7070677 application of sectionalizers on distribution system

Conference Papers

Application of Sectionalizerson Distribution Systems

David M. Farmer, P.E.Kent H. Hoffman, P.E.

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1-4244-1002-9/07/$25.00 ©2007 IEEEPaper No.

07 A2

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Abstract -- Sectionalizers, properly applied, can be an integral

part of the distribution protection scheme. A properly designed

scheme is an essential component of a reliable power delivery

system. Where coordination is difficult or impossible with

traditional fault interrupting devices, sectionalizers can be an

effective solution. Many of the issues related to improper

operation are a result of how and where the device is applied.

Successful application of sectionalizers requires an

understanding of their operation, their proper role in the overall

scheme, and the training of operations personnel in

troubleshooting circuits where they are applied.

This paper addresses the essential attributes of integrating

sectionalizers into the protection scheme, as well as potential

pitfalls and failure modes and how they can be minimized.

Coordination with other protective devices and device reach will

be discussed along with their potential impact on reliability.

Index Terms— Power Distribution Protection, Power

Distribution Reliability, Power Distribution Control, Power

Distribution Faults

I. INTRODUCTION

An automatic line sectionalizer (Sectionalizer) is an

automatic switch that does not interrupt fault currents, does

not have time-current characteristics, and is dependent on the

operating of a source-side device for proper function. Because

it does not interrupt fault currents and is not capable of

operating independently, it should not be thought of as a

protective device in the classical sense, but should be thought

of as an automated switch. These characteristics give

sectionalizers distinct advantages over protective devices.

There is: 1) no need to be concerned about interrupting rating,

2) no need to time-current coordinate with load-side fuses or

source-side reclosers, and 3) they are a solution for temporary

faults in areas where the fault currents are too high for fuse

saving. But most good things come with trade-offs.

Automatic line sectionalizers have the disadvantage of relying

on assumptions rather than direct information for determining

proper operation. This reliance on assumptions, which may be

faulty, is more likely to result in unexpected operation or

failure to operate than fuses, reclosers or circuit breakers.

There are two general types of current sensing

Manuscript received January 12, 2007.

D. M. Farmer, PE is with Synergetic Design, Inc.; Raleigh, NC 27607

USA; phone: 919-787-7000, ext. 223; fax: 919-787-7055; email:

[email protected].

K. H. Hoffman, PE was with Progress Energy, Raleigh, NC 27602 USA.

He is now with the Synergetic Design, Inc.; Raleigh, NC 27607 USA; phone:

919-787-7000; fax: 919-787-7055; email; [email protected].

sectionalizers: hydraulic sectionalizers that look like small

single phase reclosers and electronic sectionalizers that look

like a solid barrel or blade cutout with a “donut” current

transformer around the middle of the barrel. In past decades

the dominant sectionalizer was the “hydraulic” sectionalizer.

Its application was limited to light loading behind a single

recloser with a 1-3 operating sequence. But the development

of electronic sectionalizers in recent years has resulted in

sectionalizers that can operate properly when carrying large

loads; behind reclosers with a 2-2 operating sequence; and

when placed to the source side of reclosers.

II. HOW SECTIONALIZERS WORK

Sectionalizers are automatic switches that are controlled by

a built-in logic system. The logic system uses operations of a

source side reclosing device to determine if a permanent fault

is occurring in the sectionalizer protection zone and, if so, to

automatically open the sectionalizer during one of the source-

side recloser temporary open periods. After the sectionalizer

opens, the source-side recloser closes, restoring service to

unaffected sections of the system. If the fault is temporary

and is cleared before the sectionalizer count reaches the

predetermined number, the sectionalizer remains closed and

resets to its original state after a predetermined time period.

Sectionalizers may be single-phase or three-phase switching

and the logic system may key on current or voltage. The focus

of this discussion will be single-phase current controlled

sectionalizers, which are the most commonly applied

sectionalizers. The logic system of current sensing

sectionalizers must make three decisions, and if the outcome

of those decisions match the logic scheme, then it will

automatically open the sectionalizer while the circuit is de-

energized by a source-side reclosing device.

