.

Also, the communication link between the relay configuration tool

PCM600 and the relay is encrypted. All rear communication

ports and optional protocol services can be activated according

to the required system setup.

User accounts can be managed by PCM600 or centrally. A

central account management is an authentication infrastructure

that offers a secure solution for enforcing access control to

relays and other systems within a substation. This incorporates

management of user accounts, roles and certificates and the

distribution of such, a procedure completely transparent to the

user. The central server handling user accounts can be, for

example, SDM600 or an Active Directory (AD) server such as Windows AD.

Access control and cybersecurity

Cybersecurity measures are implemented to secure safe

operation of the protection and control functions. The relay

supports these measures with configuration hardening

capabilities, encrypted communication, Ethernet filter and rate

limiter, security event logging and user access control.

The relay supports role-based user authentication and

authorization with individual user accounts as defined in IEC

62351-8. All user activity is logged as security events to an

audit trail in a nonvolatile memory and sent as messages to the

SysLog server. The nonvolatile memory does not need battery

backup or regular component exchange to maintain the

memory storage. File transfer and Web HMI use communication

encryption protecting the data in transit.