Substation Comms Intro

Substation Communications: Introduction

Communications : Why use it ? Why would utilities/industry use communications to substation equipment? 

To get power system data into a remote SCADA / DCS system

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To set IEDs, aid commissioning and extract data for analysis (“local access”)

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Remote control of plant

Communication Requirements Retrieval       

Measurements Plant status Trip information Fault location Setting files Fault, event & disturbance records Maintenance information

Change settings Plant control (CB, disconnector, Tap Position, etc.) Peer-to-peer communications

Digital Communications : Definitions PROTOCOL: Rules and procedures that communications networks use to communicate on the communications medium HARDWARE CONNECTIONS  Physical shape  Electrical characteristics

Prot oco ls / F orm ats

DATA FLOW  Control transmitter/receiver rate  Detection of data corruption DATA CODING  Code information

Language

Serial Transmission : Definitions

Transmitter

11101010

00001101

Receiver

SERIAL TRANSMISSION SIMPLEX  Transmission in one direction only HALF DUPLEX  Two way means of transmission but data can

only travel in one direction at a time FULL DUPLEX  Transmission in both directions simultaneously

Transmission Systems SYNCHRONOUS

 Bit periods controlled by synchronizing the clocks at the

transmitter and at the receiver  Framing bits are added to blocks of data ASYNCHRONOUS

 Tansmitter and Receiver clocks run at approximately the

same rate  Framing bits are added to raw data bits

Transmission Medium EIA 232

- 9/25 pin D connector (was RS232) - Maximum data rate ~19200 bps - Maximum distance 15m EIA 485

- 2 or 4 wires (was RS485) - Maximum data rate ~19200 bps - Maximum distance 1000m Optical fibre - Immunity to electrical interference

- Advantages in distance and speed Ethernet

- Electrical and fibre media - Data rate 10Mbps, 100Mbps

Data Security Noise corruption of data 

Parity bit check

 

Checksums Cyclic redundancy check

Unauthorized access – “cybersecurity”     

Password protection Modem dial back Firewalls Encryption Authentication

Transmission Definitions : Client/Server MASTER/SLAVE

Slave (IED) can only send when it receives a

request from the Master (e.g. RTU) Slave sets flags to indicate functions need servicing by the Master CLIENT/SERVER

same relationship as Master/Slave but can have multiple Clients!

Transmission Definitions : Point to point REMOTE

LOCAL

Laptop

Engineering Station Modem

IED Modem

IED

Transmission Definitions : Shared Access

Star Network Topology

Ethernet Standard - 30/05/2012 - P 11

Token Ring Network Topology

Bus Network/Multidrop

Network Terminology Network

An interconnected group of nodes or stations linked by communication channels

Node

The interface point where one or more functional units are connected

LAN

Local area network (