The sectionalizer must determine that a fault exists in the

circuit beyond it (the load-side circuit). It does this by

recognizing a current flowing through the sectionalizer that

exceeds a predetermined current “threshold”, typically 160%

of the sectionalizer rating. This current is called the actuating

current or the arm-to-count current.

The sectionalizer must determine that the fault is not

temporary in nature. It does this by “counting” the number of

times that a source side reclosing device operates, determined

by the number of times in a set time period that an actuating

current has occurred followed by a low current indication. A

low current indication is a current below the “minimum

threshold” (indicating a de-energized circuit), typically 64% of

the sectionalizer rating for hydraulic sectionalizers and 300

mA for electronic sectionalizers. For hydraulic sectionalizers,

Application of Sectionalizers on Distribution Systems

David M. Farmer, PE, Member, IEEE and Kent H. Hoffman, PE

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currents below the minimum threshold may include load

current, while for electronic sectionalizers, currents below the

minimum threshold should be below minimum load current

levels. It is typical for sectionalizers to assume that a fault is

permanent if there are 2 or 3 counts in a set time frame (about

two minutes for an electronic sectionalizer).

The sectionalizer should determine that the fault is not

being cleared by a load-side protective device, such as a fuse

or recloser. Hydraulic sectionalizers typically can determine

that the actuating current has been cleared, but are not able to

determine if the current was cleared by a source side recloser

or a load side fuse. This must be taken into account when

applying a hydraulic sectionalizer, usually by reducing the fast

operations of the source-side recloser by one to account for the

fuse blowing. Electronic sectionalizers will “actuate” or “arm-

to-count” when they see current in excess of their threshold,

but when the actuating current goes away, they will not count

if they sense load current (typically defined as 300 mA or

more), assuming that a load side fuse or recloser cleared the

fault. If an electronic sectionalizer does not sense 300 mA

following an actuating current event, it will assume that a

source-side reclosing device cleared the fault, so the

sectionalizer will count [1]-[3].

These determinations are made without direct

communications with the associated source and load-side

protective devices, thus are assumptions deduced from current

measurements made at the sectionalizer location. For this

reason, sectionalizers are more likely than protective devices

to fail to operate as expected. This is caused by unusual

circumstances which cause the operating assumptions to be

inaccurate. For example, a sectionalizer will never open

automatically when the source-side recloser is set for non-

reclosing or any situation where the source side reclosing

device does not go through the operating sequence.

III. SECTIONALIZER APPLICATION EXAMPLES

Below are examples of typical sectionalizer operations. All

of these examples include a sectionalizer with a source-side

reclosing device and a load-side fuse or recloser.

Hydraulic Sectionalizer (3 count) sequence for a fault

beyond a load-side fuse when the sectionalizer is behind a 2-2

recloser

• Fault 1 – Current flows through the recloser, sectionalizer,

and fuse. The sectionalizer arms. The recloser opens on

the fast curve, protecting the fuse. The sectionalizer

counts “one”

• Fault 2 – The recloser closes and the sectionalizer arms.

The recloser opens on the fast curve, protecting the fuse.

The sectionalizer counts “two”


The recloser opens on the slow curve, the fuse blows.

The sectionalizer counts “three” and opens because the

current falls below 64% of the sectionalizer rating. There

are now two devices open.

Hydraulic Sectionalizer (3 count) sequence for a fault


recloser

• Fault 1 – Current flows through the recloser,

sectionalizer, and fuse. The sectionalizer arms. The

recloser opens on the fast curve, protecting the fuse.

The sectionalizer counts “one”



The sectionalizer counts “two” because the current falls

below 64% of the sectionalizer rating but remains

closed because it has not reached full count. There is

now only one device open, the fuse closest to the fault.

