GeneralThe Cooper Bussmann Automatic Sectionalizing Link (ASL) is a self-contained circuit-opening device that, when used with either an upstream auto-recloser or multi-shot circuit breaker, sectionalizes and isolates the network thereby reducing the number of customers disconnected due to permanent faults.

The ASL differentiates between transient and permanent faults, greatly reducing the number of outages caused by transient no-damage faults such as lightning.

Using the Bussmann ASL, an economical system can be installed utilizing most existing expulsion dropout fuse mounts in conjunction with multishot circuit breakers or auto-reclosers. Even where no expulsion fuse mounts exist and these have to be provided, significant benefits can still be achieved.

DesiGn Featuresincreased network reliability with an overall reduction in costThe ASL differentiates between transient and permanent faults, providing automatic disconnection of permanent faults. By virtually eliminating nuisance outages, significant reduction in system running costs are achieved.

Comprehensive range of ratingsASL is available with voltage ratings up to 38 kV, pick-up currents from 16 to 320 A and 1, 2 or 3 count options. Color bands are located on the body of the ASL for easy identification of count and pick-up rating.

Fits into existing expulsion fuse mountsThe ASL C-type version fits all the common NEMA interchangeable mounts such as the Type L cutout from Cooper Power Systems. They swing down upon operation, providing visual identification of a fault downstream. This allows for fast system restoration. ASLs are installed and removed using existing pole head equipment. Detailed installation instructions are available with every ASL and also on request.

silent, reliable drop-out actionHigh output force of the replacement actuator provides rapid, reliable drop out action, even under icing, to provide visual indication of a faulty line. Dead time operation ensures no sparks, ionized gas or contact erosion, minimizing fire risks.

immunity to magnetizing inrush currentThe logic circuit ignores the first half-cycle current and reacts only if both the negative and positive half cycles exceed the pick-up current. As magnetizing inrush currents are largely unidirectional they are ignored by the logic circuit.

Fusing equipment

automatic sectionalizing link

electrical apparatus

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Figure 1. Cooper Bussmann Automatic Sectionalizing Link (ASL).

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surge and eMi protectionElectronics are shielded from magnetic field influences by being enclosed within the conducting tube. The ASL is tested to withstand lightning impulse currents and to be immune to radio frequency interference.

self powered, no maintenanceThe logic circuit and actuator are powered by two current transformers during the passage of fault current. No additional power source is required, and no maintenance is needed.

low threshold for hold off current (250 milliamps)A return to load current following a temporary fault will not result in a mistaken count by the ASL.

ConstruCtionThe ASL houses a fully encapsulated logic circuit within its main conductive tube powered by encapsulated small current transformers mounted on the outside of the tube. This ensures that the electronic circuitry is free from electrical interference as the tube acts as an effective Faraday cage. The logic circuit is also environmentally protected to prevent moisture ingress. Energy derived from the current transformers under fault conditions allows the ASL to be self powered to ensure operation even when there is no initial load current.

In appearance the upper and lower contacts of the ASL resemble that of the fuse holder it replaces. Instead of a fuse element melting to release the holder from the mount, operation is accomplished by discharging a capacitor into a small actuator (or ‘striker’) which unlatches the holder tube and causes it to swing down in the manner of an expulsion fuse holder (See Figure 3).

The actuator is an extremely reliable device with high mechanical advantage, providing rapid, reliable drop-out action even under icing conditions. The actuator is completely safe to handle and there are no special storage or transporting requirements.

The ASL is reset by installing a replacement actuator and re-inserting the holder into its mount. The resetting operation takes less time than that needed to change a blown expulsion fuse link.

operationUnder normal load conditions the electronics remain inert. However, should the line current increase above a pre-set value (the pick-up current) the logic circuit activates.

The upstream auto-recloser then opens, temporarily removing the fault from the line. The ASL’s logic circuit, powered by an internal capacitor, stores the incident for around 25 seconds (the ‘reclaim time’).

When the upstream device recloses, typically 3 to 10 seconds later, if the fault current is no longer in evidence, the ASL will ignore the incident after the reclaim time and eventually reverts to an inert state again. However, if the fault current (i.e. current above the pick-up current) is still present, the logic circuit will decide that this represents a permanent fault on the lateral line and for a two-count unit will prepare to de-latch.

