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Tri-Phase control normal load

At normal system current, the Tri-Phase control is effectively

dormant. Load current is continuously being compared to the

selected minimum-trip settings, but the TCC and trip circuits are not

activated.

Tri-Phase control overcurrent protection

The TCC circuit is activated when current above the pre-selected

minimum trip value is sensed. Once activated, the TCC circuit

uses the magnitude of the overcurrent to establish a time delay.

At the completion of the delay, the trip circuit pulses the Flux Shift

Tripper, which causes it to trip open the vacuum fault interrupter

mechanism.

Tri-Phase control coordination flexibility

The E time-current curve has long been an industry standard for

underground distribution switchgear fusing. However, when several

protective devices are present on the same line, it can become

difficult to obtain proper system coordination. The Tri-Phase control,

with the EF TCC installed, combines classic switchgear protection

with state-of-the-art vacuum fault interrupter technology. The Tri-

Phase control eliminates the problems normally associated with

fuses, but preserves and extends the familiar E-shaped curve to

higher currents.

Coordination and application of the Tri-Phase control is identical to

fuse application, but with the benefit of a greatly expanded offering

of trip ratings and timing curves. In the following example, the

EF TCC provides ideal coordination when protecting single-phase

distribution transformer loop schemes. The cable can be protected

to its rated load with sufficient margin between the EF and the

substation breaker.

Tri-Phase control instantaneous trip

Instantaneous trip, a standard feature of the Tri-Phase control,

extends the range of coordination with upstream devices, at

higher fault levels. A switch on the control circuit board enables

the instantaneous trip feature and programs a multiplier that is

applied to the standard minimum trip setting. When current above

the predetermined fault level is sensed, the instantaneous trip

feature causes the control to bypass the normal TCC delay and trip

immediately; thus eliminating any intentional time delay. For faults

below this actuation level, the control operates according to its

normal settings.

Figure 8. Normal load diagram.

Tri-Phase Control

Flux

Shift

Tripper

(Magnetic Latch)

VFI ClosedCT

Table 9. Tri-Phase control overcurrent protection diagram.

Tri-Phase Control

Flux

Shift

Tripper

(Magnetic Latch)

VFI Open

1000

100

0.10

0.010

CURRENT

100000100001000100101

EF-300A Tri-Phase

2OOT

Composite:

200A ELSP &

50A BAYONET

500 kVA, 3Ø

Phase-trip, three-

phase transformer

protection.

1000

100

0.10

0.010

CURRENT

100000100001000100101

CO9-800A

GND

CO9-1200A PH

EF-300A

Tri-Phase

Composite:

50A ELSP &

15A Bayonet

50 kVA, 1Ø

Phase-trip, single-

phase transformer

protection.

Technical Data 285-10

Effective April 2014

VFI underground distribution switchgear

www.cooperpower.com

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Wells SW-10T Manuale Utente Pagina 6

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