Electronic Sectionalizer (3 count) sequence for a fault


recloser

• Fault 1 – Current flows through the recloser,

sectionalizer, and fuse. The sectionalizer arms. The

recloser opens on the fast curve, protecting the fuse.

The sectionalizer counts “one”


The recloser opens on the fast curve, protecting the

fuse. The sectionalizer counts “two”



The sectionalizer does not count and remains closed

because more than 300 of load current exists. There is

now only one device open, the fuse closest to the fault.

Both hydraulic and electronic sectionalizers function by

counting combinations of over currents and over current

interruptions. This generally prohibits application beyond

more than one hydraulic recloser. This can be illustrated by

the example of an electronic sectionalizer (3 count) beyond

two 2-2 reclosers

• Fault 1 – Current flows through the reclosers,

sectionalizer, and fuse. The sectionalizer arms. If the

fault current is a relatively lower value, the smaller

load-side recloser will operate on a fast curve,

protecting the fuse. The sectionalizer counts “one”


The smaller load-side recloser opens on the fast curve,

protecting the fuse. The sectionalizer counts “two”


The larger source-side recloser opens on a fast curve,

protecting the fuse. The sectionalizer counts three and

opens. The fault is beyond the fuse which has not

blown, misleading service restoration personnel into

searching for the fault in the sectionalizer zone of

protection.

In most fault conditions it is probable that the two reclosers

in the above example would operate simultaneously on their

fast curves, resulting in correct operation of the sectionalizer

and fuse. But the risk and consequences of improper

operation leads us to recommend against applying

sectionalizers beyond two hydraulic reclosers. One exception

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to the rule might be sectionalizer placement beyond two

hydraulic reclosers of the same size but coordinated by

different slow curve types, such as a 2A-2B recloser

coordinated beyond a 2A-2C recloser. In this case the “A”

curves should operate simultaneously, resulting in correct

operation of the sectionalizer and fuse.

A similar consideration should be the “fast operations”,

such as an instantaneous relay, on feeder circuit breakers or

source-side electronic reclosers. If this “relay” is faster than

the slow curve of the hydraulic recloser that is being

coordinated with the sectionalizer and if it “reaches” into the

zone of the sectionalizer, then it may result in an additional

operation of the sectionalizer. For a three count hydraulic

sectionalizer beyond a 1-3 recloser this might result in a

simultaneous sectionalizer and fuse opening. A three count

electronic sectionalizer will coordinate properly with fuses if

the source-side 2-2 hydraulic recloser is replaced with a 1-3

recloser. Potential problems in this area can be avoided by

assuring that feeder circuit breaker or source-side electronic

reclosers have fast operations that do not “reach” into the

sectionalizer zones or have fast operations that are “sequence

coordinated” with the hydraulic recloser fast operations.

Sequence coordination is a logic function in most electronic

relays and reclosers that cause the relay or recloser to bypass

fast operations when they detect fault currents greater than the

fast curve “pick-up” that are interrupted before reaching the

fast curve trip time. Sequence coordination assumes that

faults meeting these conditions are interrupted by a load-side

recloser. The fast operation is then bypassed, allowing the

load-side recloser to operate on slow curves without causing

an unnecessary interruption of customers on the breaker or

recloser.

Hydraulic sectionalizers are limited in loading due to

potential mis-operations from inrush currents. The design of

electronic sectionalizers eliminates this problem through

inrush restraint and blocking count if load current (greater than

300 ma) is present following an over current event. The

ability of electronic sectionalizers to carry high load currents

(up to 200 amps) and not be affected by inrush makes it

possible to use them to the source-side of hydraulic reclosers.

The key consideration in applying sectionalizers to the source-

side of reclosers is to assure that there is a minimum of 300

milliamps of load current on each phase of the zone between

the sectionalizer and the reclosers, even during the lightest

loaded off-peak condition. A secondary consideration is to

assure that during peak load conditions, opening of a

sectionalizer will not create an imbalance capable of tripping a

ground protection of the source-side breaker or recloser.