The logic circuit is inhibited from operating the latch mechanism until the upstream recloser has tripped for the second time and the line current has fallen to a value of less than 250 mA (the ‘hold-off’ current) for a period

of at least 0.1 seconds.

The ASL thus operates during the dead time of the upstream protective device and does so quickly, without sparks or ionized gas emission and without contact erosion.

The logic circuit is designed to inhibit response to transformer magnetizing inrush current surges. Thus ASLs on non-faulted lateral lines are not spuriously operated by such currents, following repeated operations of the upstream recloser.

In practice, any lateral line fault condition that persists for a time long enough to operate the upstream recloser will operate the ASL, isolating the lateral. Any transient or ‘no-damage’ current will be ignored (See Figure 4).

Automatic Sectionalizing Link

Figure 2. ASL Construction Detail.

DIMENSIONS Voltage Length Rating In (mm)

15 kV 11.50 (292) 27 kV 14.96 (380) 38 kV 18.43 (468)

UPPER CONTACT

LOWER CONTACT

LATCHING RING

ACTUATOR

COLOR BAND INDICATES PICk-UP CURRENT

16A YELLOW24 A RED40 A BLUE56 A Green80 A BLACk112 A WHITE160 A BROWN224 A ORANGE320 A NO BAND

COLOR BAND INDICATES NUMBER OF COUNTS

1 COUNT BROWN2 COUNT NO BAND3 COUNT GREEN

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Figure 3. ASL in NEMA style fuse mount.

Figure 4. Operational sequence of a sectionalizer isolating a lateral line fault (sequence shows a 2 shot device).

CLOSED CLOSED

AUTO-RECLOSER CONTACTS

TRIP

OPEN

RECLOSE

DEAD PERIOD NOTED

RECLOSE

LATERAL ISOLATED

SECTIONALIZER OPENS

LINE RESTORED

MAGNETIC INRUSH CURRENT

TRIP

OPEN

NOMINAL LOAD CURRENT

FAULT CURRENT

LEVEL OF CURRENT IN THE MAIN LINE

LATERAL LINE SECTIONALIZER OPERATION

SECOND PULSE NOTED

FIRST PULSE NOTED AND STORED IN SECTIONALIZER’S MEMORY

LATCHED POSITION DE-LATCHED POSITION

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appliCationThe Auto Sectionalizer Link can be installed in existing cutouts at the head of the laterals or branches on a distribution system, downstream from an auto-recloser or multi-shot circuit breaker. Figure 5 illustrates a typical protection scheme used on a distribution system, utilizing ASLs instead of the typically used fuse links.

The most common type of overhead primary distribution circuit is the four-wire multi-grounded neutral system. A main line (feeder) with a recloser near its head originates from a substation with several laterals tapped off this feeder. Often further branch lines are tapped off the lateral which in turn supply power to end users. Transformers are individually fused and fuses at the head of branches and laterals provide further sectionalizing of the system.

In general, the individual transformer fuse links are sized to operate on all selected overcurrents without causing the recloser to operate. Operation of this fuse link affects a small number of customers making such operations easily justifiable.

The fuse link at the head of the lateral or branch coordinates with the recloser with some limitations. There is a maximum current beyond which the fuse link will operate before the recloser has a chance to clear a temporary fault. Under high transient fault conditions, such as a lightning strike, nuisance fuse link blowing can result.

Most distribution circuits have multiple expulsion fuse links in series. Due to the non-current limiting nature of expulsion fuse links, there is a maximum current at which coordination can be achieved. Above this current it is likely that both the upstream and downstream expulsion fuse links will operate at the same time.

By replacing a fuse with an ASL at the head of a lateral or branch, as illustrated in Figure 5, the coordination range is extended to the maximum short time withstand rating of the ASL. ASLs have no time-current characteristics and are easily applied between two fault-interrupting protective devices. Accordingly, they are easily added to an existing system or to an existing

coordination plan when additional circuit sectionalizing is needed.

The main advantage of the ASL is that transient fault interruption can be effectively achieved with the pole-mounted auto-recloser or multishot circuit breaker down to the minimum operating current of the ASL, without the necessity for delayed trips. Auto-reclosers can therefore be set for instantaneous trip, minimizing system damage. Fault withstand is not an issue as the short time-current withstand rating of the ASL will be greater than the available fault current except for a few possible applications next to a substation.

