Copyright © SEL 2009

Then Versus Now: A Comparison of Total Scheme Complexity

Bob Morris, Roy Moxley, and Christina KuschSchweitzer Engineering Laboratories, Inc.

OR

Protection Fails to Clear Fault in the Prescribed Time

52

AND

Top Event

Logic Gate

Basic Events

RelayA

RelayB

Breaker Fails

CT Fails

Battery Fails

Wiring Fails

52

50A 50B

Simple-Scheme

Fault Tree Analysis

Real-World Transmission Scheme Is More Complex

Leading to More Complex

Fault TreeKD KD

KD

RC

CVE NGV

TD-5

IRD

XX

X

X

2X 2X

2X

2X

X2 + X

X2

4X2

X + 4X2

8X3 + 2X2

8X3 + 2X2 + 2X8X3 + 3X2 + 3X

Protection Reclosing

Protection Fails to Trip and Reclose for a Line Fault

OR

OR

OR

OR

AND

AND

AND

Connections Are Part of Critical Path

Many Benefits to Reducing Yard Wiring

Protection Fails to Trip for a Line Fault

KD KD

RC

CVE NGV

TD-5

IRD

XX

X

X

2X 2X

2X

2X

X2 + X

X2

4X2

X + 4X2

8X3 + 2X2

8X3 + 2X2 + 2X

8X3 + 3X2 + 3X

KD

OR

OR

AND

OR

AND

OR

AND

“Critical” Path Wiring Is

Substantial Part of Total

Wires

“Unavailability” Time Is Function of Multiple

Inputs

• MTBF

• Detection time

• Time to repair

Mean Time to Failure

• 30–400 years

• Not “tested” into product

• Environmental impact

Detection Time

• Most important factor

• Self-test vs. scheduled test

Time to Repair

• How difficult is repair?

• What else is out of service during repair?

Guide to Fuse Replacement

97 A 243 A 612 A 1482 A (Slow Blow)

Subcomponents and Adjustments Are Part of Scheme Complexity

Even Subcomponents Have Subcomponents

Microprocessors:More Components, Fewer Adjustments

Va

Vb

Vc

V neutral

V busbar

I neutralMerging

UnitDigital

Communication

Pow

er

Sup

ply

Clo

ck In

put

(If R

equi

red)

Dis

cret

e S

tatu

s an

d A

larm

la(meas)

lb(meas)

lc(meas)

la(prot)

lb(prot)

lc(prot)

Merging Unit Concept

Advanced CT Application Topologies

MV and HV

GIS Switchgear

IEEE C37.92

IEC 61850-9-2

Ethernet

Ethernet

IEC 61850: Switched Ethernet Station and Process Bus From Beginning

IEC 61850 Defines Suite of Protocols – Not Just One

UDP / IPGSSE

T-Profile

Sampled Values

(Multicast)

Generic Object-

Oriented Substation

Event

Time Synchronization

(Method 2)

CoreACSI

Services

Generic Substation

Status Event

ISO / IEC 8802-3

ISO / IEC 8802-3 Ethertype

SV

(Type 4)

GOOSE

(Type 1, 1A)

GSSE

(Type 1, 1A)

GPSIRIG-B

Time Synchronization

(Method 1)

Time Synchronization

(SNTP)(Type 6)

MMS Protocol Suite

(Type 2, 3, 5)

Sampled Values on LAN

• Takes decentralization one step further

• Separates sampling physically from

♦ Measurement

♦ Metering

♦ Calculation

• Publishes constant message at predefined rate

• Sends SV to multiple subscribers

Traditional Topology:

Wires Vs. Components

PhysicalEquipment

TerminalBlock

RelayMarshallingCabinet

TerminalBlock /

Test Plug

44 Wires 44 Wires 44 Wires 44 Wires

Yard House

Relays in Yard: Fewer Wires, Where Do You

Test?

PhysicalEquipment

TerminalBlock /

Test PlugRelay44 Wires 44 Wires

Yard

Relay-Based Process Bus System

Process Level

BayLevel

Instrument Transfer

Merging Unit

50, 51, 21

Breaker ControllerBreaker

Station Level

Time Source

Ethernet Switch

Station Controller

HMI

Ethernet Switch

87BFR

Merging Unit Reduces Wire Count, Increases Device Count

PhysicalEquipment

TerminalBlock /

Test PlugRelay

Merging Unit

Switch or Processor

44 Wires 44 Wires 1 Cable 1 Cable

Yard House

Moving I/O to Yard:

Replace Wire With Fiber

PhysicalEquipment

TerminalBlock

RelayTerminalBlock /

Test Plug

MarshallingCabinet

I/O Transceiver

44 Wires 24 Wires

20 Wires

24 Wires24 Wires

1 Cable

YardHouse

Where Should Testing Be Performed?

It Is Colder (or Hotter) Outside

Conclusions

• Number of wires and number of devices are key elements of complexity

• Reduction of wire count AND device count both need consideration

Conclusions

• Firmware complexity and qualitative measures are as significant as hardware measures

• Measuring and evaluating scheme complexity are how we improve