Where these considerations are met, a typical fault would

produce the following operation.


beyond a load-side 2-2 recloser when the sectionalizer is

behind a 1-3 circuit breaker or recloser

• Fault 1 – Current flows through the source-side

breaker, sectionalizer, and load-side recloser. The

sectionalizer arms. The recloser opens on the fast

curve, clearing the fault. When the recloser opens, the

over current disappears but the load current in the

sectionalizer zone does not drop below 300 milliamps.

Therefore the sectionalizer does not count.

• Fault 2 – The load-side recloser closes and the

sectionalizer arms. The recloser opens on the fast

curve, clearing the fault. The sectionalizer continues to

see load current and does not count.


sectionalizer arms. The recloser is now on the slow

curve, causing the source-side breaker to clear the fault

on its fast curve (this would not occur with properly

applied sequence coordination). The sectionalizer sees

current drop below 300 milliamps and counts “one”.

• Fault 4 – The source-side device closes and the

sectionalizer arms. The recloser opens on the slow

curve, clearing the fault. The sectionalizer continues to

see load current and does not count.


sectionalizer arms. The recloser opens on the slow

curve, locks out. The sectionalizer continues to see

load current and does not count. The sectionalizer will

reset to “zero” count after about 2 minutes.


between the sectionalizer and a load-side 2-2 recloser when

the sectionalizer is behind a 1-3 circuit breaker or recloser

• Fault 1 – Current flows through the source-side breaker

and sectionalizer. The sectionalizer arms. The source-

side breaker opens on the fast curve, clearing the fault.

When the breaker opens, the sectionalizer sees current

drop below 300 milliamps and counts “one”.

• Fault 2 – The source-side breaker closes and the

sectionalizer arms. The source-side breaker opens on

the slow curve, clearing the fault. The sectionalizer

sees current drop below 300 milliamps and opens.

Note: Had Fault 2 been on a fused tap beyond the

sectionalizer, the fuse would blow, the sectionalizer would

continue to see load current and would not count.

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Figure 1. Some possible recloser and electronic sectionalizer configurations

where the feeder circuit breaker (SEL) and the three-phase recloser (R3ph) are

sequence coordinated.

IV. APPLICATION CONSIDERATIONS

Sectionalizers have no time-current characteristics.

Therefore, the source-side reclosing device must be able to

reach to the end of the line beyond the sectionalizer. Pay close

attention to this when replacing an existing device with a

sectionalizer. The existing device may have been there to

provide adequate reach for that line section.

Sectionalizers are switches and not protective devices.

They will never open automatically during Non-Reclosing or

any situation where the source side device does not go through

the full operating sequence.

Both Hydraulic and Electronic Sectionalizers can be

cascaded, 2 count behind 3 count.

Electronic Sectionalizers may be used on the source-side of

hydraulic reclosers provided the minimum load between the

sectionalizer and the load-side recloser exceeds 0.3 amperes.

Hydraulic Sectionalizers are not typically applied to the source

side of reclosers.

Sectionalizer application should account for the fast

operations of all source-side reclosing devices when

determining fuse clearing beyond a sectionalizer. The fast

operations of source-side reclosing devices with properly

applied sequence coordination do not need to be counted since

they will only occur for the sectionalizer applied in their zone.

Also, fast device operations that will not reach into the

sectionalizer zone do not need to be counted.

V. POTENTIAL PROBLEMS

A. Hydraulic Sectionalizer Potential Problem One –

Nuisance Sectionalizer Operation Due to Inrush Current

Sometimes a hydraulic sectionalizer may open when there

was no fault in the line section beyond the sectionalizer. This

is referred to as nuisance tripping and is typically due to

magnetizing inrush. Magnetizing inrush is produced by

saturation of iron in transformers and can be as high as 25

times transformer rated current at 0.01 second and 12 times

transformer rated current at 0.1 second. Magnetizing inrush

current on tap lines and feeders is the sum of the inrush

current at individual transformers. Maximum inrush current is

limited as impedance (distance) to the source is increased.