In the case of low ground fault currents, by selecting an ASL with minimum pick-up current at or below the minimum trip current of the auto-recloser, where possible, these ground faults will result in operation of the ASL on the faulty lateral, thus preventing lockout of the recloser and wide loss of supply to customers. To achieve the optimum level of coordination and to take account of tolerances, the lowest rating of ASL should be 80% of the ground fault or sensitive ground fault

Automatic Sectionalizing Link

Figure 5. Typical distribution system using ASLs.

POLE MOUNTED AUTO RE-CLOSER

PMAR

ASL

ASL ASL

ASL

TRANSFORMER

CUTOUT

2 COUNT ASL 2 COUNT ASL

2 COUNT ASL

3 COUNT ASL

MAIN OVERHEAD LINE OR FEEDER

LATERAL

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settings, dependent on the scheme employed.

seleCtionWhen selecting an ASL for a specific installation, a number of factors should be considered.

system VoltageThe ASL is insensitive to system voltage, and being in effect a solid conductor, has no insulation requirements. Hence the sole criterion concerning voltage is that the ASL fits into a mount of the appropriate voltage rating, meeting the dielectric values required (BIL and power frequency).

pick-up Current (actuating Current)For optimum coordination the lowest rating of ASL should be 80% of the minimum ground fault or sensitive ground fault settings allowing auto-recloser operations.

However, depending on the position of the ASL, it must be chosen to withstand the possible transformer magnetizing inrush currents.

When a recloser switches in and out attempting to clear a fault on one branch circuit, all the non-faulted circuits experience surge currents due to magnetizing inrush determined by the transformer kVA.

The anti-magnetizing inrush circuit in the ASL ensures against spurious operation, provided both positive and negative going half cycles are below the pick-up value. If the ratio of transformer capacity/pick-up settings is made too small, then even the smaller loops of the highly asymmetrical magnetizing inrush current, may be of sufficient value to override the inhibiting circuit and allow operation to occur.

Ieee Std C37.63™ standard for mainline sectionalizers allows a ratio of 1.6:1 for pick-up current to total available transformer current.

Present experience suggests that this is satisfactory for most applications of 2 and 3 count ASLs. For 1 count ASLs and applications where the transformer kVA is dominated by one large transformer, (i.e. more than 60% of the total), a ratio of 2.5:1 is recommended.

For example: for 2 and 3 count ASLs a 40 A pick-up setting allows for maximum installed transformer capacity of up to 25 A. even though the maximum loading on the line might be 5 A, a small percentage of the maximum available, magnetizing inrush

dependent on the installed kVA is the determining factor.

number of CountsThe number of counts to operate is factory preset. The ASL should be chosen with at least one less count than the up-stream recloser. For example, a 4 shot recloser should be matched with a maximum of a 3 count ASL downstream. To reduce the number of recloser operations, a 2 count ASL unit would be the most common. Where ASLs are used in series, the downstream ASL should be one less count than the up-stream ASL. 1 count ASLs are also available for applications such as underground cables where transient faults are unlikely. The choice of an ASL over a fuse eliminates the coordination issues discussed previously.

Maximum Fault CurrentBe sure the ASL has a short time-current withstand equal to or greater than the available fault current (See Table 1 Performance Characteristics).

Continuous CurrentThe ASL's continuous current rating must be equal to or greater than the system load current. This is normally not an issue, as all ASLs are rated at 200 A continuous.

reclaim timeThe reclaim time is the time that the memory of the ASL retains prior counts and is nominally 25 seconds. However in practice this time will vary with the value and duration of fault current pulses. For high values of fault current, particularly where the upstream recloser is operating in delayed mode, the ASL reclaim time may extend by up to 15% while for instantaneous tripping operation at lower values of current near the pick-up value, reclaim times will be reduced. For details see Performance Characteristics. For these reasons it is recommended that the maximum reclose time (dead time between shots) of the recloser be 15 seconds, as this must be shorter than the ASL reset time for correct coordination. If the auto-recloser is operating in the instantaneous region of the trip characteristic near the pick-up current of the ASL, the auto-recloser dead time should not exceed 10 seconds.

overvoltage WithstandCooper Bussmann ASLs have been tested to withstand 65 kA lightning surge current as defined in IEEE Std C37.63™ and IEEE Std C62.11™ standards and IEC 60099 for surge

arresters.

load BreakingThe ASL is designed for deadbreak operation only. If the unit is manually opened under live line conditions, an arc will be drawn across the contacts exactly as in the case of an expulsion fuse. If the current is low enough and if conditions are favorable, the arc may extinguish as the unit drops down to the isolating position. Therefore the same operating procedures will apply for the ASL as for expulsion fuses with regard to breaking load.

