Faulted Circuit Indicators Application Overview

Anthony PatenaudeApplication Engineer I - FIS

Schweitzer Engineering Labs

Locating Distribution FeederFaults Is Challenging

Operating Voltages

System Voltage Levels

Transmission 765 kV, 500 kV, 345 kV, 230 kV,169 kV, 138 kV, 115 kV

Subtransmission 138 kV, 115 kV, 69 kV, 33 kV, 27 kV

Primary distribution 33 kV, 27 kV, 13.8 kV, 4 kV

Secondary distribution 120/240 V, 120/208 V, 240/480 V

FCIs Reduce Outage Time

Line Truck

What Are FCIs and How Do They Work?

Theory of Operation

• Sensor detects fault current greater than system load

• Larger amount of current flowing through conductor increases magnetic field

• FCI triggers display

I

B

–

+

Sensor and Display

• FCI has two main components♦ Sensing unit

♦ Display

• Display is integral or remote

• Remote display allows indication from a distance

Fixed Trip-Level FCIs

300

Time (Cycles)

40 A load

FCI trips when current exceeds trip rating and response time

500 A fault

5000

1 2 3

1.5 cycles

Operating Energy

• Line powered♦ Current and/or voltage

• Battery powered♦ Microprocessor based

♦ Timed reset (typical)

♦ LED products

• Fault powered – no arming quantity necessary

Backfeed Protection

• Back-feed currents can cause false tripping

• Backfeed protection option provides immunity from back-feed current surges faster than 24ms

• Sources of back-feed♦ Capacitor banks

♦ Motor spin down

♦ Inductive loads

• Back-feed and discharge currents can cause

♦ False trips (over tripping)

♦ False reset

SOURCE CAPBANK

Backfeed Protection

• Backfeed protection provides immunity from back-feed current surges faster than 1.5 cycles♦ Prevents false trips (over tripping)

♦ Prevents false reset

SOURCE CAPBANK

Backfeed Protection

Advanced Fault Detection Using CT and Microprocessor

• Load current measurement algorithms

• Auto-adjusting trip ratings

• More dynamic FCIs

• Single self-configuring unit placed across entire system

Applications - Overhead

Application

• Single- and three-phase overhead conductors

• Midfeeder disconnect

• Unfused taps

• Underground transitions♦ Dips

♦ Risers

Feeder Exit Riser Pole

Dead-End Riser

Underground FeederSubstation

Quickly Determine Overhead Versus Underground Fault

Dead-End Riser

Underground FeederSubstation

Closer Look at Fault in

Underground Cable

SourceSide

LoadSide

FCI identifieswhether fault is in

underground section or on overhead

system downstream

SourceSide

LoadSide

FCI identifieswhether fault is in

underground section or on overhead

system downstream

Closer Look at Fault in Overhead Conductor

Installation

Reference “A”: Maximum recommended distance from pole of 6’-0”

Reference “B”: Minimum distance from pole of 3’-0”

Reference “C”: Minimum distance from energized hardware of 2’-0”

Minimum Installation Spacing Requirements

Inrush Restraint Mechanism

Example #1: Recloser Lock-out / Fault Downstream of FCIs

• Downstream fault – low impedance♦ Assume a 13.2 kV L-L system

– Line has been energized long enough to power up / arm the FCIs

– FCIs downstream of a 3 phase sectionalizing automatic recloser

To Source

To Load

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Fault

Time

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Recloser operates

Time

Fault

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

TimeInrush Restraint Activated

Fault Recloser operates

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Recloser closes back inFault Recloser 

operates

Inrush Restraint Activated

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Fault Recloser operates

Recloser closes back in

Inrush Restraint Activated

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Fault Recloser operates

Recloser closes back in

Recloser Lock‐out

Recloser Lock‐out

Inrush Restraint Activated

Example #1: Recloser Lock-out / Fault Downstream of FCIs

Example #2: Recloser Lock-out / Fault Upstream of FCIs

• Upstream fault – low impedance♦ Assume a 13.2 kV L-L system

– Line has been energized long enough to power up / arm the FCIs

– FCIs downstream of a 3 phase sectionalizing automatic recloser

To Source

To Load

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

Time

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

TimeInrush Restraint Activated

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

TimeInrush Restraint Activated

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

TimeInrush Restraint Activated

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Trip Rating

Load

Trip Rating

Load

B&C Phases

A Phase

TimeInrush Restraint Activated

Recloser Lock‐out

Recloser Lock‐out

Example #2: Recloser Lock-out / Fault Upstream of FCIs

Applications - Underground

Live-Front Switchgear Air insulated

Cables terminated to exposed live bus

Cable termination uses voltage stress relief

No test point availability

Not applicable in subsurface applications

Install FCI units below stress relief

Install FCI with Snap-Action clamp onto terminal lug

Three-Phase Live-Front Switchgear

Four-Way Switch

Install FCIs at unfused outgoing feeds

Side view Top-down view

3 2

14IN

Dead-Front Switchgear Designed with no exposed high-voltage parts

Pad-mount and subsurface applications

Uses standard connector system interface (Elbows & T-Bodies)

Connectors are shielded with semi-conductive rubber outer surface

Likely that test points are available

Three-Phase Switchgear

Three-Phase Switchgear

Three-Phase Switchgear

LOAD

SIDE

Concentric Neutral Training

Four Acceptable Options• Double Backed

• Braided

• Pulled Back (drain wire inside core)

• Pulled Back (drain wire outside of core)

Tape-Shielded Cable and Adapter

Fault Indicators Are a Good Value

• Meet needs of a large-scale deployment♦ Easy to Install

♦ Low cost

♦ Little to no maintenance

♦ Long service life (10+ years minimum)

• Reduce fault finding time by half

• Easy to spot and determine status in field

Thank You for Your Time!Any Questions?