The problem is likely to occur when a source side breaker

or three-phase recloser opens multiple times for a single phase

fault. When the breaker or recloser closes there is

magnetizing inrush on all un-faulted phases. If the connected

transformer kVA beyond the hydraulic sectionalizer is

sufficient and the number of reclosing operations equal or

exceed the sectionalizer count, the sectionalizer may open.

A solution is to limit the application of hydraulic

sectionalizers to locations where sum of transformer rated

currents does not exceed 16 to 32% of sectionalizer rating.

Cooper Power Systems, manufacturer of hydraulic

sectionalizers, recommends limiting load current to 16% of the

sectionalizer rating to assure that there are no inrush problems.

For loads between 16% and 32% of the sectionalizer rating

inrush may be a factor. Where loads exceed 32% of the

sectionalizer rating, inrush current will probably exceed

actuating level [1].

It should be noted that on the most commonly used

electronic sectionalizers the logic circuit is programmed to

recognize an over current only if both the negative and

positive half cycles of an over current exceed actuating current

level. Because magnetic inrush is usually unidirectional, they

are ignored by the logic circuit. The asymmetrical nature of

magnetizing inrush current is shown in Figure 2.

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Figure 2. Magnetizing inrush currents are asymmetrical and ignored by

electronic sectionalizers

B. Hydraulic Sectionalizer Potential Problem Two –

Simultaneous Sectionalizer and Fuse Operation

A second potential problem with hydraulic sectionalizers is

simultaneous opening of the sectionalizer and load-side fuse

when the fuse blows.

This problem can occur with a three count sectionalizer

behind a 2-2 sequence recloser that is protecting fuses beyond

the sectionalizer. The fault is on the fused tap. The fuse

blows on the third operation of the recloser and the

sectionalizer opens when fault current is interrupted. A

common solution to this problem is to always use 1-3

sequence reclosers with hydraulic sectionalizers when

protected fuses are installed beyond the sectionalizer.

This problem may occur even with 1-3 sequence reclosers if

the feeder breaker fast relays reach into the sectionalizer zone

of protection, but as a general rule, feeder breakers with

instantaneous relays will probably operate simultaneously

with the recloser fast curve, producing no impact on the

sectionalizer.

C. Electronic Sectionalizer Potential Problem One –

Insufficient Load (Current less than 300 mA)

One of the most significant functions of an electronic

sectionalizer is the ability to distinguish between a fault in the

sectionalizer zone of protection or a fault being interrupted by

a load-side protective device. This is the function that blocks

sectionalizer counting when a load-side fuse blows or when a

load-side recloser operates, allowing placement of

sectionalizers to the source-side of reclosers. When a fault

current through the sectionalizer is interrupted, the

sectionalizer determines if there is load current present. If

there is load current then a load side device cleared the fault.

If load current is not present then the sectionalizer assumes

that the source side reclosing device cleared the fault. If the

current that follows fault clearing is greater than 300

milliamps, then load is considered to be present [2],[3].

One potential application error is to install a sectionalizer to

the source side of a reclosing device when load currents do not

exceed 300 milliamps in the sectionalizer zone at times or on

all phases. For example, one utility had successfully installed

three count sectionalizers on the source-side of four shot

hydraulic reclosers (Figure 3). The reclosers had been located

a little more than a mile from the beginning of the tap line, the

closest they could be without exceeding the recloser

interrupting rating. Electronic sectionalizers had been

installed at the beginning of the tap line and had successfully

isolated several faults in their zone of protection. Because of

the success of this installation it was decided to apply

sectionalizers to similar situation at another location. At the

second location a tap line went through a forest, starting near a

substation and going to a set of reclosers on the other side of

the forest. The fault currents were too high to apply reclosers

on the substation end of this line but were low enough for

reclosers where the line exited the forest. Sectionalizers were

installed on the substation end of the line so that a tree falling

on the line would not lock out the feeder circuit breaker.