NEMA Interchangeable mounts are fitted with hooks, for use with a load-break tool. To open the ASL under load, use an appropriate load break tool designed for use with interchangeable cutouts and follow instructions provided with the tool.

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Dead timeThe time for an ASL to drop down to a safe isolating distance (from the instant when the line goes ‘dead’ after the correct number of counts) is approximately 250 milliseconds. To prevent any possibility of the unit attempting to open under live conditions the upstream recloser should have a dead line time of not less than 0.5 seconds.

perForManCe testsThe only fully applicable standard for ASLs is the Electricity Supply Industry (eSI) standard 41-27 Part 5. There also exists an Ieee Std C37.63™ standard, which covers traditional enclosed tank-type sectionalizers. In verifying the performance of the ASL, as listed in the Performance Characteristics, these two standards have provided the basis for evaluation. As many of the test clauses of Ieee Std C37.63™ standard are inappropriate, only those

applicable have been carried out.

In addition to those listed in the Performance Characteristics, a number of other tests have been performed to demonstrate the suitability of the ASL. These include load make, mechanical operation, icing, salt fog (corrosion) and other environmental tests including thermal cycling, rain-UV, and ozone. Details of all these tests are available on request.

Every ASL is functionally tested at least twice during manufacture. Current pulses of 10% below nominal pick-up value and 10% above nominal pick-up value are applied. ASLs are checked to ensure that they do not react to the lower value but operate at the higher value.

orDerinG inForMationTo order a Cooper Bussmann Automatic Sectionalizing Link, first choose the voltage rating and pick-up current from available options in Table 1. Then build part number as shown in the example in Table 2.

The part number for a replacement actuator is 4772968BS.

TABLE 2Ordering Codes: First Select the Part Code from the Table Below

Symbol

DefinitionVoltage Rating

Product Type

Pick-up Current (A)

Mounting Type

Number of Counts

SystemFrequency

15 Sectionalizer to be used in 15 kV Cutouts

ASL Automatic Sectionalizing Links

112 Pick-up current set at 112 Amperes

C Type C is for NEMA inter-changeable cutout mount

2Number of current shots unit will accept before operating (1, 2, or 3)

US US for 60 Hz (no mark for 50 Hz)

15 ASL 112 C 2 US Total Part No.*

* In the example above the Part number would be 15ASL112C 2US

Rated maximum voltage: 15 kV (110 kV BIL), 27 kV (150 kV BIL), 38 kV (170 kV BIL)

Maximum thermal rating: 200 A

Rated frequency: 60 Hz

Pick-up current: 60 Hz operation (+/-10%) 16, 24, 40, 56, 80, 112, 160, 200, 320 A

Number of counts: 1, 2 or 3

Hold off current: 250 milliamperes

Current withstand: Continuous 200 A

Momentary 1st peak 16,000 A

1 sec 8,000 A Symmetrical

10 sec 2,600 A Symmetrical

Reclaim times: 25 seconds (+/- 15%)

Response time: Minimum duration of current pulse 25 msec @ 1.5 X pick up setting for overcurrent memory response: 60 msec @ 1.2 X pick up setting

Circuit breaker dead time range: 0.5 sec to 15 sec

Minimum time of dead line after fault pulse for count: 80 msec

Ambient temperature limits: -22 ºF to 176 ºF

Surge current withstand: 65 kA per Ieee C37.63™ and Ieee C62.11™ standards and IEC EN 60099-1

TABLE 1Performance Characteristics

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© 2011 Cooper Industries. All Rights Reserved.Cooper Bussmann and Cooper Power Systems are valuable trademarks of Cooper Industries in the U.S. and other countries. You are not permitted to use the Cooper Trademarks without the prior written consent of Cooper Industries.Ieee Std C37.63™ and IEEE Std C62.11™ standards are trademarks of the Institute of Electrical and Electronics Engineer, Inc., (IEEE). This publication/product is not endorsed or approved by the IEEE.NEMA® is a registered trademark and service mark of the National Electrical Manufacturers Association.

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Automatic Sectionalizing Link