These sectionalizers would have worked well if a tree had

fallen in the sectionalizer zone of protection. Instead the tree

fell in the recloser zone of protection. The recloser began

going through four operations to lockout. The sectionalizer

detected each flow of fault current and each subsequent

interruption by the load-side recloser. But because there were

no customers in the forest, and therefore no load, the

sectionalizer assumed that the source-side feeder circuit

breaker cleared the faults. After three interruptions by the

load-side recloser, while the recloser was open but before it

closed into the fault for the last time, the sectionalizer opened.

Because the wrong device opened utility personnel were

misled into searching for and correcting the fault in the

sectionalizer zone of protection, when the fault was actually

beyond the load-side reclosers.

To avoid this potential problem, install sectionalizers in

locations where there will be a minimum load of 300

milliamps on any phase in the sectionalizer zone at minimum

load periods, particularly where coordination with a load side

recloser or fuse is critical.

A2-6

Figure 3. Insufficient load in sectionalizer zone

D. Electronic Sectionalizer Potential Problem Two –

Feedback Currents

A second potential problem unique to electronic

sectionalizers is the possibility of feedback on the distribution

line causing the sectionalizer to assume that load current

exists, therefore blocking sectionalizer count. This can result

in a failure of the sectionalizer to open for a fault in the

sectionalizer zone of protection. This problem can occur

when there is a phase-to-ground fault on a three phase circuit

and the source side reclosing devices are single phase. A

delta transformation or large three-phase motor loads beyond

single phase reclosers can back-feed current into the phase

opened by the single-phase recloser. The result is that small

currents continue to flow through the sectionalizer. If this

current exceeds 300 milliamps the sectionalizer will not count,

and therefore not open. Figure 4 illustrates a situation where

expectations were that a faulted tap line would result in

opening of the sectionalizer. But in actual practice the motor

continues to be energized by two phases and acts as a

generator to the faulted and open phase. The currents supplied

by the motor exceeded 300 milliamps, blocking sectionalizer

count. The single-phase recloser locked out for the tap line

fault.

Feedback will never occur where sectionalizers are applied

beyond a single hydraulic recloser (a single-phase line) or on

three-phase circuits beyond three-phase reclosing devices.

When electronic sectionalizers are applied behind single-phase

reclosers on a three-phase line the feedback risk can be

minimized by avoiding circuits with delta connected

transformers and large three-phase motor loads beyond the

reclosers [2]. Since sectionalizers are not typical protective

devices, but automated switches, the risk can be further

reduced if operating personnel treat the sectionalizer as a

manual disconnect switch if the fault is not found in the

source-side zone.

Figure 4. Three-phase motor feedback through sectionalizer

E. Electronic Sectionalizer Potential Problem Three –

Fault Drifting

A third potential problem with electronic sectionalizers can

be called Fault Drifting. This condition occurs when line-to-

ground faults shift from one phase to another and the source

side device is three phase. This situation is more likely on

three count sectionalizers than on two count sectionalizers.

An example of this situation is illustrated in Figure 5. A small

tree falls into phase A, operates the breaker two times and

causes the three shot sectionalizer on A phase to count two

times. The tree shifts to B phase, operates the breaker two

more times to lockout and causes the three shot sectionalizer

on B phase to count two times. The breaker is now locked out

for a fault beyond the sectionalizers and the sectionalizers are

still closed.

Fault Drift will not occur with single-phase source-side

reclosers. To minimize potential problems, minimize the

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number of counts on the sectionalizer when the source-side

reclosing device is three-phase. For example, if the source-

side breaker is a 1 fast and 3 retarded sequence device, two

count sectionalizers would be preferable. Since sectionalizers

are not typical protective devices but automated switches, the

risk can be further reduced if operating personnel treat the

sectionalizer as a manual disconnect switch if the fault is not

found in the source-side zone.

Figure 5. Fault drifting

VI. SECTIONALIZER IMPACT ON RELIABILITY

How can we assess the impact of sectionalizers on

reliability? A simple approach is to compare the relative

reliability of a circuit with sectionalizers installed against a

circuit with a manual alternative. For example, if some

branches of an urban circuit have existing manual switches to

sectionalize it from the main feeder, then replacing manual

switches with automatic sectionalizing switches may result in

significant customer-minute savings. An operating area was

examined where electronic sectionalizers had been installed in

portions of the “backbone” feeders. Customer-minutes

interrupted on sectionalizers (which were typically single

phase interruptions) were compared with theoretical

interruptions of the whole feeder for the same durations

(which would have occurred without the sectionalizers in

place). The SAIDI improvement for the study period

exceeded 10 percent.

One reliability concern to be considered with sectionalizers

is additional operations of the source-side reclosing device,

since it is the operating sequence of the reclosing device that

directs the operation of the sectionalizer. If the alternative for

a sectionalizer is a manually operated switch, then both

operations and lockouts of the source-side reclosing device

will be reduced. If the alternative is a fuse or recloser, then

source-side reclosing will be increased. This can be

significant if the source-side device is three-phase, such as a

circuit breaker. As a general rule, protective devices which

interrupt fault currents are preferable if they can be used.

Another concern is the reliability of the sectionalizers

themselves, particularly their ability to function as expected.

Many functional failures of sectionalizers are related to

treating them like fuses or reclosers and as a result failing to

apply them properly. Recognizing that sectionalizers are

automatic switches and not classical protective devices is

essential. The logic functions built into sectionalizers are

dependent upon load currents, load or transformation types

and the operating characteristics of surrounding protective

devices. These must be understood and carefully considered

in the application of a sectionalizer.

Another factor in using sectionalizers to improve reliability

is to set realistic expectations. Because sectionalizers operate

on assumptions, like the operating sequence of a source-side

recloser, then changing conditions, such as a source-side

recloser set for non-reclosing, may result in sectionalizer mis-

operation. If sectionalizers are properly applied with regard to

load, then the typical failure mode will be for the sectionalizer

not to open. If operating personnel treat sectionalizers as

switches instead of protective devices, then trouble searches

will extend beyond the sectionalizer if the trouble is not found

to the source-side of the sectionalizer. If the alternative to a

sectionalizer is a manual switch, then treating it as a switch

will be no more challenging operationally than actually

replacing it with a switch, but will retain the benefits that

result when the sectionalizer does operate properly.

Like all components of a distribution protective scheme,

there are trade-offs involved in using sectionalizers and proper

application is critical. But where the unique operating

characteristics, strengths, and weaknesses of sectionalizers are

integrated appropriately into the design and operation of the

overall protection of the distribution feeder, significant

reliability gains can be achieved.

REFERENCES

[1] Sectionalizers – Reference Document 270-10, Cooper Power Systems,

Waukesha, WI 2003.

[2] Resettable Electronic Sectionalizer – Selection and Application,

Hubbell/Chance Power Systems, Inc., Centralia, MO 2005 .

[3] Electronic Resettable Sectionalizer – Section D10, Hubbell/Chance

Power Systems, Inc., Centralia, MO 2005 .

David M. Farmer, PE (M) is Manager of Consulting Services for Synergetic

Design, Inc. He is a graduate of West Virginia University Institute of

Technology, a member of IEEE, and a licensed professional engineer in

several states.

Since 1983, he has worked with electric utilities in power delivery

planning, reliability analysis, engineering and operations, system design,

training, and project management. He has worked for both investor owned

utilities and electric cooperatives, and has extensive consulting experience.

Kent H. Hoffman, PE is a Senior Consultant for Synergetic Design. A

graduate of NC State University, he brings over 30 years experience in

distribution system protection, standards, and reliability.

During his career at Progress Energy, Mr. Hoffman held various technical

leadership positions including Manager of Distribution Planning &

Coordination where he was responsible for standards and practices related to

distribution system protective coordination. He has served on several

technical committees and currently provides assistance and expertise on

Synergetic Design’s training programs and projects.

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7070677 application of sectionalizers on distribution system

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